mylk[386]blog

I started this page when I first embarked on my quest to design my own amp circuit mainly just so I had somewhere to write testing notes and put photos but a couple of people have said they have found it helpful or interesting and I use it for reference all the time so I thought I might as well keep it going.

I have actually created the circuit which you can learn how to build it here but as always with projects like this there are always things that can be tweaked and new things to try. Plus with the circuit done I am free to do what I really love and that's designing and making things to use it in. Have an endless list of ideas I want to use the circuit for now I am done so really this where the fun begins



 

 

 

 

 

 


 

 

 mylk386 [Brushed Alu]


 

 

 

 

 

 

 

 



mylk38 [Kit Tester[22/9/2014]

   

This one is just me doing some testing for the mylk[386] kit which I hope to be able to offer quite soon. Have been searching for a while for some boxes to put the kits which could also be used as the enclosure for the amp. My initial thoughts were to try and get some sturdy cardboard gift boxes but I just can't seem to get any that are rigid enough in the size I want. Anyway stumbled across these jewelry boxes which might just be perfect. Have bought and experimented with quite a few wooden boxes but the problem is the walls are always too thick to put the pots, jacks, and switches through without recessing the holes. Also the quality is usually really inconsistent from box to box . The nice thing about these ones is that the front and back is a 2 or 3 mm laminate sheet while the side walls are 5mm solid wood meaning they are really nice and sturdy but the front and back face are perfect for easy drilling and mounting of the controls and sockets. The other thing I really like is after buying the initial box to have a look at I ordered 5 more and everyone was exactly the same, perfectly clean and square....nice.

   

 

 

 

 

 

 

 

mylk[386]amp - Prototype No.3 [19/9/2014]

Right......finally feel like I am getting there in terms of the aesthetics. Found an awesome etching technique although  creating the mask is still proving to be less reliable than I would like. Have a few processes in testing at the minute including screen printing the mask directly on to the box but I'll let you know more when I get the technique refined. Control labels still aren't perfect, still a bit under etched in places but definitely the getting much closer to how I want them.  

  


 

 

 

 

 

 

 

Wooden [Box] amp 

 

 Bought a load of different plain jewelry boxes of ebay to have a play around with for amp enclosures. No really sure if any of them will be suitable at the minute but sanding and shaping wood has been a welcome distraction from filing, scouring and polishing aluminium boxes and all the horrible grey dust that comes with it 

 

 

 

 

 

 

Circuit Layout Graphics [][][]


 

 

 

 

 

 

 

 

 

 

 

 


Prototype No.2 - Getting there [][][]


Finally getting there. Still not exactly what I am after in terms of the finished product but definitely going in the right direction. Still need to refine the etching process and the control labels and really not happy with how the speaker sits on this one. Getting the speaker to sit flush is much more difficult and time consuming but it looks a million times better. I am still loving the black trim and really like the PC thumbscrew feet on this one.  

      

 

 

 

 

 

 

 

Vero Layout graphics testing [][][]


Playing around with some ideas for graphics for the stripboard layouts. Although I have nothing but love for  the D.I.Y Layout creator software, the graphics it puts out are grim. If you are trying to use this layout to build the circuit from just be aware that  I got the volume pot wires wrong way round on the picture above (the volume would work backwards, just swap the 2 outside wires around on the 1k pot ).  

 

 

 

 

 

Box etching antics [][][] [25/03/14]  

Spent the weekend, inbetween soldering up and verifying the circuit board layouts I created, playing around with box etching techniques. There are lots of different ways to create the mask and etch away the aluminium so I thought I bets try some to find out what works best for me. Am absolutely set on etching the boxes for the amps as it gives a really sharp and professional feel to the finished item.   

   

The 2 main ways to mask up or create a "resist" for the etching are toner transfer or vinyl mask. The vinyl mask technique is much easier, quicker and sharper, but there is a limit to how small you can cut out lettering and image detail so is only really suitable for big  bold text  and simple image designs. The toner transfer method relies on the heat transfer  properties of laser printer toner and although you can produce tiny text and really detailed images, It's a much lengthier, more faffy process with lots of opportunities for things to fuck up. I'll talk more about the whole etching process when I get my technique down. There are plenty of "How to's" out there so I won't waste time adding my 2 penneth until I have something valuable to contribute. 

  

 

 

 

 

 

 

Amp box graphics [][][]


 

 

 

 

 

 

 

 

 

Circuit Layout stickers [][][] [18/03/14]



Was playing around with the PCB's I made the other day thinking about how best to mark out the component placement on the top of the boards, trying to decide whether to make up a screen to screen print them with or try and use some kind of transfer when the idea occurred to me that I could just print the layout on some sticker/label paper and  stick straight to the top. This way if I make any changes after I have verified or not verified ....? De-verified...? Falsified....?...... not sure what the correct verb is here? Anyway if the layout turned out to be wrong and and I had to change it,  I wouldn't have wasted hours of my life making, and then re-making a screen to print with. 

 So after doing this to the PCB and spraying a coat of frog Juice on it to seal it, I was really impressed (The frog juice soaks right into the paper and when it's dried it looks like some kind of printed plastic laminate has been applied). Then I thought why can't you just do the same thing with vero board (stripboard) or pad board to make building layouts quicker? Well you can, and it works really fuckin well, don't understand why this isn't a thing? Or maybe it is but I have never seen anyone do it. Anyway if it's not a thing, I am gonna make it one because it takes away a lot of the margin for error when building internet layouts. The trick to printing the sticker the right size is to know that the standard hole spacing for veroboard and padboard is 0.1 inch or in proper units, 2.54 mm. So if you create a grid with 2.54 mm spacing in illustrator or photoshop  and line up the holes on your layout with the grid, it will be the perfect size. Use a drawing pin to punch out the holes and hey presto...instant sudo PCB.

   

 

 

 

 

 

 

 

 

 

 

Etching my first PCB's [][][] [28/02/14]

 

Had a random day of work on friday as a result of having a few days annual leave left which I have to take before the start of April. I thought I would put it to good use and finally have a go at etching some PCB's and also do some Logo test etches on the aluminium boxes I am using to build the amps in. All round success really. For the PCB's I just used the vinyl cutter to make the resist which is much easier than fucking about with laser jet toner and nail varnish or photoresist boards and developer. The box etching also worked really well apart from not quite doing it for long enough resulting in a slightly shallow etch, but the technique (9v battery and some salt water) worked a treat


The design is just about at the limit of what the vinyl cutter can cope with, any smaller and it wouldn't be possible to do it with the cutter. Probably isn't the best way to do large batches, but for these little test runs it's perfect. Now just need to wait for my micro drill set to arrive from ebay and the PCB's will be good to go. 

 

 


 

 

 

 

 

 
New Stripboard Layouts [][][] [26/02/2014]

 

 

 Getting to the point now where I am pretty much done with the electronics and am ready to publish the circuit and start building batches of amps. Just a little bit of work to do on the graphics and detailing and where there. In preparation I thought it might be a nice idea to do a stripboard layout and walkthrough for anyone who needs it so I started working on a refined layout that fits on a standard 25 hole x 9 hole pre-cut veroboard [Pictured above] sheet and is versatile enough to accommodate a number of different wiring options and has a little bit of free space for extras [pictured below] such as LED resistor and wire, input volume or tone control. Just need to build one quickly to verify the diagram and i'll get it labeled up and published. 

Also been working on a new PCB design based on a smaller 22 x 8  version which I have been using to fit inside the little 1590 hammond boxes as pictured below. 

 

 

 

 

 

 

Prototype No.2 - Refined [][][] [24/02/2014]

Ok... so after the last build my main priority was to shrink the circuit layout down a touch so it would fit in the box a little bit more comfortably  and to optimize the pot values and tapers for best function.  The pot values I sorted using my [386]Amp breadbard  picutred below. I managed to shrink the board down slightly by optimizing the stripboard layout (which I will publish as some point over the next week once I have double verified it) slightly by doing things such as running a couple of the jumper wires under the chips, I also reduce the height by swapping out the polyester Teardrop caps for polyester box caps which sound the same (to me at least) but take up a lot less space. I also saved some extra space by laying the low value electrolytes in their side and reducing the 220uf output cap and 470uf power filter cap to 16v rather than 25v which reduces their size (both height and circumference) by a couple of millimeters. All of which combined gives me a lot more room to maneuver inside the small hammond 1590  pedal enclosure. =

Testing the circuit board before mounting it in the enclosure   

[Notes] - 

  • Don't need to add and twist ground wires on the input and output, actually adds noise rather than reducing it.
  • Do need 1 extra ground wire (other than battery ground) coming from the circuit board just for convenience - makes it much easier to connect a ground wire to the back of a pot in order to earth the box/enclosure
  • wire 8ohm 1w power soak resistor to back of pot then connect pot to ground
  • connect switched side of input jack tip to ground. When the jack is unplugged this grounds the input stopping hum and noise caused by the op-amp running away with itself. 

This is the first one I have built that I have been 100% happy. Everything fits in the box nicely, there are no hums, squeals or noises. There are no crackley pots and all the tapers and values work perfectly. 

The details of this one are -

  • 500k [audio log] Drive/ Distortion pot.
  • 3 position Switched 386 gain. (open / 1k resistor / break) 
  • 1k [audio log] Output volume 
  • 2 position Bright/presence switch 
Which all works really well together. With the drive pot at minimum , the 386 gain switch  gives you Flat clean (minimum x20 gain, centre position), sparkly driven clean (1k resistance, switch at top) to full on blues rock ( fully open,  x200 gain, switch down).  

    

The distortion pot  goes from totally clean to full on metal with a lot of variation in between and even with the drive maxed out the 386 gain switch still has a big impact on the amount of drive.  Putting the distortion on full and playing with the switched gain takes you from vintage metal, to metallica, to screaming lead with massive amounts of sustain. You really can play full on tapped, and legato solos with the amount of drive on offer and it really isn't that noisy at all. 

 The last switch controls the 47nf cap in the feedback loop of the 386. Which works as bright/presence switch. The whole point of this amp is that I want it to do big sounds at low volumes and one of the first things to go when you start turning the volume down (particularly with big speakers) is the treble. The whole amp is tumed to be fairly bright (particularly when compared to other 386 amp circuits), but when you have the volume really low, or are using a dark sounding guitar with humbuckers this switch allows you to add some treble back in. Works really  well on pretty much all settings, only losing some of its effectiveness when everything is maxed out. But even then there is still perceivable presence increase.  

 

 

 

 

 

 

 

 

[386]Amp - PotTesting [][][] [12/02/2014] 


Got some more pots through the post yesterday and after a bit of testing have finally decided on the best values and tapers for use in the amps which I know I can get hold of consistently.

Op-amp Gain/Dist/drive -  50 - 500 [Audio log] 

  •   Needs to be audio log for best performance, linear taper far too abrupt. 500k for full on metal, 100k for classic rock, 50k for vintage fender vibe. 500k is favourite as it gives you the full range 
[Optional] Input volume (between op-amp and 386 chip)  10k - 500k  [audio/linear]?  
  • Still not tested this one properly yet as I have been focused on getting the pre-amp gain sorted. should be the same as runby/noisy cricket. 10k best value, audio log preferable but linear works fine 

386 chip gain  2k - (2k2 preferable) [Linear]  

  • 2k linear works great much better than 1k, more clean available, do not use audio taper as the taper is the wrong way (have ordered some revers log pots just to test, but no real need, linear is perfect) Am interested to try a 5k but I suspect value will be too high. The internal resistance of the gain loop is 2k3 or 2k6 if I remember rightly,  so anything above that should allow you to select minimum gain. With a 1k pot, there is not enough resistance to completely break the circuit (such as on the ruby and noisy cricket amps, which is why you need an input volume control to reduce the signal entering the 386 enough to be able to get a clean tone).  a 5k pot is way too much so although you will be able to select minimum 386 gain (x20), nothing will probably happen for the last 1/2 of the pots travel. 2k2 is the best compromise but it is often difficult to get a regular supply with the right taper and shaft length etc. In the end I have settled on 2k [linear] as I know I can get these consistently and they work really well. Much more clean available and smooth roll on of gain throughout the pots travel  
Output volume  470r - 1k [Audio]  
  • ok so here the absolute best value to use would be a 470 / 500 ohm [audio log]pot  but I can't get hold of any of these for love nor money. Values below 1k seem relatively rare, and if you can get them, getting the right taper and shaft length is a nightmare. I can get the 470 ohm [Linears] but only in a longer shaft length which means cutting the pots down which is time consuming and messy. I would say that 470 ohm linear actually works ever so slightly better (smoother roll off) than a 1k [audio] but all things considered - 1k [Audio] is the one I will be using. The roll off is a bit sharp when using the internal speaker (although no where near as bad a 1k linear), but about right when using a proper, full size external guitar speaker.

 

 

 

 

 

 

 [386]Amp Testing Board [][][] [5/02/2014] 


        

Built this on my days off, another prototyping breadboard. 386 circuits can be very temperamental when it comes to component choices and position so I wanted to build a board I can test all the components for an amp build  before soldering everything together. Also at the stage where I need to make some firm decisions on pot values and tapers for best functionality of the amp. This board allows me to test and switch values ready for the final design   

The board features are as follows

  • Input, Speaker out, on/off switch, DC jack (centre -) and internal speaker.
  • Hardwired Distortion pot (op amp drive), Gain pot (386 gain) and Output volume control 
  • Internal (variable voltage divider) hard wired to the back +/- Rails  giving me a 4.5 Vref for the op amp
  • 9v +/- hardwired to the front rails 
  • 470k (linear) Distortion pot
  • 2k (Audio Log) Gain pot 
  • 1k (Audio Log ) Output volume 

    

[Notes] - The 1k (audio) output volume works fine. Roll off a bit steep with little internal speaker but fine with proper guitar cab. The 470k (linear) Distortion pot works ok, good range but not that smooth. Have found and ordered some 500k audio log pots so will give one of those ago when they arrive. The 2k drive pot isn't working that well goes from nothing to all out in the final 1/4 of the pot travel. I think this is because the pot needs to be either linear or reverse log. Again have found and ordered some 2k linear pots (couldn't find reverse log) so will give one ago when they arrive. 

Really like the glowing blue breadboard although could have done with using 2 LED's, one at each end,, rather than just one in the middle. Power filter cap needs to be placed as close as possible to the +/- pins on the 386 chip. Mounting it even on the main +/- rails of the board sounds noticeably worse (more digitally sounding artifacts) 

 

 

 

 

Notes to self [31 January 2014]


 Amp and PCB Design Notes 

  • Don't need input/output Ground wires board mounting, only need battery ground. All others can be wired off board (from DC JAck)  
  • Wire 8ohm, 1w power soak resistor to back of output volume pot when used. No need to be board mounted.
  • Use box caps on board, rather than poly plastic coated. Sound the same but box caps are physically smaller (and shorter).
  • Use 2x 100k resistors for Voltage divider rather than trimmer pot. It's just cheaper and having the voltage divider being adjustable provides no actual benefit.
  • Mount small value (1uf, 47uf) electrolytes on their sides to reduce height of PCB
  • Modify LED holders and prewire LED with (3k3 resistor) and leads 
Audio Testing notes 
  • 1k Audio Log pot works fine for master volume (instead of 470ohm) and is probably louder on fully open (more resistance to ground) and are much easier to source (1k chassis mount, audio log  available from http://www.bitsbox.co.uk/)
  • 470k (500k) drive pot works absolutely fine (was worried not enough control over drive) 
  • 1k gain pot is fine for [Buffer]-[386] configuration. Needs a bit of power amp gain for sparkle 
  • 2k much better for [Boosted]-[386] combination, needs minimum power amp gain to achieve a proper strummy clean, flat, rhythm sound although it does sound more lively with 1k resistance.
  • the blue polyester 470pf caps sound the same if not better than the ceramics.
The [386] gain control has a really good range regardless of boost settings, starting to think that having a 3 position boost switch (clean/OD/Dist) on the Op-amp and a 2k pot for the power amp gain (+ an output volume and a bright/presence switch)  is the best wiring solution, rather than having switched power amp gain and a pot for distortion. 

 

 

 

 

 

 

Prototype No.1 - Aesthetic notes [][][]


There are a few things I have not even got round to thinking about yet such as the graphics and finnish (well I have thought about it, but not started testing ideas yet) but I like the way things are progressing.

The good -

  •  The chunky black plastic sockets and switches 
  • The black powder coated bow handle on top
  • The Black base and spiked feet
  • The fecking massive orange LED's with chunky black bezel 
  • [NEW] The black washers round the switches (I really wanted black switches but they don't exist so this is the next best thing, a bit of black detailing)
  • So.......essentially all the black bits. I'm not a lover of chrome and shiny things 
The not so good -
  • The LED on this one was way too bright used 1k resistor.    (3k is the perfect value for a warm orange glow).
  •  The controls are maybe a touch high (need to adjust the drilling template by a couple of mill ).
  • LED is too far to the left, problems with clearance due to internal structure. Light seeping from round the bezel. (need to move the LED position rightt by a millimeter or 2). 
  • The spade toggle switches, I thought the looked more sophisticated but the toggle shafts are too long and wide, they also swivel in their sockets meaning most of the time they are wonky unless you straighten them. Not cool!

The pictures below show the comparison between the - 2 knob, 2 switches version and one with 3 knobs and a switch. I actually prefer the look of the 3 knob one, which actually has more internal space (the back of a potentiometer is much shallower than the back of switch) but it is a little bit cramped on the front and I want things to be simple. I may revisit the 3 knob box design when I develop a tone control I am happy with. 

   

 


 

 

 

Prototype No.1 - Electronics notes [][][]

I designed the stripboard around a standard -  25 hole x 9 hole pre-cut veroboard sheet for convenience. The fit is pretty snug. I had to trim the (thankfully unused) top row off the stripboard to get it in. The speaker mounted on the base plate  protrudes into the box slightly meaning I needed another couple of millimeters clearance, normally a 25 x 9 strip will fit sideways in a little hammond box. It did all fit but it's all a bit ugly and Heath Robinson.

   

If I didn't have the on/off switch and the DC jack mounted between the Jack sockets on the back the battery would easily fit between them leaving loads of room for the Circuit board but I don't really want to remove them and they wouldn't look right mounted on the side.  There are however a couple of things I can do to shrink the board down.

  • Use smaller 16v electrolyte caps for the output cap and power filter 
  • Use box caps instead of the taller tear drop ones I have been using.
  • Mount all resistors axially to reduce the length 
  • Make the board in 2 parts (pre-amp / power amp)
  • Mount bigger components ( output  and power filter cap ) off board
  • Essentially I just need to make the circuit board shorter and the Lower
The circuit board needs to be multi purpose so I can use it in a number of different applications (travel guitar, combo amp, retro radio, etc) The little hammond boxes are probably the smallest thing I will need to squeeze it into so if I can get it to fit comfortably in this, then it should fit in anything else fine. 

 

 

 

 


 

 

PCB to Stripboard [][][]   04/01/2014

Before I wasted a lot of time and potentially materials etching an untested PCB design it seemed prudent to do a stripboard version first. This way I can 1) Make sure it works, and 2) Make sure it all fits in the box. Below is just the PCB design I made earlier transposed onto stripboard ( or Veroboard) using  this excellent free D.I.Y Layout creator. The green triangle indicates where a small trimmer pot should be placed to create a voltage divider (2 equal value resistors mounted axially could also be used). 

[Notes] - Please don't use this layout - IT IS WRONG. I have the ground rail running straight through pins 4 and 5 (the 2 bottom ones) of the opamp and on straight on to pin 3 of the 386 chip. In my notes I had pin 5 down  as n.c or not connected. Turns out on some op amps this pin is offset null and having it connected to ground causes bad squealing. 

 

 

 

 

 

 

 

 

 

 

Stripboard & PCB design No.1 [][][]


Got a PCB etching kit for Christmas as it seems the right time to start thinking about producing the circuit board in batches so I can build multiple amps. The design must be versatile enough to be able to be wired a number of different ways while still being small enough to fit in a small pedal sized hammond enclosure. Never designed or made a PCB before so there is probably going to be a fair bit of trial and error.


 

 

 

 

 

Amp work update - [December 2013


 

ok....So I am at the stage now  where I am happy with the basic circuit design and want to start churning out some amps. With all the circuit design work more or less taken care of, I want to focus on the aesthetics of the boxes. There are lots of things I want to try such as etching, sand blasting, polishing, sublimation printing, screen printing, powder coating, and of course good old fashioned painting. At the moment my goal is to design a few really nice basic box designs which I can produce in small numbers and then to also put my airbrush skills and equipment to some use and do some one off custom painted amps. with that in mind my goal was to create a standard box template I can use to drill multiple boxes and also to create a base stripboard layout for the amp and eventually do some PCB's 

   

So Job number one is to decide on what controls and other offboard components will be needed and how best to lay them out. As previously stated the amp can be wired up a number of different ways so the PCB and box layout need take this into account. 

It is possible to fit 3 pots/ knobs and 2 switches ( with LED's) on the front of the little Hammond boxes I am using [Like this one here] but only just. Space is very tight and function of the 2 knobs which are side by side is compromised. This can be improved by using knobs like these but it still isn't great. I would probably find a little bit more room if I didn't insist on using a massive 10mm LED for the power light but I really like the oversized chunky look so the LED stays ( for now at least). 

   

Anyway to cut a long boring story short(er) I have decided to go for 2 potentiometers and 2 switches ( 1x 2PDT and 1x 2P3T) This means I can wire the Amp several ways :

  • Distortion [Pot] / Bright Switch / Output Volume [Pot] / 3 way power amp Gain switch 
  • Master Volume [Pot] / Clean, OD, Dist switch / 386 Gain [Pot] / Bright switch
  • Master Volume [Pot] Bright Switch / Distortion [Pot] / Power amp Gain switch
  • Distortion [Pot] / Bright switch / Power amp Gain [Pot] Output Volume swtch 
  • etc, etc.... You get the idea 

 


 

 

 

More Random box pics [][][]


 My ideas often come a lot quicker than I can actually build stuff so I often find it prudent to photograph mock ups of ideas to jog my memory later. I find this much more useful than writing things down or drawing crap sketches . Click here to view - my [386 ]amp design ideas page. 

   

 

  

 

 

  

mylk[386]amp - circuit done [][][] [9/10/13]


 

Well it's been a busy few months have been working hard on my mylk[386]Amp Projects. Have tested and tweaked and test built till I am  blue in the face but and I think I have finally found a circuit I am happy with. The basic template being an op-amp buffer/booster section mated to my take on a Ruby/Noisy cricket style 386 power amp section (I'll explain all the details of the circuit  in another post).

The real struggle has been to keep it as simple as possible as I keep thinking of different tweaks and ideas to add to it (i.e if your gonna use an op amp, why not use a duel op-amp and get an extra channel, why not add mid scoop  or buffered tone stack), but keep having to remind myself that the idea (at least in the 1st instance) is to build an improved, more versatile version of the Ruby/Noisy Cricket amps, that is still a simple build for the D.I.Yer and first time builder. Something that retains all the great tones available from the aforementioned amps while adding a few more to the repertoire i.e more sparkle,  more gain and lots more gain (all of course without letting the circuit get wooly or muddy). I also want the circuit to function as  base for further development and  modification so I can create small batches of modified amps tailored to specific sounds or styles (Sort of boutique 386 amps, although that sounds a bit pretentious).

The real beauty of the circuit in my opinion in my opinion is it's versatility. The op-amp itself makes a much more versatile preamp than a Jfet buffer as it can easily be switched between a buffer and booster. It does all the great buffered tones of the Ruby  and Noisy cricket, while also offering much more gain should you need it. Also the basic circuit can be wired up a number of different ways to give a number of different results. If you wire the circuit up with a 500k drive pot on the op-amp and an output Volume control, you have an amp that will do Metallica. I you wire it with a 100k drive pot and a tube amp style master volume (i.e between the pre-amp and the power amp) you  have an amp that is much more vintage / classic rock sounding. Instead of controlling the op- amp gain with a pot you could use a 2 or 3 way switch to change from Clean / Overdrive / Distortion while retaining the  Drive (386 input volume)  and Gain (386 gain loop) controls of the  Rube or Noisy cricket. Essentially you would have a buffered amp that works exactly the same as the ruby/cricket with an extra 2 stages of gain boost available at the flick of a switch, just like adding a distortion or overdrive pedal to the front of the amp.

 

The diodes are essential for softening the clipping at anything much above unity gain, not even worth having them switched. In buffer operation they are not clipping anything except the nasty spikes in the signal which just adds a tiny bit of compression. As the gain is increased the diodes start to round off the clipping and prevent any nay harsh distortion. Sounds best with 2 odd diodes to give slightly asymmetrical clipping, let your ears be your guide. Can't tell you which ones I used because I tried loads and now can't read the markings on the tiny cases. But they are definitely 2 different ones.

 

 

 

 

 

 

 

Testing Notes [8/10/13]


 

 Changed input Z resistor to 1M5 - Clean Sounds fuller more complex (less reedy)

  • More than enough Clean volume available  (Min Drive / No power amp gain - [1k  gain pot not enough, use 2.2k pot or break completely) without needing to use volume between op-amp/power amp, (but only with low output pickups) although this is   still a useful addition which completely changes the  character. (Good range of cleaner sounds)
  • There is still quite a good range of drive available from the 386 gain pot with the op-amp drive on minimum (buffer operation)  or low settings, not quite so much on highest drive settings - Still cant decide id its best to switch this 3 ways (break /1k and 2.2uf cap/ open with 2.2uf cap) and control crunchy sounds with op-amp drive and 3 way gain switch.
  • Definitely use switched 47nf cap in feedback loop - Produces a noticeable treble boost on all gain and drive settings.
  • Not sure what to do about drive pot, both 100k and 500k sound good. The 500k pot is thicker with more sustain at max drive but the range of the pot is not particularly smooth on higher settings. The 100k pot is much smoother / more linear in its rotation but has less overall gain. Still sounds really good, just more vintage/classic rock which isn't necessarily a bad thing it just won't do metal/lead like the 500k pot. One solution is to use a 100k pot  switch in an extra 400k resistor as a gain boost or just change the pot for a 3 way switch (Buffer/Gain x 10/ Gain x 100)  Either would sound really good, could even use 250k and split the difference.

Really does sound good, can't actually believe how good it sounds. And the range of sounds from sparkly clean to full blown metal distortion and all the vintage overdrive and  classic rock tones you could ever want in between. 

To come later ...........

Could easily do a 2 channel amp using 2 halves of a TL072 with a Drive and output volume each. Could also use switched clippers for each channel to further alter character ( Different tone filters for each channel?)

Could also use the other half of a duel op-amp for -

1.     active Tone control

2.     Extra gain stage (cascade)

3.     2 completely different channels 

4.     Pre-amp out (use as booster/distortion with own power amp)

5.     Compressor (Rockman)  / metronome (NE555)/ Looper (recordable greeting card module) / Reference tone (NE555)

6.     2 different op-amp based classic distortions i.e Tube screamer / Proco Rat / MXR dist+

 

 

 

Card Amp [project]

Running in parallel to this project blog is my  Card Amp [project]. I have kept the 2 projects separate as the I wanted to keep the focus of the card amp project on the construction rather than the electronics but there is obviously going to be a fair bit of overlap between the 2. This has become more true as the projects have progressed. I initially imagined that the card amp project would use a simpler circuit than my main 386 amp project but as time has gone on and I have started to make much more headway in developing my own circuit I have realises there really is no need. The schematic above is not the actual schematic I recommend building, It's pretty close but I really wanted to get cracking on the first proper prototype of my card amp so I adapted the circuit to work with the values of pots I had in my parts bin. It does sound pretty good, just not quite as good as the proper one. Also the Orange LED clippers sound dreadful, don't use them. I just wanted to see what the flashing LED's would look like. 

See more of my CardAmp [project] - HERE 

 

 

 

 

 

 

More Booster pics [][][]


 

 


 

 

Op-Amp epiphany [][][]


 Throughout all my amp testing and designing work so far I have been solely fixated on using Transistors (BJT's and Jfets) Partly because thats what the circuits that kindled my love of d.i.y electronics and inspired me to embark on this project used, and partly because I just didn't understand how op-amps actually work. I also think that subliminally  I had just written op-amps off because of all the statements you tend come across on the internets, along the lines of "Jfets sound like tubes" or "op-amps sound clinical".  These statements are usually opined by 14 year olds on forums who have read 2 web pages, built one fuzz pedal from a schematic someone else designed and published and now think they are Roger Mayer. Anyway I happen to stumble across a little 741 op-amp buffer [Schematic pictutred above] I made as breadboard module ages ago, in my electronics box. I don't know where the I got the schematic from, (probably muzique) I decided to whack it on my amp testing board and do some A/B testing between the Jfet (ruby/noisy cricket) buffer and this op-amp one. Basically the op-amp one just sounded better, brighter, clearer.....just better, at least in this particular application. Anyway with my prejudices removed I thought I best learn how op-amps work and how the are biased so I could try and come up with something of my own. 

Recommended reading 

The thing that struck me most is how amazingly simple it is to  bias an op-amp is and how easy it is to switch it form a buffer to a booster. The gain is controlled by the ratio of 2 resistors. If the resistors are the same (or missing altogether) you have unity gain or a buffer if you increase one of the resistors by a factor of 10, you have 10x gain (or as near as makes no difference) if you increase the value by a 100, you have a gain x 100. Obviously you are limited by the voltage of the circuit but it is essentially that simple. Use a pot instead of a fixed resistor and you have a pre amp that will go from buffer to booster at the turn of a pot 

 For anyone who thinks that op-amps are clinical, build the schematic below and give it a try 

 

 

 


 

 

Little box [No.2] - Jfet Booster 


This is my modified version of the Jfet booster from the Run off groove "Big Daddy" amp. It uses a rotary switch to change the bypass cap on the  bias network which alters both the amount of boost and fullness of the boost as well as controlling the LED's . There is also a switched output cap to further tailor the tone. There you go a simple decent sounding boost that can be used with a 386 power amp or run straight into the front of a tube amp. 

    

 

    

 

 

 


 

 

Designing Box Layouts [][][]

 

 

 

 

 

 

 

Back to [386] Basics [][][] (29/6/2013)


Over the last month or 2 I have spent a lot of time reading, researching and testing ideas for my 386 Amp [project] and in a bid to save time and money soldering and wiring up the same power amp section over and over again or working on a messy breadboard with wires coming out left right and centre I have decided to just build everything in modules so I can play around with different boosters, buffers, tone controls etc. so I can find the perfect combination. The main thing I want accomplish with this project is to come up with my own circuit, something that really feels like my own work and not just a rehash or tweak of what someone else has done. I am not expecting to reinvent the wheel or anything (certainly not with my limited electronics knowledge) but I would like to feel like I have really put the work in. I had originally built the first module using just the power amp section of the 'Ruby' and 'Noisy cricket'  which are almost identical but on my day off this week I decided to return back to 386 basics and play around with the basic circuit using the Datasheet information and examples and see what I could come up with.

 

If you are building it on a breadboard........build this. The highlighted components can be switched in and out to change the sound 

You don't need a buffer to make a decent sounding amp out of a 386 chip as anyone who has ever plugged a 'Smokey amp' into a proper guitar cab will tell you. And although adding a buffer definitely does add a little bit of extra sparkle, for someone tackling their first d.i.y build I really wouldn't bother. The extra complexity is not worth it for the marginal improvement in tone. Also if you just build the back end of the circuit on it's own you can have loads of fun making and testing different buffers and boosters until you find something you like.......or if you can't be bothered with that, you can just stick any buffered pedal you own (any Boss or Digitech should do the trick) in front and hey presto, you've added a buffer.  

 

If you are building it in a box and want controls........build this (the 10k input volume is optional as is the 47nf input cap which isn't shown,  there will probably be the equivalent output control and cap on any preamp/pedal you are using) 

 

 386 amps can sometimes sound a bit dull so most of my component choices centre around adding more brightness and sparkle to the circuit   

  •  The generic Zobel values (resistor and cap to ground from the output) I left the same. Changing the values makes very little difference to the sound if any unless certain other components such as the boost cap or Bypass cap were different or missing.
  •  Instead of having a switched boost cap from pin 5-7, which without the buffer has a much more profound but buzzier and less pleasant effect, I opted for a fixed or switched 47nf cap which feeds back a bit of sparkle and boost back into the signal without messing up the DC offset and causing the unpleasant/messy distortion the 100nf cap does. This has the effect of a treble boost when switched in (Anything above 100nf starts to sound terrible and anything below 10nf is virtually inaudible).
  •   The bypass cap I changed to 47nf which sounded best with the 47nf boost cap. Without the boost cap in place you can use pretty much anything from 47nf to 100uf without it making too much difference. 
  • I initially added in the 10uf cap from the datasheet example back into the gain loop as in certain circumstances this did seem to tighten up the gain a bit and get rid of some of the fartyness. However after doing some testing I found that a 2.2uf cap works even better to tighten up the distortion  (If you are going to use a pot to control the gain, use a 2.2k or even a 5k rather than the 1k specified on the Ruby/Cricket circuit. A 1k pot is not large enough to completely break the circuit meaning you will never be able to select minimum gain which will affect how much clean you can achieve). 
  •  I also added a 47nf input cap which has a much more pronounced and pleasant effect on tightening up the low end than changing the output cap to a 100uf I like the 47nf input cap and 220uf output cap combo much better.  With it, the amp sounds tight and focused. Without it you get an apparent bass boost. 
  • I also used 470uf power filter cap which is not listed on the schematic above. The bigger the power filter cap the better the amp seemed to sound but 470uf is probably the biggest practical value (1000uf caps are physically pretty big)
  • The only other thing of note is the master volume which I have added to every 386 Amp I have made and as far as I am concerned is essential. 1/2 a watt is more than enough to annoy the neighbours when run through a proper guitar cab so if you can have a true MASTER/OUTPUT  volume control......why wouldn't you (The 1w  8ohm power soak  resistor is optional, have built several amps without it and never had any problems. You could also use a rehostat instead)

So there you go, probably 8 hrs of my life completely wasted but at least now I can get on with the fun stuff safe in the knowledge that I put in the work in and tried all the possibilities. 

 


The TDA7672a - Power amp chip [][][]


 

Ok........so might have to take back some of the things I said about the Orange micro crush circuit back. I breadboarded the power amp portion of the circuit up last night from thTDA7276a Datasheet and ran it through my blackheart 1x10 Eminence cab and it sounds great. I think the reason the Micro Crush actually sounds so dreadful is the speaker. When I ran the breadboarded circuit into the micro crush cab using the speaker in jack I added, it went back to sounding dreadful. They have obviously used a full range car speaker or something which sound awful with guitars unless you use some kind of cabinet/speaker emulation. Anyway the good news is the not only does the chip sound really good and has loads of clean headroom but the circuit was so easy to build it's ridiculous. Out of 16 pins you only really use 3. 

Pin 1 is power ( datasheet recommends a 100uf power filter cap. Pin 2 is the output (through a 470uf cap). Pin 3 is for standby which isn't needed in a guitar amp so can be left unconnected and Pin 4 is input ( through a 10nf cap). Pins 5,7 & 8 are not connected and  Pin 6 plus pins 9-16 all go to ground (datasheet recommends connecting pins 9-16 to a heat sink). Thats it, 1 chip 3 caps and you have a decent sounding working amplifier, even without adding a buffer or booster. 

 

 

 

Orange Micro Crush [Cab]


Been playing with the little Orange Micro Crush I bought last week and my initial impression still stands. It's a pretty little thing and it seems really well built. The clean sound is decent but the drive channel is dreadful. Shrill, buzzy and entirely un musical. The 386 Amps sound a million times better  although  they just can't muster that amount of pure clean headroom (even the higher powered 1w 386 D running at 12 volts ) so I was intrigued by the schematic. A quick search of the interwebs didn't bring up much except this post at diystompboxes.com but the hand drawn schematics were indecipherable so i decided to just take the back off and have a look for myself. 

 

The power amp IC is a TDA7276a which a 3 watt chip designed for  putting inside small TV's and as stated on the forum post it does seem to be wired up exactly as the Data sheet example right down to the 470uf output cap. This is buffered and boosted (when the overdrive is engaged) by a couple  TL072  dual op-amps. Orange seem to have gone to absolutely no effort whatsoever in designing the circuit for this amp and have simply stuck a generic op amp booster in front of cheap power amp chip and it sounds terrible. I can only assume that people commenting on reviews of this amp about how 'Orange have really captured the sound of the bigger amps in this little micro crush' have been smoking some kind of space crack. While I had the back off I thought I might as well stick in  a pair of speaker in/out jacks. As the little cab and it's 4 inch speaker might come in handy for testing my circuit designs. Also I can bypass the speaker and run the Orange amp out  into a full size guitar speaker although I can't see that happening anytime soon.

 

 

 

 

 

Little Boxes - What Next [][?][]


  

 Next up for my modular boxes will be my modified version of the 'Big Daddy'  booster. The more I play with it the more I love this booster. Not only will it be used as one of the modules for testing on my amp [project] but also as a pre amp for my blackheart.

 

 

 

 

 

Sketchbook......er... sketches [][][]


     

 

 

 

 

 

Good Vibrations [][][] [16/06/20 13]


  

 Ordered a couple of vibration speakers a couple of weeks a go to play about with. There only seems to be 2 main types available so I bought one of each. One of these from maplin and one of these from ebay. I've been playing with em for a couple of weeks now, trying them on different surfaces and amplifying different sources and I have to say I am really impressed. They certainly aren't high quality Audiophile devices but neither are a pair of shitty powered laptop speakers and a vibration speaker takes up a lot less space and puts out a much bigger sound. The little X-vibe is actually my favourite despite being the cheapest and the lowest power. The maplin can shaped thing actually sounds too bassy and muffled on mosts situations but the both sound excellent on glass. The thing I am most excited about and the real reason I bought them was to test with a guitar amp........and it works, it really works, and you can stick em to different surfaces to tailor the sound. Imagine having a little practice amp, that instead of using a reedy, farty little, full range Hi Fi speaker,  it had a built in vibration speaker that used any surface you placed it on to amplify the sound and make it sound massive. You could have an amplifier built into a guitar and just plug a cord in with a vibration speaker on the end. Stick it to a table and you have an amplifier and cab. It's never going to sound 'Amazing' but neither do most little travel amps. The only problem I am having at the moment is finding a supplier of just the speakers. The 2 units I have both have built in power amps which is great if you're trying to amplify your iPhone but unnecessary with a guitar amp. The only ones I have come across so far are these but I will have to find something cheaper if I gonna develop a commercial product using them. 

 

 

 

 

 

 

Little box [No.1] - 386 power amp


Little box No.1 in my modular odyssey. This is just the 386 chip power amp portion of the 'noisy cricket' and 'ruby' amps with the boost cap switch from the noisy cricket. I also added an output volume control as I have on all my 386 builds (not shown on schematic). It has a small built in speaker (as well as a speaker out jack)  mounted underneath which actually sounds pretty good. This will be my base for testing different buffers boosters and preamps for my Amp [Project] 

 

 

 

 

 

 

 

Gone modular, back in 5 minutes [][][] 


 Right........suppose if I am gonna crack on with a modular approach to designing a guitar amplifier I best build some modules. First up will be the power amp or at least one of them. I do plan on testing some other power amp chips but for now at least I should probably stick with what I know,  and thats the 386 chip. 

 


 

 

 

Going Modular [][][] [29/05/2013]


 
In my quest to create the best sounding  D.I.Y mini/practice amp possible, I have decided to go modular. I'm sick of faffing with circuits on the breadboard so I am just gonna build separate power amp and booster/buffer sections. I can also add in tone modules or distortion modules in a bid to find the perfect combination for my guitaamp[project]

 

 INSERT - MODULE IDEAS SKETCH >

 

 

 

 

 

Fecking Massive orange L.E.D's [][][]


 Found these Fecking  massive orange L.e.d's  (along with some littler ones) on ebay. I didn't know you could get 10mm L.E.D's let alone big orange ones. I love these and will be using them in everything from now on. 

 

  

 

Design Sketches [Paper53]


    

 

 

 

 

 

 

 

Reading Material [][][] Friday, May 03, 2013


National Semiconductors - Transistor Data sheet (mu amp/mini booster - origins

Darlington pair (transistors linked) 

Biasing a Transisto


 

 

 

 

J201 Fet [BoosterFriday, May 03, 2013


With my pedal breadboard now free I wanted to do some testing with other boosters, particularly FET boosters which I am led to believe have  much nicer overdrive characteristics when pushed to the max but have less overall gain. Have seen about a million different variations of booster schematics so wasn't really sure where to start but after spending a bit of time over at http://www.runoffgroove.com/salvo.html listening to sound samples I decided to just build the booster section from the Big Daddy schematic. Have tried to build one of these amps a couple of times but neither of them worked. Don't really know why as it's not a particularly complicated circuit.  

 

Due to an error in reading the schematic I used a 2.2nf cap rather than a 2.2uf cap which turned out to be a bit of happy accident. Playing with through my little 1w blackheart it sounded fucking great. The amount if boost wasn't earth shattering but it did add some sparkle and life to tone which I absolutely love. Trying it in front of the 386 amp was a bit disappointing, although it sounded really good the drive was nowhere near as much as I was expecting after listening to the sound samples at runoffgroove. It was at this point I realised my mistake with the cap selection and changed the 2.2nf part to the proper 2.2uf one indicated in the schematic. Much more like it, higher drive and much more distortion from the 386. 

 

It was this that led me to start playing around with the cap selection by switching between different caps in the biasing network it is possible not only to vary the amount of boost but also the fullness of the boost. After much experimenting I settled on 2.2nf, 100nf and 2.2uf. The sound goes from mild boost with some extra sparkle, to a treble boost, to full fat full range boost. It's a really good range of sounds which I think could form the basis of a really nice booster pedal.  Switching between a 47nf and 100nf output cap also has a really nice effect on the boost and could be used as a body switch on the pedal, cutting or boosting bass frequencies. 

 

 

 

 

 

LPB-1 Booster box [][][] Wednesday, May 02, 2013


  

The circuit is just a standard LPB-1  with the addition of a 500k pot as a variable resistor between the 9v + and the circuit to vary the voltage. Reducing the voltage reduces the headroom making the circuit get all lo-fi and spitty which I quite like. Reminds me a lot of the black keys sort of tone. The big knob is volume, the small one is the voltage, and the switch is on or (true) bypass. 

      

 

 

 

 

 

 

Breadboard [Testing]


Ok...so now I have got a better idea of what to try and what to change it's back to the breadboard. I have same circuit on the breadboard as is in the amp plus I have a the original NoisyCricket MPF102 buffer on black breadboard no. 2 for comparison.So things I would like to try now are - 

  • Clipping diodes for more distortion compression 
  • Changing cap values to sort bass
  • MPF102 into LPB-1 and LPB-1 into MPF102 buffer
  • Fet Transistor Booster (softer less fizzy overdirve)
  • Op amp Booster 
  • Any other pre amps I can find e.g. Pedals, headphone amps etc. to find a target sound 

Notes

  •  Clipping diodes sounded rubbish - need to do more research into how best to implement them 
  • MPF102 Buffer into LPB-1 sounds a touch brighter but nothing to write home about - not worth the extra parts 
  • LPB-1 into MPF102 buffer sounds ok. Fair bit brighter and Gain sound (with everything on max) is much edgier and better but difficult to get a good clean sound (MPF102 overdriving) without fiddling with all the Booster settings. Sound is definitely brighter. 
  • NEED MORE GAIN - Want to be able to play the beat it solo with it 
  • Bad Monkey (overdrive pedal) sounds really good - Need pedal gain (clipping/distortion) maxing - overdriving 386 by setting pedal level to max is not enough [needs external gain stages up front for higher drive]
  • DS-1 (boss) sounds really good for rhythm - pedal just doesn't have that bite for leads
  • After trying different pre amps Amp on it's own (buffer/booster only) does sound really dark 

Tried LPB-1 on pedal breadboard with 100k pot as a variable resistor between 9v battery and circuit. Gave a really nice low fuzzy edge to the tone [made little wing sound really good through blackheart] 

Really like LPB-1 as a pedal in front of Blackheart tube amp. Just fattens up the tone nicely. Decided to make myself a little LPB-1 booster box to clear space on my pedal breadboard for other booster testing.

 

 

 

 

 

Testing notes [][][] Monday 22nd April 2013


Revised amp slightly  - lowered trimmer volume - Full gain now usable was just squealing before with gain switch on. Other possible solution is to add small resistor to reduce gain slightly when fully open.  Shortened pot shafts so i could fit decent knobs . Still oscillating with everything on Full - goes away when reducing the master volume slightly

Strat straight into prototype amp. 1 x 10 blackheart cab (no reverb, buffered pedal). 

On full - (Dive and Gain)

  • Full GAIN sound is actually really good - Tiny Bit fuzzy and a bit Dark but not bad. definitely something to work with ( try op amp buffer )
  • Good AC/DC Highway to Hell (Dirty Clean)  tone with guitar volume backed off - Bit more sparkle 
  • Good Danzig Mother sound (with Guitar vol backed off a touch) - Marshall 
  • Good dark classic rock sound 

Could definitely do with a bit more bite and clarity for Metal riffs  - sustain not bad bit could do with a little bit more for lead work. Could add mid scoop tone control - Big Muff pi Tone [?   

 

 Drive (LPB-1) full / Gain switch off  (minimum 20x gain)

  •  Decent clean sound with volume back down - just missing a bit of sparkle 
  • Goes into Jimi Hendrix territory with volume up slightly but gain just missing that sparkle 
  • wide open -  Decent 'Back in black' sound but again a bit dark, and flabby  in bass end.


With the gain switch on minimum and playing with the LPB- drive control between 0 and 12 o'clock

  • there are some decent Jimi Hendrix tones which go from only just breaking up on minimum to slightly dirty driven clean at half way. With a bit of reverb these would be pretty good but again just a tad muddy and missing a bit of sparkle. Don't sound great when using neck pick up.

Op amp Buffer  

  •  Tried with (TL702) op amp Voltage follower / buffer in front (mounted in pedal bradboard) - Definitely more sparkle both Clean and driven. Still a bit flabby on the base end - Could try altering caps on LPB-1 to reduce bass boost [?]

 

 

 

 

 

Could Try now [][?][] 21/04/2013


  • Simple op-amp buffer (voltage follower) before LPB-1 Booster - Better input impedance match
  • JFet Booster (better/softer clipping 
  • LPB-1 into JFet - to overdrive fet
  • Clipping diodes 
  • Build speaker boxes for testing small speakers
  • Iphone as Multi Fx / Pre Amp 

 

 

 

 

 

 

Research, research, research [][][]


Done a Lot of reading  this week on electronics, really want to understand how it all works. The most useful resource I have discovered ( or rediscovered it - not of it made any sense the first time I cam across it) is www.muzique.com by Jack Ormen which I can't recommend highly enough. Have read so much this week it's hard to link everything I have absorbed but below is a collection of links to some of the things I am most interested in exploring. Also did on awful lot of reading about how transistors and op-amps work which was incredibly enlightening. 

 

  • Could try AMZ Mosfet Booster  http://www.muzique.com/schem/mosfet.htm
  • LOW POWER LPB-1 Booster Article  http://www.muzique.com/lab/lowvolt.htm

  • LBB-1 Driving Jfet

    ......the next logical step is using the bipolar booster to drive the jfet circuit. The bipolar can produce plenty of gain that will overdrive the jfet and produce smooth distortion with musically pleasing harmonics... a 3 volt screamer! 


     The two stages generate a mild overdrive with rounded edges as the signal clips. The low gain and lack of bypass capacitor on the jfet contribute to the production of tube-like harmonics. Its simplicity is part of its attraction.

  • Leaky Germanium Transistor CLIPPING / BUFFER (have a few leaky germaniums - left over from fuzz face)  http://www.muzique.com/news/leaky-transistor-buffer/

 

 

 

 

 

Time to Build a  [Prototype]


 There are still loads of things I would like to try with the circuit, but to stop me faffing about till the end of time and not getting anywhere I decided to just build one to play around with while I experiment with other ideas 

Circuit specs  - 

  • LPB-1 Booster up front with a 470 ohm pot instead of  R3 as gain/distortion control 
  • Trimmer pot for output level of LP-1 
  • Back end of Ruby/Smokey with fixed 47uf boost cap (Feedback loop - pins 5 and 7)
  • Switched Gain (pins 1-8) 2 or 3 postition (skimmed / semi skimmed /full fat)
  • Master Volume  

 

 

 

 

 

 

The LPB-1 Booster [][][]


 

 Have been playing around with the LPB-1 circuit which I have had on my little pedal breadboard for a while now but have never really done much experimenting with. I started by drawing out the circuit in a way i find easier to read (Thanks again to beavis audio for it's excellent LPB-1 explanation page). I built a little LPB-1 module (totally bog standard)  on a bit of stripboard so I could free up my Pedal Breadboard to start messing around with a modified version of the circuit using trimmer pots as variable resistors.

   

 

 

 

 

 

Breadboard A/B Testing [][][]


............So thats what I did [For a more detailed explanation of how the Chip amp development board works click here The chip amp part is on the white breadboard on the Right and the 2 buffers are on the black breadboards to the left. The second toggle switch (from the left) switches  between the 2  buffers  (inputs is on pin 2 and added a 100uf power filter cap)] It quickly became apparent that they don't actually sound any different ( the Noisy Cricket is ever so slightly brighter, probably down to the higher input impedance)  and all my previous thoughts about the differences in the sound were actually either in my head or down to the difference in construction. I went back and checked the 2 amps I built (the white Cricket and new black Ruby) and the definitely sound very different. The circuits just don't sound any different when built on the same breadboard which highlights how temperamental these 386 chip amps can be The circuits are 'very sensitive to component placement and the length of the battery leads '[observations on the smokey circuit - Dave stork]. Also struck by how little gain is available when playing through a full size guitar speaker, (when using smaller speakers a lot of the distortion is coming from the speaker) which makes me think I am going to use the LP-1 Booster circuit as the basis for my own amp circuit rather than the MPF 102 buffer as used in the Noisy Cricket and Ruby.  

 [Update]  - With hind sight I now realise that the reason the Noisy Cricked and Ruby sound so different when you build them as stand alone amps is because the Tone control on the Noisy Cricket actually sucks a lot of the signal which gives it less overall gain. That's why I always thought the Ruby had more drive until I build them together on the breadboard. Removing the Tone control increases the gain and makes them virtually identical. 

 

 

 

 

 

Comparing the Circuits [][][]


  

Sat down the other night and did something I never thought to do before, and that was to draw out the circuits side by side and examine the differences. Feel a bit stupid now as I didn't realise just how similar they are. If you ignore the tone control and the boost switch on the Noisy Cricket they are pretty much identical apart from the values of the bias resistors on the buffer (higher values/higher impedance - on the Noisy cricket) and an extra 100nf cap after the drive pot and before the input on the 386 chip, this cap as far as can tell does nothing. Sounds the same with or without it . If I had realised this before I could have saved a lot of time building the new Ruby. The Power amp/chip part of the circuits are Identical so I  could have just built the 2 circuits on my 386 amp testing breadboard and just A/B tested them with the flick of a switch.............

 

 

 

 

Testing Testing 123 [][][] 


Spent some time  on my days off playing with the amps. Mostly I ran them through my Blackhert 1x10 cab, but also tried them through a few different smaller speakers such as the Little 6 inch speaker (on the Left) which  I found in my workshop hidden under a pile of shit and small oval speaker in an orange box  (pictured below) which is from a Vintage Alba  record player. Tried them with pedals, Ipad, iphone, Korg pandora, Looper and generally just had fun. I still can't believe how good an amp made from a 20p power amp chip designed for powering cheap radio/Alarm clocks sounds. They both sound good and take pedals really well but after much testing the NoisyCricket wins hands down. I had previously said i preferred the harder drive of the Ruby but after playing with them side by side I have changed my mind. The noisy cricket just sounds better. The cleans are cleared and the drive is less fizzy and smoother. It may just be down to my building skills or the components I used,  but the Ruby seems to have a lot of Digitally sounding artifacts in the sound on the  higher gain settings.  

 It also sounds really good with a simple LPB-1 booster stuck in the front as seen in the picture above. Super saturated gain. One thing I am particularly interested in is using  a 386 amp as power amp driven by  a multi FX / Headphone amp / iPhone etc - to use in my Travel guitar [Project

  

 

 

 

 

 

Building another Ruby [][][]


 Decided to build the new test Ruby in exactly the same style as my Noisy Cricket build (i.e in a plastic enclosure with a downward facing internal speaker)  because 1)  this will give the fairest comparison, and 2) I am trying to save money to move house and I all ready have all the shit in my back porch to make another plastic one. The metal enclosure on the one I made for my brother in law did sound better (with the internal speaker at least) but then I would have had to buy 2 metal enclosures and re build the Noisy Cricket in a different box and I just couldn't be arsed. 

      

       

      

I also built the Big Daddy circuit at the same time from the Veroboard layout above provided by Guitar FX Layouts but the circuit didn't work. It could be I just built it wrong or have a solder bridge or something ,  but the Layout is unverified so beware If you plan on using it (Schematic for Big Daddy Here). I'll try and investigate the problem when I find time. The Ruby went together fine however and apart from a scratchy Drive pot it works like a charm (I should just mention I had to change the input pin from 2 indicated on the schematic, to pin 3 to stop motrboating noises). Next step is to just spend some time playing with the 2 amps and deciding which one sounds best. 

 

 

 

 

 

So....First things first [][][] 10/Feb/2013


First thing I need to do is build myself another Ruby. The white Noisy cricket mkII amp I have at home, but the Ruby was a present for my brother in law so I don't have that anymore. Although the Circuits are very similar they do sound quite different. The Noisy Cricket is more vintage sounding and the Ruby has more drive, so the first thing to do is build another Ruby so I can do some comparison tests to see which on I prefer and work out which direction to take my own circuit. I will also be building a Big Daddy which is another runoffgroove.com circuit using the 386 chip, very similar to the Ruby, but this one has a booster rather than a buffer at the front end so should drive harder still than the ruby. Have never built a big daddy before so am interested to see how this sounds. 

I don't want to waste too much time building or thinking about the layouts for these 2 Circuits so will be using this  Vero board layout I found at the excellent Guitar FX Layouts blog for the Big Daddy. (please check out their excellent site full of easy to build Vero Board layouts of literally 100's of pedal and amp schematics, thanks guys) They didn't actually have one for the Ruby which is a shocker (I may do one if I get a chance), So i was just gonna freestyle from the Schematic but then I found this one here  on my mac  (No idea where i found it and  cant find it again so if this is your hard work let me know and I'll add a link )

    Ruby schematic 

 

 

 

 

mylk[386]blog

 

I've been meaning to get around to this for a while. The time has finally come for me to work on my own 386 amp circuit. I, along with many other people who have built themselves a Ruby or Noisy Cricket, have been totally bowled over by how good a simple little solid state 386 Chip guitar amplifier circuit can sound. I had loads of fun building these little amps and can and can see a ton of potential in an improved version of the circuit for use in some mini amp and travel guitar designs I have planned so I decided I best get my shit together and design my own circuit.

(Massive thank you for all the hard work done by the guys at http://www.beavisaudio.com/ and http://runoffgroove.com/ without whom this project would not be possible).