This is an extension of my mylk[386]amp project. I really like the idea producing a totally self contained kit for building an amplifier that would utilise the cardboard packaging to create the enclosure for the amp. No painting, drilling or sanding required. Sort of like a D.I.Y Smokey amp on steroids ........Read more here






Card Amp [Inspiration]









Card Amp Protype 1a [][][] 


  • LED clippers  sound bad 
  • Resistors - Gain loop
  • Double Boost Caps
  • Switchable clippers - Better left on 
  • Fade on LED
  • LED clipper look good 
  • Form factor
  • internal frame design 





More Prototype [No.1] pics







Finished Prototype [No.1]






Working Prototype [No.1] 









Starting Prototype [No.1]

Right....well, with the basic design taken care of suppose I best have a go at building a working prototype. Reamde the chassis with a little bit more care as the first one was a bit scrappy. The actual circuit board is a real fucking mess as I just winged it and soldered all the components as I went but amazingly it worked first time.  The handles in the pictures were just some cheap ones I picked up in wilco's, I don't actually plan on using them in this build but I do like the look of  'em so I thought I would take some snaps to remind me what they look like. 







Amp frame test [][][]









Designing the internal structure [][][]


Couldn't sleep at all the other night, on a bit of hyper one lately. Head is so full of electronics and design ideas that I don't seem to be able to turn my brain off. Hate it when I get like this, it's fun at first but soon starts to become tiring. Anyway the fruits of my restless night in bed was that I designed the whole structure of the amp inside my head. So all that was left to do in the morning was to mock up the idea to make sure everything fits as I imagined it would. Had to make a couple of small tweaks but this is the result. A double layer of padboard,  the  bottom one to hold the jacks, pots and battery and the top one to house the amp components a further 2 switches. Am particularly proud of this little space saving feature. The switches fit like a dream between the Jack sockets and the dual gang pots I am using. 






More mock ups [][][]

Just a couple more design mock up's to illustrate the idea. In the top pic I have literally just stuck components through the cardboard fag packet to get a sense of what it would like with components mounted on the top. Am quite struck with idea of using top mounted Leds [a big 10mm one and couple of 5mm one] as power and distortion indicators while giving a visual nod towards the tube amps I am getting my design inspiration from. Could even use the 2 smaller LED's as clippers which will flash, and flash more the higher the drive is, although am still not sure yet whether that would be a step too far. Next job is to design the internal structure of the unit, I want it to be rugged, strong internal structure with a cardboard skin which can be potentially changed or customised.  




What's been Happening [][?][]

 Well it's been a funny couple of months my wifes been off work so I haven't been doing nearly as much building and testing as I would have liked as it seems cruel to torture my wife with my terrible guitar playing. As it turns out this has been quite a good thing as means I have had to find other less anti social ways to fill my time, namely reading everything I could get my hands on on the subject of audio electronics in order to expand my knowledge and make my quest to design my own amplifier circuit that much easier. To cut a long story it's totally paid off and I do now have my own  [386] amp circuit which I have designed from the ground up. It's essentially a more versatile, Op-Amp driven version of the Ruby/Noisy cricket circuit with lots of modification to improve clarity and with a shit load more gain available. You can  read more about the circuit here. But what about the Card Amp? I hear the 2 people a week who view my website cry......well I've been doing a lot of playing around with cupboard door handles and fag packets as you can see above and think I have come up with a pretty fucking cool design concept for a small cardboard amp that is basically like a Smokey Amp on crack wearing a Savile Row suit. The idea is to house all the external parts e.g Jack sockets, pots, switches and battery etc. within the cardboard body of the amp and all (or some) of the components outside of the box in the style of Audiophile tube Hi-Fi amplifers' or this ZVex nano guitar amp. Don't know about you but I think the handles look cool as fuck.  






What next [][?][] 

Suppose I'll just play around with it for a while and try different pre - amps in the front end till I find Something I like and make some notes about the sound  ................


Notes [][][]


  • Very Loud 
  • Bit buzzy and farty - lots of vibration (cardboard) but so does smokey  
  • Sounds really airy with internal speaker - Reverby
  • Could do with base cap lowering - farty through small speaker - too boomy with big cab try 100uf
  • REALLY fucking loud through big cab definitely needs MASTER VOL
  • actually sounds really good AC/DC shook me tone completely nailed 
  • Really good high Gain sound with LPB-1 booster (everything on full 
  • Good clean (od) sound with gain backed off and guitar volume backed off a bit
  •  sounds really good with pedals - Brilliant high gain sound with DS-1 and Bad Monkey combined (beat it - solo)
  • Sounds marginally clearer / more sparkly with buffer(ed pedals) 
  • could maybe do with a bit more sparkle on top end




First sort of  prototype [][][]


So after playing around with boxes for a bit I thought i should actually just build an amp. If it sounds terrible, doesn't fit or doesn't work at least i will have learned something. Having already decided that a decent clean sound is out of the question in a cardboard amp with a small internal speaker and that high gain is the way to go. I opted for a simple LPB-1 preamp, which I had been experimenting with for my proper 386 amp [project] into the Power amp section of the Ruby/Noisy Cricket circuit. 



Rather than solder up the whole circuit on strip board I opted to use a mini breadboard for main bit of the circuit with the controls and jack sockets soldered to stripboard with solid core jumper wires to plug into the breadboard at the appropriate points. Everything was glued down to a stiff bit of 6 x 9 card as a base to pop into the cardboard housing. 

 I built the power amp (386 chip) part on the breadboard and used a little LPB-1 stripboard module I made for testing for the preamp. 

 For  some reason I had loads of problems with noise and oscillation this completely went away when I mounted the LPB-1 module on a separate breadboard and ran it into the card amp (power amp bit only) as if it were a pedal into an amp. Hopefully this won't be problem when making the whole circuit on on PCB if i decide to go with the LPB-1 front end. for the time being at least the card amp Just contains the power amp portion of the Ruby/Noisy Cricket circuit and an internal speaker. A Gain pot (386 pins 1 & 8) and a 470 0hm master volume pot.







Greetings card amp [][][]  12th March 2013

 1st thing to do  today is to do a test of the Conductive paint / greeting card amp idea - loads of potential here if this works as it should - really excited. 

Also really excited about working on a no parts Jack socket which could help save loads of space on some of the other amp projects. To start off with I am gonna be testing a very basic idea of a Greeting card with a speaker and 386 power amp Chip stuck to it, powered by a flat C cell watch battery. This way all the components are super thin and all the traces can be made with conductive paint. If this works the follow on idea to this would be a greeting card which could be folded up by the user (scored perforated fold lines - done with cutter) Origami style into an actual working amplifier.  

  • Little (GBA) Speaker works well and sounds pretty cool ( as looked @ from front,  + is on right / - is on left) really surprised by how loud it is. 


 Speaker stuck the front card with double sided with the solder pads fed through a slit in the card and folded over on the inside of the front face. The chips legs were just stuck through 6 holes in  the card and folded over on the inside. The jack sockets at this stage are just crude puckered bum holes punched into the card with one of my wifes craft punches which just happened to be exactly the right size to accommodate a 1/4 inch guitar jack. The puckered shape holding the indent in the tip of a jack nicely. All that remains now is to paint on the traces and cover the punched holes in conductive paint. If this works I should be able to screen print the traces onto the final designs Just like these cardboard Ohm Noise makers 






Super tiny amp in a box [][][]


  One idea that really appeals to me although I know it's a bit of a silly novelty, is to build a really small (if not the smallest) amplifier head possible, either to run through a full size guitar cab or maybe even a matching cardboard speaker cab - Giving you the worlds smallest proper stack. Could even have one straight cab and one slanted marshal style or you could mix and match -  could even have 2 x 12 (although it would have to be 2 x 12 mm ). Built this just to get some idea of how much space there is to play around with to put the circuit on. Fits a 9v battery fine  







Another Speaker Cab [][][]  11th March 2013 

 What I wanted to do tonight was Make an amp or 2 (One big one small) and see how  the boards / controls / Jacks etc fit in the boxes.......what I ended up doing was making  revised speaker cab with better internal bracing and much more sturdy Jack socket (hot glued internal bracing/speaker mount)


Actually sounds pretty good, lot of speaker and box distortion but this can definitely be worked with. Also, as with smokery speaker, it really good -   less harsh and buzzy, more base and air  - when turned face down. So having the speaker totally enclosed in the box (with maybe just a couple of ports / holes)  I think the best thing to do with the cardboard amps is to just focus on the High Gain / Drive sound. Am never gonna get a convincing clean out of vibrating and buzzing cardboard box but I can get a good High gain sound [ LPB-1 Booster --into-- Smokey ] which will be fun to play.  







Cardboard Speaker Cab [][][] 10th March 2013

 As  am not yet decided on which circuit I will be using just yet it makes sense to make a Cardboard speaker cab for for breadboard circuit testing. Small speakers distort a lot and so have a significant impact on the sound. So does the material used for construction. Cardboard vibrates and buzzes a like fuck  (as anyone who has ever owned a smokey Amp will be well aware) so I want all these variables present when I am testing the circuit to be used in the cardboard amps. 


Results are actually pretty good. Slightly altered box template to be 1cm wider on back and face to be a better fit for speaker (Box dimensions now 7 x 5 x 10). Looks really nice,  Is pretty sturdy although the method of holding mounting speaker could be much better and there is not enough bracing for the Jack socket which if bending when I try and insert a Jack. 

Could also try.........................

  1. Try open Vs. Closed back - does it make much difference with tiny speakers?
  2. try internally mounted speaker - [muffled/baffled] - Like turning a smokey face down to tame the treble. Also feel like this might add a bit of air/reverb to the sound 
  3. Try 2 x really small speakers (ones from GBA SP in A5 box) what do 2 small  speakers sound like together
  4. Try greeting card mounted  GBA speaker (no box to amplify sound)






Size comparisons [][][]

It's all very well having a load of pretty and sturdy boxes, but it won't do me much good if they are not the right size and shape to fit in the components I need which will be at least - One 9v Battery, 2 Jack sockets (in and out), at least on potentiometer (possibly 2) and a speaker. Luckily all the box temps I made, even the small A5 card ones were large enough to accommodate these requirements in. [ A4  box = 6 x 6 x 9 ] [ A5 Box = ? x ? x ? ] [ A5 Cube = ? x ? x ? ]






Making Little Boxes [][][]



This round 2 of fun with cardboard. After wasting literally hours trawling the web for suitable, inspiring and efficient 
(least amount of waste/cutaway card) I got really bored and decided the best thing to do was just freestyle. Also this time had bought some nice A4 brown recycled card which i really like the look of, so wanted to establish the size and strength  possibilities using a sheet of  fairly thin A4 card 








Breadboard modules [][][]


These are just little stripboard modules of variations on the standard smokey circuit. They just plug directly into my 386 Amp testing board (Power +/- and Input and output wires). When plugged into the 2 black Breadboards they can be toggled between at the flick of a switch to compare the differences 








Testing testing [234

Further testing on 386/smokey circuit this time focusing on what adding components to the basic smokey circuit  does to the sound 



Smokey Circuit [adding stuff]

  •  Tried adding  10ohm resistor and 0.022uf (220nf)  from output to ground (Zobel Network). Big increase in noise (input on pin 2) and unpleasant sounds - No positive results (also tried 100nf cap - No difference) .
  •  There was however a big difference when using pin 3 as the input. Normally pin 3 is unusable because of oscillation. That goes away when using the resistor and cap to ground from the output. (the 47uf cap from pin 7 to ground must also be present or noise occurs) The clean sound is ever so slightly louder and clearer when using pim 3 with this setup. Unfortunately the circuit went back to motor boating when I increased the gain.
  •  Tried with power supply to see if the problem was related to battery. No difference, but interestingly the standard Smokey circuit (input on Pin 2 ) went all farty and digital sounding (but not with input on pin 3).
  • Tried with iPhone (no iRig with us so had to use normal lead) was feeding back like mad because of the lead but the Test Circuit with the added components and input on pin 3 definitely sounded clearer and better than the smokey.
  • Tried a 10uf cap between gain pins (polarity didn't make any difference) gain possibly ever so slightly crisper with Cap. But difficult to tell. Sound certainly not different enough to justify the extra part. Tried with iPhone and sound is definitely crisper and louder with the cap but sound is distorting due to extra gain. Would need to do tests with the cap in place and lower (variable) gain to see of this is a worthwhile addition to the iPhone amp.
  •  Needs an output cap - bass very farty with iphone 







Testing testing [123

Am starting with the basic Smokey circuit - 1 chip and 2 x 47uf caps  and then adding and taking away components to see what difference they make. Goal is the best sound with the least amount of parts. 



Smokey Circuit [simplified]

  • Smokey Circuit seems to work just fine with iPhone - As Long as Gain is set to Minimum - Pin 1 & 8 open ] . The 47uf cap to Ground can be removed without any noticeable difference to sound. Use pin 2 only as input - problems when using pin 3  ]
  • Sounds better with 47uf output cap removed - fuller sound. Particularly noticeable when using looper  or backing track (with small speaker). Would probably need output cap if going through bigger/external speaker. 
  • Adding buffer makes very little difference at all when using iPhone ( iRig is all ready buffered for guitar input. Signal  from iPhone should not need to be buffered - low impedance signal  > Low impedance  )
  • Guitar direct sounds much better with buffer ( brighter and clearer ) but buffer causes bad feedback squeel with standard Smokey circuit (with no stabilization -  cap and resistor to ground from output)
  • Chip only amp (removal of 2 caps) sounds indistinguishable with guitar direct through small speaker [Definitely possible to make amp with a single chip and nothing else ]
  • Makes sense to use a bigger output cap. Makes no difference to tone using small inbuilt speaker and guitar direct but iPhone (Loop/Beats/Backing) sounded much better with bigger output cap. Also an external speaker  (if used/needed) will sound fuller.



 iPhone Size Box - From A5 Card 



Possible to make a really sturdy, good size box from A5 card same dimensions as iPhone 4 and about same depth and width as cigarette packet . iPhone would fit perfectly on top in a snap in case (e.g. Clear on in cupboard) 






So....First things first [][][]

 Ok before I start doing anything interesting there are a few basic questions that need answering  

  • How big can you make a boxe from an A5 greeting Card ?
  • What's the simplest, best sounding amp you can make with the fewest parts ? 
  • What's it sound like using iPhone as pre amp ?


Playing with Cardboard