Amplifier type circuit in a stompbox?

[reynardine]

Hi all,
This is my first post here, so I do apologise a lot if this is a really stupid question. I joined specifically to ask this, but I will hang around now I'm here, there seems a lot to do =]

Well anyway, I was looking at a pedal by EHX that is an amplifier in a stompbox, the 22 Caliber. You use it as you would an amp, then just plug the output into your speaker cabinet. It got me thinking, would this be achievable with a DIY stompbox? Could i enclose an amp circuit of something that sounds better than the 22 caliber does into a stompbox case? I don't know much about this kind of thing but I am a quick learner, it just seems quite possible that this could be done? but then again, if it was that simple, why wouldn't it already have been done a lot more by existing companies... hmm

Please, any thoughts you have on this would be really very much appreciated, thank you for your time and patience

[jkokura]

If you search for "murder one" you'll see that it's been done lots! There are lots of potential circuits you can use to power your cab here!

And welcome,

jacob

[Top Top]

Also check out the Ruby amp. It is a small amp based on the LM386 chip which is found in countless mini-amplifiers. It sounds decent, easy/low parts build, and can run on 9v. You would just put a jack on it and connect a 1/4" cable to the cab of your choice.

http://www.runoffgroove.com/ruby.html

[PRR]

The EH 22 is an awful lot of power in a small box. Duplicating it would not be easy.

Any organized builder can put lower-power amps in very small boxes. I've seen a stereo headphone booster built inside the shell of a 9V battery, including in/out jacks and volume pot, so the whole rig was just the size of two 9V batteries. A part-Watt guitar amp would be easier, except for the huge plug guitars and speakers use. Certainly stomp-box size, maybe Band-Aid box size. (Hmmmm.... seems to me my first college dorm amp was in a Band-Aid box.... and that was before LM386.)

[sean k]

The chips available for things like this are normally ones that were designed for car stereos which have a ton of amperage available at 14 odd volts DC. Add to this that they are usually quite small chips then it's quite simple to put one in a very small box.

The problems occur due to your power supply and if it's a tranformer and caps supplying about 15V DC at a few amps... your pretty hard pressed to put that in a small box or have any battery last long trying to supply it. So the considerations are about being able to get a class of amp that is effecient enough to use small amounts of power for less dissipation as heat, having a power supply to feed it and still sound "guitary"

That said the LM386 is a great little chip to play with and makes enough noise to keep me happy... for most things.

[rikhi]

The Ruby looks interesting.
I've been using the 22 Caliber as a bass head which frankly sounds great. Very transparent,
although I've only used this for low volume bedroom practice.

I'm piqued about the mods for the Ruby where you can replicate the sound of the Fender Bassman.

Has anyone heard of anyone making one of these specifically for bass?
[sorry if this is dumb too, my first question on joining.]

®

[LucifersTrip]

don't forget the classic:




http://www.youtube.com/watch?v=creY959fH8c
http://www.youtube.com/watch?v=iqbe69nxd-U
[start: 2:25]

[Bullet79]

something with TDA2030 chips also a good choice

[Johan]

search for Taylor's "Forum-amp"   its a ~20watt amp built around a ship made for car stereo's...might need some kind of preamp/overdrive, but it's near what you asked for.
J

[petemoore]

It got me thinking, would this be achievable with a DIY stompbox?
  Unknown.
  Otherwise EH has gotcha...thinkin about buying your way around difficult design issues, or building an amp in a box say >2x this big as a way of guaging the difficulties involved in extreme power amplifier size reduction.
  Could i enclose an amp circuit of something that sounds better than the 22 caliber does into a stompbox case?
  No. You can purchase components that = high performance amplifier, the circuit can be very simple as dirtbox, the power supply and heatsink/layout take a bit more study and investment to get right.
  I've bought them and built them, chips and mosfets and power supplies etc.
  The only time I 'bettered' selected bought amps...was in terms of price by using free materials...apples and oranges, slick looking Vs. pressure cooker pot.

[earthtonesaudio]

MAX9708 delivering a maximum of 42W into 4 ohms, inside a 1590A built by a friend of username "HEAD" over at the other place:



The chip claims 87% efficiency at 42W so it only has to dissipate a bit over 5W as heat.  You'd have to do some work to get rid of that heat but definitely not impossible, even in a 1590A.

[Renegadrian]

386s give little power...I'd say go with a 2822 - quite easy, same chip size and more power

[petemoore]

  Start with your speaker.
  Work your way back to the power supply.
  The power supplies, on average keep us occupied the longest per amp[s.
  The chips wire quickly, and there's not much more to it except..
  The heat sinks [cobbling may take time] and the layout/chassis.
  Once all that is all figured out, calc the buy-options.
  Hafta say that buy SS type amp decisions have not been difficult at all to live down, check yer specs and...build or buy, buying has meant chances are very excellent specs are very good, building has been hit, miss, peel onions etc. only then =y very good.
  the 22cal ultra compact-amp is wonderfully impressive design [as long as I don't have to look at or deal with the Mfr-ing details] not so good for DIY.
  Otherwise it makes sense in terms of funciton to simply choose your components, then size the box accordingly, not the other way around.

[Hides-His-Eyes]

Taylor has absolutely got your back on this one. I'd build his kit, it's exactly what you're after and he built his in a 1590B.

[SISKO]

Google: Class D

[thedefog]

You can get those TDA car amp chips for dirt cheap on Mouser. I've always thought about getting one of those 40+ watt chips and trying to make a super small solid state amp out of one.

http://www.mouser.com/catalog/catalogUSD/642/366.pdf

[Taylor]

Taylor has absolutely got your back on this one. I'd build his kit, it's exactly what you're after and he built his in a 1590B.

1590A, actually, so even smaller than EHX's.   

http://www.diystompboxes.com/smfforum/index.php?topic=89233.msg756328#msg756328

[thedefog]

Oh awesome! I might have to built one of these. It's a cheap enough project, and it could work as a back-up amp in a pinch at a gig.

[Fuzz Aldryn]

Sadfully the preamp section doesn't work properly. It isn't capable of driving the poweramp hard enough. I would suggest to try something like a fetzer valve as a preamp circuit. Otherwise than that the power section does work. It's basically like suggested in the datasheet so have an run on your own.
Oh, and this wasn't actually my work but a work of a friend of mine. It's his idea and built. And no, i have no schem and no layout at hand as it wasn't and still is not my work. My part was just the initial idea and some aspects what it should be able to do. We both have no time to rework the design at the moment.

Helge

[SISKO]

The thing with those TDAs chips and audio car chips is that they need a large heatsink to operate nicely.
Class D, instead, doesnt requiere big heatsink, if any