Playing a acoustic guitar thru a electric guitar amp

[caspercody]

This may be a dumb question, but is there a circuit one can build to be able to plug a acoustic guitar (equiped with a piezo) into a solid state electric guitar amp? And be able to get the acoustic sound as a acoustic guitar amp?

[mattthegamer463]

I would think that you could do this without any kind of circuitry at all.  Have you tried?  A simple piezo doesn't need any power source (IIRC) so it should just work.  You might need a booster circuit to make it work well and sound good, but I can't see why it wouldn't work at all, just straight, for testing.

[petemoore]

  Peizo is 'one' preferred method.
  Certainly easy to try, inexpensive but that doesn't matter.
  May need buffer, also easy to try if you have any 'factory' stompbox. Peizo's have extremely small current output that is very easily loaded, buffer makes it drive most suitable inputs, doesn't voltage gain so should be about the same volume with or without buffer, I built a little Jfet/9v buffer and played around with it until the piezo found a happy place, it's clamped between where my mustache bridge presses on the body top.
   Can't say about exactly what an accoustic amp sounds like or what amp is hoped to achieve that sound.
  If it has reverb or some other delay or compression or HF horn, any of those things might help close the difference gap.

[mattthegamer463]

An amp that isn't distorting should convey that acoustic goodness without issue.  Maybe an internal mic would do the sound more justice though.  I have non-electrified acoustics, presently.

[StereoKills]

Like Pete said, you may want a buffer or a preamp, but certainly possible and works nicely in most cases. Fun to run an acoustic through effects as well, a totally different experience.

[Mark Hammer]

There are a couple of things that differentiate an "acoustic guitar" amp from an "electric guitar" one:

1) Extended bandwidth from the speakers.  "Guitar" speakers tend to roll off around 6khz.  "Acoustic" amps will often include a tweeter to extend the audible range outwards.  You can simply add a piezo horn tweeter in parallel with your guitar speaker already in the amp, to give a little more "air" to the acoustic guitar.  Though that presumes a number of other things (see below).

2) A tendency towards cleanliness rather than dirt.  Acoustic players generally want an amp that doesn't break up (which is why acoustic amps are often similar to bass or keyboard amps).  So if there is anything about the amp you intend to play through that inherently injects some distortion at any appreciable volume, you'll want to attend to that.

3) EQ controls oriented towards resonant boosting and "cutting power", rather than feedback management and "naturalness".  You may not be able to get the acoustic to sound like one unless some changes are done to the EQ-ing.

Can all of that be built into a box that goes between your acoustic and the amp?  Not necessarily.  You may be able to get a little more brightness out of the amp without adding extra tweeters by using something like the the Jules Ryckebusch "Harmonic Sweetener" circuit ( http://www.christianmusicweb.com/schematics/harmonic_sweetener.jpg ), which is a budget Aphex Aural Exciter (a rack unit traditionally used to add a little more sizzle to things like acoustic string instruments, snares, cymbals, etc.).  If the amp lacks any sort of feedback-negating capability, that could be built into a box in the form of what is essentially a manually-sweepable 2-stage phaser that uses a dual-ganged pot instead of FETs.  And if the EQ controls in the amp do not address anything of relevance to your guitar, you could include something more pertinent in an add-on box.  Of course, you can't do anything in the form of an add-on box that would make the amp cleaner.

FWIW, I've seen these things for sale dirt cheap: http://gizmodo.com/5385654/altec-lansing-stage-gig-is-a-guitar-amp-for-guitar-hero-guitarists  In my city, they can presently be bought for $35-40.  They have the bandwiodth, and clean power, and they're pretty well built.  Make yourself a suitable preamp box, with some EQ-ing and feedback control, and you've got a decent acoustic amp for well under $100.

[caspercody]

Thanks everyone! I have previously made the AMZ simple Jfet buffer, and I will try to find this and try it thru my acoustic to the amp. I also found The mint-Box Piezo buffer by Scott Helmke. I will make this and give it a try. I think he (SCott Helmke) describes it better than I did in his article that the soound is thin. It sounds to treblely, and not much bass. I have a Taylor E110 and when I plug into my SS amp, it sounds thin.

[petemoore]

  Elegant is anything from easy to tricky.
  Feedback 'areas' need to be avoided, a 'point' [that's basically where a Peizo gets it's input off the guitar] chosen for balance [fat and skinny strings] and volume output of strings, the more 'bodysound' that is let into the peizo, the more control speaker will have over resonance [especially prone to this in the bassy frequencies] hence unwanted feedback may be easier to get and harder to avoid.
  That generally equates to a bit toward the skinny string side [since they don't overcome the stronger bass] where the low E string still dissipates some vibe-power.
  Buffer on a perfchunk, quite a mild build to test the peizo output when not loaded by the cable and input, getting it into a non-invasive form at a hidden sweet spot such as in the guitar with the battery and associated wiring is a bit trickier.
  Then by the time the buffer's figured out, the TC which makes sense to have on an accoustic that will be expected to make 'this input' [and wherever that leads..to that speaker...] accoustic sounds under common-extreme conditions [accoustic in performance mode, is pretty extreme conditions, extreme feedback is to be avoided], the Eq on the guitar really helps keep feedback time to minimum, 'volume'.
  By the time it fits and works really good there will probably have been a whole host of considerations.