Guitar Amplifier (for the space)


I was thinking of building a guitar/bass amplifier that would be left in the Hackspace. I like to build effects pedals for my bass, and I know that there’s one person who has spent much time recently constructing an electric guitar (out of a crutch). I will probably be willing to bring my bass to the hackspace sometimes for testing new pedals, but bringing the amp would probably be too much. So this amp could be useful for testing.

I probably would have started an attempt at this in the past two weeks if I could get to the space while it’s open, but it has barely been open for two weeks. I would also want to know what parts we already have at the space.

Searching “Guitar Amplifier Schematic” on Google Images brings up a variety of results. But they all look so complicated. It would be much faster for me to put together something like the image below, with a simple volume control stage at the input. Is there any reason I can’t do that?

I want to make the case out of wood panels. But I’m not certified on the table saw, so someone would have to do it for me. I’ll probably also use one of the 3 big Hammond power transformers that we have sitting around.

I don’t know what power transistors we have at the space, but I have two TIP41C NPN transistors and two TIP42C PNP transistors that I can bring. Do we have any heatsinks for TO-220 packages?
Also, do we have any linear regulators (matching negative and positive)?


Give me a shout when you get close to enclosing it and we can CAD up a design and I can help you create the enclosure.


Also, if you haven’t built one before, check out LM386 based amps, you can make a nice little practice amp out of that, and it can run off of 9V.


Thank you, but I won’t use that. I have read about it being one of the few op-amps with poor sound quality. Also, it has an unusual feature (which it shares with it’s LM38x-series siblings) in that the input is biased to the V- terminal, while the output is relative to the midpoint of the supply voltages. But I don’t think this feature would be of any benefit here. So I’m not going to use any LM38x op-amps. I also feel like the simplicity will take away the “fun”.

I would rather make a Class AB (aka “push-pull”) output stage with Sziklai pairs driven by a more typical (but higher quality) op-amp.
But if I did use a power op-amp, I would use something like TDA2003, or LM1875.

I might actually build the enclosure before soldering the parts together if I have you or someone to assist me at the hackspace. That would give the benefit of having something to hold the transformer and speaker while I test the circuit.


Sure thing, let’s get together at some point and sketch out what you want it to look like. I’ll be opening the space tonight or I can come down next week. PM me for time arrangements.


The main expense for a guitar amp seems to be the Speaker it self.
Can one use an old Stereo Speaker instead of a specific Guitar amp ditto?


Also I think that most guitar / bass amps have tubes in them? Am I correct?


Stereo speakers generally aren’t voiced for guitar specific applications.
It can be done. But doesn’t sound the same.


A Question: I am The guy that is busy with making the crutch guitar. but I am by no means a full fledged musician.

I recently decided for several reasons to re-equip it with nylon strings combined with a standard under saddle piezo-electric pickup. My guess is though that it will have a very different sound to a regular electric guitar.
Do the piezo under saddle acoustic guitars benefit from the same kind of amplifier as a plain electric or an electric base guitar?
Could stereo speakers work better in this case?


Acoustics if they have a built in preamp can be few directly into a pa and
skip the amp altogether. So in a sense they Should be ok to go into a
stereo more so than an electric guitar.


Thanks for answering. Trying to follow up with:

Most Aucustic guitars with pre-amps That I 've listened to on line seem to have a problem with amplifying the bass strings or getting the heavy vibrations through.

(Maybe this is this just the way it all sounds on youtube)?

or: Are there gadgets out there that focus on this problem?


Could be balanced issues. The saddle could botto. Could not be flat and not
have very good contact under the higher strings. Lots of factors. The
particular guitar could be bassy sounding to begin with.


Acording to what I read up on out there you bass guitars doesnt come to their right using a regular guitar amp.


True. There are more and more guitar amps voiced for lower registers with
djent genre picking up steam. But they need to be paired with the
appropriate speakers as well otherwise you get a loud flubby mess when you
want a nice tight punchy punch punch type tone.


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