Convert Mp3 player AMP to guitar amp
So my friend gave me a portable speaker which I prompty decided to rip open and pry inside. Upon getting the PCB out I see it uses a TDA2822m IC with a 3V power supply and two tiny 8OHM speakers. is it possible to convert this to a portable guitar amp with a switchable headphone jack or use the inbuilt speakers? I;ve attatched pictures of the PCB and what I think is the current wiring for it. It has a stereo input as well but would it be possible to just wire the L and R inputs into the one input coming from my guitar lead (mono 1/4 jack). Would I need to use some sort of pedal in front of it since its expecting a signal from an mp3 player not a guitar? What about the power supply as well, would it better be connecting a 9V battery, the 2822M specs state that it can handle up to 15V? How much extra work would it be to incorperate a pot or a germanium tranny (or diodes) to get some sort of clipping or fuzz? Thanks PCB SHOTS: https://imgur.com/gallery/ACDJg DIAGRAM : https://imgur.com/a/Qjrkz
Posted Oct 1, 2017, 6:48 PM UTC
Easy peasy bud. Just hook up a 1/4 jack to the input. The smallest fuzz you can build is the 7min fuzz. Should all fit.
I've just looked up the 7min fuzz, it really does like nice and simple, I'm sorry if this question is asking a bit much but I have a bunch of 2n1306's germanium transistors lying about, do you think it would be possible to swap one of those instead of the MPSA13 or would the other components need ot change value?
Try hooking up a pair of the 2N1306's in Darlington configuration, with the emitter of the first one going straight into the base of the second one and the two collectors tied together. That still won't give you as much gain as an MPSA13, and the biases might be a bit off because they're Ge instead of Si, but it'll be a Darlington you can play with built from what's on hand.
You might need a buffer stage going between a fuzz and that amp. Fuzzes generally have ~100K output impedance; the mp3 player that amp is designed to amplify is designed to drive ~100-ohm headphones. Another 2N1306 built up as an emitter follower will at least show your ears the difference in loading.
How about using a tl071 as in Input buffer, I've never built a buffer before but it doesn't seem like it would be too hard, would I need an input buffer anyway no matter what due to the impedance mismatch? Another question is how would I wire it to also use a headphone jack? Would it be possible to use some sort or spdt or dpdt toggle to switch between both outputs?
TL071 or TL072 (your original amp is stereo) should work. [e:] Or LM358, if you need more input and output voltage range -- I've successfully driven old 8-ohm headphones with those.
Unless you like the sound of loaded-down fuzz; your call. Some people liked the original PigNose sound... Me, I thought it sounded like the guitar was struggling to get its note out.
As for the wiring... Sounds like things you have planned are gonna be awfully crowded in that OEM case. Why not build all of this in an outboard box connected by a 3.5mm TRS extension cable, that way you can still use the amp for its original purpose, amplifying an mp3 player's output, just by plugging it into one instead. Assuming I'm visualizing what's on your workbench correctly, that is.
Ask away bud. The 2n1306 wouldn't have much gain. Have a 5088?