Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hi Folks, Can anyone tell me what Ic is in the input stage. Is it an LM 741. There does not seem to be a schematic available for these amps. I have hum from the amp output but nothing from the input. Seems to point the the opamp.Thanks.

Don't think it's an LM741 and don't know why you suspect it anyway.
Post a couple good pics of the board, one above and one below.

If it's similar to a Squier 15 or an Epiphone Studio 10 (and I've seen a bunch of schematics for these little practice amps that are **** exactly identical ****, from a variety of manufacturers), then it's a 4558 or a TL072. Even when it's not identical, the structure is basically the same: a pre with a dual opamp, diode cilpper and passive eq, and a TDA2030 power amp.

I'd like to see the schematic for a Squier SA-10 to see what they have tweaked to make it "acoustic".

Just guessing, but can't be far anyway:
1) tamed the gain + pulled clipping diodes.
2) modified "Fendery/Marshally" passive electric guitar tone controls to a Baxandall or similar, more HiFi (or PA) related, and which is "flat" with everything "on 5"
3) added a Piezo or some cheap tweeter or used a speaker with a "whizzer" cone.

0) Added an input with very high input impedance, for piezo pickups.

1) I'm not sure about pulling the diodes - some acoustic units (see behringer adi 21 / samsamp acousti di) have diode clipping to "warm up" piezo pickups. Also, limiting with diodes in the pre may sound cleaner than the power chip amp distorting.

2) problably.

3) AFAIK it's just a small full range speaker just as the "electric" version, perhaps with a different (fuller?) response.