Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I figured it was time to play with some of these guys  especially since it aligns with the overall theme of this site  xP

Three specimens rescued from obscurity

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Kinda hard to read the top one

IMG_20261012_190622487 (1).jpg

Being intimidated by all the extraneous alpha numeric text I looked em up to see if there was really a difference

IMG_20261012_191937540 (1).jpg

Maybe there is but the pin out seems the same and the max voltage appears to be the same

This may be anti-climactic I think I just attach some DC voltage input a signal (or two) and watch it get bigger  xP

But with everything it's different to actually do it after reading about it and there is always stuff learn


One think I noticed is there can be a plus and minus Vcc or just a ground and positive Vcc
(Here we go again  :lmao: )

Quote from: saturated on October 12, 2026, 08:35:29 PMOne think I noticed is there can be a plus and minus Vcc or just a ground and positive Vcc

If you use a single ended supply you have to use caps to block DC at inputs and outputs, as everything will run at 1/2 VCC. 
It's easier when you use a split supply, inputs and outputs will sit at zero VDC and you don't have to use caps there.

The LM358 or the LM324 (Quad version) don't sound the best for audio. You can make them sound a little better if you install a 1K resistor from the output to the negative supply. The best feature of this style opamp is that the input common mode range includes the negative supply. They do however go crazy (the output doesn't obey the inputs) if you allow the inputs to swing below the negative supply by more than about 0.3V so don't overdrive them.

Yes sir thanks  :tu:

This is turning out to be a good venture already because it's getting divergent all over the place

I looked in a book to see if they had some experiments and started to see all kinda stuff like slew rate and common mode rejection  :'(

Anyhow they were using a 741 instead of a 358 so I looked further trying to avoid Google and came up with this

IMG_20261014_131821673 (1) (1).jpg

My assumption that a 741 would be the same as a 358 just a tad different doesn't seem to hold up.

Anyhow i don't think I even have any 741s anyway  xP

I am interested in offset null whatever that is but I'm trying to keep things simple ATM

Something I really liked was it appears they wired a 741 in two different configurations so that the first is inverted (out of phase?)

And then the second it is non inverted

So I'm really interested in this maybe I can do a similar experiment with my 358.

IMG_20261014_131801798 (1).jpg


Glancing at the two I'm looking for differences I don't like how the polarity on 2 and 3 is reversed from top to bottom with really no other difference in power supply  :grr

Ok aside from bypassing each side with resistors

Maybe I should get some 741s and others otw I think I'll order some tonight at work if you like some other ones lmk

BTW Happy Thanksgiving last Monday to our friends up north

 :dbtu:


Edit: ok just looked I actually do have some 318s and 741s