And please never power up with the transistors not screwed to the heat sink...even for a few seconds.

Iit works and sounds great?  And there ar no adjustments anyway?  Then stop fixing it and enjoy the amp.

What do you think these changes will do?  The original 50 watt part is plenty capable, the amp doesn't produce near that much.  Installing heavier duty parts will not increase the power output in the slightest.  Power comes from the power supply, not the output transistors.  Their 60v ratings are plenty for the 41v supply, of which neither part ever sees more than about 35v on peaks.  These amps are not known as transistor killers, so adding overkill ratings won't really improve reliability.

It won't be ANY louder, the parts ratings only tell you the maximum they can survive, not what will come out from them.  And as to preamp hitting downstream too hard, the signal is limited by the power supply.  The preamp runs on a single 24v rail, which the op amp has to center in so 12v either way from rest.  Minus a volt or so for limits and the signal cannot peak over about 11v.  NO stress on teh power amp.

To answer your question, yes the NTE guys will drop in place, though I consider it a waste of time.


I will say the power amp could be where your distortion lies, but not from being hit too hard.  You might have crossover distortion, and that is a matter of bias adjustment.  Yours is not adjustable other than by changing circuit part values around Q4.

One of my favorite stories is about Ken Bran, a designer for Marshall.  He went on to design his own line of amps, the NARB amps.   He reported once that he had a set of Fender transformers on his shelf and decided to put them in one of his amps instead of the Marshall ones.  he said it still sounded like a MArshall.

Duncan's calculator doesn't pretend to cover anything except the tone stack itself.  Not the whole amp or any other parts, just the stack itself.

And another alternative:   Peavey used a TON of TL604 in the 1980s, and when TI stopped making the chip, PV designed a small drop-in board to replace it.  They sell them through their parts department.

I brought up speaker curves, not so much for learning about individual speakers, but rather to demonstrate how "unflat" they ALL were, and how that is the major contributor to guitar amp tone.   For example it doesn't much matter what the amp does at 8k-10kHz when none of the speakers gets much over 5kHz.

Oh, and look at the response curves of popular guitar speakers.

Crystal clean clarity?  Foo, that would simply be a PA system, and we know that does not make a good guitar amp.   What you think of as clean in a guitar amp is not really very clean.  It just doesn't have the shrill raspy edges of dirt channels.

Go to DUncan amps and download the tone stack calculator and explore the tone stacks, you will see their response curves are not flat.  Putting all the tone controls at center on your old Fender is NOT the flattest setting.

Hi

Lug numbers mean absolutely nothing to me, a photo would help.  Are these common Switchcraft open frame jacks?

Loud hum...on a solid state amp, that so often means DC on the speaker.  And that will damage speakers.  SO check for DC voltage across the speaker that hums.  Or look at the speaker cone.  When you turn on the power, does the cone move one direction and stay there?  That means DC voltage on the speaker.

REsistors do not burnt up on their own, there is almost always a dead semiconductor involved.

R38 is in the -15v supply, if it burnt, then either the zener or cap is shorted or one of the ICs using -15 has a short to ground.

Transformers produce AC voltages, and those voltages are called RMS voltages.  SInce AC voltage changes all the time, we use an average.

36v AC, moves from zero up to a peak of About 51v, then back down through zero and out to -51v and back.   The average of that zero to 51v is 36v.  When you rectify and filter that, the caps charge up to the peak of 51vDC.   This is how it works.  You take the RMS AC voltage of the transformer, and multiply by 1.414 to get the peak voltage, which will be the rectified and filtered result.We might subtract a volt or two for losses in the rectifiers or some such, but that basic formula is close enough.

Um... how did you test the op amps with a battery?

I don't know how you could get 77 volts on an IC, the highest voltage in the amp is 46v.


Ther op amps run on +15v and -15v, the 15v supplies are not AC.

Note the schematic voltages have polarity signs, and that means they are DC.  AC has no polarity

He said it was the Studio Pro

There are some test voltages on the schematic, start with those.