#54 (photos)

[Smokebreak]

Anyone built this up yet? I'm gonna try and put it in one of mine this week if I get a chance. I'm really curious about all that peaking.

[Structo]

[Structo]

Are the PI plate resistors really 151K and 100K?

[Smokebreak]

Are the PI plate resistors really 151K and 100K?

I think what you're referring to is the date code. Looks like 7513, or 7518.

You can barely see that it looks like the value is 1003 like the one on the right.

[jelle]

PI looks like 1M at grids, 820r cathode, 18K tail, 220r, with a 1.8K NFB resistor. 220K powertube grid references. 100k? plate resistors. This would be designed around a 12AX7.

Yes, 100K.

[Charlie Wilson]

cap on bass pot .005 or .001?

Also- lower right corner of main board @ PI- RC 5/23/79 - Ry Cooder?

Hello, the cap is a .005 with a 10k tail on the bass pot.
CW

[stevlech]

Thank you sir!!!

[Dr d]

Here are some photos of a nice 70s amp I had the chance to visit with for a while(this was a few years ago).
CW

Hi Charlie, I know this is an old thread, but is there any chance that you recall what the ceramic cap value was that bypassed the 1M OD exit resistor was? Looks like it might have been 200Pf or so.

[Charlie Wilson]

Hey, sorry I missed seeing this. Give me a couple and I’ll take a look at my photos. I think it is a pretty small cap, maybe 25pf but I’ll double check.
CW

[Charlie Wilson]

Yeah I think I just can make out Z5U,25M,1kV.
CW

[Dr d]

Yeah I think I just can make out Z5U,25M,1kV.
CW

That is amazing, thank you Charlie!

[Dr d]

Here are some photos of a nice 70s amp I had the chance to visit with for a while(this was a few years ago).
CW

One last one, I hope, Charlie. I can just about see a small green tant. cap on the accent switch. Would you hazard a guess and say that it is still 1uf like a typical 2nd/3rd gen amp? I notice there is another green 4u7 tant on the FET board. Same type of cap but different value?

[Charlie Wilson]

Again, I didn’t see this question. Sorry. No pictures that actually show the written value but it is a different cap than what is on the FET board. It looks 1uf to me.
CW

[Dr d]

Again, I didn’t see this question. Sorry. No pictures that actually show the written value but it is a different cap than what is on the FET board. It looks 1uf to me.
CW

No problem! Thank you for your reply. I have tried to replicate this circuit, but couldn't replicate the "medium gain warm OD". I can only think that the OD entrance bypass cap must be a very low value.

[Charlie Wilson]

You duplicated the PI with a 12ax7?
CW