Would any of you more knowledgeable people take a look at this. It's an experiment done with a friend messing around with an old #102 amp.
the pre amp is this: it then goes to the P.I and power section of a #102. PI and power like 102 apart from PI caps - .01 each and the caps after that - .02 each No NFB or presence just a vox cut control on the P.I.
Sounds great but not sure what's happening and if it's safe
Phils amp.bmp
TIA
M
p.s. excuse my fumbling schematic it's my first.
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Last edited by norburybrook on Mon Jul 27, 2020 4:53 pm, edited 1 time in total.
There's no harm in driving the PI section like that , the that being a Cathode follower stage.
The only thing is that such a stage has no gain, in fact it has less the unity gain , so in other words if it was receiving 1 volt of signal on its grid it's output would be about .9 .
It's also low impeadance so it will no load down the PI section.
As long as the PI section can then have enough output to drive the output tube(s) into clipping your sonically ok.
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Stevem wrote: ↑Mon Jul 27, 2020 4:24 pm
There's no harm in driving the PI section like that , the that being a Cathode follower stage.
The only thing is that such a stage has no gain, in fact it has less the unity gain , so in other words if it was receiving 1 volt of signal on its grid it's output would be about .9 .
It's also low impeadance so it will no load down the PI section.
As long as the PI section can then have enough output to drive the output tube(s) into clipping your sonically ok.
thanks for the reply Steve. the amp is loud as it is. No issues with volume or gain, apparently. I say apparently as I've not heard it yet. Going to visit this on monday and have a play on it. My friend, who is a great professional player and has built lots of amps over the years really loves this amp so I'm interested to hear what it's like.
martin manning wrote: ↑Mon Jul 27, 2020 6:12 pm
The 4k7 following the CF is going to cause severe clipping, so a lot of distortion is coming from that.
I was going to mention that...I thought that was an odd choice
martin manning wrote: ↑Mon Jul 27, 2020 6:12 pm
The 4k7 following the CF is going to cause severe clipping, so a lot of distortion is coming from that.
it's only clipping when the gain is turned up and in a nice way. It transitions from lovely clean to OD like a tweed. I was aware it wasn't very conventional but strangely sounds great in practice.
So if it sounds good is it safe to leave as is ? it wont set on fire or blow up in a weeks time?
martin manning wrote: ↑Mon Jul 27, 2020 6:12 pm
The 4k7 following the CF is going to cause severe clipping, so a lot of distortion is coming from that.
I just see a voltage divider with 220k/4k7. How is that going to "cause severe clipping" ?
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