Metropoulos Forum

Posted: **Wed Jan 12, 2011 2:14 am**

novosibir wrote: They've also introduced some kind of solid state clipper after the 5-th gain stage, still before the Master.

Check the attached schem!

Larry

Nah, just the Bass boost circuit. The FET's are normally on, and exhibit a low impedance path effectively shunting/shorting out C15, and C16, when the switch is pulled, the negative voltage from the bias supply gets applied to their gates, and turns them off, C15/C16, now effectively are the lower impedance path to AC signals, and are shunted to ground creating passive bass boost

Posted: **Wed Jan 12, 2011 11:59 am**

Posted: **Wed Jan 12, 2011 11:59 am**

joey wrote:
novosibir wrote: They've also introduced some kind of solid state clipper after the 5-th gain stage, still before the Master.

Check the attached schem!

Larry
Nah, just the Bass boost circuit. The FET's are normally on, and exhibit a low impedance path effectively shunting/shorting out C15, and C16, when the switch is pulled, the negative voltage from the bias supply gets applied to their gates, and turns them off, C15/C16, now effectively are the lower impedance path to AC signals, and are shunted to ground creating passive bass boost

Horrible waste of a tube if you ask me....

Posted: **Sun Feb 13, 2011 9:09 am**

briango wrote:A quick clip of the amp I was working on before this thread started, but none the less inspired from listening to clips. It is a 50watter that is switchable from Plexi/JCM800/AFD/Modern. This is just 3 gain stages with a footswitchable boost.

Id love to know how you wired that. Did you loose the normal channel on the plexi?

Posted: **Wed Jun 13, 2012 1:20 am**

i have a question regarding plate driven tone stacks......

1. are you supposed to have a coupler coming off the plate before driving the TS?
2. what is this caps purpose, as ive seen many with and without it? is it a more biting tone without it? should i keep it or ditch them?
3. on this amp im working on, on the input it has a 33k into a 100n cap with a 470k to ground then to grid, what kind of input circuit is this? im working on my peavey valvking, so im trying to marshallize it a bit. ive since replaced it with the classic circuit, but im just curious about a few of these things....this is not a stock amp by any means, so any info is needed......

Posted: **Wed Jun 20, 2012 12:10 pm**

Ad 1 and 2: no, a coupling cap is not necessary here since in a FMV tone stack, the treble, mid and bass caps take the function of blocking DC. Sometimes amp manufacturers use a separate coupling cap to allow them to choose tone caps with lower voltage ratings. If the main coupling cap is large enough you will most likely not hear a difference, otherwise the cap will introduce a bass reduction.

Ad 3: 33k = grid stopper to eliminate/reduce radio frequency, 100n = cap to prevent the scratching volume pot syndrome if there is any DC on the tube grid, 470k = grid leak resistor, which is needed as a ground reference for the tube grid. For this purpose it must be placed after the 100n cap.

Cheers Stephan

Posted: **Sun Aug 03, 2014 11:36 pm**

univalve1234 wrote:Hey guys , this is my take on the Cameron mod , i have added a 4th tube and tweaked the preamp and power section to get as close as i could . Let me know what you think.

this sounds great sir!

Posted: **Wed Jul 06, 2022 9:31 pm**

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