36watt voltage question

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lespaulblues
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36watt voltage question

Post by lespaulblues »

Hi,
I just built a 36watt using el34 with fixed bias using the 18watt power
rail up to v1,i had to change the 2k2 2w resistor to 10k going to v1 plates.
My b+ is 390v at the first filter cap.
All voltages seem about right apart from v1 pin1 is 157v and
pin 6 is getting 200v.
It's got a hall vvr3 and it's starting to sound really good btw.
Any ideas where to look.
Thanks.
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guitarmike2107
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Post by guitarmike2107 »

Hi it might help if you post the circuit you have built. we would just be stabing in the dark otherwise.

cheers

Michael
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lespaulblues
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Post by lespaulblues »

It's a standard 50 watt non master volume layout using
36watt ig mains transformer,valvepower output.
Then i used the resistor values for the power dropping up to v1,like normal.
I've already changed the 2k2 2 watt to 10k which dropped it down
tp 157v on pin1 v1 and 200 pin6 v1.
It could posibly need dropping further,but i'm not sure.
The fixed bias vvr is really good btw.
I built the trinity plexi amps before,which are great,but i don't use
the volume tone channel,if anyone knows how to incorporate the
gain tmb channel with the normal channel i'd like to know and use a
presence for the unused cap.
The layout i'm using uses 2 470k mixer resistors with a bright cap then
going to pin 2 v2,standard plexi.
The trinity uses the 470k to ground on normal channel so i'm not sure
what the difference is and how to connect it up,so i stuck with the
50watt layout.
Cheers.
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zaphod_phil
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Post by zaphod_phil »

So this is based around a Marshall 50W design, rather than being a Marshall 18W with EL34s in an otherwise typical cathode-biased 18W power stage? In that case, I hate to say it, but you're asking in the wrong place. Somewhere like ppwatt.com or Plexi Palace would be more likely to be able to help.
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Nature abhors a clean tube amp

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lespaulblues
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Post by lespaulblues »

What i wanted is this amp like my trinity plexi but with 2 volumes and
the gain control as i don't use the volume tone side of it.
I'd like to know if this is possible.
I did use the 36 watt power side of the layout.
I will be adding the cathode bias side of it so i can switch between them.
Any suggestions are welcome.
Cheers.
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zaphod_phil
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Post by zaphod_phil »

You should take a look at the 18W Plexi in the Downloads section, which has a Plexi style preamp with an 18W style cathode-biased power stage. You could easily do the same amp with a pair of EL34s or a quad of EL84s. If you want to use this amp design, which is still 18W based from the PI to the power amp, then we can help you.
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