PP 6c33c-b

[zivhackman]

hello!
in the past fiew months i was tring to desing an amp that would have 30W/channel and would be all triod.
and i started to think about PPP 2a3, but this would be very expensiv and I will get berly 30W at class AB1.

so now I'm thinking about PP 6c33c-b that should give me 30W in class A1 and will cost much less!

It should be somthing like the schematic below.
(obviosly it is not a full schematic, it is just the idea of the desing..)

I still haven't desided what would be the operation point of the 6c33 (200V,200mA @ 600 ohm or 160V,300mA @ 600ohm)

all the power supplys will be regulated.
the otput supply will use a 6c33c-b as a pass tube for the regulation and the supply for the drivers would use shunt regularor tubes.


the supply for the 27 tube would be 450V that float on a 91v zener diode to avoid a capling cap..
(It should be 541v not 441v on the schematic)

now, the questions part:

1. is the schematic is fine?
2. should I go for fixed or self bias? (26 and 6c33)
3. what should be the size of the cap?
4. what operation point should i choos for the 6c33?

thank you very much!
ziv.

[Bas Horneman]

If you don't mind I'll skip your questions. And ask you one. You do know that the 26 is a very difficult tube to get quiet?

Ok. I'll answer some questions.
1.) The essence of the schematic is good. Only you need to fill in the details. Such as the centertaps of the input transformer need to be grounded, grid leak resistors have been omitted, etc. etc.

For the rest of the questions I would find existing pp 6c33 amplifiers via google to get an idea of operating points and self or fixed bias etc. I do know the 6c33c has some quirks you need to know about.

[vuki]

here is what I did TPPP_6c33c

It sounds very nice

You should know that you'd have to buy a lot of 6c33's to get 2 matched pairs or buy them already matched.

Output tubes are biased at 150mA each.

[zivhackman]

thank you for your replys!

yes, i know abot the problems whith the #26 tube..
I would use a regulated current supply for the fill's. and if i get this right, the PP operation of the 26 should cancel alot of the nois, right?

ther is alot of things that is not conected in the schematic because i hadn't decided about them..
the input transformer's CT isn't grounded because i'm considering the option of fixed bias for the 26.

there is not alot of PP 6c33 in the net...
but I did my homework and read alot about this russian beast!

vuki, I saw your desing befor and it looks very impresive!
but I don't understand the language..

[Bas Horneman]

but I don't understand the language..

I use chrome as browser. And then you get the option to translate.

[Zen Mod]

even if hilariously funny , there is a translation :

Google Translate

[Shoog]

Originally Posted by vuki

here is what I did TPPP_6c33c

It sounds very nice

You should know that you'd have to buy a lot of 6c33's to get 2 matched pairs or buy them already matched.

Output tubes are biased at 150mA each.

Is that plate to plate feedback in there.

Shoog

[vuki]

Originally Posted by Shoog

Is that plate to plate feedback in there.

Shoog

Yes. It really helps. I found that 150k sounds best in my system, but somewhere else lower value could be better.

[Shoog]

Your amp looks very good and very similar to my current one. Its a shame that its not in english.

I have a little 6080 amp with plate to plate feedback, with the driver direct coupled using the anode load resistor as the feedback resistor. It works and sounds fantastic. This approach requires the input transformer and a negative supply for the driver - but it works really well.
I found the 12L8GT which is an octal dual pentode which I use as the driver configured as a LTP. The overall amp works differential front to back. I certainly think this differential approach brings benefits across the board. I use CCS under the outputs and tie the cathodes with back to back caps - this eliminates the need for bias adjustment and the cost of bypass caps.

My design is based upon Gary Pimms Tabor amp.

Shoog

[vuki]

Originally Posted by Shoog

Your amp looks very good and very similar to my current one. Its a shame that its not in english.


Shoog

Thanks! It's a shame that you don't know croatian