• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6C33C-B. PP or SE ?

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korneluk

korneluk

Member
Joined 2005
Consider going single ended, and most important of all, choose cathode bias. The 6C33 has a tendency to drift when operated in fixed bias and run away with cherry-red plates.

Another recommendation is the operating point: 200V @ 200mA is conservative, but sounds good and provides trouble free operation.

Here some reference cathode bias designs:

http://www.borbelyaudio.com/adobe/15wse.pdf

http://www.metaleater.narod.ru/6c33c.gif

Enjoy,

-- jose k.
 
E

electronic

Member
Joined 2008
Thank you guys !

I saw yesterday the Borbely design after some searches.

Found this schematic in a romanian electronics forum:



l_9fe68fba8d90458c9d4a099e89f1470e.gif
 
tubetvr

tubetvr

Member
Joined 2003
qtron.se
That schematic is very close to an early one by San-Ei in Japan, San_Ei was owned by Dakesue who was the one in Japan who "discovered" 6C33C in Japan and imported this tube and sold it as EC33C. The only differences I can find is that San-Ei used a 12BH7 as the 2nd tube and used local feedback to the cathode of the SRPP, see here http://www.tubetvr.com/se.html

I have one of these amplifiers myself and it gives a very nice sound.

As is evident the amplifier used fixed bias to the output tube and I can vouch for that the output tube current is very stable, it usually doesn't drift even over a year. IMHO 6C33C tubes that are burned in correctly and is not used with more than ~40W anode dissipation doesn't drift.

Regards Hans
 
E

electronic

Member
Joined 2008
tubetvr said:
That schematic is very close to an early one by San-Ei in Japan, San_Ei was owned by Dakesue who was the one in Japan who "discovered" 6C33C in Japan and imported this tube and sold it as EC33C. The only differences I can find is that San-Ei used a 12BH7 as the 2nd tube and used local feedback to the cathode of the SRPP, see here http://www.tubetvr.com/se.html


Regards Hans
Click to expand...




You must be talking about this :

http://www.bonavolta.ch/hobby/en/audio/6c33c_5.htm
 
P

pukka

Member
Joined 2002
Jeb-D.

Jeb-D.

Member
Joined 2005
diyaudio.com/forums/swap-meet/157276-garage-sale.html#post2023179
I'm about to start building a 6C33C (will try 6C41C also) SET. I'm using UBT-1 Tranformers.
Click to expand...

6C41C would be a better match for the UBT-1. Both current and impedance are pretty much ideal for 6C41C. Where as you would have to run a 6C33C very conservatively.

Speaking of UBT-1, I have one on my shelf collecting dust. It's a little dinged up, but I'd let it go for cheap. If your interested shoot me an e-mail.

Here is an experiment UBT-1 with 6C33C.
http://www.geocities.com/dmitrynizh/ecc99-6c33c-se.htm
 
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