Dear Rodents,
I came across this SET amp for sale but forgot where I seen it. I had a good
discussion about it with Turner, but I would like to hear other opinions.
The SET claimed an output of 22Watts out of a single 6C33C-B tube. This is
the one with the two tits on top. The specs were almost too good to be true.
Has anyone had any experience using this tube in a project? Are there any
caveats one should be aware of if trying to build one of these amps
incorporating this seemingly amazing tube?
It just seems a bit strange that an SET that puts out all that power is
hardly mentioned on this NG. I welcome all comments. Thank you in advance.
Cordially,
west

What shade of orange was the plate?

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

What shade of orange was the plate?

LOL !!! ;-)) Yellow I think .......

I have plans to design my own 6C33 SET .
Did some research on the curves and don't want new tubes every week
so I'm going for a lower plate diss. (3/4 of max) .
This way I think I can get about 12W . Maybe 15W max .
And BTW hwo cares about that few W more . To double volume you'll
need 10 x W anyway .....
Here's a link that might help or lighten up things ......
http://www.borbelyaudio.com/15wse.pdf
And if you can read German you can find some info here too :
http://www.jogis-roehrenbude.de/

Ronald .

west wrote:

Dear Rodents,
I came across this SET amp for sale but forgot where I seen it. I had a good
discussion about it with Turner, but I would like to hear other opinions.
The SET claimed an output of 22Watts out of a single 6C33C-B tube. This is
the one with the two tits on top. The specs were almost too good to be true.
Has anyone had any experience using this tube in a project? Are there any
caveats one should be aware of if trying to build one of these amps
incorporating this seemingly amazing tube?
It just seems a bit strange that an SET that puts out all that power is
hardly mentioned on this NG. I welcome all comments. Thank you in advance.
Cordially,
west

An audio club friend made a SET amp using 2 x 6C33 and he gets a more
comfortable
less distorted 35 watts from the pair using a tranny which I designed for him.

The tube is a triode, and its plate efficiency isn't all that high,
and it doesn't really like being run at maximum ratings like 90 watts plate
dissipation.
22 watts is 25% efficiency. Most triodes in class A produce the best sound when
set up for
20% efficiency.
But that's at only one RL, and there is less power either side of the power peak

like all tube amps.
I like to set up the tubes to make the peak power at clipping at 4 ohms,
which means that one might get a lot less at 8 ohms or 2 ohms.
But since most speakers are between 4 and 12 ohms, the thd remains lower
because the load is higher, and if more po is needed, use more tubes.

The 13E1 I like has a rated plate diss of 90 watts, but they mention this for
class B operation where the duty cycle is less than 100% like is is with an
SE class A circuit.
Thw 13E1 requires 13v x 2.5 amps to heat it, or 32.5 watts,
and I founs running them at 90 watts Pda made the annodes glow dull red
which utterly ruined the sound.
So I seettled back to 72 watts plate dissipation, and I get a healthy
25 watts into 6 ohms, using 66% UL taps.
Triode connection didn't sound any better, and gave only 15 watts.
Tetrode connection is so distorted as to be quite unacceptable for hi-fi.
I have not tried CFB on the OPT with 13E1, which could be better than plain UL.
GM70 is another tube capable of 25 watts. Also 211, 845? but these tubes
require a very high B+, and a highish RL and voltage swing,
which makes the OPT harder to wind,
and there is no guarentee the sound would be any better.
Some doubt exists about GM70 life time.
I am just finishing an SE amp with cfb opt,
and 37 watts with 4 x 6CA7 or EL34,
or even 6L6 with about 32 watts of comfortable power.
The secret is to use a screen voltage of about +250v, and anode supply of +350v,

which minimises screen current, but still allows a good clean load swing.
Getting from 7 to 10 watts from a large octal tube in SE isn't hard
and paralleling them gets a ceiling, and a very wide sweet zone.
2 x 13E1 would be very nice in parallel SE perhaps with cfb, but certainly
UL, where 50 class A watts is easy with a 480volt supply, CLC filtering,
and cathode bias.
In PP two such tubes set up for class AB1 cfb would be awesome.
About equal to 6 x KT88/6550.


Patrick Turner.

Hi Patrick ,

The tube is a triode, and its plate efficiency isn't all that high,
and it doesn't really like being run at maximum ratings like 90 watts
plate
dissipation.
22 watts is 25% efficiency. Most triodes in class A produce the best sound
when
set up for
20% efficiency.

Would be nice if Pa max = 90 W , but all the data I found so far said it's
60W and
that is when both kathodes are used . With a single kathode it's only 45W
IIRC .
So a P-out of 22W is almost 37% efficiency and that's hard to believe I
think .

Best regards ,

Ronald .

west wrote:
Dear Rodents,
I came across this SET amp for sale but forgot where I seen it. I had a good
discussion about it with Turner, but I would like to hear other opinions.
The SET claimed an output of 22Watts out of a single 6C33C-B tube. This is
the one with the two tits on top. The specs were almost too good to be true.
Has anyone had any experience using this tube in a project? Are there any
caveats one should be aware of if trying to build one of these amps
incorporating this seemingly amazing tube?
It just seems a bit strange that an SET that puts out all that power is
hardly mentioned on this NG. I welcome all comments. Thank you in advance.
Cordially,
west




Hi
The only problems I have heared about the 6C33b is they take a very
high drive voltage, so unless you use a suitable driver they sound very
dead. Advantages they give 22 watts at low voltage.
Also the Heater current is high, the sockets need to be very good.
There have been some designs in Glass Audio/X press.
Phil