6C33 Circlotron

[tubetvr]

I don't have a version of mu circuit diagram that I can post yet, only handwritten.

As you may remember I don't use a circlotron but an inverted Futterman circuit.

Basically I use the same circuit as I have on my WEB site here http://www.tubetvr.com/otl.html that is used in my earlier amp but I have introduced cathode followers to drive the output tubes , the cathode followers are DC coupled to the output tubes. So it is a very simple circuit but with good performance, distortion is 0.03% at 1W and 0.3% at 1dB below clipping, (clipping defined as the point of 1% distortion), I use higher feedback than you, around 20dB

Regards Hans

 

[tubetvr]

Hi,

I have now posted a schematic diagram of my high power OTL here http://www.tubetvr.com/otl.html (bottom of page) together with some measurement results.

Regards Hans

 

[pat49hk]

Dear Hans,

Thanks for your information. You have owned a nice website.

Seems the output state is not works as a cathode follower, isn't it?

Regards

Patrick

 

[pat49hk]

PS. I wish can have chance to taste your Graviax sauce.

 

[tubetvr]

Seems the output state is not works as a cathode follower, isn't it?

Yes, it does due to the feedback from the output to the cathode resistor of the phase splitter, this was what Futterman invented even though he made a mistake. Futterman thought that due to the feedback both output tubes should function as cathode followers but actually with the original Futterman circuit both output tubes work as ordinary cathode grounded stages, by shifting the drive signals to both output tubes this is corrected and both tubes work as cathode followers giving the lowest possible output impedance for 2 tubes.

That both tubes give equal signals and that the circuit is balanced is evident from the amount of 2nd order distortion which is as low as 55dB below max output power without any feedback, this is as good, (or better?) as can be achieved by any other OTL circuit including the circlotron.

Regards Hans

 

[el`Ol]

Some news for the circlotron fans: The new circlotron power amp from Thorens (valve circlotron driver stage, transistor circlotron driver stage) is the new reference of the German Stereoplay magazine.

 

[Giaime]

Some news for the circlotron fans: The new circlotron power amp from Thorens (valve circlotron driver stage, transistor circlotron driver stage) is the new reference of the German Stereoplay magazine.

Some schematics avabile?

 

[el`Ol]

There was a schematic of the valve driver stage, as far as I remember, not for the transistor power stage. But I don`t have the magazine.

 

[pat49hk]

Dear el'Ol,

Any drafts for references is welcome.

Regards,

Patrick

 

[el`Ol]

Hello!

I got the magazine and here is the block diagram. Driver stage is EC86, CV6189, and 6S3P-EV in series, no circlotron. No coupling capacitor is used in the whole circuit. The transistor type of the circlotron power stage is not mentioned, just that they are identical.

Greets, Oliver

 

[Circlomanen]

Post #46
Some news for the circlotron fans: The new circlotron power amp from Thorens (valve circlotron driver stage, transistor circlotron driver stage) is the new reference of the German Stereoplay magazine.

That amp is basicly a rip of of my amp i posted 2 years ago here on these forums.
The idea to use a ECC86 as a input device is not new. I hade that idea 3 years ago but I have not had the time to build it.
See post 49 in this thread.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=3802

Or this one a year ago.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=55361

Its very fun to see this being used.
I can only agree with them on the sound. These kind of amps sound VERY good!😎

Johannes.