Circlotron Preamp with ECC88.

[Circlomanen]

I had this idea a couple of years ago, but lack of high value bifilare winded chokes has stopped me. Im seriously thinking of building this one as I think its a very simple and elegant design.
Its a Circlotron equivalent to a long tailed pair / diffpair. You can see the cathodes being connected ontop of the big chokes.

Any and all technical comments are most welcome, since I have never seen anything like this anywhere before.

Cheers Johannes.

[Circlomanen]

And here is the chematic.

[Dave Cigna]

I don't understand the purpose of the chokes or the direct connection of the cathodes to one another. The circlotron that I know is just two tubes and two power supplies in a circle with the load taken between the cathodes. A reference for the input signals is usually derived from the load somehow.

[SY]

What is the problem that you are using this circuit to solve?

[Circlomanen]

What is the problem that you are using this circuit to solve?

I dont want any capacitors in the circuit at all. I want as few active devices as possible, yet I want balanced operation and the cancelation of second harmonics.
I dont like having the output at a high voltage because of the startup peaks that will destroy the poweramp and my speakers. I like the symmetry.

I don't understand the purpose of the chokes or the direct connection of the cathodes to one another.

The chokes are there to isolate the plates from the cathodes to stop the feedback mekanism that makes them into cathodefollowers. The connection between the cathods are there to provide a low impedans connection , kind of like "ground". Its basicly a LTP. Works in the same way. The chokes also serves as plate load, It converts the current variation inte voltage variation.

Johannes.

[SY]

Normally, the Circlotron is used as a work-around for mediocre transformers in power amps. As a demerit, the signal is now run through two sets of capacitors and the circuit becomes much more complicated.

You can get all the balance and harmonic cancellation with a simple differential amp and an output transformer. Much, much simpler and there's only one set of power supply caps (they ARE in the signal path, after all).

[Circlomanen]

Normally, the Circlotron is used as a work-around for mediocre transformers in power amps.

That might be true among those with not enough understanding of the circlotron circuits. The circlotron circuit is a very versile and usable kind of circuit. Almost anything you can do with any other circuit, you can do with a circlotron.

[SY]

No doubt true, but like any other circuit, it has faults and virtues. In this application, it seems that the virtues aren't of much use, thus my question.

[Alastair E]

I am familiar with the circlotron, having just built a circlotron power amp....

BUT I cannot for the life of me, see how the posted schematic can possibly work, let alone solve your problems.....

Whats wrong with caps anyway.....Your source CD player and other devices probably have them, as well as your power amp.....

This scheme is slightly similar to my own but without the chokes, or the cathode short and taking the out-put accross the cathodes......Shorting both cathodes together, effectively shorts the output in your scheme as far as I can see.....

[Tom2]

I think the circuit does work as shown.
The DC biasing works in terms of a conventional circlotron circuit.
The AC gain works similar to Circlomanens quaditron circuits posted in Pass Labs forum.

I guess I would call it some sort of circlotron/floating differential balanced amp thing???
With the feedback network shown, it exhibits NP's SuSy effect.

Also removing the feedback network might make understanding the circuit easier.

Circlomanen posted a similar circuit in Pass Labs forum
using his Zenitron circuit with Power JFets.

It does seem like overkill for a preamp though.

But hey, this is DIY audio. If it makes you happy build it.

I don't belive it, I'm in the tube forum.

Tom