tube circlotron for headphone amplifier

[stephanbrenner]

Hello everybody,

Sure many of you have heard about the circlotron schematic, which is
used in many OTL architectures to ensure a DC free amplifier output
without having the need for a transformer or capacitor coupling
stage.
I wondered whether whether it is possible to use this configuration in
an headphone amplifier (stereo version). The point of my uncomplete
understanding is the following: the typical circlotron circuit requires
2 floating voltage sources and drives a floating load in between the
cathodes of the 2 output tubes. When connection a normal speaker to
this system, I see no problem. In the case of a headphone load, the
twi ground terminal are typically connected together (3 wires on
connector). Hence, the cathodes of one path in each amplifier are connected
together. But there is another point in the system, where the amps
are shorted: the GND of the input signal.
Now the question which arises is: is there any problem in this configuration?
I'm not sure about this, not feeling good about this additional short
of the cathode potenzials.
Best regards and thanks in advance...

Stephan

[stephanbrenner]

nobody interested in this discussion?

[tinitus]

Originally Posted by stephanbrenner

I wondered whether whether it is possible to use this configuration in
an headphone amplifier (stereo version).

probably the most 'beaten horse' google

[oshifis]

Stefan,

Most headphones have a 4-wire cable, with the negative tied together at the jack connector. In this case you need to replace the connector only.

[stephanbrenner]

oshifis, yes this is clear to me as well. But to have a version, which is more general, the question arose. I'm nearly sure, that it is not possible, but only wanted to have a second opinion.

[tinitus]

ups! my post was wrong, sorry
I obviously thought of OTL
and now also remember reading about 'certain' possible safety issues

[stephanbrenner]

yes, safety may be of concern. I'm just wondering, whether a capacitor coupled output stage (class a operation) is more safe. In deed, I have qualms about having this high voltage on the ear in case of damage.

[atmasphere]

Originally Posted by tinitus

ups! my post was wrong, sorry
I obviously thought of OTL
and now also remember reading about 'certain' possible safety issues

There are no safety issues.

We make a preamp that has a Circlotron output, is all tube and has enough output power to drive headphones.

In doing so, the preamp does rather well with the 3-wire connection, but there is a big difference in sound quality when the 4-wire connection is used instead- enough to make one wonder why anyone would use the 3-wire connection after going through the effort of building a nice headphone power amp from scratch regardless of the circuit used

So yes, it can be done.