JFET-only Headphone Amp "Circlotron КП903B".

Designed to isodynamic-orthodynamic headphones.
Maximum on the output power of 7.5 and 15 Ohm - 1,7 W, 100 Ohm - 1,06 W.
The output impedance of 3.3 ohms at 1 kHz at a voltage at the output of 2.5-3 V.
Band power at a voltage of 90% of the level of restriction is longer 200 kHz.
With a downturn in the upper frequency (200 kHz) of less than 0.5 dB.
Spectrum of push-pull amplifier is similar to a tube triode SE. )))
 

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rayma

Member
2011-04-29 8:37 pm
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Thanks for filling me in. In your post #5, you are saying that substitute JFETs would have to closely match the characteristics of the JFETs making up Svjatoslav's Circlotron, is that correct?

Regards,
Pete
 

There is a rough equivalent in a non-Russian part - that is a high power JFET made in Russia, surplus stuff these days. Fairly rare, and hard to source regardless. They do show up on ebay. Probably the best way to get some, since you only need a handful for a headphone amp.

The reason for the Circlotron is that there are no complimentary parts for this device.

To find the USA made equivalent you'll need to do a bunch of online research looking for power Jfets made 30-40+ years back. I did locate the part number years back, and you can source them, but they are fairly pricey IF you can get any. The Russian parts handle a bit more power, iirc.

I think the driver circuit could be made more simply, but a bit depends on what sort of result you're going for, and what sort of voltages need to be swung.

_-_-bear

PS. DC offset might be a concern with drift? Or does the Circlotron try to self balance? Never thought about it, since most are tubes with transformers...
 
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It would be nice to see the FFT plots with the sensitivity of the measuring device/input attenuator set so that the peak of the fundamental was ~6dB of "0", so that the harmonics might emerge from the noise floor?

_-_-bear

Thanks for the datasheets!!
I was unable to find them online some time back - but I do not speak/read Russian.
 
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I shall sit here, waiting... hoping to "mature" or maybe "ripen"?

...eating some snacks.

My comment was that IF those are actual measurements (??) and not simulations, that the level of the fundamental was ~-40dB, so the resulting information is all in the noise floor. This makes it of very limited value.

But since I have some of these devices, I am following with interest. :D