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I just posted about this amp in another thread but i wanted to open a new thread about this amp.7
I read about Ixys having a high power depleationmode fet, and i got realy intressted. Thiis is what i would like to build.
I can not imagine a better topology for a ultrasimple amp.
Its a supersymmetric fully balanced one stage pushpull amp. Quite a mouthfull to say!
That looks like a really interesting design. I like it. To be honest I'm having a little trouble following this. Are you saying it's a super symmetric Circlotron?
Okay, I see the two circles, and the susy feedback. Looks like the 33 ohm resistors set the bias current? I'd love to see this built. Good luck!
Okay, I see the two circles, and the susy feedback. Looks like the 33 ohm resistors set the bias current? I'd love to see this built. Good luck!
Iwas going to write more about it yesterday...
Its a supersymetric circlotron amp. The two 33 ohm resistors just make a groundreference point. Nothing else.
Bias is set by the depletionmode-fets and the DC-resistans of the big inductor.
The bifilare inductor does two things. It isolates the Sources from the drains on the Fets so they can provide voltage-gain, and it provides a I/V converting - like a constant currentsource or a powerresistor does in an normal Zenamp.
Here is a simplified version, with power-resistors instead of inductors.
I have left out bias-arrangement for clearity.
Its a supersymetric circlotron amp. The two 33 ohm resistors just make a groundreference point. Nothing else.
Bias is set by the depletionmode-fets and the DC-resistans of the big inductor.
The bifilare inductor does two things. It isolates the Sources from the drains on the Fets so they can provide voltage-gain, and it provides a I/V converting - like a constant currentsource or a powerresistor does in an normal Zenamp.
Here is a simplified version, with power-resistors instead of inductors.
I have left out bias-arrangement for clearity.
An externally hosted image should be here but it was not working when we last tested it.
I have been building different Circlotons since 2001, and i came to think of this one when i read Nelson Pass Zen V-7. Its in many ways the same amp but with floating supplies and no need for any CCS to set the currentflow though the devices.
I guess i could call it The Circlotronic Zen V-7.
A diffence from the Zen V-7 is this amp will runn in class A/B, but with a lot more distortion. I got something like 50 watts out of this circuit with 2 x 15 volts supply and 500 mA quisent current tjhrough each Fet.
I guess i could call it The Circlotronic Zen V-7.
A diffence from the Zen V-7 is this amp will runn in class A/B, but with a lot more distortion. I got something like 50 watts out of this circuit with 2 x 15 volts supply and 500 mA quisent current tjhrough each Fet.
If i remember correctly, its about 0,6 ohms. Maybe a bit high for the Ixys depletion-mode-fets.
I dont know the rated output. It can be scaled up or down as you want. With 20 volt supplies and 2 amperes of current through each fet, i can get a clean 20 watts, but it will give about 50 something watts before clipping. The distortion rises a lot when leaving class A.
With really powerful devices and a lot of heat-sink you could probably get 100 watts out of it. But I haven't tried that.
I have to buy some fets before i can build this one. I have built a similar design with IRFP250 before.
I was going to build one with normal Hexfets this past weekend, but i was to tired, so all i manged was this thread.. I hope to get some time in the near future.
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Its from my old thread.
Just Search on Zenitron.
Hey CM,
Sure your chokes must be big. I have a pair of Hammond 2A/200mH/1,7ohm on the shelf and they aren´t small. Your amp will neither be light or cheap with four of those.....
About your circuit it still puzzles me a bit. Have to sim it to get a better picture
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Have simmed some circuits with the IXYS and the depletion seems a lot more unlinear than a typical IRF...
Sure your chokes must be big. I have a pair of Hammond 2A/200mH/1,7ohm on the shelf and they aren´t small. Your amp will neither be light or cheap with four of those.....
About your circuit it still puzzles me a bit. Have to sim it to get a better picture
.Have simmed some circuits with the IXYS and the depletion seems a lot more unlinear than a typical IRF...
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I only need two of them. They are bifilare winded. Two closely connected windings, so the DC on each half cancels out any core saturation.
I already have two of these. I only need the Ixys. The last version i built in 2005 had some problem with the bias and stability, but i think that the depletion-mode fets will be stable enough in their self biasing to make a simple stable circuit.
I like the simplicity and the fact that the amp is DC/coupled throughout. No caps in the amp, except in the power-supplies. (if not run from batteries) It will have very small DC-offset because of the susy/feedback and the depletionmode-fets.
Hey CM,
Simmed your circuit with the IXYS. Iq was then 0,6A. Gross distortion predominantly 3rd order at all levels. -3dB at 18k.
Removed the strap and the coupled coils and then it worked. First with 0,6ohm in place of the coils and then strapped them. Iq went up to 1,1A and now it worked well. -3dB at 60kHz.
But this is no news as it now is a std circlotron with local NFB.
Anything I might have done wrong?
Simmed your circuit with the IXYS. Iq was then 0,6A. Gross distortion predominantly 3rd order at all levels. -3dB at 18k.
Removed the strap and the coupled coils and then it worked. First with 0,6ohm in place of the coils and then strapped them. Iq went up to 1,1A and now it worked well. -3dB at 60kHz.
But this is no news as it now is a std circlotron with local NFB.
Anything I might have done wrong?
I have only built this kind of amp with IRFP250, and that one sounded nothing like"gross distortion, predominantly 3rd order at all levels"
It sounded much like a Zen-amp or some really good tubeamps i have heard.
It distorted a lot when driven hard (+20 watts) but i could swing something like 40 volts on the output with a 8 ohm load connected. Above 40 volts i started to clip hard.
Maybe the Ixys fets are not that suitable for this amp.
It sounded much like a Zen-amp or some really good tubeamps i have heard.
It distorted a lot when driven hard (+20 watts) but i could swing something like 40 volts on the output with a 8 ohm load connected. Above 40 volts i started to clip hard.
Maybe the Ixys fets are not that suitable for this amp.
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