2sk1058 mosfet amp

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You want a single ended power supply. Try a crc or clc.
What you already have seems adequate, accept if you want to use 50V then you will need a new transformer and caps rated at 60V or higher.
However to start just use the power supply you already have. To lower the bias increase the value of the 17k resistor, and obviously to increase the bias lower the value of the 17K resistor. I would put a 20k multiturn pot in series with the 17k resistor for bias adjustment.
The other thing you might need to do is change the 20k and 30k resistor to 15k and 25k and put a 10k multiturn pot between them with the wiper attached to the node with 1Meg resistor.

When setting up you want to set the bias pot at maximum resistance and the other pot to mid way.
First, adjust the 10k pot to get half the supply voltage between r1 and r2.
Then measure your bias. Slowly increase the bias in increments and checking both bias and half supply voltage point.
 
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I for got to mention.
Once you have built this, all you have to do to turn it into a ccs fed single ended amp is to remove or short out R2 (0.47 Ohm resistor).
So it is very quick to see what the difference might be.
I'm somewhat familiar with various circuits on tubecad,alot of them are theory only.Has anyone actually built some of these other zen type design circuits, if not I might be the guineypig trying them.They most likely would need further refining once you have a beast up and running.I never stop doing mods on this stuff anyway:eek:.
 
I had been requested for a long time to come up with a new design. It thought about it for a year or so, tossing many ideas around. I wanted the active power component to be bipolar (no not crazy) and get away from FETS. So the MCA is born. As of yet no one has built it not even me. Want to be the first?

DIY Audio Projects Forum • MCA - Son of ZCA
 

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It has the classical error of misunderstanding maximum output swing.

There's similar information here, the original one transistor amplifier (I think posted a year or more before Mark's version, but they are all very much the same idea), claim is that output should be biassed at 66% of rail voltage.

http://www.diyaudio.com/forums/pass-labs/73598-ota-one-transistor-amplifier.html

I had been requested for a long time to come up with a new design.

I like the concept of choke loaded single transistor amplifier more, offers lower power dissipation and lower distortion. Not sure that the 2SK170 has the stones for a high current into the base of a 2N3055 with it's well-known low hfe problems and distortion will be more complex - don't like it myself. If you want to add an extra active device you may as well add a CCS load (like the SEWA amplifier:http://www.diyaudio.com/forums/pass-labs/66822-sewa-seven-watt-amplifier.html)

What about a choke load:

http://www.diyaudio.com/forums/solid-state/145156-choke-loaded-mosfet-easy-build.html
 
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That's rather strange, I thought you said you hadn't built it yet ?
No it has never been properly assembled. It was a hand full of parts linked by alligator leads and tacked solder points. I had to do some sort of prototype to test the theory. I ran it on the CRO and was very impressed with square wave results etc. Far superior to the ZCA.

What I did find experimentally was the output cap didn't have to be any bigger than 3300uf (snubbed by 0.1uf) driving 8.2ohms and the input cap not larger than 0.1uf. In fact when I reduced the input cap the square wave at 10Khz looked a lot better. The amps good to 125Khz (-3db) and had a punchy driving sound. With a 24V PS the 2N3055 ran cold.

I think there is more in the tank if the PS is 48V and the Re (load) reduced to 8ohms. But I haven't proved this. I think then it will deliver about 2.5W. I have all the parts required to build the 48V version but I'm currently building tube preamps and power amps. I will get to it. So be the first.
 
A Russian have studied the subject.... he made a video in 2012

and another Russian have tried several options.

I will post the link to the Russian, Mark Houston schematic that has something included in green about the modifications made ...about something Russians tried... some graphics and some funny image copied from the video.

The guy is Stalker 29218.... it looks he is very skilled technician....watch harmonics in the image.

https://www.youtube.com/watch?v=_SWOmO_3H_c

I have assembled.... but i had only 1 watt.... a lot of THD.... 5 percent efficiency ...not too much appreciated.... but very interesting to assemble because a single stage......it is nice despite performance not that good in my point of view.

https://www.youtube.com/watch?v=_SWOmO_3H_c

regards,

Carlos
 

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and another Russian have tried several options.

I will post the link to the Russian, Mark Houston schematic that has something included in green about the modifications made ...about something Russians tried... some graphics and some funny image copied from the video.

The guy is Stalker 29218.... it looks he is very skilled technician....watch harmonics in the image.

https://www.youtube.com/watch?v=_SWOmO_3H_c

I have assembled.... but i had only 1 watt.... a lot of THD.... 5 percent efficiency ...not too much appreciated.... but very interesting to assemble because a single stage......it is nice despite performance not that good in my point of view.

https://www.youtube.com/watch?v=_SWOmO_3H_c

regards,

Carlos
I didn't know someone had done more work to get more power. Looks good. Only one thing to highlight, reduce the input cap to 0.1uf. But then try it for yourself.
 
I hate pirates..if you see someone around just tell me

that i gonna be, instantaneously, against them.

I am glad no one have copied your design.... this is nice...i have visited the internet and search deeply with several titles about one stage, class A, FET, audio power amplifiers and no one stole your idea....several have assembled.

Congratulations!.... no one said the circuit belong the them...all them said it is a Mark Houston amplifier..... i am glad to see decent people in our community.

regards,

Carlos
 

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The design is barely mine as I got the original idea from a test cct. for the FET. I saw an amp in the test cct. and developed the original ZCA from that point. Since then the amp has had a almost cult following. I still have the original build though it doesn't get played these days.

I don't think anyone is claiming original design here. I posted my version on the internet so I'm happy for anyone to build or modify the cct. Any mods or developments should, of course, be claimed as theirs. Think of it as the Linux of amps.
 
and another Russian have tried several options.

I will post the link to the Russian, Mark Houston schematic that has something included in green about the modifications made ...about something Russians tried... some graphics and some funny image copied from the video.

The guy is Stalker 29218.... it looks he is very skilled technician....watch harmonics in the image.

YouTube

I have assembled.... but i had only 1 watt.... a lot of THD.... 5 percent efficiency ...not too much appreciated.... but very interesting to assemble because a single stage......it is nice despite performance not that good in my point of view.

YouTube

regards,

Carlos
I see you squeezed 6W from the ZCA. Are you still using it? I'd you ever try the MCA?
 
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