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Old 29th July 2010, 08:20 PM   #21
tubem is offline tubem  Canada
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Default caveman amp

Quote:
Originally Posted by thanh1973 View Post
This might be interesting, it wouldn't take too long to try it out.
This is something I would like to try,is there a power supply schematic and does it require an adjustable current source for bias, Thanks tubem.
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Old 29th July 2010, 10:22 PM   #22
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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.

Last edited by Melon Head; 29th July 2010 at 10:32 PM.
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Old 29th July 2010, 11:45 PM   #23
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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.
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Old 30th July 2010, 02:11 AM   #24
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I'm somewhat familiar with various circuits on tubecad, Alot of them are theory only, If no one else has actually built the mosfet design circuits ,they will most likely need further refining once the beast is up and running.
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Old 30th July 2010, 02:22 AM   #25
tubem is offline tubem  Canada
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Quote:
Originally Posted by thanh1973 View Post
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.
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Old 30th July 2010, 09:40 AM   #26
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Everything needed is contained in post 22
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Old 21st December 2012, 11:17 AM   #27
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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
Attached Images
File Type: jpg MCA.jpg (51.9 KB, 259 views)

Last edited by mhouston; 21st December 2012 at 11:19 AM.
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Old 21st December 2012, 09:46 PM   #28
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by ilimzn View Post
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.

OTA - One Transistor Amplifier

Quote:
Originally Posted by mhouston View Post
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:SEWA - Seven Watt Amplifier)

What about a choke load:

CHOKE Loaded MOSFET, easy to build
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Last edited by Bigun; 21st December 2012 at 09:56 PM.
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Old 21st December 2012, 11:47 PM   #29
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The MCA is a lot like the ZCA: it all looks wrong, tests wrong, has shocking efficiencies and sounds great.
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Old 21st December 2012, 11:55 PM   #30
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by mhouston View Post
The MCA is a lot like the ZCA: it all looks wrong, tests wrong, has shocking efficiencies and sounds great.
That's rather strange, I thought you said you hadn't built it yet ?
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