Oh Sorry, Terry,
Its the CRC PSU PCB thread that Tripmaster asked about and zman01 further inquired.
here it is as posted in #1754. http://www.diyaudio.com/forums/group-buys/301682-crc-power-supply-class-amplifier.html#post4937661
I hope you are well engaged in your diy activity
regards
Prasi
Its the CRC PSU PCB thread that Tripmaster asked about and zman01 further inquired.
here it is as posted in #1754. http://www.diyaudio.com/forums/group-buys/301682-crc-power-supply-class-amplifier.html#post4937661
I hope you are well engaged in your diy activity
regards
Prasi
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Hi
With first Test i have used a simple dual Supply from Elektor projekt- mono: 4x UF MUR860+ 4x6800uF/50V- works very good for my listening opinion.
And i have only a 100k Alps Pot on hand and find no problems to drive the Amp.
Next is nearly finished- with bigger MJL4281- come soon with results here.
Regards
With first Test i have used a simple dual Supply from Elektor projekt- mono: 4x UF MUR860+ 4x6800uF/50V- works very good for my listening opinion.
And i have only a 100k Alps Pot on hand and find no problems to drive the Amp.
Next is nearly finished- with bigger MJL4281- come soon with results here.
Regards
Wow! Beautiful.
Has anyone built and tested it yet? I think I would like to build it - if the layout has been error checked can you please provide the Gerbers? Or are you organizing a GB?
Thank you very much, Hugh!
Well, first of all, I need to power the original, 1-pair, version up!
Still not finished...
Is Onsemi's NJW0281G just as good as Toshiba 2SC5200 (very hard to find genuine ones nowadays) in this application?
http://www.onsemi.com/pub/Collateral/NJW0281-D.PDF
http://www.onsemi.com/pub/Collateral/NJW0281-D.PDF
I would think NJW3281 are better due to 200w capability in same TO-3P package. They carry the same price tag on element14. Could be a mistake, don't know.
Best of course are TO264 package MJL device recommended by Hugh and for many of his amps (P3A and P68) by Rod Elliott.
Quasi as Ultimate Power Headphone Amp?
I got a request from a member on Head-Fi.org to see if I could get an amp that has the sonic signature of a SE Class A amp (predominant 2nd order, less 3rd order, and not much else) but with enough power to drive 2w into 50ohm HiFiman HE-6's (but have ability to drive 4w or more for headroom). I was looking into true SE Class A designs and they can do it but would put out massive amounts of heat. Then I thought about this Quasi amp.
Anyhow, I set it up in semi-class A with 500mA bias current and +/-32v supplies (measured under load) and added a 3300uF Panasonic FM 35v cap with a 100uF Elna Silmic II and 1uF Wima MKS in parallel for cap coupling the headphone in true SE Class A fashion. I listened with my 8ohm speakers first and was amazed at the bass that was coming out. My calcs say that the corner frequency should be about 6Hz. I am doing this to ensure that the DC offset of this amp can never damage a sensitive headphone driver.
I am using a new CRC filter from the GB - it works very well. Also using my 2mF low ESR cap bank. Anyhow, with 96dB sensitive 250ohm headphones connected I cannot hear any hum or noise/hiss when music is off. FFT shows that 60Hz (and H2 and H3) are -85dB below main signal so not audible. A very nice result considering that the PSU is not regulated and has no cao multiplier.
Intiial tests with an 8ohm dummy load with 2.83v into 8ohm (1w) shows a nice harmonic profile that is very SE Class A like:
Here is same test with 4.0v into 8ohms (2w):
Next tests will be to rig up a 51R dummy load and see what that looks like. One takeaway from this is that I may use cap coupling on more of my speaker amps in the future and not worry about DC protect circuits.
I am auditioning it now with a 33R dummy load and my 250ohm headphones paralleled onto that load. Sounds is very nice. As you can imagine, the dynamics and headroom is huge. Very clear and articulate. Very quiet - a superb headamp that can drive any headphone.
I got a request from a member on Head-Fi.org to see if I could get an amp that has the sonic signature of a SE Class A amp (predominant 2nd order, less 3rd order, and not much else) but with enough power to drive 2w into 50ohm HiFiman HE-6's (but have ability to drive 4w or more for headroom). I was looking into true SE Class A designs and they can do it but would put out massive amounts of heat. Then I thought about this Quasi amp.
Anyhow, I set it up in semi-class A with 500mA bias current and +/-32v supplies (measured under load) and added a 3300uF Panasonic FM 35v cap with a 100uF Elna Silmic II and 1uF Wima MKS in parallel for cap coupling the headphone in true SE Class A fashion. I listened with my 8ohm speakers first and was amazed at the bass that was coming out. My calcs say that the corner frequency should be about 6Hz. I am doing this to ensure that the DC offset of this amp can never damage a sensitive headphone driver.
I am using a new CRC filter from the GB - it works very well. Also using my 2mF low ESR cap bank. Anyhow, with 96dB sensitive 250ohm headphones connected I cannot hear any hum or noise/hiss when music is off. FFT shows that 60Hz (and H2 and H3) are -85dB below main signal so not audible. A very nice result considering that the PSU is not regulated and has no cao multiplier.
Intiial tests with an 8ohm dummy load with 2.83v into 8ohm (1w) shows a nice harmonic profile that is very SE Class A like:
Here is same test with 4.0v into 8ohms (2w):
Next tests will be to rig up a 51R dummy load and see what that looks like. One takeaway from this is that I may use cap coupling on more of my speaker amps in the future and not worry about DC protect circuits.
I am auditioning it now with a 33R dummy load and my 250ohm headphones paralleled onto that load. Sounds is very nice. As you can imagine, the dynamics and headroom is huge. Very clear and articulate. Very quiet - a superb headamp that can drive any headphone.
Attachments
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Uhh... thread subject was "Quasi complementary" and output stages are hybrid MOSFET and BJT.
And there are psychoacoustic reasons (the harmonic profile is similar to a SE Class A amp) for the quasi-complementary MOSFET/BJT. That's what makes it sound great.
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MARV, those are lateral FETs, that in some cases, with certain care, may be used with no source resistors in place.
For HexFETs, used here, source resistors are a must for achieving appropriate thermal stability.