After half a bottle of Bordeaux, I am probably not entire in sane.
So I hope Nelson would forgive me for messing around with his creations.
Following the ideas published in :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=128571
Here are a couple of equivalents which could be applied to an Aleph-X or Zen-2 like circuit.
Values are approximate, only to demonstrate principle.
Only output stage shown.
I hope there are no grave mistakes.
Patrick
So I hope Nelson would forgive me for messing around with his creations.
Following the ideas published in :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=128571
Here are a couple of equivalents which could be applied to an Aleph-X or Zen-2 like circuit.
Values are approximate, only to demonstrate principle.
Only output stage shown.
I hope there are no grave mistakes.
Patrick
Hi Patrick,
thanks for the hint!!
A very cute thing, such an all jfet "Aleph" (if one ignores the cascodes for a moment).
It's a pity, I just have the wrong speakers for that beauty. Some high impedance, high SPL speakers would be best, due to low damping factor and way lower distortion at high impedances.
To get the output impedance down, you can just crank up negative feedback, which was not the point of the exercise
Also the stupid resonances in the frequency response should be taken care of by a more sophisticated mind, I can't imagine that adding a Zobel is the last word on that.
Anyway, that amp will be stored and revived when the right speakers come
Have fun, Hannes
thanks for the hint!!
A very cute thing, such an all jfet "Aleph" (if one ignores the cascodes for a moment).
It's a pity, I just have the wrong speakers for that beauty. Some high impedance, high SPL speakers would be best, due to low damping factor and way lower distortion at high impedances.
To get the output impedance down, you can just crank up negative feedback, which was not the point of the exercise
Also the stupid resonances in the frequency response should be taken care of by a more sophisticated mind, I can't imagine that adding a Zobel is the last word on that.
Anyway, that amp will be stored and revived when the right speakers come
Have fun, Hannes
You would be pushing it with 4 LU1014s per channel, at 8 ohms.
If your speaker is 4 ohms, then you certainly need 8.
So I would start with 8, biased at 1.3A each.
Probably +/-22-24V rails, total bias per channel 5.2A.
Power will peak at 6 ohm, about 80W.
About 50W at 4 & 8 ohm.
And of course you need equal number of cascode devices, such as IRFP240s or FQA19N20C.
Patrick
If your speaker is 4 ohms, then you certainly need 8.
So I would start with 8, biased at 1.3A each.
Probably +/-22-24V rails, total bias per channel 5.2A.
Power will peak at 6 ohm, about 80W.
About 50W at 4 & 8 ohm.
And of course you need equal number of cascode devices, such as IRFP240s or FQA19N20C.
Patrick
> My own favourite is the third one, which is not Taylor.
Well, I like this third one so much that I decided to build a quick prototype to test the principle and see whether I made any mistakes in the design.
The Zip file shows the test circuit built, based on the standard Rollins AX with 4 IRFP044s, with the modified current source AND a JFET frontend (matched 2SJ74BLs cascoded by J174s) diffpair with 1.2k drain resistors.
The frequency response shown is without any optimisation and with a reactive load. The small hump can be flattened by increasing the feedback cap to 8p or so. But I did not bother, as I could not stop listening to it for some 3 hours even with an iPOD as source and not with my reference speaker, though I initially just wanted to have a quick test.
A proper A-B test against the original Rollins AX and an equivalent Lindsley-Hood Xed MOSFET with almost identical layout and component choice is planned in October.
I would encourage the experimentally minded to try this for yourself.
Patrick
Well, I like this third one so much that I decided to build a quick prototype to test the principle and see whether I made any mistakes in the design.
The Zip file shows the test circuit built, based on the standard Rollins AX with 4 IRFP044s, with the modified current source AND a JFET frontend (matched 2SJ74BLs cascoded by J174s) diffpair with 1.2k drain resistors.
The frequency response shown is without any optimisation and with a reactive load. The small hump can be flattened by increasing the feedback cap to 8p or so. But I did not bother, as I could not stop listening to it for some 3 hours even with an iPOD as source and not with my reference speaker, though I initially just wanted to have a quick test.
A proper A-B test against the original Rollins AX and an equivalent Lindsley-Hood Xed MOSFET with almost identical layout and component choice is planned in October.
I would encourage the experimentally minded to try this for yourself.
Patrick
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