Aleph J Schematic - Page 139

buzzforb · 3rd January 2013, 06:10 PM

Look on the fourm about ACS explanation. Altering R27 changes the the acs gain/modulation and with it, contribution of upper fet to output. Nelson decided on his values for a reason and I would imagine it is better overall performance. I have read that performance at 1w can be improved slightly, but at the expense of performance at higher power levels.

schultzsch · 3rd January 2013, 06:42 PM

in the future I wish to listen to the amp without R27(pure class a) in the circuit but the bias on my side is already high(1.6A/fet and 60C on the sink measured last summer) and I don`t want to get everything on fire

How high the bias/fet gets in the original circuit without R27?

buzzforb · 3rd January 2013, 06:45 PM

THE bias of the current source is .65V divided by the Rs of the top fet. If you cut modulation component, then you have a SE amp driving a CCS load. With 1.6a, you better have beefy sinks. The original was bout 1.2A(.66/.47)

schultzsch · 3rd January 2013, 07:06 PM

I don`t understand, 1.2a with or without R27 in the circuit?

schultzsch · 07:19 PM

ups

i did it again
for pure class a I have to remove R24
I remember now that i read somewhere here that also without R27 the sound gets better

confused you a little bit..sorry

buzzforb · 3rd January 2013, 07:54 PM

Here is basic schematic. If you want to have just SE amp with CS, you dont need R24, r27, r20-23, and c3. These are the componenents that turn it into a modulated current source, where the signal affects the response of the current source and its contribution to the output.

schultzsch · 3rd January 2013, 08:34 PM

so the trick it`s that I have to remove all those components to achieve pure class a, not only R24...ok now I get it
you cleared a little bit the things for me, thank you!

buzzforb · 3rd January 2013, 08:55 PM

Look at Zen V2 article on Firstwatt site. The second part of the article he sets up a SE amp with a CCS load. He follows that article up with ZV4, where he introduces the ACS. THe AJ just adds a LTP too the front end and creates nice feedback point as well as ability to drive with balanced signal.

ticktock · 4th January 2013, 11:53 AM

Quote:

Originally Posted by schultzsch

A journey started a long time ago...

hope to finish it soon

Happy New Year to all!!

Happy New Year !!!

Looks nice !!

schultzsch · 4th January 2013, 04:42 PM

thanks!

another day of work..

3rd January 2013, 06:10 PM	#1381
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	Look on the fourm about ACS explanation. Altering R27 changes the the acs gain/modulation and with it, contribution of upper fet to output. Nelson decided on his values for a reason and I would imagine it is better overall performance. I have read that performance at 1w can be improved slightly, but at the expense of performance at higher power levels. __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

3rd January 2013, 06:45 PM	#1383
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	THE bias of the current source is .65V divided by the Rs of the top fet. If you cut modulation component, then you have a SE amp driving a CCS load. With 1.6a, you better have beefy sinks. The original was bout 1.2A(.66/.47) __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

3rd January 2013, 07:17 PM	#1385
schultzsch diyAudio Member Join Date: Mar 2009	ups i did it again for pure class a I have to remove R24 I remember now that i read somewhere here that also without R27 the sound gets better confused you a little bit..sorry Last edited by schultzsch; 3rd January 2013 at 07:19 PM.

3rd January 2013, 08:55 PM	#1388
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	Look at Zen V2 article on Firstwatt site. The second part of the article he sets up a SE amp with a CCS load. He follows that article up with ZV4, where he introduces the ACS. THe AJ just adds a LTP too the front end and creates nice feedback point as well as ability to drive with balanced signal. __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

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3rd January 2013, 06:42 PM	#1382
schultzsch diyAudio Member Join Date: Mar 2009	in the future I wish to listen to the amp without R27(pure class a) in the circuit but the bias on my side is already high(1.6A/fet and 60C on the sink measured last summer) and I don`t want to get everything on fire How high the bias/fet gets in the original circuit without R27?

3rd January 2013, 07:06 PM	#1384
schultzsch diyAudio Member Join Date: Mar 2009	I don`t understand, 1.2a with or without R27 in the circuit?

3rd January 2013, 08:34 PM	#1387
schultzsch diyAudio Member Join Date: Mar 2009	so the trick it`s that I have to remove all those components to achieve pure class a, not only R24...ok now I get it you cleared a little bit the things for me, thank you!

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