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Old 3rd January 2013, 06:10 PM   #1381
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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.
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Old 3rd January 2013, 06:42 PM   #1382
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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?
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Old 3rd January 2013, 06:45 PM   #1383
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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)
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Old 3rd January 2013, 07:06 PM   #1384
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I don`t understand, 1.2a with or without R27 in the circuit?
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Old 3rd January 2013, 07:17 PM   #1385
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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.
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Old 3rd January 2013, 07:54 PM   #1386
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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.
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Old 3rd January 2013, 08:34 PM   #1387
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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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Old 3rd January 2013, 08:55 PM   #1388
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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.
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Old 4th January 2013, 11:53 AM   #1389
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Quote:
Originally Posted by schultzsch View Post
A journey started a long time ago...
hope to finish it soon

Happy New Year to all!!

Happy New Year !!!

Looks nice !!
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Old 4th January 2013, 04:42 PM   #1390
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thanks!

another day of work..
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