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Old 20th February 2004, 03:52 PM   #1
Stefano is offline Stefano  Italy
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Default aleph follower

Has anyone tried to use aleph ccs for a follower output stage?
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Old 20th February 2004, 05:36 PM   #2
Stefano is offline Stefano  Italy
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Dear Nolson, is't real that in the XA amps from Passlabs the output stage is configured as a follower, like X-1000 and others?
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Old 20th February 2004, 07:08 PM   #3
Stefano is offline Stefano  Italy
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Default Hey

Hey is there anyone who knows if is possible to use the aleph corrent source for a source follower?
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Old 20th February 2004, 08:07 PM   #4
Netlist is offline Netlist  Belgium
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Hi Stefano,
Do you have any ideas in mind, perhaps a small sketch might give you more replies.

/Hugo
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Old 20th February 2004, 08:58 PM   #5
gl is offline gl  United States
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Hugo and Stefano,

I had thought of using the Aleph CCS in a recent experimental design I have been playing with. To answer your question - I think it should work fine. The question is: Is the Aleph CCS output follower design superior to an ordinary complementary follower? It is certainly is more complex and uses more parts, but would it sound better. Nelson Pass used source followers in the Aleph 0 and 0s. But he augmented them with a CCS so that the circuit would work as a SE amplifier up to a certain output. I've wondered whether the added CCS current source sounded better than a straight complentary output biased up to the same current level?

Graeme

P.S. I'm not sure if this posted so please excuse me if this post appears twice.
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Old 21st February 2004, 03:42 AM   #6
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It can be done, but you'll end up with a more complicated front end as a result. Consider a folded cascode, perhaps, to drive the output.
Don't forget that you'll need to bias the follower, which won't be quite as easy as the grounded Source in the 'normal' Aleph output stage, since the follower will bias relative to the output line rather than the negative rail.
Another point: You'll need to think about your gain. In an Aleph, the front and back ends each contribute about 20dB to the overall open loop gain of the amp. If you convert the output to a follower, you'll lose that 20dB. Plan accordingly, either by building more gain into the front end or having plenty of drive available from your preamp.

Grey
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Old 21st February 2004, 02:20 PM   #7
Stefano is offline Stefano  Italy
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Default Tank you

I'm thinking about a more complex design, as an integrated amp using BZLS, volume control, another BZLS and a follower out of the feedback loop to isolate completly the amp from the speakers, obviously it would be a little amp, 30W/ channel or so; i'm considering to use X-feedback to make it work like a whole amp. I prefear a follower because irf MOS are not so complementary...
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Old 21st February 2004, 03:04 PM   #8
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You may want to look at this thread

Aleph's Topology Questions

for Mr.Pass's response to this issue. Basically it is:

"The Common Source is used to develop additional voltage gain,
as the input differential pair is not enough to develop the full
voltage gain or rail-to-rail voltage swing, and I did not want to
add additional stages." -- NP


-Sean
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Old 21st February 2004, 03:23 PM   #9
Stefano is offline Stefano  Italy
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Default I want to add an additional stage!

I want to add an additional stage!
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