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.
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.
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
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
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...
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...
You may want to look at this thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=27680&highlight=
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
http://www.diyaudio.com/forums/showthread.php?s=&threadid=27680&highlight=
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
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.