Getting rid of an active current gain in Aleph
I would like to try converting the Aleph output stage into a simple current sourced stage. All the feedback around the current source, the out series resistors, all the parts hanging on the output are influencing sonics in some way. A simple Mosfet with a fixed current source should sound probably better. I do lose the power into 4 ohms and lower but this is not an issue here.
Natural progression of course, is SOZ with single resistor for current source, but at the cost of efficiency. So I would be leaning towards simple, active CS.
Anybody tried doing that already?😉
I would like to try converting the Aleph output stage into a simple current sourced stage. All the feedback around the current source, the out series resistors, all the parts hanging on the output are influencing sonics in some way. A simple Mosfet with a fixed current source should sound probably better. I do lose the power into 4 ohms and lower but this is not an issue here.
Natural progression of course, is SOZ with single resistor for current source, but at the cost of efficiency. So I would be leaning towards simple, active CS.
Anybody tried doing that already?😉
Peter
Gray did this nice job:
http://www.diyaudio.com/forums/showthread.php?threadid=772
and you can X it if you want, but the cost is lower inputimpedance if you dont want to use a buffer.
Gray did this nice job:
http://www.diyaudio.com/forums/showthread.php?threadid=772
and you can X it if you want, but the cost is lower inputimpedance if you dont want to use a buffer.
Thanks for a link, somehow I never got to see that thread. But it's more of a variation on SOZ design.
What I'm looking for, is a modified Aleph, with mosfet as a current source, but without the circuit associated with active current gain. I'll be using that amp in tri-amp system with efficient drivers, so I don't need extra power and if I'll be able to achieve better sonics, it's worth it.
What I'm looking for, is a modified Aleph, with mosfet as a current source, but without the circuit associated with active current gain. I'll be using that amp in tri-amp system with efficient drivers, so I don't need extra power and if I'll be able to achieve better sonics, it's worth it.
CCS
Hi Peter,
Take any Aleph and throw out the outputresistors and the RC
back to the CCS (C10, R21 in Aleph2) thats it!
Uli😉
Hi Peter,
Take any Aleph and throw out the outputresistors and the RC
back to the CCS (C10, R21 in Aleph2) thats it!
Uli😉
Peter
It is. Obvious I misunderstood you. But Uli is right.
I have used that circiut topology (changed the outputdevices to irf610´s) to drive a push pull outputstage.
It is. Obvious I misunderstood you. But Uli is right.
I have used that circiut topology (changed the outputdevices to irf610´s) to drive a push pull outputstage.
Because I'm sentimental about Alephs. 
And I would like to use X topology, and experiment a bit with the boards I got.😉
And I would like to use X topology, and experiment a bit with the boards I got.😉
It will not surprise you to imagine that I have
worked with this a bit.
There are occasions when a constant current source
or even a resistor will sound better, but this is highly
dependent on taste and having the proper speaker.
A good example is a nice efficient horn midrange or
tweeter. If you don't need the power, you have less
need of gain in the circuit.
pass/ - likes a good horn now and then
worked with this a bit.
There are occasions when a constant current source
or even a resistor will sound better, but this is highly
dependent on taste and having the proper speaker.
A good example is a nice efficient horn midrange or
tweeter. If you don't need the power, you have less
need of gain in the circuit.
pass/ - likes a good horn now and then
Nelson Pass said:
Yes, especially if you already have a preamp in the loop, which for loudspeakers in the 95dB+ wouldn't necessarily require any additional voltage gain. And if you don't need any voltage gain, the circuit can reduce to an emitter/source/cathode follower, which is simpler, more linear and has a lower output impedance (assuming an active current source).
se
Peter,
When you replace the Aleph current source with a standard current source I would up the bias a bit.
Please let us know your results.
Jam
When you replace the Aleph current source with a standard current source I would up the bias a bit.
Please let us know your results.
Jam
Re: sound
I just wanted to try to make a Push Pull for a change. I am shure Neslon coud do a much better job, actually he once said he would consider it, but you know.......
´s!
The sound was OK, but compared to my XSOZ not so good.uli said:
I just wanted to try to make a Push Pull for a change. I am shure Neslon coud do a much better job, actually he once said he would consider it, but you know.......
´s!
Re: Getting rid of an active current gain in Aleph
peter:
i saw a project for this. i'll find the link and send it or the schematic later.
mlloyd1
peter:
i saw a project for this. i'll find the link and send it or the schematic later.
mlloyd1
Peter Daniel said:
" pass/ - likes a good horn now and then "
Nelson,
where's the emoticon for that one?
Rgds
13th Duke of Wymbourne
Nelson,
where's the emoticon for that one?
Rgds
13th Duke of Wymbourne
Re: CCS
For a simpler experiment, I might make CCS just by soldering a wire across the output resistor (i.e. short-circuit across R22).
JH
uli said:
For a simpler experiment, I might make CCS just by soldering a wire across the output resistor (i.e. short-circuit across R22).
JH
You could place a pot in series with R21 to increase its
value, or a switch across the output resistors. Then you
can play all night long.
😎
value, or a switch across the output resistors. Then you
can play all night long.
😎
Nelson Pass said:
Yeah, all night long...
I have three different Zens in hand:
- The original Zen with constant current source
- Zen with active current source
- Zen-X with active current source
I like all three, particularly the Zen-X with the "active current source." It attracts me best for the clear sound with the musical texture, harmony and resolution. The Zen-X has performed its duty on 1.32A bias current. By the way, why not lower bias if the sound remains the same? I have thought about the lower bias to my curiosity. To lower the bias, however I have not changed the bias resistor value. Instead, I have approached the current source of Aleph, by adding R19 (of Aleph 2). I have got 1.16A with 120k and 0.96A with 60k. Now, it is fixed with 1.16A.
Expecting a valuable conclusion of Peter Daniel...
JH
I'm in a process of doing that mod. I also removed 100 ohm output to ground resistors, and the DC offset didn't change at all, it stays at 0.5mV. More later.
Peter Daniel
May I propose you to change the thread title to "rate and effect of the ac current gain" or similar?
I actually experimented on Zen-X with ac current gain variation from 0 to 50%. I felt that the +/- ac current rate control worked as if to be equivalent to the +/- focus control of camera lens. My preference zone was 0-30%. In between these values, the differences were not very distinctive, and the preferences were dependent on the different music and mood.
Again, looking forward to your results¡¦
JH
May I propose you to change the thread title to "rate and effect of the ac current gain" or similar?
I actually experimented on Zen-X with ac current gain variation from 0 to 50%. I felt that the +/- ac current rate control worked as if to be equivalent to the +/- focus control of camera lens. My preference zone was 0-30%. In between these values, the differences were not very distinctive, and the preferences were dependent on the different music and mood.
Again, looking forward to your results¡¦
JH
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