The Aleph Design Reloaded

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generg

generg

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Joined 2009
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No A., I was so occupied with the Gamut, the Aleph2/30 and just now with some boards from Jims Audio.

But I built an Aleph J some years ago, it is so long away that I cannot say how the sound was in comparison to.....xxx.
But a friend lent his Aleph J to a loudspeaker factory and he never got it back, they bought it. They liked extremely the way the J did voices!
 
generg

generg

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Joined 2009
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Does anybody know why the Aleph 3 tends to sound darker when I give more juice to the upper 244 by reducing the Aleph current source resistor?

So we get not only more juice but also a clear change in sound, a nice feature!
I am inclined to make a pot there with a small range similar to SIT-1 to change a bit the sound when lousy bright CDs are in to the more darker side......:))
 
generg

generg

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Thanks 6L6,

Hm, the 50% is the recommended value in the FW papers, yes.
But I have the impression that Nelson chooses mostly in the original old Pass Labs amps for this Aleph current resistor values lower than the one delivering 50%.
At least wanting the 50% contribution in my clones always ended in values higher than the ones shown in the revision 0 papers of Aleph 3.
Maybe the darker sound is the result of higher k2, when you do not chose the 50%.

And interesting Aleph 3 adjusted for the 50% rule was to bright for me.

But I mostly like darker amps....:))
 
N

needtubes

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Joined 2003
generg said:
Hm, the 50% is the recommended value in the FW papers, yes.
But I have the impression that Nelson chooses mostly in the original old Pass Labs amps for this Aleph current resistor values lower than the one delivering 50%.
Click to expand...

That seems to be the case. Looks like he varied the AC gain to get certain amps like the Aleph 2 and 3 to power double into 4-ohms. As far as I can tell, those amps use 66% AC gain. Perhaps the Aleph 5 does as well, but I haven't looked carefully at that amp. The Aleph 30 seems to use closer to 60%, assuming my calculations are correct.

generg said:
And interesting Aleph 3 adjusted for the 50% rule was to bright for me.
Click to expand...

Perhaps not surprising since you suggest increasing AC gain seems to darken the sound and the original used 66% instead of 50%.

Interestingly, my SPICE fiddling has shown certain iterations of the Aleph give better THD figures with more AC gain from the CCS. Not sure if that carries over into real life or is just an artifact from the models, though. As I understood it, the AC gain of the Aleph CCS is a type of positive current feedback. Circlomanen has reported the sound from varying the PCF level in one of his circuits some time ago: too much gave a dark, aggressive sound and too little gave a brighter, more tinny sound, if I remember correctly.

I am about to start on another Aleph, something more akin to the 3 this time, with 66% AC gain. Will be interesting to hear it to see if I like the "66% sound" or if I end up closer to 50% like in my Aleph-mini.
 
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generg

generg

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Joined 2009
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very interesting….

and clearly the Aleph CCS lowers the distortion considerably…
Yesterday on the bench with sound card THD measurement

a. Aleph 3 without Aleph CCS resistor not connected at 1W/8R shows 0.1% THD

b. with Aleph CCS connected at supposed 66% 0.02% THD

So I can tell you … it is real!

:--))
 
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