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Pass Aleph 3

To avoid OT'ing the other thread...
https://pinkfishmedia.net/forum/thr...n-the-price-or-lukewarm-reviews.275277/page-4

Tony L said:
I’m not convinced we are listening to the same amp. Yes, mine is ultra-refined and far from ‘in yer face’ (I suspect my available preamp options really don’t help here), but it is also very dynamic and tight.
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I think we are. I agree with the above description.


Tony L said:
What did you hook your DIY job to? Did you faithfully copy the Pass input stage? This is certainly the lowest gain amp I’ve ever owned!

PS I notice that in the absolute rave Stereophile review the reviewer was using a variation on the Pass ‘Bride Of Zen’ preamp, which I get the impression was designed to give the similarlt insensitive input of the Zen power amp a bit of a kicking. I may be wrong, but my suspicion is we may both have fallen at this hurdle. My impression is the Aleph 3 is very demanding of the preamp as it is effectively missing a gain stage that is usually present in a power amp.
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You could be right, I found these notes from my original build (seems like it was a 5/30 not a 3, as I took advice from NP's info on DIYAUDIO to make an optimal Aleph):

"Home designed PCBs with careful attention to grounding (separate power and signal grounds) and power supply layout. High current loops have minimal enclosed area and feedback traces carefully teed off (as per Doug Self’s recommendations). The circuit is the Aleph 5 with the Aleph 30 input configuration – this gives a higher input impedance that the Aleph 5. The Aleph 5 is thought by some (including NP himself) to be the best of the Aleph series combining the sweetness of the lower power models and some of the grunt of the larger ones.

3 IRFP244s each are used for the amplifier and current source, each set is matched for VGS within 20mV. The input IRF9610s are matched within 10mV for VGS.


The zener used in the current source for the differential pair has a 1uF decoupling capacitor added compared to the Alephs, NP now recommends this.

With supply rails of +/-33V and quiescent current of 2A per channel the power dissipation of 132W per channel is just about manageable with the heatsinks I used.

Input impedance is approx 40K Ohms (single ended). The PCB has the capability to accept the parts for a balanced input but they re not fitted.


Gain is approx X 12.5 (single ended) so a preamp with high gain is needed.


Power output is 60W according to the Aleph 5 service manual on 34V rails. The Aleph 30 claims 30W into 8R and 40W into 4R running on 25V rails, which seems more realistic."

I think I tried the Aleph with the Aleph line stage, a Bruce Rosenblit Grounded Grid and a couple of other discrete SS and op-amp based preamps. The low gain was not really an issue, it went loud enough, and I had avoided the low input impedance (although most of my preamps could drive 600 ohms easily).
 
Sounds like quite a few differences there. The Aleph 3 has an input impedance of 23k and 20db gain. Its output is 30W into 8 Ohm, 60W into 4.

My preamps (Verdier valve pre and Audio Synthesis stepped attenuators) are both outliers in different directions here. The Quad 303 is a similar input impedance but way, way more sensitive at 0.5V for full out. I think the Pass equates to about 2V. That is a big ask of a passive attenuator with a CD player upstream. The Verdier is a great match with the 303 on its lower output setting (the Verdier has jumpers internally that as I understand alter the negative feedback and the output level). I’ve not felt it matches the Pass well and actually prefer it with the almost wide-open Audio Synthesis. The only other preamp in the house is a Quad 34 which is a total non-starter as it can only put out about 0.5V unless you count my little Teac Model 2A mixing desk! I might actually try that at some point as it would certainly have the gain…
 
Took a while, but I've managed to get through this 'resurrected' thread. I take it from the recent post that you are still using the Aleph 3 @Tony L ?

As an Aleph 3 owner myself, I have to say I'm not surprised it stayed. They are fabulous amps.

I was so impressed with mine, I had an Aleph 5 built for me by Joe Henry which I use in my living room (second system). Same design, but double the power at 60W.

I think the magic has a lot to do with the single-ended design. There's something ever so convincing about music from an Aleph. Transparent, but not in the way many people think of transparency I believe.

What is really interesting when reading your journey back, is how, over time, it took a hold of you. If you look back, you were really quite disappointed with it with your Tannoys early on, even after you had serviced it.

Glad to hear you stuck with it. Mine is going nowhere either.
 
karlsushi said:
Took a while, but I've managed to get through this 'resurrected' thread. I take it from the recent post that you are still using the Aleph 3 @Tony L ?
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Yes, I still have it.

karlsushi said:
What is really interesting when reading your journey back, is how, over time, it took a hold of you. If you look back, you were really quite disappointed with it with your Tannoys early on, even after you had serviced it.
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I’ve still not managed to get anything I like out of it with the Tannoys, though it shows a lot of potential with the JR149s. I don’t think I’ve got the right preamp for it yet. What are you running yours with?
 
Tony L said:
Yes, I still have it.



I’ve still not managed to get anything I like out of it with the Tannoys, though it shows a lot of potential with the JR149s. I don’t think I’ve got the right preamp for it yet. What are you running yours with?
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Previously used a buffered passive (an LDR), but I now use it with a Chord DAVE plugged straight in, so effectively, no preamp. The Aleph 3 is more than capable of getting the detail out of the DAVE and into my little LS3s (Wilmslow Audio's take on the LS3/5A). It is a small room, near field set-up though.

The system with the Aleph 5 in the living room is very much a work in progress at the minute, but it is the one piece of kit that's staying for the foreseeable.
 
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