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Pass Aleph 3

My Mark Levinson takes a good 30 min to an hour to warm up but in use never actually gets that hot, just warm to the touch, it initially sounds very ordinary from switch on.
 
I always found that Sugdens A21a and A21SE take around half an hour for the bass to assert itself and the sound to become something special
 
I suspect the Aleph is actually closer to that. I turned it on just before the C4 news and came up at 7:40 and it was ready to sound very decent (temp 44c, up to 48c now).
 
Just gone between the JR149s and LS3/5As and the Pass seems to have a pretty distinct preference for the former. The 149s sound wide open and alive, really very good indeed, the LS3/5As are just too polite and warm in this context. Their bass bump slowing everything down whereas on the TL12 Plus or Stereo 20 it doesn’t at all - they really sound wonderful there. It’s odd, but the Pass just doesn’t shine with them, whereas it is possibly the best sound I’ve had out of the 149s to date. It really works well, just so clear and open, like big headphones or Quad 57s. As such I think I now have two distinct second systems and will view the Pass and 149s as one system, and the TL12 Plus and LS3/5As as another.

I’m coming to the conclusion that the Pass, like so many products I really like, is everything everyone says it is, be that praise or utter contempt. I’ve heard so much shit said about Tannoys, Klipsch, LS3/5As, Naim amps, Quad amps, idler decks etc over the years, and if you hear them in the wrong context (or badly serviced examples) it is absolutely true, they can all sound utterly awful and I’ve heard it, but get the match right, grasp the basic engineering concepts etc and they can be as good as their fans say.

PS I didn’t turn it off when switching speakers so no warm-up. Pass claim it’s pretty much impossible to blow this thing up and it can cope with shorts etc, not that I’m anything like that clumsy.
 
I haven't heard an Aleph 3, but contextually it seems very similar to my Pioneer M-22. Both are 30W class-A amplifiers and they have a beguiling yet solid presentation when paired with the right loudspeakers. My M-22 sounds absolutely superb driving Yamaha NS-1000Ms, but less so with my inefficient Ergo E-IXs. The E-IXs come alive with more powerful amplifiers like Dynavector or Densen, but curiously the Yamahas do not sound as good with those.

So sources aside, I effectively have two playback set ups: Vintage Japanese comprising Pioneer C-21 and M-22 into Yamaha NS-1000M, or contemporary Danish comprising Copland CTA-301 and Densen B-350s into E-IX. I can't pick a favourite between the two.
 
I always found that Sugdens A21a and A21SE take around half an hour for the bass to assert itself and the sound to become something special

Same here, I always thought it took about 1/2 an hour to come on song, the Alecto monos take a good hour, although they're Class A/B
 
I haven't heard an Aleph 3, but contextually it seems very similar to my Pioneer M-22. Both are 30W class-A amplifiers and they have a beguiling yet solid presentation when paired with the right loudspeakers.

Quite different engineering though. The Pioneer is a fairly standard push-pull topology using bipolar transistors throughout, with high feedback factor. The Pass is an unusual single-ended topology using FETs wherever possible, with low feedback factor. The Pioneer also has a regulated supply for the front end.
As far as it's possible to tell from a schematic I would say that the Pioneer is intended to be as close as possible to a straight wire with gain. The Pass was designed to be a slightly wonky wire (according to NP himself, albeit not in those words:)).
 
Audiophiles seem to revel in minor controversies - vinyl vs CDs, tubes versus solid state, capacitor, wires, magic dots... and negative feedback.


At one extreme, the position is that "feedback makes amplifiers perfect". At the other extreme, "feedback is a menacing succubus that sucks the life out of the music, leaving a dried husk devoid of soul".


The former viewpoint usually belongs to so-called 'objectivists' who have a fine appreciation for electronic theory and measurements. Their opposites would be the 'subjectivists' who emphasize the listening experience and often own tube amplifiers. Accusations are occasionally made that objectivists can't hear, and conversely that subjectivists hear things that aren't there. This being the entertainment industry, I hope everyone is having a good time.


From an interesting interview/discussion with Nelson Pass here on 6 Moons.
 
Audiophiles seem to revel in minor controversies - vinyl vs CDs, tubes versus solid state, capacitor, wires, magic dots... and negative feedback.


At one extreme, the position is that "feedback makes amplifiers perfect". At the other extreme, "feedback is a menacing succubus that sucks the life out of the music, leaving a dried husk devoid of soul".


The former viewpoint usually belongs to so-called 'objectivists' who have a fine appreciation for electronic theory and measurements. Their opposites would be the 'subjectivists' who emphasize the listening experience and often own tube amplifiers. Accusations are occasionally made that objectivists can't hear, and conversely that subjectivists hear things that aren't there. This being the entertainment industry, I hope everyone is having a good time.


From an interesting interview/discussion with Nelson Pass here on 6 Moons.


I would class myself as an open minded objectivist.
IME low feedback is a way to make things very difficult, both in terms of engineering and sound.
My favourite amp has lots of local feedback and medium (split) overall feedback.

I tend to go for the unfashionable mediums: feedback, class A/B, speaker efficiency etc. :)
 
I really haven’t formed any opinions yet. I certainly like high efficiency horns and SETs, but I also like low-efficiency mini-monitors, ESLs etc and big amps, and a lot of stuff in the middle. The one thing I am convinced of is there are no absolutes, some stuff works great in some contexts and sounds awful in others, other kit the reverse. At this point in time I haven’t got an opinion with regards to negative feedback as I’m not even sure which amps I like have what amount, though again I only like/dislike amps in very specific loudspeaker contexts as the subject of this thread highlights perfectly. There is no universal answer to my mind.

My Verdier preamp is quite interesting as, as I understand it, the five preset variable output settings work by varying the negative feedback. I’ve never been able to get beyond the middle setting so far, though I will be able to when I take it upstairs to use with the inefficient mini-monitors. Even the insensitive Pass was loud on the middle setting downstairs (the Tannoys are a good 10db louder than JR149s). I’ll maybe be able to learn a little more about feedback character when I next drag it upstairs again.
 
This could just be relevant, at a stretch. I 'won' a DIY Sony VFET amp in part 2 of the lottery. You might say it's a distant relative of the Alephs, since Nelson's philosophy hasn't changed. First impressions were with the LX-minis, so just providing the upper registers, and I loved it. Now I've had a chance to hear it solo with ESL57s/Townshends it's without question the best sound I've enjoyed in this room. Ths sound stage is so pronounced I had to adjust the angle of the 57s wrt the listening chair and clarity is exceptional. (The only downside I can think of: how can any of the other amps in various stages of completion possibly sound as good as this one?)
 
This could just be relevant, at a stretch. I 'won' a DIY Sony VFET amp in part 2 of the lottery.

I don’t understand the lottery reference, is this a Pass or DIYAudio thing?

Now I've had a chance to hear it solo with ESL57s/Townshends it's without question the best sound I've enjoyed in this room.

Sounds quite familiar. The more time I spend with the Aleph 3 driving the 149s the more I like it. It certainly has a very 3d, clear and precise soundstage, all of which plays to the 149s strengths. I gave their tweeter pots the very tiniest nudge up last night, barely a degree or two, which has opened things up even more without bringing any over-brightness. I’m surprised how well the passive attenuation is working, it is not sounding undynamic at all, both from a short drum hit etc perspective and allowing the real ebb and flow of say live Jarrett to shine through (he is a master at dynamic shading etc). I’m not sure how the ProPassion responds with regards capacitance etc being a shunt attenuator. Maybe it is happier at this much lower (i.e. louder) attenuation range of the dials (typically -12db).
 
Sorry - I was referring to this in the diy section: (If you can "quote" across forums I'm not sure how....)
DIY Sony VFET kit store information page...

If I want to actually get any work done here, I have to turn the music off. 'Background music' isn't an option - which is as it should be.:)
 
Just been trying the Verdier against the Audio Synthesis ProPassion through the Pass and 149s and it’s really interesting. No clear winner, more a taste thing. The Verdier being a bit warmer and friendlier, the stepped attenuator just astonishingly clear and open. Both sound great, I could easily live with either. I suspect the better the source material the more things tip to the AS, the more average the more it tips to the Verdier (which can make pretty much anything sound great). They both sound great and far closer than one might think. The thing I was very pleased about is there is absolutely no hint of dynamics being sat on with the passive. It really is punchy in this context, so I assume the minimal attenuation of the CD player signal produces an input the Pass is happy with, and it goes as loud as I’d ever need with a digital source.
 
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No, not at all - there is an awful lot of thermal mass to be brought up to temp; and while that happens- all of it is designed to reject heat efficiently (by convection.)

I think the more interesting question is to wonder why being 'warm' makes such an obvious difference - when it really, really should not. At all.

(to the extent that - if temp is the determinant - covering the thing with a teatowel, to bring it up in 10mns from a cold start should be no different to wasting 2hrs and 0.4KwH on 'warmup')



PS - This is no slight on what it may or may not be in terms of enjoyment!


Not really a BJT varies it’s current gain by a factor of about eight over its temperature range, MOSFET gain doesn’t vary as much but the threshold voltage changes a lot, SITs are quite benign but I think the gain drops slightly as the temp rises and as for electrochemical capacitors, chemical reaction rate doubles every ten degrees temp rise. I remover one guy fitting the wrong spec capacitors to a display and it would be just random patterns and then suddenly a picture would appear as the ESR of the caps dropped and the smoothing on the reference for the ADC supply came within spec. In low feedback amplifier designs any parameter changes will be much more noticeable.
 
There’s a service manual here with a schematic. Assuming it arrives safe and sound and works ok I’ll work on the assumption that I’ll eventually at least recap it, check the heatsink gloop is still gloop etc, and probably try and find a full set of the power mosfets to keep safe as a spare. Apparently it used very good quality Panasonic caps which seem to have lasted well/better than expectations, but even so they are likely getting tired by now. I’ve yet to find evidence of folk having issues these amps despite the age, but I’ve not read the whole internet yet. I’ll pop the lid and if nothing is obviously leaking or bulging and the DC offset looks reasonable I’ll assume it is safe for a while. I’ve also got a heat meter so I can spot if it is running too hot.

The MOSFETS are obsolete, about the only place I would trust is Rochester Electronics but they have a high MOQ. When I wanted some hard to find mosfets I had to try aliexpress and eBay, I got them eventually but about half the deliveries had to be scrapped as they were fakes, get a transistor tester and see how a kosher one measures with it, one that measures capacitance, threshold voltage, gm etc and you should be fine.
 
The MOSFETS are obsolete, about the only place I would trust is Rochester Electronics but they have a high MOQ. When I wanted some hard to find mosfets I had to try aliexpress and eBay, I got them eventually but about half the deliveries had to be scrapped as they were fakes, get a transistor tester and see how a kosher one measures with it, one that measures capacitance, threshold voltage, gm etc and you should be fine.

Given just how good Pass support is and the whole community around it I’m not going to bother. If it ever dies it can be fixed, of that I’m certain. I’ve been doing a real deep-dive of the DIYAudio Pass room and I have yet to find a single reference of a real Aleph 3 needing anything more than a recap, they seem remarkably robust for something that runs so hot. Pretty much bomb proof. There also seem to be several substitutions that people use when building clones with arguably better properties, so if it ever does blow up I could likely get it working nicely if Pass themselves didn’t have any of the Mosfets to sell me. I’m certain I’d get a lot of help and it would end up working again.

I’ve been reading a lot. I’m obviously way, way, way out of my depth lurking on DIYAudio (when it comes to electronics I’m neat and tidy, very careful, but I know nothing - I can just follow instructions, that is all), but I’m gaining huge respect for Nelson Pass. He has an amazing attitude. A very clever, generous and decent bloke. This industry would be a way better place with more folk like him in it.
 
Given just how good Pass support is and the whole community around it I’m not going to bother. If it ever dies it can be fixed, of that I’m certain. I’ve been doing a real deep-dive of the DIYAudio Pass room and I have yet to find a single reference of a real Aleph 3 needing anything more than a recap, they seem remarkably robust for something that runs so hot. Pretty much bomb proof. There also seem to be several substitutions that people use when building clones with arguably better properties, so if it ever does blow up I could likely get it working nicely if Pass themselves didn’t have any of the Mosfets to sell me. I’m certain I’d get a lot of help and it would end up working again.

I’ve been reading a lot. I’m obviously way, way, way out of my depth lurking on DIYAudio (when it comes to electronics I’m neat and tidy, very careful, but I know nothing - I can just follow instructions, that is all), but I’m gaining huge respect for Nelson Pass. He has an amazing attitude. A very clever, generous and decent bloke. This industry would be a way better place with more folk like him in it.


Yes, the Pass community will let you know what replacements will work. Incidentally the IRF244 is metal can and the IRFP244 is the plastic version, I think metal can look the business in a class A amplifier but the plastic package will work fine, you would maybe need to drill a hole to make sure it dissipated heat efficiently, having said that if used properly the IRF244 is as tough as old boots and unlikely to fail in normal use.
As regards to Nelson Pass it’s interesting to see how much he has given away for nothing compared to how little John Westlake has given us for a hundred odd thousand euros!, Adam Worsfold as well for that matter.
 


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