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Pass Aleph 3

The Aleph 3 definitely gets better the longer its been on with either preamp. After two hours it’s at 44-48 degrees C depending on which face I point the IR thermometer at.

I remember my Mark Levinson ML2 Class A monoblock amps, now long gone, took at least 2 hours from switch on to start sounding good...
 
dateposted-friend

Just came across a picture (which I can't seem to post unfortunately) of an Aleph3 with a pan on top and two eggs frying. :D
All the diy build guides tell you to set o/p bias after an hour or so, which generally means at ambient temp + 25C, so in use taking a while to come on song makes perfect sense.

Having a possible heat transfer issue with the Pass amp I've switched back to the Meridian temporarily. It used to be my 'ultimate' choice - it still has all the same virtues and yet is somehow much less involving. With the VFET every track felt like a performance. How do you measure that I wonder?
 
@davidjt - Was this the egg picture?

CFE5C751-4F1C-4CB8-BC44-3E61A44FCBD2.jpeg.520707e2fd455bc8970f091fc4088c45.jpeg


Photo poster comments:

"The amp is a 30W (into 8 ohms) fully biased Class A single ended design and I have used it to drive a number of speakers (although speakers which dip into 2 ohms territory may struggle). It is extremely musical - later Pass Labs amp tend to be less lush. The preamp is an excellent match for the amp. The combination produces what I consider to be Pass' archetypical sound - musical, sweetness in the mids, holographic soundstage. I remembered the first time I heard it - just Wow. There are drawbacks of course - the amp does get quite warm and needs a bit of ventilation space (no, it won't fry an egg - tried that). It takes about an hour to warm up to its best. And it sucks a lot of current even while idling. But as Nelson Pass will say, who cares as long as it sounds good!"

Nelson Pass' comment about the different Aleph amps:


"The Aleph 2 was my favorite in terms of neutrality and all-round compatibility. The Aleph 0 would drive anything, The Aleph 1 had the most power, and the Aleph 3 was the best for full range and mid/high applications."

http://www.diyaudio.com/forums/pass-labs/158580-aleph-power-amp.html
 
Must admit the J2 fails NP's touch test ("You should be able to hold your finger on the heatsink for at least 5 seconds") even on-idle, so I will check the biasing at some point; sounds fine and stays steady at that slightly-elevated temp, so no real worry. Perhaps I'm just a wimp...?
 
My Aleph 3 hasn’t measured more than 49c yet, and that’s right by the mosfets, the majority of the heatsink is cooler. Thankfully nothing to adjust in this model, it just is what it is! I’m pretty certain it is working exactly as it should now it’s been recapped.
 
Yes, that was the picture.

My concern about the VFET is that the heatsinks weren't as hot as I think they should be. The two FETs are bolted to an aluminium bracket which is in turn bolted to the sink, and I think that second interface may need attention. Missing it already.
 
My Aleph 3 hasn’t measured more than 49c yet, and that’s right by the mosfets, the majority of the heatsink is cooler. Thankfully nothing to adjust in this model, it just is what it is! I’m pretty certain it is working exactly as it should now it’s been recapped.

That's not bad at all for a fully Class A amp.

My Rega Elicit sits at a constant 48 idling and moves into the the low 50s at average listening levels, again at the heatsink hotspot.
 
That's not bad at all for a fully Class A amp.

The heat-sink as case design is very cool, I love the look of it, just total ‘form dictated by function’ but with a nice brutalist aspect too. It is only a little amp though, just 30 Watts. The 23 Watt Sugden A21 is not that much less powerful and has but a fraction of the heat-sink area. I remember the past (‘90s) generation of Sugdens getting very hot, to the point you’d want to let them cool a bit before moving them. The Pass feels fine, you could pick it up at full temp without hurting yourself at all. This is relative I guess, e.g. running the Pass in an Australian or African climate likely gets it a good bit hotter (Leak valve amps tended to leak transformer goo in such climates if in enclosed spaces!).

I’m surprised the Rega gets that hot being (I assume) class AB, though it is way more powerful. Are the output devices mounted on the case sides like Sugdens?
 
The heat-sink as case design is very cool, I love the look of it, just total ‘form dictated by function’ but with a nice brutalist aspect too. It is only a little amp though, just 30 Watts. The 23 Watt Sugden A21 is not that much less powerful and has but a fraction of the heat-sink area. I remember the past (‘90s) generation of Sugdens getting very hot, to the point you’d want to let them cool a bit before moving them. The Pass feels fine, you could pick it up at full temp without hurting yourself at all. This is relative I guess, e.g. running the Pass in an Australian or African climate likely gets it a good bit hotter (Leak valve amps tended to leak transformer goo in such climates if in enclosed spaces!).

I’m surprised the Rega gets that hot being (I assume) class AB, though it is way more powerful. Are the output devices mounted on the case sides like Sugdens?

It's quite heavily biased into Class A (for an AB amp) as it draws nearly half at amp at idle.
The Elicit has finned sinks either side running the depth of the case and the transistors bolt straight on.
 
Just spent the morning comparing the Pass to the TL12 Plus via the 149s. It really is fascinating, no clear winner, more a character thing.

The little Leaks are just so crisp and alive, they sound huge, are really happy at low volumes and I just instantly relax with them. There is something just so ‘right’ about the way they do things. They make me shake my head in disbelief, they really are crazy good.

The Pass snaps things more into tight focus; it is astonishingly clear, very spacious, plus I think it is more dynamically capable so does tend to be more critical of recordings. It seems to want to play a bit louder to get the same ‘impact’. I guess the Leaks are bringing just a little valve compression, but in a way that sounds wonderful. There is also a difference in noise floor, the Pass is absolutely silent, I can’t hear anything with my ear to the speaker, the Leaks have just a very tiny bit of hiss/hum as you’d expect, but nothing intrusive even in the extreme nearfield.

Bottom line: they are both seriously good. They just present a surprisingly different window onto what is happening.

PS The Leaks certainly demonstrate how mature power amp technology actually is. They date from the mid to late-50s and are not embarrassed at all in this company. I honestly couldn’t tell you which was the “better” amp, they both do things I really like and value.
 
Just spent the morning comparing the Pass to the TL12 Plus via the 149s. It really is fascinating, no clear winner, more a character thing.

The little Leaks are just so crisp and alive, they sound huge, are really happy at low volumes and I just instantly relax with them. There is something just so ‘right’ about the way they do things. They make me shake my head in disbelief, they really are crazy good.

The Pass snaps things more into tight focus, it is astonishingly clear, very spacious, plus I think it is more dynamically capable so does tend to be more critical of recordings. It seems to want to play a bit louder to get the same ‘impact’. I guess the Leaks are bringing just a little valve compression, but in a way that sounds wonderful. There is also a difference in noise floor, the Pass is absolutely silent, I can’t hear anything with my ear to the speaker, the Leaks have just a very tiny bit of hiss/hum as you’d expect, but nothing intrusive even in the extreme nearfield.

Bottom line: they are both seriously good. They just present a surprisingly different window onto what is happening.

PS The Leaks certainly demonstrate how mature power amp technology actually is. They date from the mid to late-50s and are not embarrassed at all in this company. I honestly couldn’t tell you which was the “better” amp, they both do things I really like and value.

It’s the sort of thing I’ve heard with some of my amps. This is the sort of reason which makes me want to experiment with a switch for two amps into one set of speakers from one source. Imagine, the music doesn’t turn you on, you flick a switch, and bingo, a fresh window!

But these sort of switches feel so difficult to achieve! I’m never sure whether I’m going to damage something.

(Just had a weird experience, I fitted a Velleman DC blocker into the system with the Krell and ESLs - and it sounds better! That must be imagination surely?)
 
KSA 50. I'm using an Elcotrocompaniet ECI-2 as a pre.

Very nice. I like that first era of Krell a lot (aside from the fans!). The Pass reminds me of it in many ways, though I don’t think it has the same visceral slam or heft to it. It is just a more gentle take, though the Krells I’ve had the most experience of are all a lot more powerful (KSA100, KSA200 etc), plus very different systems and decades ago. Regardless to my mind there is a very identifiable ‘class A’ thing when it comes to the soundstage, acoustic space, air etc that I very seldom if ever hear from non-class A solid state. They just seem more 3d, spacious and believable, a substantial shift away from the ‘2d images hanging on a washing line’ of a lot of transistor amps. Nothing is ever just ‘a thing’, it is always ‘a thing in a space’. I recognise it from Sugden, Krell, the class A Accuphases, Luxmans etc. There is definitely something different about this approach and it is very beguiling despite the obvious inefficiency.
 
It’s the sort of thing I’ve heard with some of my amps. This is the sort of reason which makes me want to experiment with a switch for two amps into one set of speakers from one source. Imagine, the music doesn’t turn you on, you flick a switch, and bingo, a fresh window!

But these sort of switches feel so difficult to achieve! I’m never sure whether I’m going to damage something.

I have such a thing and use it all the time with a Yamaha B-2 vfet and a Musical Fidelity A1000 Class A at the moment.. get the levels exactly the same (via the MF Volume control in this pairings case) and I can switch between them really easily. It’s a brilliant tool for ‘upgrading’ (or sticking with what you’ve got as it happens!!….VFETFTMFW)

Beresford TC7210, speak to Stanley - it also has dummy load for a valve amp..
 
That's not bad at all for a fully Class A amp.

My Rega Elicit sits at a constant 48 idling and moves into the the low 50s at average listening levels, again at the heatsink hotspot.

My home brew class A amp output transistors sizzle if swipe a wet finger across them, I think the case temp is about 120C.
 


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