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Pass Aleph 3

I don’t think so. It looks like the transformer is ‘glooped’ to the bottom panel, I assume to help deaden vibration (it is physically very quiet for such a large unit). It does need dismantling anyway to do the smaller caps, i.e. I need to take the heatsinks off and release the four vertical boards anyway. The only thing I can’t work out is just how much slack there in in the transformer wiring to the PSU board. I’m hoping I don’t need to desolder that board, but I’ll figure that out later.
 
One nice thing is the four vertical boards are all subtly different so hopefully I can’t make any mistakes putting them back later, they each obviously go in one location!
 
PSU done…

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Heatsinks off.

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Front and left boards removed.

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Gaining access, which remained tight. Thankfully I could squeeze the Hakko in and didn’t accidentally hit any wires, which was quite a risk.

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New caps going in. All done now. I’ve just got the little ones to do after lunch, and they are easy access so that won’t take long. Then reassembly and testing….

PS I honestly can’t recommend a proper vacuum desoldering tool highly enough. This would have been a bloody nightmare without the Hakko FR301.
 
Plenty of thermal paste between the output devices and the alloy u-shaped beams, but no evidence at all of it between the alloy beams and heatsinks. I’m kind of tempted to add it, but I detest the stuff and I know I’d get it everywhere. It obviously wasn’t part of the original design. I’ll not add it now, but I may consider doing it later.

PS Small caps done, next reassembly…
 
All now done…

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Boards all soldered back in.

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Bolting the heatsinks on and aligning everything (actually quite fiddly to get everything square and all panel gaps the same).

Seems fine, no explosions or anything and an expected amount of DC offset on the output. I’ll not try it in a system until it’s cooked for a while.

The original little caps all seem fine, all pretty much bang on 220uF, so may have been a waste of time replacing them. My meter can’t deal with 22000uF, so no idea what they are like. They do look a bit bulged to me though. I have no way of testing leakage, ESR etc. This may have been a waste of time, especially given I couldn’t find the PSU caps I wanted (ideally Panasonic, Kemet or equivalent), but hopefully it’s all good for another 20 years or so moderate use. The next month or so will be deciding if it is something I want to keep or whether to flip it. I have to admit if it takes an hour to warm up that may be a deal-breaker for me even if I like it otherwise. All my systems sound great from cold at present, not sure I want to change that!
 
Nowt wrong with Philips BC caps. (My NCC200 has 6x4700 40V per channel running at +/-37V for over 10 yrs now)
Nice job Tony.
 
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Here’s a pic of one of the old PSU caps hopefully showing why I was concerned with the bulge. They all had signs, though none had actually crapped themselves yet. Two had popped their plastic tops off, and another was half way there (it fell off when desoldering it). I think these are definitely best out of the amp!

PS This is one of the ones that popped it’s plastic top, the ruler is on the bare metal top.
 
I can confidently say that recapping has improved it, and by quite some margin. It’s not been on long at all and it is sounding very good indeed. The ‘dead in the water’ thing isn’t there anymore, its grooving along nicely and it has some real size, scale and heft to it. I assume it was pretty obvious what I thought about it on first assessment upthread, but to put it bluntly the 303 absolutely killed it! Not the case now, it certainly sounds like my system again. It will take me a long time to learn what I like, what I don’t like etc, but it’s certainly starting from a better grid position. I’ll give it a proper listen tonight.
 
Here's my (dual mono) Aleph 5 incomplete with flatcap TSUs:

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I did recommission is a few months ago just to check if it sounded how I remember it the 1st time round.
 
Here's my (dual mono) Aleph 5 incomplete with flatcap TSUs:

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I did recommission is a few months ago just to check if it sounded how I remember it the 1st time round.
A tad OT, but S-Man, where did you get those heatsinks from please?

And Tony, that is one very good looking amp. Well done with the cap swap.
 
A tad OT, but S-Man, where did you get those heatsinks from please?

And Tony, that is one very good looking amp. Well done with the cap swap.

They were a slice from a huge heatsink for serious power electronics (100s of KVAs). I chopped the slice in two.

I just found a pic of the Aleph assembled (as a prototype). Originally I used CLC filtering, but removed the Ls for this Mk2:

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Listening notes/impressions #1:

I’ll document this here just to see how my opinion changes over time. I gave it a good listen last night and as the neighbour is out I’ve got a couple of hours on it today too.

First off I’m far from convinced the synergy with my main system is good. I’ve long felt that vintage speakers are voiced for the amplification of their era, i.e. these Tannoys dating from the late-60s will have been voiced for valve amps and early transistor designs such as the Quad 50E and 303. The common denominator here is a little output impedance and comparatively low damping factor. The ‘modern’ (i.e. after the market change to inefficient little ported speakers) solid state I’ve tried are just totally wrong to my ears, e.g. I tried a Naim 42/110 with my first Monitor Golds and more recently my (lost in the Onix scam) OA21S, both of which sounded terrible in this context; thin, flat, small, gutless and without swing or groove. The valve stuff I’ve tried (Prima Luna Prologue 2, Leak Stereo 20, Radford STA15) sounds great, as does the Quad 303.

The Pass seems to sit between the two schools. It is really detailed and clear, remarkably so in many ways, but it is also a bit restrained and dark in this context. Too measured somehow. By saying that it is also really, really good. I stuck Spanish Key from Bitches Brew on last night, and it picked the bones out of it very well indeed. This is a dense and busy recording with a lot going on and it takes a very good system to retain the scale, drive and heft of it whilst allowing the various bass lines to be easily followed. The Pass did this very well. I’ve flung all kinds at it, mainly jazz, classical, rock, though also some pretty full-on techno etc.

I also tried it with my Audio Synthesis ProPassion single input stepped attenuator passive. This was rather interesting as, contrary to expectations, it worked rather well with the DPA PDM3 upstream. I ended up with it about half-open into the Tannoys (typically about 24db attenuation). It told me what I already knew about my Verdier preamp, that being that it sounds like a valve preamp; it is warm, fat, spacious and big-sounding. It’s a lovely thing currently stuffed with a few £hundred worth of vintage Mullards, though I’d not argue it was 100% transparent (like I care). The combo of the Verdier with the 303 in this system is superb, but in some respects I preferred the passive with the Pass as it sounded less dark and the bass was maybe more in balance. It’s surprisingly close though. It would be interesting to try an equivalently high-end solid state pre with the Pass.

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.

Clearly a seriously good amp, but maybe not where it is right now. As ever system synergy is everything, and it was very good beforehand. As stated I’m going to leave it here for a good while to get used to it, but after that I’m very interested to try it with the JR149s as I suspect that could be a very good match indeed.
 
I suspect I’d like it a lot. I’ll have to come round for a listen, not sure I’ve got a free weekend until November now though!
 
Those temps are not too bad at all for a Class A amp. I guess the issue is it will be running at over 200w even idling, and needs a decent warm up period.

Probably needs to substantially better the 303 to justify the ongoing cost.
 


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