Pass Aleph 3
- Thread starter Tony L
- Start date
Tony L
Administrator
No, I’ve not seen the Listener review. I’ve read the Stereophile review and the ETM review of the Aleph 30.
One thing I certainly think I agree with from most reviews and comments I’ve read based on the past hour or so through the Verdier/Tannoy rig is it certainly takes some warming up. Dead in the water cold, no groove, no funk, it just sits there having no fun at the party. I’m now about an hour in and it’s now sounding decent. It also made a rather disturbing fart/buzz on boot-up which I guess could be an inrush/tired caps thing (it went after maybe two seconds). I actually thought I had an earth loop until it just went!
Anyway I’m going to assume it desperately needs a full recap and take it out of the system until I’ve done that. Really I just wanted to establish it worked, which it does, so a fair eBay sale. The restoration is on me, and thankfully that looks pretty easy; eight big caps, six little ones, and nothing to adjust. The construction is a bit awkward, but I think I’ve figured out how to get at everything (I’ve got a proper desoldering gun so I can be very quick and neat). It will just be an afternoon’s work.
One thing I certainly think I agree with from most reviews and comments I’ve read based on the past hour or so through the Verdier/Tannoy rig is it certainly takes some warming up. Dead in the water cold, no groove, no funk, it just sits there having no fun at the party. I’m now about an hour in and it’s now sounding decent. It also made a rather disturbing fart/buzz on boot-up which I guess could be an inrush/tired caps thing (it went after maybe two seconds). I actually thought I had an earth loop until it just went!
Anyway I’m going to assume it desperately needs a full recap and take it out of the system until I’ve done that. Really I just wanted to establish it worked, which it does, so a fair eBay sale. The restoration is on me, and thankfully that looks pretty easy; eight big caps, six little ones, and nothing to adjust. The construction is a bit awkward, but I think I’ve figured out how to get at everything (I’ve got a proper desoldering gun so I can be very quick and neat). It will just be an afternoon’s work.
Tony L
Administrator
Here’s a fully clothed pic including the aforementioned blue LED. Really quite subtle, certainly not the hideous helicopter landing lights Musical Fidelity etc stick in their kit.
Not crazy hot after one and a half hours. I guess it stabilises here unless the ambient temperature is higher. It certainly doesn’t kick out the heat of the larger Krells etc.
Well it must rank as one of the coolest looking solid state amps ever for me at least. Knowing it comes from Nelson Pass is reassuring I think. And as noted he provides so much information to the audio community. I don’t think it’s been running due to Covid? But the Burning Amp Fest in the Bay Area always seemed very cool event for DIY. You probably know about the kit amp as well that either comes from Pass or was inspired by him and uses his design. Steve Guttenberg featured it in one of his videos.
Tony L
Administrator
I very nearly bought the Amp Camp Amp kit a few years ago as it looked like such fun, but I came to the conclusion 8 Watts wasn’t enough for me, the Leaks being valve seem more powerful for their 10-12W, and I’ve got lots of those. This Aleph 3 makes way more sense to scratch that itch and would be far easier to move on at little/no loss should I wish to down the road. The fact Nelson Pass is so much a part of the audiophile community and such a positive force from an intellectual property and support perspective was a *huge* factor in this purchase decision. Thanks to his attitude this is a high-end amp I am confident I can restore to a professional level myself, and it doesn’t get much more Right To Repair than that.
Yank
Bulbous Also Tapered
The ones in there now appear to be Panasonic TSU, I wonder if direct replacements are still available? Digi-Key are Panasonic component specialists.
Tony L
Administrator
I’m struggling to see any Panasonic TSU available anywhere, googling brings up nothing.
I’ve found these Nichicon at RS which look to fit at 25mm diameter, 105c, though only in 25V and as Rob suggests I would like to up that a bit, say to 35V if possible. These Vishays are contenders too, as are these more expensive shorter fatter ones (I bet I can get 31mm in!). By saying that it has lasted 25 years on its original caps! If I could find the right Panasonics I’d be very tempted to grab them as that way you’d never know I’d been in there short of reading date-codes! The Vishays seem to have a better lifespan plus are 10mm lead pitch, the Nichicons are 12.5mm, which depending on style of lead (e.g. ‘snap on’) may be a deal breaker.
PS The RS site is good that you can search by multiple parameters, e.g. diameter. I find some of the others impossible to navigate.
I’ve found these Nichicon at RS which look to fit at 25mm diameter, 105c, though only in 25V and as Rob suggests I would like to up that a bit, say to 35V if possible. These Vishays are contenders too, as are these more expensive shorter fatter ones (I bet I can get 31mm in!). By saying that it has lasted 25 years on its original caps! If I could find the right Panasonics I’d be very tempted to grab them as that way you’d never know I’d been in there short of reading date-codes! The Vishays seem to have a better lifespan plus are 10mm lead pitch, the Nichicons are 12.5mm, which depending on style of lead (e.g. ‘snap on’) may be a deal breaker.
PS The RS site is good that you can search by multiple parameters, e.g. diameter. I find some of the others impossible to navigate.
Werner
pfm Member
Ever since COVID bit I found parts availability bordering on the problematic. It may be that you will need a bit of patience for this patient.
Here is a quick first selection at Mouser:
https://www.mouser.be/Passive-Compo...zm175Z1yzmxstZ1yx4atvZ1ypb2ikZ1z0vn3sZ1z0vhz5
And yes, I would certainly aim at 105C and 35V!
Here is a quick first selection at Mouser:
https://www.mouser.be/Passive-Compo...zm175Z1yzmxstZ1yx4atvZ1ypb2ikZ1z0vn3sZ1z0vhz5
And yes, I would certainly aim at 105C and 35V!
earlofsodbury
Wastrel.
I'm on a similar cap hunt and am finding operating temp is a bit of a red herring as it's an expression of life-at-temperature, so (e.g.) 13,000 hours at 85C is going to be better in this application than 3,000 hours at 105C, since the amp will never approach either temperature unless you have a house fire (and I presume you don't own any NVA...).
I would also suggest not getting too hung-up on absolute capacitance, as it's already so far overspec that I suspect you could lose 50% and not get an iota more ripple through.
I do strongly agree that uprating the operating voltage would be sensible.
Kemet do some nice 20,000uF 40VDC caps of the right size, but unobtainium SFAICS.
I would also suggest not getting too hung-up on absolute capacitance, as it's already so far overspec that I suspect you could lose 50% and not get an iota more ripple through.
I do strongly agree that uprating the operating voltage would be sensible.
Kemet do some nice 20,000uF 40VDC caps of the right size, but unobtainium SFAICS.
Tony L
Administrator
A lot of stuff looks to be listed that isn’t in stock with crazy back-orders etc. The only 35V 22000uF cap with a 105C rating that I can find so far that will fit is this Cornell Dubilier at Mouser, which is zero stock and a 25 week lead time. I can get the Vishays I linked above within a day from RS! If we really are looking at a out of stock/vapourware situation I’m tempted just to replace like for like with 25V 105C. As I say it lasted for 24 years with the original ones, though in fairness I bet those Panasonics are better than the vast majority of caps today. I’ll keep looking and I’m open for suggestions, but I don’t see the point of waiting for stuff that may not even exist. It is all high quality glass-fibre boards and I’ve got a Hakko desoldering gun so doing it all again in ten years or so isn’t a terrible option.
martin clark
pinko bodger
TBH Tony - I would fire it up, as it is - those caps look fine.
Watch the DC offset for 1/2 an hour; plug it in, and play music for some while/days to get a handle on what it does you like - then either enjoy now and then while you wait for parts to arrive; or not, if otherwise for any reason.
It's not going to immediately detonate on you: very, very far from it. Pass has long-used a CRC layout on the PSU boards, so it's the first two from the rectifier that might have had the hardest life on ripple current loading, and they appear to show nothing untoward.
Watch the DC offset for 1/2 an hour; plug it in, and play music for some while/days to get a handle on what it does you like - then either enjoy now and then while you wait for parts to arrive; or not, if otherwise for any reason.
It's not going to immediately detonate on you: very, very far from it. Pass has long-used a CRC layout on the PSU boards, so it's the first two from the rectifier that might have had the hardest life on ripple current loading, and they appear to show nothing untoward.
S-Man
StrivingON
If the amp has not had much use the electrolytics could all be fine. I suggest measuring them with an ESR meter before changing them. Even an in-situ measurement should give you some idea of the state of them.
It is also worth measuring the supply voltage next time you have the lid off. Then you will know if 25V is fine. If your mains is at 253V and the measured voltage is <25V then you will be fine with 25V "working voltage" caps. If your mains is lower then simply adjust the ratio to ensure the voltage is OK.
You could also measure the supply ripple using the AC setting on your DVM. It is possible to determine the "correct" amount of ripple (at 100Hz) based on current draw and total capacitance.
Not sure if this amp uses CRC or just lots of C.
I believe Pass uses a varistor to limit the inrush current. Point your thermometer at the disc thingy on the cap board - it should be pretty hot when the amp is on.
I will be interested to read if the Aleph floats your boat medium/long term.
It is also worth measuring the supply voltage next time you have the lid off. Then you will know if 25V is fine. If your mains is at 253V and the measured voltage is <25V then you will be fine with 25V "working voltage" caps. If your mains is lower then simply adjust the ratio to ensure the voltage is OK.
You could also measure the supply ripple using the AC setting on your DVM. It is possible to determine the "correct" amount of ripple (at 100Hz) based on current draw and total capacitance.
Not sure if this amp uses CRC or just lots of C.
I believe Pass uses a varistor to limit the inrush current. Point your thermometer at the disc thingy on the cap board - it should be pretty hot when the amp is on.
I will be interested to read if the Aleph floats your boat medium/long term.
Tony L
Administrator
The tops are very obviously bowed up, it’s actually visible in the ones that have lost their plastic top-caps in the pic, you can see a very distinct arc in the cross-hatch. I’d say they were all about 1.5mm up from being square. This concerns me as with computers etc it is a sign the thing is about to crap itself all over the mainboard! Obviously you know *way* more about this stuff than I ever will, but the tops of these are anything but flat. In comparison the little 220uF ones look absolutely fine based on what I saw behind the heatsinks I removed.
I’ve already taken it back out of the system, shelved it (it will actually fit in an Ikea Expidt!) and I’m really hoping there are some suitable in-stock caps out there somewhere and I can get it boxed off next week sometime. I’d be interested to hear what you & Rob think of the Vishays at RS. They are available and will fit!
It is in nice condition, but I suspect it has certainly seen some use, the caps wouldn’t be bulging if it had just sat in its box, plus there is some evidence of ‘purpling’ to the heatsinks which is apparently what happens to these with use. Annoyingly I haven’t got an ESR meter, only a multimeter (and an oscilloscope). The whole thing about the way this thing is constructed makes me want to just replace the caps once I’ve got it far enough apart to test. To get to the main PSU cap board really does involve full disembowelment and a fair bit of desoldering as part of that process.
Yes, there are two of them in there.
No idea at the moment. I only really want to judge it after the rebuild. My impression so far is I don’t think much of it cold, but it certainly starts to open up and get some groove after a while. So far, and I know no one will believe me, but it really wasn’t worrying the 303 much! After a good hour running it was getting there, and it clearly does some things very well indeed, but there is something very restrained about it before that point, and that didn’t entirely go away. This particular 303 (which has far larger coupling caps than normal and is a totally obsessive rebuild) just swings into Tannoys. It has the funk, sounds big and punchy, and great at low levels. I just kept wanting to turn the Pass up to get the impact I’m used to (I’ve got a sound meter handy so I know where I was). Some of this may be psychological as I just don’t trust a 25 year old notoriously hot-running amp with obviously bulging PSU caps into a pair of such valuable and exceptionally hard to replace loudspeakers!
Once rebuilt I’ll certainly get to know it properly and leave it in the system as a daily driver for a couple of months to get used to it. I’m naturally very patient with this sort of thing, so I’ll wait until I’m confident everything is exactly as it should be and then give it a fair chance.
S-Man
StrivingON
WRT the bulging caps - I had some in my Leach amp which runs very cool. They were running at 60V and rated and 63WV - so maybe I don't know much about caps 
. I replaced them anyway.
OTOH I seem to recall tales of the chap at Sugden telling people off for replacing bulging caps in their amps
I think I would play safe and replace them.
Regarding the sound, I have been biting my tongue and really wanted you to form your own opinion, which I'm sure you will anyway.
In another thread somebody was asking for an add-on dc offset protector. This would be easy to build but surprisingly they don't seem to exist as a finished unit. This would be ideal for protecting cherished speakers.
. I replaced them anyway.OTOH I seem to recall tales of the chap at Sugden telling people off for replacing bulging caps in their amps
I think I would play safe and replace them.
Regarding the sound, I have been biting my tongue and really wanted you to form your own opinion, which I'm sure you will anyway.
In another thread somebody was asking for an add-on dc offset protector. This would be easy to build but surprisingly they don't seem to exist as a finished unit. This would be ideal for protecting cherished speakers.
Tony L
Administrator
They exist and are called valve amplifiers!
Robert
Tapehead
The big Vishays have almost identical specs so go with the cheapest.
My go-to small caps were always Panasonic FC but FM are also excellent and probably slightly better in most situations.