Help with re-capping Pass Alephs 2's

just missed out on Jim’s Pass Aleph 2’s, but should be a getting a pair from Italy! I don’t think they have had any work, so my question is does anyone know good replacement caps for the power supply section. I would imagine they will benefits from replacing. Also are they soldered onto the circuit board or bolted? Any info or folk that have worked on the amplifiers would be gratefully received. I am also getting a preamp p and ono phono. Should be interesting to go with my Impulse H2’s.

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Yep, I had a PM from David last Saturday at the bake, about 20 minutes after @thebiglebowski said give me your bank details and I’ll take them with me!

I almost bought them to go with my Impulse Ta’us, I don’t think you can go far wrong.

You need to start by letting us know what components are currently used in the PSU.

Generally it’s worth improving the smoothing caps (improved ripple current behaviour), the bridge diode/s (low noise/soft recovery) and voltage regulation (World’s your oyster).

Something upstream of the PSU to remove HF and DC offset from the mains is worth indulging too - and doesn’t necessarily need soldering skills.

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And stones? You need some stones.

I don’t have the amps in hand yet. Hopefully they will be on their way to me next week. All I was looking for initially was a straight swap out of the main power caps like for like. But I don’t know what is in there right now. Thought someone might have had experience with this amp to answer from first hand experience. If not, I can open up and see what is in there…

Is this one of those Naim style re-cap every six months discussions?

No

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Not intended, just reckon a class A amp over 20+ years old, these caps will be well passed their design life. I actually have had an old NAP250, and the hum was very noticeably before replacing old power caps too. So just looking for practical advice on what caps can be used to replace old ones, so I can order them…

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I don’t believe you.

This is pretty sensible given how hot these run - though electrolytics can last a lot longer if they’re good quality :+1:

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I will listen to them, and if quiet when they are meant to be, I will not rush out and replace.

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It might be worth checking the tops and bottoms (if you can see them) for signs of bulging. If the tops look suspicious though then try pressing on them gently - it might just be that the thin plastic disc which insulates the top has domed up. If so then it will squash down easily and is nothing to worry about.

If you can see the temperature rating on the caps then that would be worth noting too. The design life of an electrolytic cap roughly doubles for every 10 degrees C that it’s run below its labelled rating. So 85C rated caps which are run at 55C (too hot to keep your hand on) should last 8 times longer than their design lifetime. Running them below their rated voltage helps a lot too.

VB

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very good advice, thanks

Not shakti. Fail.

Is this the sort of thing you had in mind?

https://airlinktransformers.com/category/advanced-filter-power-supply

Those look good quality, but I wouldn’t use a transformer for that job unless it was also needed to step-down mains voltage, and then I’d deffo want DC blocking upstream of it :+1:

So what sort of things do you rate?

I know studios often utilise balanced PSUs and are becoming more common in home audio, is there a downside to them?

Congratulations by the way, where is the stag bake and what time are we dining on the big day? :wink:

Yes, they’re potentially dangerous, unless the equipment is designed with Baka fed power in mind. Hint: pretty much all domestic equipment isn’t.