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Old 17th May 2005, 11:28 AM   #1
Sony is offline Sony  Europe
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Default Pass Aleph 0s capacitors

Hi!

I am considering refreshing the capacitors of the secondary system of my Pass aleph 0s.
According to service manual original capacitors are 4x 31.000uF, and the secondary DC voltage is approximately plus and minus 40 volts.

What replacement capacitors do you recommend (without changing the bridge rectifier or anything else):

- 33.000, 39.000 or 47.000uF?
- 50, 63 or 80V?

Thanks and regards!
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Old 17th May 2005, 12:19 PM   #2
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Sony,

>> Pass aleph 0s. original capacitors are 4x 31.000uF, and the secondary
>> DC voltage is +- 40 volts.

>>What replacement capacitors do you recommend (without changing the >>bridge rectifier or anything else):

>> 33.000, 39.000 or 47.000uF?
>> 50, 63 or 80V?

Keep the same voltage > or = 45 volts but 80v is not necessary and costly!
check for 85 degree C at > 2000 hours or 125 degree C at > 2000 h types
and considering the size go as high as you can in microF ...

But the original size is already a very good package.!!!

Regards.

Alain
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Old 17th May 2005, 03:56 PM   #3
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Thanks Alain.

Main idea is to refresh the original caps, since they have already done their job.
Since caps got smaller, I can use equal size ones with higher capacitance, if there are any sonic advantages on doing so, like better performance on low frequencies (?).

So, I will fix 63V for a better lifetime, 105Cdegree to resist well to those high temperatures inside this amp.
The decision will be between 39.000uF and 47.000uF...

What sonic advantages can I expect from raising the cap. in the Aleph 0s or in an Aleph 3, which I also own?
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Old 17th May 2005, 05:51 PM   #4
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Sony,

What sonic advantages can I expect from raising the cap. in the Aleph 0s or in an Aleph 3, which I also own?

There are several approches to this:

- A lot of little cap's ~ 8 to 10.000 microF to lower the global impedance
- A few big cap's 2 to 4 * 30.000 to 50.000 microF type "Computer grade"

Don't hide a thing, you are in a Class A amplifier, the dynamic comes from the speed and quality of the power MosFet used. Currently the power supply is here in a stable state, the current is used for the Bias. But it is asked to compensate the adjustable bias for peeks then the supply caps have to do their work. Question: Do you use it hard ; often at full power or at low levels?

The designs of Mr Pass are maximized ; so I think there is little place for tweaks, and the caps are a way to get a little more "punch" so choose cap's
of high quality and low impedance to get something more in this operation.

Good luck with your tweaks.

Alain.
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Old 17th May 2005, 08:43 PM   #5
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Alain, thanks once again!

I understood your message - the amp is balanced and more uF won't really make any difference.

Answering to your question, I don't use it hard, but I use it with difficult loudspeakers that really need power and current to give their best. Without current, the metalic woofers won't bring out the music dynamics with speed and transparency.

The Aleph 3, for instance, just can't handle them - too short of power/current. Bass loses all the definition and depth. Can only use it on the tweeter, where it is brilliant.

The Aleph 0s does a fine job with the metallic woofers, but I feel there could still be place for some improvement (on the sound, probably not on the 0s).

Regards
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Old 17th May 2005, 09:23 PM   #6
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Since I must use 2.5" diameter caps (as original ones), so that the distance between screw ports matches the PCB, from my capacitor supplier, I've found out the available caps with compatible size have much higher uFs...

My new question is:
- Can the aleph 0s handle 4 x 68.000uF without any other circuit/component modification?

(original caps are 4 x 31.000uF)
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Old 17th May 2005, 09:33 PM   #7
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If you want to make an upgrade, look into a top grade PSU cap like the Rifa PEH169, they have become obsolete a few years ago, but there is a Swedish guy who sells them at VERY low prices. As far as I know those are the best PSU caps out there, and for the price Svalander is offering them, they are even the only reasonable choice.

Magura

EDIT: oups, forgot the link : http://www.svalander.se/shoppen/lytar.htm
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Old 17th May 2005, 09:45 PM   #8
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Quote:
Originally posted by Sony
I understood your message - the amp is balanced and more uF won't really make any difference.
I don't think that's correct. The amp has a balanced input, but
is otherwise ordinary in that regard. More capacitance will
lower the ripple on the supply, and if you really want to go to
town you can consider some sort of CRC filter with the 4 caps
that come with it.

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Old 17th May 2005, 09:52 PM   #9
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My take at this (considering that I have just figured that svalander is out of PEH169's) would be PEH200-40V-68.000uF and making it a CLC filter with 2mH inductors.

That's cheap easy and probably the best solution there is.

Magura
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Old 17th May 2005, 10:28 PM   #10
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Mr. Nelson, Magura, thanks for your posts!

When you refer a CRC filter are you considering adding extra caps? If that is the case, there is an obstacle - There is not much space left inside the Aleph 0s chassis for extra caps...

Since you didn't mention any possible complications on the extra capacitance (on the contrary), I will consider to use caps of 68.000uF or 100.000uF and will try to learn more about the filters in the meanwhile.

Mantura, since the DC voltage is +-40V, using 40V caps couldn't be dangerous to the point of making the caps explode?

When I used the term 'balanced' what I meant was 'well projected, made with the right parts, hard to improve'.

I was initially considering Nippon chemi-con caps as I can get them from a local dealer. I suppose these must be inferior to those Rifa, correct?
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