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-   -   Advice on capacitors in Pass Aleph 4 (http://www.diyaudio.com/forums/pass-labs/191290-advice-capacitors-pass-aleph-4-a.html)

Andy5112405 21st June 2011 04:56 PM

Advice on capacitors in Pass Aleph 4
 
1 Attachment(s)
After disappointing results with an Aleph 4 build, I think the culprit may be my choice of capacitors.

Can the capacitor experts have a nose at the diagram and make their recommendations for each of the 6 capacitors.

I can't see that C1, C8 and C9 make much difference as they are in the constant current leg.

C4, C11 and C12 may be more critical.

Mark Finnis chose:-
C1 = 103 Poly
C4 = 680pF Silverd Mica
C8, C9 = 220uF 35V Low ESR Radial Electrolytic
C11 = 220uF 10V Tantalum
C12 = 10pF Silvered Mica

With this combination I have awful sibilance on both channels.

Andy Bartha 21st June 2011 08:12 PM

I am far from being an expert but poor capacitor choices can cause major sonic problems which can be tough to chase down. I have done the same on a couple of these without a problem. The only cap that I wouldn't have used is the 220 tantalum. I would change it out for just about any decent quality 220 uf cap. A decent low cost option could be a Panasonic FM or FC, there are many options. Another choice would be a Cerifine Silmac.

TheLaw117 21st June 2011 08:30 PM

Panasonic FM/FC. Nichicon HE/PW.

Panasonic is a bit more pricey typically, but they are usually more highly regarded. The Nichicons aren't talked about much, but they are pretty much the same specs as FM/FC, and they'll probably sound the same. Panasonics are prettier though. =D

Marra 21st June 2011 08:57 PM

Quote:

Originally Posted by TheLaw117 (Post 2614436)
Panasonic FM/FC. Nichicon HE/PW.

Panasonic is a bit more pricey typically, but they are usually more highly regarded. The Nichicons aren't talked about much, but they are pretty much the same specs as FM/FC, and they'll probably sound the same. Panasonics are prettier though. =D

I agree about the Panasonic FC's; used them in an Aleph 5 build 6 years ago and never had any props with sibilance.

AudioSan 22nd June 2011 12:01 AM

i have the panasonic's in my aleph2. glad to hear they are a good:) i really did gamble on them:)

EDIT: my amps are not up and running yet:)

Marra 23rd June 2011 02:17 PM

Quote:

Originally Posted by Marra (Post 2614472)
I agree about the Panasonic FC's; used them in an Aleph 5 build 6 years ago and never had any props with sibilance.

My bad turned out they were Nichicon KZ's

Andy5112405 23rd June 2011 03:46 PM

2 Attachment(s)
I've ordered some Panasonic FCs from RS.

Strangely the sibilance is much better with NO PUMPKIN and NO ATTENUATOR. ie the CD player driving the Aleph 4 directly.

I don't think that the PUMPKIN itself is the issue but there may an impedance mismatch somewhere.

Normally I'm feeding CD36 into PUMKIN. PUMPKIN into 100K ladder attenuator and then attenuator into Aleph 4. All driving B&W DM683s.

In the first photo the Aleph4 is still awaiting painting. It's been painted in photo 2 but is still waiting for a lid.

That's now in the process of being drilled for ventillation.

jacco vermeulen 23rd June 2011 03:59 PM

Quote:

Originally Posted by Andy Bartha (Post 2614421)
Another choice would be a Cerifine Silmac.

What the F..,.(oh, oh, goosfraba time again) is that ?

Elna Cerafine, or Elna Silmic ?

Conrad Hoffman 23rd June 2011 04:08 PM

Tantalums = Yecch! That's the only one I'd seriously question. I use silver-micas for many things and are pretty happy with them, but IMO polypropylene, polystyrene or Teflon is better for the truly fussy.

Andy5112405 23rd June 2011 04:18 PM

Quote:

Originally Posted by Conrad Hoffman (Post 2616567)
Tantalums = Yecch! That's the only one I'd seriously question. I use silver-micas for many things and are pretty happy with them, but IMO polypropylene, polystyrene or Teflon is better for the truly fussy.

Mark Finnis did produce an Aleph 4 with Tantalums. I believe his rationalle was that tantalums are better in situations where a normal electrolytic will not normally see its polarizing voltage.

220uF is too large to be fabricated from non-electrolytic type caps. I'm just asking for advice as to which caps to try next.

Now that the amp is built it is not an easy job to change them.


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