Cap upgrades

Marty · 2863

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Offline Marty

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on: May 17, 2023, 04:09:00 AM
I'm looking at getting some higher end caps for my pre. Can the three .01uf wired in parallel be replaced by one .033uf cap? And if yes what voltage? Are there any advantages or downsides?



Offline Paul Birkeland

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Reply #1 on: May 17, 2023, 05:16:50 AM
It would be much better to replace the three 0.01uF caps with one 0.030uF cap (which is what we use in the Eros).  If you go with a 0.033uF cap, you are introducing an error into the RIAA EQ that wouldn't otherwise be there with the stock circuit, so objectively that would be making the amp perform worse. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Marty

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Reply #2 on: May 17, 2023, 12:00:54 PM
Thanks



Offline Larpy

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Reply #3 on: May 17, 2023, 04:10:30 PM
The only problem is that finding high quality .03uF caps isn't that easy. Lots of good .033uF caps around, but upgrade-worthy .03uF caps are hard to find.  Anyone have recommendations?  Because I've looked.

Larry


Offline Paul Birkeland

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Reply #4 on: May 17, 2023, 04:15:12 PM
Put two 0.015F caps in parallel.  If you buy a few extras, you should be able to get two pairs that make very close to 0.030uF when paralleled.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Paul Joppa

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Reply #5 on: May 17, 2023, 05:26:38 PM
The history of the design is that in the Seduction I originally used 0.033uF caps, with the second cap being 0.010uF + 0.0012uF in parallel. (The two RIAA caps are very close to 3:1 ratio). Precision caps (i.e. 1% or 2%) are not available in as many different values, so even that was hard to find - in the end we just used 5% caps.

In the Reduction I switched to 0.030uF and 0.010uF since multiples of 10 are almost always available in precision lines. By paralleling three to get the 0.030uF, you need 8 identical 0.010uF caps. Usually there is a price break for 10 caps, so if you have a capacitance meter you can select the best 8. In fact, by paralleling the outliers carefully, you are likely to be able to get excellent precision even with 5% caps.

Of course, few (if any?) ever took me up on this option.  :^)

Paul Joppa