Crack PSU capacitor questions

[Loquah]

Hi all,

I have a few questions to help me help a fellow enthusiast. Specifically in the power supply circuit of the Crack we are thinking about upgrading 1 or all of the 220uF capacitors and I'm wondering the following:

• I've read that audio caps aren't necessarily good for power supply filtering - is this true and should we therefore not go for a Mundorf MCap (poly cap)?
• Is there any noticeable benefit / drawback to adding some extra capacitance or is 220uF heaps already? I remember using 1F capacitors in my car audio days to great effect, but we're talking headphones here, not loudspeakers so I understand that more than 220uF might be overkill.
  
• Is there benefit in upgrading all 3 PSU caps or just the final one?

Thanks from me and from my friend! 

[galyons]

I would replace the 2nd PS resistor, (270R, 5watt) with a Triad C7X choke and use a film cap as the final PS cap.  I think that would provide more sonic benefit than replacing all three 220uF electrolytics.  In another post PJ recommended, IIRC, that the final PS cap be close to the capacitance of the output caps.

I run 60uF aluminium foil/ wax paper caps for output with 30 aluminium foil/wax paper caps bypassed with a 2.2uf mylar/foil/oil caps.  Works wells with my 300 ohm and 600ohm phones.  (real estate gets really precious, there just was no room for more caps or larger caps!)

Cheers,
Geary

[Paul Birkeland]

I've read that audio caps aren't necessarily good for power supply filtering - is this true and should we therefore not go for a Mundorf MCap (poly cap)?

I would generally say the opposite.

Is there any noticeable benefit / drawback to adding some extra capacitance or is 220uF heaps already?

There is a functional benefit to adding more capacitance, but there are diminishing returns.  In one Crack I built a long time ago, I used 500uF per section with good results.  (Less power supply noise)

Is there benefit in upgrading all 3 PSU caps or just the final one? [/li][/list]

The biggest benefits are reaped from the last cap in the supply, as it has the most signal current across it.

If you're looking for upgrade electrolytic caps, the Panasonic TS-ED's are worth looking at.

[Loquah]

Thanks all.

I'm thinking of suggesting that he starts with 3 Panasonic 470uF electrolytics as a starting point and then consider replacing the final Panasonic with a Mundorf later if he feels the need.

Does that sound like a reasonable upgrade option or have I missed something?

PS to add context, I have built multiple amps, but not gotten into modifying the designs until now. I'm helping by building this for a friend and providing the best advice I can (also learning more and more as I go), but because it's not for me I want to keep the upgrades safe and sure-fire - I'll happily experiment on my own gear, but not someone else's hence my conservative approach

[Paul Birkeland]

You may like trying these:

http://www.digikey.com/product-detail/en/UPW2E471MRD/493-2030-ND/589771

[Loquah]

Great! Thanks CB.

I'll suggest he buys 3 of those and we'll go from there.

Thanks all for your help.