Bottlehead Kits > Smack

The usual question: cap "upgrades" (real or imagined)

<< < (3/3)

earwaxxer:

--- Quote from: adamct on May 17, 2013, 01:58:57 AM ---.....So as a practical matter, I'll buy some caps that people generally seem to find good (and that I have used in my Crack to excellent effect), drop them in, and be done with it.

--- End quote ---

I wish I could do that!.... I think I need therapy!

adamct:
LOL! That actually made me laugh out loud...  ;D ;)

adamct:

--- Quote from: Paul Joppa on May 16, 2013, 10:38:26 AM ---3x 220uf 250V electrolytic caps - these are in the high voltage power supply, isolated from the audio by two C4Ss and a shunt regulator, and not going to be directly audible. There are two areas for possible improvement - you can look for caps of higher temperature rating (105 degrees C) and higher voltage (up to 450v) which will help the caps live longer, and you can bypass them in the hope that it will reduce switching noise at radio frequencies. For the latter, snubbers and AC line rated ceramics are good candidates.

*** for switching noise, consider replacing the UF4007 rectifiers with Cree silicon carbide Schottky diodes, 600v or greater; that will likely make more difference than bypassing the filter caps. ***

--- End quote ---

I recently replaced all 3 220uf 250V electrolytics in the power supply of my Speedball'd Crack with 200uf metalized polypropylene film caps. I can't explain it, but I feel like the change is distinctly audible, much bigger than I ever would have expected. Frankly, I was really sort of shocked. Bass seems much stronger and resolution (if possible) seemed to get even better than it was before.  Best of all, the cost was surprisingly low.

Since I already have one of the Schottky diodes you recommend above, along with replacement film caps for the parafeed output caps, I'd like to perform the same mod to my Smack. I would have to mount the caps externally and run fly leads to them. I would be using 200uf film caps rated at 450VDC. Two questions:

1. Putting cost aside (again, the cost is fairly minimal), is there any reason not to do this? Is there a chance the fly leads will cause problems? Is there any reason why films caps are a bad idea here?

2. Are 200uf film caps sufficient, or should I use 250uf caps instead? The price difference is negligible. Or do the caps really need to be exactly 220uf?

Best regards,
Adam

Paul Joppa:
Crack, being a cathode follower, has the power supply in the output signal current loop and should be much more sensitive to improving the PSU capacitors.

For Smack or Mainline, the shunt regulator reduces the effect of power supply - but that also means you can get away with less capacitance. So no worries about the smaller value.

Experience tells me that someone will immediately ask "how low can I go?"  I have no answer, since there will probably be audible effects before you reach a purely theoretical limit. Try it and find out! It won't hurt anything except your wallet.  :^)

adamct:
Thanks, Paul. Since I have 200uf caps I like, I'll stick with those and won't try to go lower. And since I don't think there are too many people building Smacks anymore, you should be safe from others as well!

Best,
Adam

Navigation

[0] Message Index

[*] Previous page