[rookster]

I am thinking about adding some filter caps across the +ve and neutral line on the switched output of the power switch on my Aspen Amplifiers DIY AKSA 55N+ power amplifier.  It is based on the ideas at VH Audio and other websites, but on the amp instead of an offboard power filter. I am using a DPDT switch that switches both +ve and neutral.

Some sites recommend Auricaps or such for this application and others recommend an X2 rated cap. If I have a fuse before the switch, what is the danger or risk of using an "audiophile" cap (600VDC or 800VDC) for this application?  We use 240V AC here in Australia

Is filtration just prior to the transformers a worthwhile addition or am I being very pedantic?

Bear in mind I have not finished my amps, so don't have the option yet of listening before and after, because I am still at the before stage, but would like to incorporate all mods up-front to avoid too many rebuilds.

[speedcenter]

according to Chris VH, you should use the 1200V Auricaps on 240V, I think,

The risk? dunno, but there's real manufacturers who put Auricaps across power outlets in power conditioners they sell for retail, and they apparently aren't worried to get sued by some fire insurance.

I have had a pair of Auricaps in my preamp and transport for over 18 months now, behind the fuse. In the transport, there's always power on them, since unless you unplug it, it's on standby.

One thing though - in power amps, you're probably a lot better off to put the Auricaps in parallel with the last pair of PSU filter caps - that's where it really matters, and you're working at a much lower voltage there, i.e. safer.

Peter

[Bill Baker]

For the AC tweak, I would not go below a 1500v cap on a 240 line.

you're probably a lot better off to put the Auricaps in parallel with the last pair of PSU filter caps - that's where it really matters, and you're working at a much lower voltage there, i.e. safer

 I have to agree with Peter here. I think you would be better off with bypassing the filter caps in the power supply. I would recommed going with as large a value as physically possible within the chassis. In regard to volatge, you need only to match the rated voltage of each filter cap you are bypassing,. Usually 400v-600v works fine in this application. I have one amp where I use a 100uF/400v Solen, 10uF/400 Solen and .47uF/400v AuriCap as the bypass arrangement with very good results. I do not think all this capacitance is truly needed but I had these capacitors laying around.

 I think the diodes would give you more bang for your buck.

[rookster]

Peter, Bill,

Thankyou for your replies.

I had already planned to parallel the PSU caps.  The existing caps are 4700uF Nichicon Gold Tunes and I was going to parallel each one with a 4.7uF / 400V Mundorf M-Cap (Standard type).  I was going to use that value due to cost reasons more than anything.  I am building 2 stereo amps, so would need 8 Mundorf caps.  I also have BYQ28E-200 ultra-fast rectifiers.

I imagine I should do something similar for the pre-amp when I build it.

Would this be better than adding any filter caps either before the transformers or in a power filter/power board type unit?  I can see that it should.

[Dan Banquer]

Have you thought about using some of the power entry filters from companies like Corcom, Delta, Schurter or Qualtek?
              d.b.

[JoshK]

Have you thought about using some of the power entry filters from companies like Corcom, Delta, Schurter or Qualtek?
              d.b.

Are these the Y type of filters that contaminate ground?

[Dan Banquer]

I'll let you be the judge of that because I have no idea of what you are trying to tell me when you say "Are these the Y type of filters that contaminate ground?" If you can explain this I would be most appreciative.
             d.b.

[Occam]

Dan -  I'll take that one for Josh. What I believe he is referring to is whether these filters have 'Y' caps, from ground to neutral and line. I assume they do. The only hermetic filters I've seen without Y caps are some medical specific filters as the Caduceus wielding basturds seem to be concened with ground leakage.  
In the best of all possible worlds, I don't want any more crap on the ground line than is already there. (yes, I know we can put a big honk'n inductor on the ground line to somewhat ameliorate this). But as a practical matter, Y caps do effectively deal with differential mode noise, and provide incremental benefits over filters sans these, even those with CMCs flanked with X caps. And certain designs don't have 'Y' caps, the UO fron PSaudio, DeZoral, Felicia....

Do you use hermetically sealed filters on your own LNPA power amps?

[Dan Banquer]

Hi Paul;
   I use the EDC1A, the 10 amp version on the power amps from Corcom, The pre amps get the generic 3 amp filter such as the 3EEB Series if I remember correctly. These units are sealed but I don't think the solder seal is much of a hermetic seal. I could well be wrong on that.
             d.b.

[Occam]

Dan,

I shoulda known.... the EDC Corcom filters have a inductor on the ground. I don't think I'll drop one of my Corcoms in a bucket of water to find out if they are really hermetically sealed  

Regards,
Paul