snubbers for AKSA TLP's PSU

Junior · « **on:** 2 Dec 2005, 04:55 am »

Hi guys,

Is it recommended to have 4 sunbbers (22nF/63V) for the 4 rectifier bridge? And any benefit for doing that?

Rgds

ginger · « **Reply #1 on:** 2 Dec 2005, 06:08 am »

Junior,

**** IMPORTANT - DO NOT PROCEED TILL YOU'VE READ THIS ****

Snubber capacitors across the rectifier diodes can help and certainly won't do any harm - except for the 22nF/63V you suggested - THEY WILL BLOW UP.

On any half cycle of the sine wave from the transformer two diodes of the 4 diodes in the bridge are conducting and the other 2 are reversed biased with the full transformer secondary voltage plus the stored voltage in the first filter capacitor across them. On the next half cycle the two ON diodes turn OFF and the two OFF diodes turn ON. That means any capacitor you fit as a "snubber" across the diodes in the bridge has to be rated for TWICE the transformer secondary voltage MINIMUM. For the TLP say about 600 volts (Your 63V caps are going to be crispy rather than happy).

Typically for the TLP you would fit 10nF/1000V Ceramic Capacitors across each of the 4 bridge leads (that is across each internal diode).

If you do this post a reply to tell us if you notice any difference.

Cheers,
Ginger

Junior · « **Reply #2 on:** 2 Dec 2005, 09:59 am »

ginger,
thanks for pointing out my mistake.
i was thinking about chip amp PSU when i post my question.
yup, i am using a snubbers (more than 230V for sure).

to be honest, i did not notice any difference.
maybe my ear aren't that sensitive to pick up the changes (or maybe there aren't). just my 2 cents.....

AKSA · « **Reply #3 on:** 2 Dec 2005, 09:19 pm »

Junior,

The TLP, like its relative the GK1, uses a bunch of ultrafast soft recovery power diodes and a CRCRC supply. Use of snubbers with this style of supply is not required, and you will find their addition makes an inaudible improvement, if at all.

Hope this is helpful,

Cheers,

Hugh

ctviggen · « **Reply #4 on:** 2 Dec 2005, 09:29 pm »

Here's an interesting article about snubber selection:

http://www.cornell-dubilier.com/tech/design.pdf

Yet another:

http://focus.ti.com/lit/an/slup100/slup100.pdf

Junior · « **Reply #5 on:** 5 Dec 2005, 05:21 am »

Guys,

Thanks for all the responses.
Actually, I was reading an article from Zero Distortion as it say:

"The first is that the rectifier diodes are now bypassed with small value capacitors (22 nF). This is always desirable because it reduces diode switching noise by a very considerable amount, resulting in cleaner DC leaving the bridge and with most surges removed."

I am curious to give it a try.
As far as I can hear, I did not manage to notice any difference.
As Huge mentioned, inaudible improvement (for my case).

Anybody else here beside me did the tweak? Did you notice any difference?

ginger · « **Reply #6 on:** 14 Dec 2005, 03:37 am »

Junior,
I ran snubbers (2R2 resistor + 100nF in series) across the transformer secondaries on my 55N+ for a while. Eventually deleted them as they made no audible difference that I could decern.
Cheers,
Ginger

enzedone · « **Reply #7 on:** 18 Jan 2006, 08:29 am »

This is interesting topic junior. I have finished my second LM3875 Gainclone, ..yes i know it's not an aksa. The first was with a standard transformer and rectifier bridge. The second had filter caps and a bigger trans. I also put 22nf/1000v polyproperlene caps across the bridges. The sound was better, but i don't know if this was due to the larger trans and added filter caps. But they are in there now and thats where they are staying.

It would be really nice to do a proper comparison though, just to see using my ears only, if there is any grate benefit. And they cost quite a bit. When I build my aksa I'll need 16 of them at $3.00 each, you got to ask yourself, "is it going to make a difference"

Brett