SS rectifier & hum magic

[Robert M. Martinelli]

Hi again tw!
Scientific? Me? You gotta be kidding!
Cheers
Bob

[tedmich]

some love avalanche rectifiers like the 1N5062 for tube amp supplies; they have an internal snubber. The real hardcores use very spendy FRED, Stealth (Fairchild) and super fast diodes, but have reported some blown diodes because the spike handling is not as robust. These guys bypass EVERYTHING with a 1-3kV 1-10nF film caps, I saw one guy explain that the super fast diodes switched too fast and needed to be slowed down to decrease noise...?


Of course a MOV across the primary and a 10nF across the secondary of the PT are standard (good) practices IME

Another observation I second; the need to add diode snubbers, chokes and bypass caps is usually obviated by using more capacitor filtering (even the PV JSX has ~360uf on its B+)

[Robert M. Martinelli]

.....the need to add diode snubbers, chokes and bypass caps is usually obviated by using more capacitor filtering (even the PV JSX has ~360uf on its B+)

Hi Ted,
( no disrespect intended ). Increasing filtering by itself helps in lowering ripple, and renders the amps more responsive and improves dynamics, but, unless the filtering caps are specially designed, they cannot respond well to fast transients/spikes or diodes' switching noise, due to their very long time constant, so these kind of disturbances could manage to slip through them.

This can be ( and sometimes is ) obviated by adding small capacitors in parallel, so that any residual "fast" disturbance can be eliminated.

Cheers

Bob

[JoeM]

There's another thread here that discusses the use of snubbers etc.

http://music-electronics-forum.com/t2738/

[tedmich]

Hi Ted,
( no disrespect intended ). Increasing filtering by itself helps in lowering ripple, and renders the amps more responsive and improves dynamics, but, unless the filtering caps are specially designed, they cannot respond well to fast transients/spikes or diodes' switching noise, due to their very long time constant, so these kind of disturbances could manage to slip through them.

This can be ( and sometimes is ) obviated by adding small capacitors in parallel, so that any residual "fast" disturbance can be eliminated.

Cheers

Bob

Wow Bob, you have become very sensitive! No offense taken and it would be ok anyway. You are correct, film bypass caps on ELs are very commonly done in high end audio amps, less so guitar amps (A Dr. Z clone is the last one I remember seeing) and they may well help clean up some noise inherent in a particular PS design. I am more dubious of their near constant inclusion in audiophile equipment and the stated benefits of added "sweetness" "enhanced sound stage" etc. etc. No obvious bad effect (save increased cost) so they are de rigeur' in some circles irrespective of actual quantifiable benefit, maybe like angioplasty. I am a cheap skeptic by default but may well come to believe with more data.

I do love film caps though...just bought 400 metal jacketed 470pF/630v polystyrenes for VERY cheap and may bypass everything with them...

[Robert M. Martinelli]

Wow Bob, you have become very sensitive! No offense taken and it would be ok anyway...

Hi again Ted,
I am simply afraid of offending someone....I always try to improve my English ( and I hope it shows ) but I am aware of my limitations, there's always the chance for me to "say" something in an unclear or "wrong" manner, so I thank you for your kind words .

Cheers

Bob

[tubeswell]

FWIW I used the snubber caps in a stand-alone reverb unit that had a FW SS rectifier and I tried the unit with and without the snubber caps, and it was definitely quieter with the snubber caps - perhaps more noticeably so because it was a reverb unit, and as such, more sensitive to hum sources.