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What would be the effect of caps paralleling the diodes in a bridge be on the diode switching noise? I know I've seen this done but I can't find any examples.Thanks, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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Small caps can be used to tune the resonance to a lower frequency that may not be as intrusive. Can be used very successfully. 0.01uF is a common value.Works better with a real snubber. More info below.
jh
Hello,I have used ceramic caps for this in the past, but in my recent build i used russian PIOs (K40); diodes are UF4007. The design is so different from the previous one that i can't assert the contribution of the caps. Anybody tried switching ceramics for PIOs? Maybe overkill?
There's no audio there. Caramic caps are excellent for the job.
to get rid of the spike. .01ufd ceramic disc and a 470K 1/2 watt resistor. Old Ham Radio trick. Ray Hughes
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
All three, the diode, the resistor and the ceramic cap are all in parallel with each other. A three leg parallel network.
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
Take a 1n4007 and lay it on the table, then place a .01 ceramic cap right beside it on the top and place a 470k resistor on the bottom. So they are now all aligned (III). Now connect all three leads on each side together. All three components are in parallel.
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
And with a bridge there would be four of these bundles. Yes I got it, Thanks.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Treat the disease first by using Ultrafast Soft recovery diodes.
Then treat the remaining (reduced) symptoms with the R and CEVERY amp Tube or SS in which I have replaced the power supply diodes with Ultra Fast Soft Recovery has sounded better immediately - sometimes dramatically so.
Yes, I have had the same experience.In some of the first amps I built, I used standard diodes, diodes
are diodes right, or so I thought. After discovering UF diodes I
upgraded and the results were remarkable.
I agree with Ian. Perhaps an International Convention could be negotiated that outlaws 1N400n diodes in audio equipment. ;~) UF400n diodes are quite inexpensive and do a BETTER job.The late John (Buddha) Camille did the "leg" work on the RRSF. He was able to reduce the already low switching noise of UF4007s to the point of invisibility on his BROADBAND o'scope.
If you don't want to bother with "snubbers", use high PIV Schottky diodes. They are "noiseless" without the use of RC networks.
Eli D.
> Perhaps an International Convention could be negotiated that outlaws 1N400n diodes in audio equipment.Most of the problems arise as a result of failure to use proper techniques. The HV supplies in many of my amplifiers include 1N400x rectifiers, and there are no spikes or any other unwanted HF noise of any significance whatsoever on the chassis, B+ lines or signal paths. I have tested this with both digital scopes and spectrum analyzers.
To keep supplies clean, I use the following techniques:
1. Locate the supply a suitable physical distance from the front end
2. Install a cap (w/ or w/o parallel resistor) across every rectifier diode
3. Use a good quality 5-20H choke (not necessarily at the input)Follow these common-sense steps and the diode issue goes away.
TK,That your B+ is clean is beyond question. The filter choke sees to that. However, that's not the whole story. SS diode switching noise can get into the amp via the power trafo and filament winding. Buddha's RRSF kills the "hash in both directions. Even CRC filters have proved adequate.
Eli D.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
".01ufd ceramic disc and a 470K 1/2 watt resistor." Would that be a .01uf cap in parallel with a 470K ohm resistor in parallel with each of the four diodes in the bridge? Or just one of each, in parallel, shunting to ground after the bridge?Thanks for your time, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi.A more common way is to go without any series resistor. Just parallel a 0.01uF to 0.1uF cap to each diode, depending on the current load. Higher load, go for larger cap values.
For ceramic disc, make sure choose HV (I would use min 3KV) to ensure linearity. LV ceramic is pretty non-linear.
If I use .03uf caps should I scale the resistance down? What is the formula?Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
although it's not clear to me that the 470K serves a purpose other than to equalize the voltage when multiple diodes are connected in series.
The caps. in parallel with the diodes do reduce "hash". Run an archive search for RRSF against the Bottlehead Forum. The RRSF can make the noise from UF4007s invisible on an o'scope.
Eli D.
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