In my Marantz amp Snubber across sec is 6.8 ohm & 470nf,i see in all new Marantz equipment snubbers of same value.Sonny use in TAE1 preamp 10ohm 2,2uf.
May I suggest that you read Hagerman's paper. It reminded me of a lot of the AC circuit analysis principles that I had forgotten.
Godfrey, the snubber cap is simply in the circuit the limit the power dissipation in the snubber resistor. Remember that for a 55V secondary there is 1.5W in a 2k2 resistor on its own. And its fundamental that oscillations in a RLC tank circuit are damped by the resistive components not by any of the reactive elements, although the natural frequency will reduce with increased C.
Andrew, the snubber resistor was increased from 1k8 to 2k2 in order to give me the most appealing scope waveform - I am comfortable that measurement inaccuracy, in particular of the resonant frequency, was the reason it was needed. You will probably understand when you try it for yourself, which I am trying to encourage.
At the end of the day I am satisfied I have eliminated a noise source from my amp, but I would also like to understand the experience of others in case I have missed something..
Godfrey, the snubber cap is simply in the circuit the limit the power dissipation in the snubber resistor. Remember that for a 55V secondary there is 1.5W in a 2k2 resistor on its own. And its fundamental that oscillations in a RLC tank circuit are damped by the resistive components not by any of the reactive elements, although the natural frequency will reduce with increased C.
Andrew, the snubber resistor was increased from 1k8 to 2k2 in order to give me the most appealing scope waveform - I am comfortable that measurement inaccuracy, in particular of the resonant frequency, was the reason it was needed. You will probably understand when you try it for yourself, which I am trying to encourage.
At the end of the day I am satisfied I have eliminated a noise source from my amp, but I would also like to understand the experience of others in case I have missed something..
OK this is way over my head.
Anyway I am winding a microwave trransformer into a lean mean green power supply for my TAS5630 amp. Its gonna be 35v ac and 20 amp.
Would this set like a rectifier bridge -
ISL9R30120 1200V 30A Stealth Diode Rectifier UFR ISL9R30120G2 | eBay
do the snubbering I would need ?
I'll be putting caps and this and and that after it to make it DC obviously.
Cool.
Srinath.
Anyway I am winding a microwave trransformer into a lean mean green power supply for my TAS5630 amp. Its gonna be 35v ac and 20 amp.
Would this set like a rectifier bridge -
ISL9R30120 1200V 30A Stealth Diode Rectifier UFR ISL9R30120G2 | eBay
do the snubbering I would need ?
I'll be putting caps and this and and that after it to make it DC obviously.
Cool.
Srinath.
John,
the capacitor prevents excessive DC dissipation. That same capacitor also prevents excessive low frequency dissipation when sized correctly.
1k8 and 2k2 seem to be far too big for elimination of ringing and overshoot in a barely stable snubber system.
That was why I asked the original question.
I still think you have done something odd with the numbers you have measured to come up with 1k8 for the snubbing resistor.
the capacitor prevents excessive DC dissipation. That same capacitor also prevents excessive low frequency dissipation when sized correctly.
1k8 and 2k2 seem to be far too big for elimination of ringing and overshoot in a barely stable snubber system.
That was why I asked the original question.
I still think you have done something odd with the numbers you have measured to come up with 1k8 for the snubbing resistor.
I'll throw in my standard procedure for snubbing, just to help those poor guys who attempt to use Hagerman's article in the future. It has done very little for me, to be honest. This procedure avoids the need to measure frequency, stray leakages or capacitances, and uses no equations. But if followed you will end up with a result much better than what you would get with Hagerman's article, as the scope doesn't lie.
1. Remove all rectifier snubbing. Chances are it is unnecessary anyway.
2. Connect scope common to HT center tap. This will vary depending on if you are using FWCT or bridge, but the idea is simply to view secondary voltage. Pay attention to grounding, as the scope is grounded. 10X scope probe to one end of the HT secondary.
3. Run the amp and set the scope to zoom way in on the switch-on spike. This is important. You want to fill the screen completely with just the turn-on ringing. Your scope is able to do this. Play around with vertical/horizontal position, timebase and vertical sensitivity, and trigger level.
4. Put on leather gloves. A little caution is a good thing.
5. Set up an RC network consisting of a 0.01uF poly (ideal) or ceramic (acceptable) in series with a 10k pot. There will be flying leads attached to this network to enable easy adjustment and connection to the secondary. Connect to either end of the secondary (not to the CT). Begin with the pot in 10k. Be sure your capacitor is able to support the AC voltage involved. This is why I have a bucket of 5 different sized CDE 940C caps at the higher voltage ratings.
6. You should be able to easily see how adjusting the pot affects the ringing. Obviously the goal is to eliminate over shoot and ringing completely, but this is not always perfectly possible. Sometimes you have more than one characteristic frequency to contend with, but I have found one RC is sufficient.
7. Don't leave the pot in the 0 position very long; you are only trying to identify ballpark values at this point.
8. Try increasing to 0.022 uF and repeat. You can now get an idea if a larger cap is providing better results or essentially the same. If you see no difference with a 0.01 cap, chances are you need a larger cap. I have never found a cap smaller than 0.01 to function effectively as a snubber for transformers; possibly for rectifiers. You want to pick the smallest cap possible to get the job done, while also avoiding having the pot at the zero position.
9. Between 0.01 and 0.047 uF seems to be the sweet spot for the size transformers and voltages typical in valve amps.
10. Once you have identified the smallest capacitor that will work, set the pot to provide just enough damping to snub the ringing. More is not always better (nor is guessing and just throwing in caps without measurement).
11. Replace this pot with a 1/2W carbon comp resistor and solder in with shortest leads possible. Expect the value to be greater than a few hundred ohms for HV valve amps, and between 10 and 200 ohms for low voltage supplies.
1. Remove all rectifier snubbing. Chances are it is unnecessary anyway.
2. Connect scope common to HT center tap. This will vary depending on if you are using FWCT or bridge, but the idea is simply to view secondary voltage. Pay attention to grounding, as the scope is grounded. 10X scope probe to one end of the HT secondary.
3. Run the amp and set the scope to zoom way in on the switch-on spike. This is important. You want to fill the screen completely with just the turn-on ringing. Your scope is able to do this. Play around with vertical/horizontal position, timebase and vertical sensitivity, and trigger level.
4. Put on leather gloves. A little caution is a good thing.
5. Set up an RC network consisting of a 0.01uF poly (ideal) or ceramic (acceptable) in series with a 10k pot. There will be flying leads attached to this network to enable easy adjustment and connection to the secondary. Connect to either end of the secondary (not to the CT). Begin with the pot in 10k. Be sure your capacitor is able to support the AC voltage involved. This is why I have a bucket of 5 different sized CDE 940C caps at the higher voltage ratings.
6. You should be able to easily see how adjusting the pot affects the ringing. Obviously the goal is to eliminate over shoot and ringing completely, but this is not always perfectly possible. Sometimes you have more than one characteristic frequency to contend with, but I have found one RC is sufficient.
7. Don't leave the pot in the 0 position very long; you are only trying to identify ballpark values at this point.
8. Try increasing to 0.022 uF and repeat. You can now get an idea if a larger cap is providing better results or essentially the same. If you see no difference with a 0.01 cap, chances are you need a larger cap. I have never found a cap smaller than 0.01 to function effectively as a snubber for transformers; possibly for rectifiers. You want to pick the smallest cap possible to get the job done, while also avoiding having the pot at the zero position.
9. Between 0.01 and 0.047 uF seems to be the sweet spot for the size transformers and voltages typical in valve amps.
10. Once you have identified the smallest capacitor that will work, set the pot to provide just enough damping to snub the ringing. More is not always better (nor is guessing and just throwing in caps without measurement).
11. Replace this pot with a 1/2W carbon comp resistor and solder in with shortest leads possible. Expect the value to be greater than a few hundred ohms for HV valve amps, and between 10 and 200 ohms for low voltage supplies.
This is the type of diode you asked about, yes. I don't think we can tell if this is what you need. Also, it is an expensive way to go about it. @$3.60 each plus shipping, a diode bridge made up of 4 diodes will cost over $18, compared to something like $3-5 for an ordinary bridge rectifier made from discrete diodes (which works for most people here).
I think that a couple of the more experienced people tried to steer you politely in a different direction, without critiquing your choices of parts, and then we went a bit off topic. A snubber for a transformer secondary winding can be as simple as a cheap resistor and capacitor, and some very successful older amplifiers only used a single high voltage ceramic disc capacitor in the range of 0.01 to 0.1uF...
If you post the transformer specs, and the likely load current, someone can perhaps give you a couple choices w/o bogging down in higher math and simulations... 😀
Having said that, I know I would welcome a thread discussing how to select a snubber using something other than my seat-of-the-pants methods... 🙄
Beautiful PMI - Thank you.
OK 35v ac no center tap, just 35v, and up to 20 amp. More like 15 amp. Using 12 guage wire.
Its a rewound microwave transformer I am making to supply a TAS5630 amp.
Cool.
Srinath.
OK 35v ac no center tap, just 35v, and up to 20 amp. More like 15 amp. Using 12 guage wire.
Its a rewound microwave transformer I am making to supply a TAS5630 amp.
Cool.
Srinath.
Would a snubberized secondary be useful for a super-reg'd DC supply feeding digital hardware? I'm using an R-Core with a 40VA secondary (non-CT) to feed a standard design LT10xx which is running a P-A SSR01 super-reg. The whole thing is powering the digital side hardware for a transport. Wondering with the multiple DC regulation stages whether I'd get a real benefit from the snub.
Probably a dumb question.
Probably a dumb question.
Not dumb.
If a PSU is liable to ring when given a jolt, then a digital circuit could be just perfect for making any PSU into a ringer.
If a PSU is liable to ring when given a jolt, then a digital circuit could be just perfect for making any PSU into a ringer.
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