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Simple, no-math transformer snubber using Quasimodo test-jig
Simple, no-math transformer snubber using Quasimodo test-jig
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Old 9th May 2019, 03:02 AM   #1561
Mark Johnson is offline Mark Johnson  United States
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Simple, no-math transformer snubber using Quasimodo test-jig
Probably the question arises because the capacitance values in that position on the two different Quasimodo schematics, appear to be wildly different. And it is too much work to read the thread to find out why.
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Old 9th May 2019, 11:53 AM   #1562
orelli is offline orelli  Italy
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Sorry Mark, the picture it's not clear, what's the right value?
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Old 9th May 2019, 12:29 PM   #1563
Mark Johnson is offline Mark Johnson  United States
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Simple, no-math transformer snubber using Quasimodo test-jig
To read post #1's schematic with perfect crystal clarity:
  1. View post #1
  2. Click on the fourth attached thumbnail (the V4 schematic)
  3. Click on the white "X" icon at the bottom left of the image. This is the diyAudio website's icon which means "Increase image display size to 100% of original".
You might want to print out these instructions, and keep the paper in hand while you're attempting the maneuver
_
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File Type: png this_thing.png (31.2 KB, 387 views)
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Old 9th May 2019, 08:10 PM   #1564
orelli is offline orelli  Italy
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thank you Mark, it's 1nF
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Old 9th May 2019, 08:12 PM   #1565
6L6 is offline 6L6  United States
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Simple, no-math transformer snubber using Quasimodo test-jig
Also 0.001uF


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Old 9th May 2019, 08:21 PM   #1566
Mark Johnson is offline Mark Johnson  United States
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Simple, no-math transformer snubber using Quasimodo test-jig
It's also shown on page 4 of the Quasimodo .pdf manual, attached to post #1 of this thread.

This is a nice alternative, because people often find it very easy to increase and decrease the magnification when viewing .pdf files. You simply activate the View --> Zoom menu pulldown.
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Old 9th May 2019, 08:22 PM   #1567
orelli is offline orelli  Italy
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yep
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Old 18th May 2019, 08:18 PM   #1568
Mark Johnson is offline Mark Johnson  United States
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Simple, no-math transformer snubber using Quasimodo test-jig
I'm grateful to member brian92fs, who pointed out this 2019 article on snubbers by Rod Elliott, on his Elliott Sound Products website. Be sure to read part 1 and also part 2 (follow the link at the bottom).

Rod starts out thinking that snubbers are stupid, and he bends over backwards never to write the word "Quasimodo" in the article, lest he point his readers towards a 20 page document full of badly misguided ideas, plus a lot of maths in the appendix.

Then as he gets rolling along, he begins to change his tone if not his tune, saying things like
Quote:
This is an article where, in an attempt to prove that something was completely unnecessary, I discovered that this may not be the case.
By the end of the article, after putting up a dozen scope photos of power supplies with various kinds of snubbers, including no snubber at all, he believes that
  1. Yes transformer secondary ringing does exist
  2. Yes it is created by diode switchoff
  3. Yes different types of diodes do create different amounts of ringing
  4. Yes adding a snubber with resistive damping, does reduce ringing
  5. Yes it is possible to adjust the component values in the snubber, to make ringing disappear completely, and here's some pictures

However I am disappointed that he doesn't add up all of these thoughts, and formulate this conclusion: "Ringing certainly does make radio frequency emissions worse, nobody actually WANTS ringing, we already know how to get rid of ringing using snubbers, why don't we simply decide we will completely eliminate ringing by adding a snubber? It's cheap and it's easy: just a resistor and a couple of small capacitors. Why on earth not?
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Old 19th May 2019, 01:32 AM   #1569
trobbins is offline trobbins  Australia
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Rod certainly wants to emphasise that there is no audible benefit to snubbing a secondary winding for an acceptably designed and integrated power supply.

For those wanting to add a snubber circuit to a secondary winding, Rod presents an almost in-situ measurement technique. I'd suggest that those with a soundcard style signal assessment tool (eg. software with spectrum analyser, and for that matter also a scope screen) would find it easier to discern the disturbance signal, and may not even need the CR filter depending on the interface they have available (although I haven't yet done this myself).

I note that Rod's technique alters the normal operating configuration by changing the ground point location, which may have an influence on how ground path parasitic currents flow, and may not be easy for those wanting to make measurements on a built amplifier. Some oscilloscopes have a battery powered capability, and similarly for soundcard based interfaces, and so should not require an alteration to amplifier grounding if due care was taken.

Having available a means for in-situ fine-tuning a snubber seems a good outcome for those wanting to go done the snubber path.

If an amp power supply was generating a diode induced ring transient (without any secondary winding snubber), and the ringing frequency was below 90kHz (as per example 40kHz waveform shown in Fig.3 of post #1 Quasimodo jig Rev A doc) then a modern soundcard interface and spectrum analyser may well be able to discern that transient when probing the power supply and downstream.

Last edited by trobbins; 19th May 2019 at 01:35 AM.
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Old 19th May 2019, 11:11 AM   #1570
JeffYoung is online now JeffYoung  Ireland
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Simple, no-math transformer snubber using Quasimodo test-jig
It's a pity Rod has such an attitude, because I otherwise find the info on his site very useful.

But you're in good company anyway. Rod gets rather cantankerous about Nelson too.
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