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Old 3rd September 2012, 06:45 PM   #2901
mikelm is offline mikelm  England
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Quote:
Originally Posted by Esperado View Post
On my amp, i used a big toroidal trasfo (1100 VA), and big caps. Adding this cap multiplier had changed the sound in an incredible way to the top:
http://www.esperado.fr/images/storie...ndo/supply.gif
In the diagram you post you still have the earth lead - which is connected to most sensitive places throughout your entire audio system - connected directly to the transformer secondaries which will resonate violently at a very high frequency every time the diodes switch off - and this resonance can carry on continuously in between each diode switch off - so the secondaries are resonating at very high frequency all the time !

I cannot imagine that any amount of capacitor multiplication will entirely eradicate this noise so I would personally not use or recommend this kind of supply.


Last edited by mikelm; 3rd September 2012 at 06:59 PM.
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Old 3rd September 2012, 06:56 PM   #2902
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Quote:
Originally Posted by bobo le chat View Post
I have not yet found a solution to replace the r380 by a current source
Using two LT3092 in serial ? They afford 40v 200ma.
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Old 3rd September 2012, 07:08 PM   #2903
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Quote:
Originally Posted by mikelm View Post
I would personally not use or recommend this kind of supply.
Despite it is very classical, exactly equal to a simple bridge used with a single secondary coil and working perfectly with no significant noise ?
If you are aware of switching peaks, use fast switching diodes and an accurate ground wiring. Plus some film caps. And remember a diode is too a hf demodulator.

Aware more of all the hf parasitics carried by the ac outlet.
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Old 3rd September 2012, 09:31 PM   #2904
shaan is offline shaan  India
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Lightbulb YO People!

Problem solved. Hum gone.

Changed the zener-parallel capacitor to 2200uF. Clean and clear.

Makes me think... 1000uF capacitors would be enough here. Those caps must be either leaky or fake. Whatever.

I'm Happy again.

Click the image to open in full size.

edit:- I recall that last year I faced the same problem with SSA, but more severely. Maybe the grounding was bad or something; and I used only gain of 10(too low?). Probably there was oscillation too. Anyway, life is good now.
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Last edited by shaan; 3rd September 2012 at 09:49 PM.
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Old 3rd September 2012, 10:13 PM   #2905
mikelm is offline mikelm  England
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Quote:
Originally Posted by Esperado View Post
Despite it is very classical, exactly equal to a simple bridge used with a single secondary coil and working perfectly with no significant noise ?
If you are aware of switching peaks, use fast switching diodes and an accurate ground wiring. Plus some film caps. And remember a diode is too a hf demodulator.

Aware more of all the hf parasitics carried by the ac outlet.
Yes, very classic, as are many types of power schemes & regulators - but they nearly all seem to focus on the noise on the rails.

My experience is that no matter how good the regulators in series with the power rails are there are still audible gains to be had by filtering the noise on the earth rail even with ALL the measures you prescribe above plus others you don't mention.
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Old 4th September 2012, 12:05 AM   #2906
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Quote:
Originally Posted by mikelm View Post
Yes, very classic, as are many types of power schemes & regulators - but they nearly all seem to focus on the noise on the rails.
And so do i ;-) My purpose, posting this schematic was about the regulation, not RC snubbers theory.

What do you prefer, parallel the 2 coils an use 2 bridges ?
I had tried the two, and really found no difference, both on the rails to ground and the ground leakages to the earth, apart the little power consumption outlet side, at rest, due to the slight voltage difference between the 2 coils.
On my side, i worry about hf transmitted by capacitive coupling between the coils and coils to chassis, not about any supposed tension with NO current to any reference, that snake oil can cure. (no change to use one or two serial switches in a closed loop).

Please, can-you post schematic of what you think a better solution from AC ?
I (and others, i presume) would be very graceful to learn something (i'm serious).
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Last edited by Esperado; 4th September 2012 at 12:21 AM.
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Old 4th September 2012, 01:19 AM   #2907
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To make the things clear (i do not like fog or smoke) concerning power supply, my "fast switching" allusion was, of course, a joke.
Any Diode in a bridge is fast enough with a 50 or 60 Hz AC. And the fastest, the hightest will be the "ring" at the switching off of the diodes.
Some would like, on the contrary, to use little parallel caps with each diode to slow them and smooth the switching..
Of course, you will like to add a EMI filter before the trasfo's primary, direct in the AC inlet of the amp.
And RC snubbers as a charge connected to the secondary coils to help dumping the switching noise.

As each particular situation (AC voltage, trasfo, charge etc.) request snubber tuning, my purpose was not to talk about that part of a PSU design. Nor recommend to use the values of this schematic to power a +-25V amp ;-)
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Last edited by Esperado; 4th September 2012 at 01:23 AM.
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Old 4th September 2012, 02:49 AM   #2908
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Well, cher Christophe, since nobody accepts the glove, I will tell one of my tricks, even if heaven knows that I am the least qualified to do so...but somehow I just cannot build stock PSs; I always have to try something new or odd...

My digital guru,-ECdesigns-, developped several tricks the last years to be tested in his ultimate NOS DAC, tricks that I (and this one also him) tried on high power circuits. The present one is very clever and cheap (if you don't use Schottkies like I did) to reduce the charging pulses. I've tried it on power amps, and though I did not measure the effect, I believe it makes a significant improvement soundwise. This is the "stepped rectification"...now I don't remember if I already recommended it on this thread or not...

[IMG]https://picasaweb.google.com/lh/phot...eat=directlink [/IMG]

Values and number of units can be adapted to specific circuits. For example, -EC- mentioned he used 5 diodes in series for power amps.
Anyway, a cheap trick, easy to try.

Amicalement
M.
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Old 4th September 2012, 04:59 AM   #2909
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Even when using fast diodes (100 kHz) is observed on an oscilloscope "tooth" and "fangs" to the spectrum up to 2 kHz. Interference from the switching diodes. At the sound of a chirping.
Decreases proportionally with increasing capacity filter capacitors.
Caps parallel diodes give a little. I have the effect was negligible.
I plan to use the CLC filter. Dialed on a small rod of steel plates. Not closed magnetic circuit.
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Old 4th September 2012, 06:17 AM   #2910
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Quote:
Originally Posted by shaan View Post
Problem solved. Hum gone.

Changed the zener-parallel capacitor to 2200uF. Clean and clear.

Makes me think... 1000uF capacitors would be enough here. Those caps must be either leaky or fake. Whatever.

I'm Happy again.
Me happy too.

It was meant to be 1000 uF parallel to zeners in the first place, nevertheless please try some 10-100 uF from emitters to GND.

Now low level details are not blurred by hum anymore, darker silences, better soundstage, more detailed view into a recorded material. Nice, enjoy.
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