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Old 4th September 2012, 07:09 AM   #2911
mikelm is offline mikelm  England
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Quote:
Originally Posted by Esperado View Post
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).

I usually have separated secondary & bridge & 1st cap for each rail and then follow each secondary with differential chokes in both legs before 2nd cap.

Only join the 2 secondaries together to make ground after the chokes. Do this throughout entire system so system ground is never connected directly to secondaries.

Also snub out the resonances in secondaries

What I have yet to do but will do next is some filter the supply ground before connecting to system ground.

I think the scheme you posted could be quite good if the secondary resonances are reduced in frequency & snubbed out but not sure if this is as comprehensive as full choke scheme.

I think full choke scheme is as close to the ideal isolated battery as is possible and probably quieter than some kinds of battery.

If the entire system can then be double insulated rather than grounded this would be ideal but if we have to add a mains ground I guess it should be as clean as is possible.
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Old 4th September 2012, 07:14 AM   #2912
mikelm is offline mikelm  England
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p.s. I noticed that my DAC sounded much better when I adopted the above earthing
scheme to my entire system
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Old 4th September 2012, 04:42 PM   #2913
mikelm is offline mikelm  England
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I just upgraded my regulation scheme to this.

The new feature is the 100R resistor between the full earth of the casing and the star ground of the amp - got this from a TI application note that Sonny gave out in his TSSA implementation.

Big thanks 4 that Sonny !

It never occurred to me to include that resistor but upon examination it comprehensively completes the filtration system of this design.

So far I just applied it to one amp but when I implement this throughout my whole system I'm hoping for a significant improvement as it will substantially decouple the mains earth from my system ground.

Might be a small choke here would be even better but in the meantime I think 100R & 22,000uF ( plus bypass ) will provide a fair amount of noise reduction !
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Last edited by mikelm; 4th September 2012 at 04:45 PM.
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Old 4th September 2012, 07:09 PM   #2914
jayadev is offline jayadev  India
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I wont use choke filter in series to high current power lines of amp. there are chances of oscillation at many place and I believe it affects the damping to some extent.
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Old 4th September 2012, 07:21 PM   #2915
mikelm is offline mikelm  England
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Doesn't really affect damping, although the rails do dip during loud passages a little with the coils resistance - but the coils on my latest amp add up to less than 0.1R Total ( both windings added together in each choke = 0.1R )

I use chokes on all my amps and never had any problems with oscillation - don't really see what you mean - unless you refer to ringing at turn on in a poorly designed choke supply - that can happen but not if you design it correctly - easy to do in spice.
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Old 4th September 2012, 07:49 PM   #2916
Struth is offline Struth  Canada
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Hi Guys

Regarding the yellow boards in the Spectral PA ref'd in post 685:

That is just FR4 with yellow solder mask. London Power uses the same, with black silk-screening

Have fun

Last edited by Struth; 4th September 2012 at 07:58 PM. Reason: forgot to quote post
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Old 4th September 2012, 10:03 PM   #2917
jayadev is offline jayadev  India
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Quote:
Originally Posted by mikelm View Post
Doesn't really affect damping, although the rails do dip during loud passages a little with the coils resistance - but the coils on my latest amp add up to less than 0.1R Total ( both windings added together in each choke = 0.1R )

I use chokes on all my amps and never had any problems with oscillation - don't really see what you mean - unless you refer to ringing at turn on in a poorly designed choke supply - that can happen but not if you design it correctly - easy to do in spice.
One cannot say it is purely resistive looking from the amp side. but it is also dependent on the current drawn.
many of the high current amps act weird for the quality of wires .if those supply lines are more inductive than its likes under heavy loads there can be many anomalies. Case in study was TDA7294 gainclone bridge mode.

I am not quite sure about Spice but I have traced spurious issues with my 300mhz tek with change of wire or addition of chokes.
Unfortunately I did not had enough time to figure out the details ,I believe the filter chokes were acting like resonating tank circuits in conjunction with filter capacitor,power transistors and output load/speakers.
of course under nominal loads there was nothing visible but with heavy dynamic loads the picture changed dramatically.


I would rather go with good power supply and proper grounding.
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Old 4th September 2012, 10:17 PM   #2918
mikelm is offline mikelm  England
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Well, I appreciate you have a different opinion, but I don't appreciate your insinuation that my supply is not good and not grounded properly just because you can't be bothered to find out how to design a good choke regulated supply.

I would agree that they, like anything else, have to designed correctly otherwise there can be ringing & over voltage during turn on but just because it is possible to design something badly does not mean that we should not make the effort to design something well.
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Old 5th September 2012, 01:43 AM   #2919
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Quote:
Originally Posted by mikelm View Post
but I don't appreciate your insinuation that my supply is not good and not grounded properly
" I would personally not use or recommend this kind of supply."
Did-you ask others to be less susceptible than you are ? ;-)
Keep cool, folk, we are all ready to afford different opinions here and it is all the fun. And we, as human beings, are less defined by our Hifi equipment or electronic knowledge than the kind of music we listen. Nobody care about the size... of your PSU.
On my side, i just try to share and help with the few things i know..

Back to the subject.
I'm a little disappointed with your PSU, i supposed you will propose some shunt regulation ;-)
Chokes were used often in tube amps. And they present, like everything else in electronic pros and cons.
First remark, your 5mH coil have a Z of 3ohms at 100Hz (rectified 50hz) + the resistance of the wires. It makes 6.2ohm on each rail ! Far to be a dream to feed high power transients . All will depend on the value and impedance of the secondary caps. While mine will add the two capacitances reserves on demand at the price of a little voltage drop.

The advantage of coils are signal ripple they provide is more like a sinus, smooth, while it is more like a saw without.

Con is that, if you want to afford big amps, you need very huge and heavy coils. Plus shields against magnetic leakages.

About filtering diode's switching noise and hf, a coil or choke will perform less than a zener or any silicium active device . A lot less.

To resume, the reason why i prefer an active solution is just it is less noisy, filter any HF more deeply (up to Mhz), and provide a very constant voltage, for less money, and less weight.

Again, there is no difference between common ground at the middle of the coils or two bridges configuration with separated coils. And if you omit the AC coupling between your two coils, you can put just 10mH on the +and- side and nothing in the ground lines with exactly the same result.
Just a different order between serial parts, It is a matter of currents. Ground will be just at the outlet earth potential in both situations.

I just believe in measurements, when it is about PSU, because measurements are very simple here.
You can look any perturbation on the Power rails both at quiescent and with music. No magic, no need for any special AC magic wire and plugs you'll pay 300$.
Just oversize everything (coper bars, trasfo, caps) is the secret.

You can easily compare your coils with the kind of schematic i provided and compare. I bet you will see less noise at quiescent, and less loss of voltages during transients with the same caps.
Then you'll make your mind on something more solid than feelings.
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Old 5th September 2012, 06:01 AM   #2920
dadod is offline dadod  Croatia
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Quote:
Originally Posted by Esperado View Post
[I

To resume, the reason why i prefer an active solution is just it is less noisy, filter any HF more deeply (up to Mhz), and provide a very constant voltage, for less money, and less weight.
I like your Cap multiplier, but it has one drawback, fixed output voltage. Why not alowe that the output voltage follows slow changes of the input voltage like common Capacitance multiplier.
I am using a kind of a cap multiplier in my amp. It contains over current and loudspeaker DC protection. If someone does not like the current limiting it can be removed.
dado
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