Power Supply Questions

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simon
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#31 Re: Power Supply Questions

Post by simon »

Cressy Snr wrote: Tue Jan 16, 2018 1:04 pm Carried out your suggestions Simon and the hum levels are now negligible. Thanks. :)
No crap being injected into the star point now, I presume.
TBH it's the first time I've done star earthing and I obviously got it wrong; a bit more to it than just running all the earths to one point.
Result :-).

Being a bear of simple brain I tend to use star earths for each stage and channel, then join those star earths to the quiet end of the PS grounding (but don't star earth the PS).

But I guess it's no different from a buss bar - noisy stuff at one end and quiet stuff at the other end.
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#32 Re: Power Supply Questions

Post by simon »

Cressy Snr wrote: Tue Jan 16, 2018 7:37 pm I'll audition the results later tonight as most of today has been spent modifying, simming, measuring and making sure nothing is about to blow up.
Ah, the proof of the pudding. Will you be able to hear the difference the sims tell you are there?! Waiting with baited breath...
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#33 Re: Power Supply Questions

Post by Cressy Snr »

After an extra duplicate RC section somehow got added to the sim (don't ask me how it happened) here are the corrected sims for startup and step response:

Startup.
Image

Step response:
Image
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Cressy Snr
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#34 Re: Power Supply Questions

Post by Cressy Snr »

simon wrote: Tue Jan 16, 2018 9:07 pm Ah, the proof of the pudding. Will you be able to hear the difference the sims tell you are there?! Waiting with baited breath...
Well it's like this.
When I had the SS rectifier followed by an EY500 damper diode and the larger amount of power supply capacitance, and took the amp to Steve's I had quite a good SET.

After I'd changed to a hybrid rectifier and overcome the flashover problems with a set of backup diodes and still had the large amount of capacitance and Paul heard it on new year's day, I had a very, very good SET.

After all the PSUD work, the earthing mod advice from Simon, and the reduction of the total amount of capacitance, and the addition of the 47u cap after the choke, and the following RC section to the output stage, I now have a great SET.

More muck has been cleaned off the window into the studio/venue; the whole thing is natural, musical, fast and dynamic.
We all know that the power supply is everything, especially with SET's and I'm over the moon with the excellent real world results given by the PSUD software.

The pink SET is an amp that I have no qualms about taking to Owston, or David's Huddersfield dem room. I haven't really been able to be as absolutely sure about anything other than those 6B4G monoblocks from 8 years ago. The pink SET blows even that creation, firmly into the weeds.
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#35 Re: Power Supply Questions

Post by Neal »

Great result there Steve!
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Nick
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#36 Re: Power Supply Questions

Post by Nick »

simon wrote: Tue Jan 16, 2018 9:05 pm
Cressy Snr wrote: Tue Jan 16, 2018 1:04 pm Carried out your suggestions Simon and the hum levels are now negligible. Thanks. :)
No crap being injected into the star point now, I presume.
TBH it's the first time I've done star earthing and I obviously got it wrong; a bit more to it than just running all the earths to one point.
Result :-).

Being a bear of simple brain I tend to use star earths for each stage and channel, then join those star earths to the quiet end of the PS grounding (but don't star earth the PS).

But I guess it's no different from a buss bar - noisy stuff at one end and quiet stuff at the other end.
if it helps any, I find thinking in terms of the current that’s flowing through the loops that include the ground. The most noisy one is the loop from the rectifier to the first cap through that cap to the transformer. There will be lots of charging spikes there. The closer to the transformer that loop connects to ground the more those charging spikes will be seen. Putting everything into one star at the negative of the first cap means those spikes pass through the start point. Connecting the start to the negative of the first cap via a single wire isolates the start from the spikes. But it has to be the cap negative, not somewhere on the wire from the cap negative to the transformer as wires have resistance and inductance, so Ac signals develop along them.

I remember moving a scope probe along 5cm of silver wire, the signal on the scope increased as I moved along the wire.
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#37 Re: Power Supply Questions

Post by Cressy Snr »

Yes, it seems I started a thread that was actually productive :D

My original 6B4G ressurrection thread is a mess and does reflect my character and absent-minded, lacking in focus, "Catweazle" approach to projects.
I think, his most frequent catchphrase was "Bah! Nuthin' works" if I remember rightly....about sums it up :lol:

I suppose plenty of other diy'ers go through the same process; it's just that they are not daft enough to document it :mrgreen:
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#38 Re: Power Supply Questions

Post by simon »

You explained it much better than me Nick
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#39 Re: Power Supply Questions

Post by ed »

Cressy Snr wrote: Wed Jan 17, 2018 12:56 pm I suppose plenty of other diy'ers go through the same process; it's just that they are not daft enough to document it :mrgreen:

nah!, some of us get it right first time....snigger
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#40 Re: Power Supply Questions

Post by Mike H »

Cressy Snr wrote: Tue Jan 16, 2018 6:49 pm That step is deliberately programmed into the software as a 1:10 current step. The step values can be seen at the current taps.
This is done to try to provoke the simulated supply into low frequency ringing.
OK then, would never have guessed! :D
 
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Mike H
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#41 Re: Power Supply Questions

Post by Mike H »

pre65 wrote: Tue Jan 16, 2018 7:21 pm I have a feeling that the cap ESR would be significantly less than 2R.
It will doubtless vary with frequency, aided and abetted by an inductive effect too, but for the purposes of 50 - 100 Hz, a single value will do. :D

If I'm guessing with large electrolytic values, I tend to use tenths of an Ohm, or maybe a bit less.


BTW Steve keep backups of your PSUD files, especially if you want to preserve a previous version to go back to, or keep as a reference, earlier version or whatever, as they are easily overwritten and hence 'lost', guess how I know. :(

(EDIT: it happens when you forget to change the file name & just do a 'Ctrl+s'. Oh bu55er! :( )


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#42 Re: Power Supply Questions

Post by Cressy Snr »

Cheers Mike.
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#43 Re: Power Supply Questions

Post by Cressy Snr »

Neal wrote: Wed Jan 17, 2018 11:41 am Great result there Steve!
Yes, I think it's a good conclusion to the pink SET project. A lot of stuff has been learned by building and modifying the power supply. Every change to the PSU has been audible, as it would be of course, but it is interesting that using PSUD to refine the supply has allowed me to see how simulation and measurement can produce results that correlate with what is heard by the listener. For example, the rise and recovery time shown with the current step sim accurately predicts the quality of speed and slam in the bass and the leading edge definition.

That sim alone is worth its weight in gold for showing me that bass control/slam, is NOT about how much capacitance you can throw at the circuit. All you do by chucking capacitance about like dolly mixture, is slug the bottom end. Yes you might get the depth, but definition and speed, suffers in comparison to a properly optimised PSU.

Class B valve push-pull is different story but even there, it is possible to go too far, as I almost certainly did with my Barbarik Monos.
The stereo version Paul has, is about right.
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#44 Re: Power Supply Questions

Post by Cressy Snr »

PSU after one or two loose ends have been tidied up:
Image
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#45 Re: Power Supply Questions

Post by Cressy Snr »

Image

Last and final PSU for 2A3-40
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