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Old 5th November 2017, 11:26 PM   #11
nycavsr2000 is offline nycavsr2000  United States
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Quote:
Originally Posted by martin clark View Post
New problems for the one example manufacturer quoted above in-thread - apparently several ..!
Here you go: selling point is the 'Supercap' supply, yet utterly massive sidebands of mains noise in every measurement:
Vinnie Rossi LIO modular integrated amplifier Measurements | Stereophile.com

- it seems to me there must be some massive/primitive common-impedance errors in the basic layout.

tl;dr: It doesn't matter how 'good' your psu scheme is, if the rest of the design and pcb/psu layout is incompetent. A basic, but well-considered jellybean 3-pin reg based supply can do 30-40dB better everywhere than this example.
+1. The incompetence in the design is very clear here. But that doesn’t matter for most audiophiles...unfortunately.

Best,
Anand.
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Old 6th November 2017, 10:36 PM   #12
mchambin is offline mchambin  France
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Default PS with Super Caps.

In a classic power supply, is there an advantage using Super Caps instead of electrolytics.
This asks for very high rating at the diodes because of a long charging time; This is easily affordable. Then, what about ripple and ringing ?

Would it be interesting in a CRC filtering to use both technologies: Electrolytic caps and super caps.

In any case, I am aware, ground layout is of a paramount importance in high quality power supplies.
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Old 7th November 2017, 05:57 AM   #13
abraxalito is online now abraxalito  United Kingdom
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Quote:
Originally Posted by mchambin View Post
In a classic power supply, is there an advantage using Super Caps instead of electrolytics.
This asks for very high rating at the diodes because of a long charging time; This is easily affordable. Then, what about ripple and ringing ?
You don't consider the long charging time to be a problem other than for the rectifier diodes?

If we take the ESR of a typical 10,000uF 63V cap as the target (say 10mohm) then its jolly hard to match that with supercaps as we need a long string of them (say 20 of the 3V kind). Which means each cap's ESR cannot exceed 0.5mohm. To get that low an ESR we'll be looking at 1000F and up for each supercap. The energy stored in a 3V/1000F supercap is 500*9 = 4500J. With 20 that's a total energy storage of 90kJ.

Let's take a 500VA transformer, if we assume it can short-term put out 500W (irrespective of power factor) then we can charge our array of 20 supercaps in about 3mins. However this neglects that charging a cap through series resistance loses as much power in the R as is stored in the C. So that gives us a 6mins charge-up time. In 6 mins perhaps our trafo has gone over temperature so we probably need some kind of electronic charging circuit (similar to a power factor correction boost circuit) to get better charging efficiency and keep the transformer within its thermal SOA. The electronics also needs to maintain charge balance amongst the cap array.

The supercap supply is going to be a huge amount better in the bass than a 10mF 'lytic, but at what cost?
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Old 7th November 2017, 09:19 AM   #14
mchambin is offline mchambin  France
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Good point, I had seen the issue of initial charging, but did not seen beyond the stress on the rectifier.
As you point, the drawbacks are:
Start up will take a long time.
If not taken care, the transformer will have time to overheat up to destruction or thermal fuse blown.
Same about the rectifier.
So this asks for a soft start and user patience.
This may be acceptable for a high power supply, then a sleep mode be handy for a quick warm start. The cold start would stay as obnoxious as a Windows at boot time.

Who knows wether, that is worth the effort and the extra cost ?
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Old 7th November 2017, 09:55 AM   #15
abraxalito is online now abraxalito  United Kingdom
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To compare the cost it might be worth specifying an equivalent performance supply built with normal 'lytics. If impedance down to 40Hz is the reference basis then we'd need 0.4F for the same impedance (10mohm) as a bank of supercaps.

Mouser wants $44 each for 1500F/2.7V so 20 of these comes to $880. Whereas 20 * 22,000uF @ $15 each (Chemicon) comes to only $300.

Not really any competition.
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Old 7th November 2017, 10:46 AM   #16
jazbo8 is offline jazbo8
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@mchambin - starting multiple threads on the same/similar topic is against the Forum Rules, as a result, your threads have been merged.
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Old 8th November 2017, 05:08 PM   #17
mchambin is offline mchambin  France
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So replacing the electrolytics by super caps makes it 3 times more expensive.
Is there some advantage to accept such cost ?
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Old 9th November 2017, 12:07 AM   #18
abraxalito is online now abraxalito  United Kingdom
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Its possible that the supercap version might be a little less bulky. But no, I can't see any other advantage for it. Presumably neither can poweramp manufacturers since no-one apart from Vinnie Rossi has adopted them, and he's doing it for the isolation not for getting a lower noise supply. For myself I think there might be easier ways to achieve the isolation - an air-cored transformer would be my first guess.
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Old 9th November 2017, 09:06 AM   #19
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Quote:
Originally Posted by abraxalito View Post
For myself I think there might be easier ways to achieve the isolation - an air-cored transformer would be my first guess.
How would the absence of a core help?
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Old 9th November 2017, 09:18 AM   #20
mchambin is offline mchambin  France
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With air core you are sure of a linear inductor.
Unfortunately, when a large inductance is needed, it is likely a soft steel core is needed. Because of saturation, the core is cut to insure a gap to improve this. However, the best core material and air gap cannot make a good linear inductor.
Only air core can do and unfortunately cannot give a large inductance of a small size.
They are very easy to make and calculate. You will find many on line calculators, use it and see what I mean about inductor values and sizes.
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