pwr supply caps
Jun 13, 2008 at 4:55 PM Thread Starter Post #1 of 3


Member of the Trade: Music Direct
May 26, 2008
Illinois USA
has anyone experimented with different brands and configurations of caps in their power supplies (solid state or tube)? do you find that one large cap works better/worse than an array of smaller ones?

any particular brands sound better than others?

any comments appreciated.
Jun 14, 2008 at 4:46 AM Post #3 of 3
...mind you this reference pertains to a power supply stage used in a high-power speaker amplifier and not a headphone amplifier, but I thought I'd post it, anyway.

excerpt from TNT-Audio: "You see, filter capacitors should be just that, FILTER capacitors, their energy storage function being of secondary importance. In many commercial units, these roles are present but reversed - larger value capacitors are used not only for filtering, which they cannot help but do, but also to act as energy reservoirs.
Of course, they always act that way, but the point is that they tend to be increased in capacity to cover for inadequate power transformer size and/or performance.
In such cases, you are not very likely to find high quality capacitors inside, but rather those of commercial quality. There are two basic reasons for this. The first is that they are cheap, and can be made to look good on ad photos and in ad sales blurb.
The second is that by connecting two capacitors in parallel, one not only doubles their energy reserves, but also cuts their output impedance in half. This is of course quite true, and in practice works every time without fail, but in essence is much less than we are led to believe.

So halved output impedance may still be above the values obtainable by using a single pair of high quality capacitors. Also, this view completely disregards capacitor charge and discharge speeds - good quality caps are expensive precisely because they are, among other things, very fast.
By way of example, a typical commercial value capacitor, rated at 10,000uF/63V and costing some Euro 8-9, will have a speed of 30-40V/uS at best. An equivalent Elna for Audio series black, costing some Euro 15-25, will have a speed in the range of 80-90V/uS, i.e. at the very worst, double the speed of the best case in commercial cap land. A Siemens Sikorel cap, costing some Euro 20-30, will slew at over 100V/uS - but at a price.

And this is hard to ignore if you want good quality sound. What's the use of ultra fast electronics, capable of tremendous speeds, if they will be bogged down by slow capacitors, which will appear as speed limiters? I can't help being sarcastic here - this is why in so many cases the advertised amp speed is never achieved in real life.
Many manufacturers measure the speed of the input stage only, and far too few of the overall amplifier - the second group will always show much less impressive results. So beware of wild figures, they are most probably not truly representative of the amp as a whole, on an input-to-output basis.

Solid State Power Amplifier Supply Part 1

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