Capacitor Choices...What's Important?

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CarlosT

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Joined 2006
I'm currently comparing various Panasonic caps for an IGC kit and wondered what are the more important specs. The kit calls for 1,000uf 63V caps and the kit comes with Panasonic NHGs. However, Panasonic makes other caps in that range that have higher endurance, higher ripple and lower impedance. What is important?

Panasonic NHG 1,000uf 63v

Cost $1.78

Size 16mm x 25mm

Ripple Current 930ma

Impedance .1

Endurance 2,000 hours


Panasonic FC 1,000uf 63v

Cost $3.33

Size 16mm x 35.5mm

Ripple Current 2,770

Impedance .036

Endurance 5,000 hours


Panasonic FM 1,000uf 50v (no 63v available)

Cost $1.30

Size 16mm x 25mm

Ripple Current 3,320ma

Impedance .016

Endurance 7,000 hours

Is it strange that the "better" spec'd FM caps are cheaper? Am I totally missing the picture here?
 
falcott

falcott

Member
Joined 2004
From what I hear, it is more the "sound" of the component itself than the specs that are important.

Many have said that the Panasonic FC is their cap of choice in GCs. The Rubicon ZL is also a good choice for inverted GCs (and the specs are excellent!)

Sometime ago, people were raving about the Black Gate caps. I don't know what their specs are, but I believe that they have a different sort of construction to the conventional electros. It seems as though BG caps have fallen from favour in the GC circles in the last couple of years...

As for specs, what we should probably look for are high ripple rate and low ESR. It makes for a longer life cap too, if I guess correctly.
 
Nordic

Nordic

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Joined 2005
users.tpg.com.au/users/gerskine/dxamp/
Yes lower is MUCH better, the lower, the faster the cap can "slew".

Forget about the capacitor as a capacitor for a second and only think of it being a resistor, now using ohm's law see how significant the impendance is on current delivery and ripple absorption.

I'm afraid what is good for a class A PSU is not good for a class AB, and probably vice versa.

I need to quote an article on solidstate PSUs 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.
Click to expand...

One source of noise is a "power vacuum" where more power is required than can be instantly provided.
 
dfdye

dfdye

Member
Joined 2005
I'll second the cap comment about 1500 being a little low. I was less than pleased with the bass response at lower cap values. I personally have about 10K per rail in the PSU and bypass that on the board. (Oh, and I like the Linkwitz LM3886 circuit better than the gainclone circuit, but that is a different story for a different day. . . )

EDIT: I just thought to add that I have tried using 1500 uf caps on the boards power input, bypassed next to the chip, with 10K caps on the PSU rails. Though this is a little overkill, it seems to sound better full range to me.
 
falcott

falcott

Member
Joined 2004
elementx said:

let's see it...
Click to expand...


Ok, I can't find pics right on the spur of the moment, but this quote is about the original Gaincard that started all this (quoted from Mick Feuerbacher's site)

The PSU (Power Humpty)

This information was collected from other sources in the internet. The Power Humpty contains a high quality non-toroidal 170 VA transformer. Secondaries are 23.5V, 3.6 A. There are only four diodes, used for the positive and negative rails. The diodes are FE5D 9808 (General Semiconductors). There are no capacitors in the Power Humpty. The ground connections of the positive and negative rail are separately led to the amp boards.
Click to expand...

Peter Daniel's LM3875 kit, and BrianGT's earlier kit, have only 4.7uF per rail in the PSU.
 
Nordic

Nordic

Member
Joined 2005
users.tpg.com.au/users/gerskine/dxamp/
Caps are not born equal

crapvsesr.jpg


Same voltage and capacitance, big diffirence in size, ESR and quality
 
C

CarlosT

Member
Joined 2006
Re: 4780 kit

Bicycleguy said:
Pete's 4780 kit has 10uf on the psu, but states you can go up to 100uf.
Click to expand...

Lets' say that there's a simple pair of little caps on the rectifying board like in Pete's AudioSector kit. Is there any interaction that one needs to worry about with the bigger caps on the amplifier board? I noticed that Peter's LM3875 amp board does not have any parallel little caps...maybe that function's already taken care by the little caps on his rectifying board?
 
A

AndrewT

R.I.P.
Joined 2004
Hi,
post 18 rev Dec2, 2006.
Is the input impedance of the non-inverting chipamp=1k0?
Is the F-3db frequency=1/[2Pi *4.7uF*1k0]=34Hz?
and phase error upto 340Hz?

The statement at the top of the schematic seems suspicious:- setting R6=R2//R3 But R3 is DC blocked by C1. I think R6=R2+-variation to trim output offset.

The feedback tapping AFTER the half Thiel network seems odd.
Should it be BEFORE the Thiel? i.e. at node 3?

How far away are C5 & C6 from the supply pins1&4?
 
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