Ripple current Q for amp capacitors

Can the CD store basically 175,000uf if needed?

No, that’s not how it works, modern electrolytic capacitors typically have a tolerance range of ±20% being a common standard. This means that a capacitor labeled with a specific capacitance value can vary that much (either higher or lower) from the stated value when measured. The benefit of wider tolerances is lower production rejection rates for manufacturers, some older or lower quality capacitors may have a wider tolerance range, and for this Cornell Dubilier capacitor, that means the capacitance can vary a lot, you might get one that’s 90,000uF and another that’s 175,000uF.

However, in power supply filtering applications, the exact capacitance value is less critical. And the TDK is superior to the CD in every parameter!

As far as which of the two caps to use: you’d have to do a little bit of research and see if both versions of the CDE caps were available at the time of the EAD1000 production. If so, then the designers made the choice. 

According to the specifications of EAD powermaster 1000, it is a 5-channel power amplifier with a power output of 200W RMS per channel into 8 ohms and 375W RMS per channel into 4 ohms. 

It looks like the 50V power supply filter capacitor might be a little too low for its duties, did you measure the rail voltage?

When I went this route I reached out to Noble Electronics who are the only authorized EAD service center to ask if there were any other possibilities or weak spots, and he only suggested the two large caps. I guess i’ll focus on those, and maybe reach out and see if he’d suggest an alternative or what he uses.

If budget and space allow, my recommendation would be the EPCOS / TDK B41456B8100M000, 100,000uF 63V capacitors, 12000 Hour life @ 85°C with 4mΩ ESR and 57A ripple current.

Lower ESR means lower internal operating temperature, and every 10°C difference will double or decrease the life of the capacitor! A capacitor rated for 12,000 hours at 85°C will have a useful life of 96,000 hours if operated at 55°C.

https://www.tdk-electronics.tdk.com/inf/20/30/db/aec/B41456_B41458.pdf

I’ve been incredibly paranoid of not getting the right part in there.

Question on that above though as that’s interesting.. I assume at the time EAD had capacitance testers, and that every cap in this size they got, would be tested first to see where it was at. Why would they pick one like this with potentially a large throw away range? Or did they pick it because on the low capacitance end they would by odds be closer to 100k which was important to not be below that, but on the top end of the error they didn’t care if it was 120 or 150? I’m sure package size would have played a part as well.. there are two of these in each amp.

Capacitors produced in the same path usually have very similar capacitance and will not cause any problems if you replace both capacitors in the amplifier. Just for a peace of mind, the TDK also comes with 150,000uF 63V. However, I wouldn’t recommend anything over 180,000uF unless the power transformer is up to the task.

BTW, the TDK is a newer design with better technology, and the CD is a three decade old design.  

So when I have read before that a lower ripple is better for SQ because it filters more

I think you got it wrong!

Yes, a power supply with lower ripple is better for SQ. However, this does not mean that using a capacitor with a lower ripple current rating will help SQ, the fact is that you must choose a capacitor with a ripple current rating that exceeds the power supply requirements. There is an equation and I recommend you read this article to better understand how circuit designers select power supply filtering capacitors.

if that’s not really true, and that the esr and ripple ratings are ’only’ an indication of how well it will take abuse, and by that it’s lifespan, and that every 100k filter cap will pretty much ’sound’ the same?

Well, since you have two powermaster 1000 on hand, you can easily compare it, one with CD capacitors, and one with TDK capacitors. IMHO, lower ESR is better, theoretically.