New Caps for amp power supply

[john111]

Hi And thanks for reading this post. I am going to replace the stock 10kuf caps in the power supply of an amplifier and have been told it is better to parallel a few smaller caps rather than using one large cap. Apparently one big 10kuf cap is slow to charge and discharge and gives a slow kind of sound. Tried googling this point but cannot find it anywhere. Do you think it could be true.
Also I was going to purchase low esr caps but have been told that this will not make a difference with the 50hz mains ac, that low esr caps only make a difference at high frequencies such as smps

Any information on either of these two points will be most appreciated.

[petehall347]

Re: New Caps for amp power supply

sort of depends on the amp really . if old school supply i would choose correct ones . maybe epcos as i have found them to be good . others may say different .

[rugger]

Re: New Caps for amp power supply

Are the existing capacitors faulty/leaky/measuring bad, or does the amplifier exhibit excessive 50/60hz hum?

If not, I wouldn't touch it. Second guessing the engineers of your amplifier isn't a good idea unless you really know what you are doing.

[john111]

Re: New Caps for amp power supply

The amplifier is a quad 405, and the caps are about 40 years old and bulging, because of this i have been worried to turn the amp on.
Yes i could use epcos as they are a good manufacturer just i have been given some advice and would love your thoughts on it.

[stj]

Re: New Caps for amp power supply

if you replace them, the most important value to match or go higher is the ripple current.

[john111]

Re: New Caps for amp power supply

Okay, good advice, what about the two questions i put up

[stj]

Re: New Caps for amp power supply

low esr will not make a difference at 50Hz (or 100 probably after it's rectified)
putting caps in parallel is up to you - it's not so easy to mount them,
i did it once simply because i couldnt get a big enough cap.

[Andrew F. Ali]

Re: New Caps for amp power supply

I don't agree with replacing a big capacitor with smaller ones in parallel. Never heard that, that is better. There are 'Audio Grade' capacitors available. That is the type you should look for.

[stj]

Re: New Caps for amp power supply

"audio grade" are for signal path, this is the linear psu section.

[john111]

Re: New Caps for amp power supply

Thanks for the replies, much appreciated.
If esr is unimportant, should i choose a cap with the max ripple current spec, is that important?
Also, should the big 10kuf cap be bypassed by a few smaller ones, something like 10kuf+1kuf+100uf, will help in any way.

[rugger]

Re: New Caps for amp power supply

You really should be trying to replace it with like for like. You are overthinking things and that is more likely to cause an error.

Normally if you use small capacitors on the power line, they go near the the power input to the ICs and transistors to reduce localized line ripple on those devices, rather than on the PSU.

Really, the most important thing is buying a capacitor from a good brand in the right size and shape to make installing it not a big pain in the butt.

[Andrew F. Ali]

Re: New Caps for amp power supply

"audio grade" are for signal path, this is the linear psu section.

Yes. You are correct. I was thinking a little too much. Thanks.

[john111]

Re: New Caps for amp power supply

Thanks. I found samwha hc caps 10kuf for £4 over here in britain, vishay pht-sr series for £20 and nippon smh for £33.
Does it make an audible difference to spend money on expensive caps, and do you have any suggestions for suitable caps, what are your favourites for 10kuf 80 volts are there any you tried and enjoyed.
The stock caps are 50 x 80mm (D X H) but unfortunatly are out of production so i cannot replace with like for like.

[stj]

Re: New Caps for amp power supply

what are the original cap specs?
uf,volts,diameter,height,connection(pins/screws) and make,series?

[john111]

Re: New Caps for amp power supply

I honestly do not know, they are 40 years old and out of production. The markings have been worn away but i did read something about SRS caps, that they were made by a company called SRS.

[Sparkey55]

Re: New Caps for amp power supply

Hi And thanks for reading this post. I am going to replace the stock 10kuf caps in the power supply of an amplifier and have been told it is better to parallel a few smaller caps rather than using one large cap. Apparently one big 10kuf cap is slow to charge and discharge and gives a slow kind of sound. Tried googling this point but cannot find it anywhere. Do you think it could be true.
Also I was going to purchase low esr caps but have been told that this will not make a difference with the 50hz mains ac, that low esr caps only make a difference at high frequencies such as smps

Any information on either of these two points will be most appreciated.

You have been deceived by the AudioFools out there thinking that they can "hear subtle differences in audio response from amps" by using certain filter caps in the power supply. It is all bullshit. The caps will be rated for at least 1.5 times the highest WVDC that powers the amp. The power rectifiers should be rated for a PIV of at least 3 times the WVDC. Preferably higher.

[rugger]

Re: New Caps for amp power supply

I honestly do not know, they are 40 years old and out of production. The markings have been worn away but i did read something about SRS caps, that they were made by a company called SRS.

Really, probably best to just measure the diameter and height of the existing caps. see if it is soldered/clipped or screwed in. Also note the voltage and uF of the capacitor.

Since it is the filter caps for a linear power supply, they are not under that much stress and you could use virtually any capacitor of suitable dimensions, voltage and capacity. The original capacitor, being of 1970's or early 1980's vintage, would not be anything special.

[stj]

Re: New Caps for amp power supply

make & model of the amp??

btw, if the ripple rating is too low then the output will clip when you have big bass thumps at high volume.
(not enough current)

[john111]

Re: New Caps for amp power supply

The amplifier is the Quad 405

[rugger]

Re: New Caps for amp power supply

Looking at the design of the Quad 405 from pictures online, the following caps would be suitable replacements:

https://au.rs-online.com/web/p/alumi...itors/8526294/

10000uf at 80v

They are not specifically high performance, but there is no reason you would need anything higher performance than this.