Filter Cap Replacement

PolkMaster1 · January 2012

I am thinking of replacing the filter caps in my amp. The amps are 15 years old and have a few changes made to them by myself. I have eight nichicon 9000u caps at 80 volts. This would give a total of 72,000 uf of filtering in the amp. I believe that the caps are connected in parallel of four caps each, one set of caps are for the left, and another set for the right channel.

First, how would I discharge a cap before I even attempt to remove it safely from the amp?

Second, assuming that I removed these caps for new ones, which caps would be recommended for a solid state amp?

Third, would it be wise to go with additional cap filtering, say, caps at 10,000 uF each, 40,000 uF for each channel with the caps rated at 80 volts, assuming that room inside the amp were no object?

Fourth, would it be wise to mix higher uF caps with lower uF caps, or to keep the uF of each cap as consistent as possible when replacing caps?

Speaking of cap replacement, I seen people add soniccap film caps (and other type of film caps, jantzen, clarity cap, etc.) to their amps. What would be the reason of adding caps to the amps? If there is a type of cap inside my amp, what would I look for as a replacement or a cap to add to, to enhance the performance of my amp?

I have schematics of my amp, so I know my way around my amp pretty well.

Thanks much!

PM1

PreCd · January 2012

PolkMaster1 wrote: »

I am thinking of replacing the filter caps in my amp. The amps are 15 years old and have a few changes made to them by myself. I have eight nichicon 9000u caps at 80 volts. This would give a total of 72,000 uf of filtering in the amp. I believe that the caps are connected in parallel of four caps each, one set of caps are for the left, and another set for the right channel.

I would not exceed the bulk capacitor rating that is installed now. If the engineers designed the amp that way then leave it alone as far as the capacitance rating is concerned.

First, how would I discharge a cap before I even attempt to remove it safely from the amp?

There should be bleeder resistors somewhere. If they are in parallel then place a 100k 2 watt resistor between the - and + terminals for 5 minutes. Check with a volt meter to determine there are not voltages present. After removal I leave the resistor in place as they can recharge.

Second, assuming that I removed these caps for new ones, which caps would be recommended for a solid state amp?

Any name brand cap with a decently low ESR. Go to digikey or mouser. Make sure to take accurate measurements and pay attention to your type cap. Screw terminal, snap-in, axial leads, etc....

Third, would it be wise to go with additional cap filtering, say, caps at 10,000 uF each, 40,000 uF for each channel with the caps rated at 80 volts, assuming that room inside the amp were no object?

It is ok to go higher on the voltage rating but I would stick with the manufacturer bulk capacitance rating for the amp.

Fourth, would it be wise to mix higher uF caps with lower uF caps, or to keep the uF of each cap as consistent as possible when replacing caps?

Keep them as consistent as possible.

Speaking of cap replacement, I seen people add soniccap film caps (and other type of film caps, jantzen, clarity cap, etc.) to their amps. What would be the reason of adding caps to the amps? If there is a type of cap inside my amp, what would I look for as a replacement or a cap to add to, to enhance the performance of my amp?

What amp do you have? On filter caps some add the type caps you mentioned to bypass the larger caps. In some cases it is said to give more detail to the music or tighten up the bass. You are going to have to determine if you would like to do this and make sure it is not already done elsewhere in the amp before you proceed with it.

I have schematics of my amp, so I know my way around my amp pretty well.

Thanks much!

PM1[/QUOTE]

zingo · January 2012

If you can pay a little more, high temp caps are worth the money and tend to last longer.

pitdogg2 · January 2012

Nichicon makes some bullet proof caps I would just go up their chain to a better cap. You could look at Panasonic that is the only two my tech use's and swears by.

PreCd · January 2012

If you really want our help tell us what size your capacitors are in your amp at this time. Manufacturers like Nichicon may not produce a capacitor in the rating you need that will fit your amplifier.

Let us know the rating of the caps currently in your amp and we can go from there.

Be careful messing around in there around the capacitors ok. High voltage present even when unplugged.

PolkMaster1 · January 2012

PreCD, Pitdogg, Zingo -

Thanks for your feedback. At this time, I am just thinking about replacing the caps. I am in no hurry at the moment to complete this project since my amp is working fine - I have a few other things going on at this time which I need to complete. At the moment, I am seeking advice from others, such as yourselves to gather as much information as possible for when the time comes to embark on this project. I am going under the assumption that I will have to replace these caps at some point. Whether I do it now or wait later for it to burn out is the question I am pondering.

If I wait until the caps no longer work or are on the brink of needing replacement, when would I know this? I do not have experience in amps dying out on me. I guess I have not had a relationship with an amp long enough to know that it is no longer in love. :cheesygrin:

PreCD - thanks for the advice - it cannot be stressed enough that voltages can still lurk in the caps even when the power cord is unplugged from the power source. Working with just a single cap of this uF rating (9000 uF) is a deterent in itself, not to mention that 4 caps are connected in parrallel - so I am not working with a 9000uF cap, but 36000uF for each channel!!!

My caps are rated at 9000 uF each, 80 volts. I estimate that they are 4 to 5 inches in height, about the size of a quater in diameter. I do not have the amp opened up at the moment, so the information that I am providing are guestimates.

PreCD - you say to leave the cap uF ratings as is - fair enough. Do you or anyone else reading this post have any thoughts that if I were to replace the caps, would it be OK to add additional caps at the same rating - say having 6 or even 8 caps on each channel - each cap would be rated at 9000 uF at 80V. This is assuming that I would have the room inside my amp to do this. I do admit that it is pretty tight in there, but I would like to explore the opportunity that if adding additional filtering would benifit the amp in some way.

Thanks much everyone for your help on this!!!

PM1

pitdogg2 · January 2012

Mallory computer grade capacitors

heiney9 · January 2012

Panasonic FC caps are excellent low ESR caps that won't break the bank. If they come in your values and size, pretty much a no brainer.

PreCd · January 2012

Agree! I had to go with Vishay because of the size of my filter capacitors.

Again I would not go over the bulk capacitance that is specified in your service manual or schematic unless you cannot find your values. A 9000uf cap may be hard to find. I bet a 10000uf cap will give you more choices. Just be sure the extra 4,000uf does not hit your circuit to hard on power up.

heiney9 wrote: »

Panasonic FC caps are excellent low ESR caps that won't break the bank. If they come in your values and size, pretty much a no brainer.

TECHNOKID · January 2012

PolkMaster1 wrote: »

PreCD, Pitdogg, Zingo -

PreCD - you say to leave the cap uF ratings as is - fair enough. Do you or anyone else reading this post have any thoughts that if I were to replace the caps, would it be OK to add additional caps at the same rating - say having 6 or even 8 caps on each channel - each cap would be rated at 9000 uF at 80V. This is assuming that I would have the room inside my amp to do this. I do admit that it is pretty tight in there, but I would like to explore the opportunity that if adding additional filtering would benifit the amp in some way.

Thanks much everyone for your help on this!!!

PM1

I fully agree with the advice on keeping consistency with capacitor values. Furthermore to your question above, adding capacitors in the circuit (be parallel or series) will affect the overall capacitance value and then defeats the purpose of capacitor value consistency. Unless you know exactly what effect the addition of capacitors will do to the overall capacitance circuit, I would refrain from doing so. Modifying the circuit this way has a greater effect than you think. Unless you had known design issue with your specific amp, you can create worsen your amp conditions rather than improve. Keep the old saying in mind, if it ain't broken, don't fix it! Preventive maintenance (replacing capacitors according to design value) value is one thing however modifying the design is another thing.

Cheers!
TK

Phasewolf · January 2012

One thing you need to think about with caps when looking at there value is most filter caps I see are + or - 20% So that is 7200uf too 10800uf and sense it's 2 banks of 4 the worse case is 43200 on the high end too 28800 on the low end of things. So I really don't see much issue with using 10000uf caps I just would not go way overboard with it. The company who built the amp I would think anyways would know that the caps they ordered would vary with in the 20% and I would hope would of built it with that in mind.

There is no way they would of taking the time too check every cap that came too them too make sure they were dead on unless it was a really small production run and being hand built.

Filter Cap Replacement

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