Recapping advise for an old amp

[Charles_b]

Hi guys, Once again, im praying to the audio Gods for their guidance!

I have a pair of Denon 4400a monoblock amplifiers (20ish years old). They have both had new Mundorf power capacitors (The largest capacitors). I wanted to replace the smaller audio capacitors myself as I wanted to learn how to do something and get a real sence of achieving something whilst improoving the sound quality.
I have already purchased decent solder/soldering tools and im about to pull the trigger on some new caps.
My question is, can I replace all the caps with capacitors from one company line e.g: replace all the audio capacitors with Elma Silmic 2 capacitors or is that a big no no?
(I have noticed from the amp scematic that 2 capacitors are bi-polar which are not manufactured in the Silmic 2 line, but Elna do manufacture audio grade bipolar caps which I can use).
I have seen in other forums that other people use different capacitors on different places of the PCB for example in the analog signal path/DC bypass-Im not really sure what those terms mean and I wouldnt know how to identify these areas on my amplifier without guidance.

This is a list of all the electrolitic capacitors that I need to buy for each amp:

Electrolytic:

2544258785 (Aluminium +-20%) 470uf/35v electrolytic

2544260935 (Aluminium +-20%) .47uf/50v electrolytic

2544256949(Aluminium +-20%) 100uf/25v electrolytic

2544256936 (Aluminium +-20%) 47uf/25v electrolytic

2544254925 (Aluminium +-20%) 33uf/16v electrolytic x2

2544250929 (Aluminium +-20%) 100uf/6.3v electrolytic

2544260948 (Aluminium +-20%) 1uf/50v electrolytic

2544263990 (Aluminium) 22uf/100v Electrolytic

2544263084 (Aluminium) 10uf/100v eleytrolytic x4

2544260980 (Aluminium) 10uf/50v electrolytic x10

Bipolor electrolytic:

2543056959 (Aluminium Bi polar +-20%) 10uf/50v SME electrolytic bipolar

2543046901 (Aluminium Bi polar +-20%) 1uf/100v electrolytic bipolar x2
https://www.hificollective.co.uk/catalog/-c-61_68_442.html


Denon 4400a service manual link: https://www.hifiengine.com/manual_library/denon/poa-4400.shtml

Many Thanks,
Charles.

 

[Vini darko]

Hi a quick warning , those silmic II caps are often substantially bigger than normal ones. Its worth checking sizes on the installed caps and checking against the elna datasheet. Last thing you need is to find they don't fit nicely ( I learnt this the hard way).
With regards to them being suitable for the whole amp. If it's an class AB topology they should be ok.

 

[Vini darko]

I just looked up your amp that's a real nice one. Your post suggests that this will be your first go at re-capping. I recommend getting some el-cheapo caps off ebay. And finding a old crappy amp or midi system and parctice your desoldering and soldering so that any learning mistakes aren't a problem (I learnt this the hard way too )

 

[gvl]

Unless something is wrong with the amps recapping is generally a waste of time and there's a chance to damage something in the process. If you must go through the pains I'd suggest to learn how to make basic measurements of the amp first and capture the baseline performance, and then once done get another set of measurements and compare if anything actually changed, for better or worse.

 

[Charles_b]

Unless something is wrong with the amps recapping is generally a waste of time and there's a chance to damage something in the process. If you must go through the pains I'd suggest to learn how to make basic measurements of the amp first and capture the baseline performance, and then once done get another set of measurements and compare if anything actually changed, for better or worse.

Unfortunately one of the amps is making random hissing/cracking/popping noises via the left speaker.
I measured all ESRs of the capacitors and I have found a bad cap. Unfortunately, the type of caps used are not made any more so I thought that I may as well change them all out whilst I'm changing the bad one.
I guess I could just buy one capacitor to replace the bad one to see if the problem is resolved rather than spending the time, money and effort replacing all of them only to find out that the problem could still be there?
Many thanks

 

[Charles_b]

I just looked up your amp that's a real nice one. Your post suggests that this will be your first go at re-capping. I recommend getting some el-cheapo caps off ebay. And finding a old crappy amp or midi system and parctice your desoldering and soldering so that any learning mistakes aren't a problem (I learnt this the hard way too )

That's a really good idea. As far as I can remember, I believe it is an AB type amplifier.
Thanks,
Charles

 

[gvl]

I have similar amps but without the 'a' suffix, they do suffer from an occasional dropout and and some cracking/popping noises. I'm pretty sure it happens due to the oxidation of the speaker protection relay contacts as if I crank up the volume it goes away. If your issue is similar I'd visit the relays first.

 

[gvl]

I guess I could just buy one capacitor to replace the bad one to see if the problem is resolved rather than spending the time, money and effort replacing all of them only to find out that the problem could still be there?

This is certainly a better plan. Did you determine the same cap checks out good in the other amp?

 

[Charles_b]

I have similar amps but without the 'a' suffix, they do suffer from an occasional dropout and and some cracking/popping noises. I'm pretty sure it happens due to the oxidation of the speaker protection relay contacts as if I crank up the volume it goes away. If your issue is similar I'd visit the relays first.

Thank you for that information! Thats very useful. Mine tends to occur when the amp is cold and just turned on. It tends to go away after the amp has played some music and warmed up. If after changing the bad cap, it still occurs, I will investigate the speaker relays.
Many thanks,
Charles

 

[restorer-john]

@Charles_b The golden rule of repair is to locate and fix the problem before doing anything else. Do not attempt a shot-gun re-capping of the amplifier, hoping to fix the hissing/crackling/popping noise. It is most unlikely it is a capacitor and you may cause a more problems.

You need to meticulously find the problem. Start with the speaker relay. Try speakers B and see if the crackling is still there.

 

[gvl]

Thank you for that information! Thats very useful. Mine tends to occur when the amp is cold and just turned on. It tends to go away after the amp has played some music and warmed up. If after changing the bad cap, it still occurs, I will investigate the speaker relays.
Many thanks,
Charles

Very common issue. Crank up the volume when it happens, if it clears the congestion it's likely the relay. You can likely restore it if replacement isn't available, there are videos on YouTube.

 

[Charles_b]

This is certainly a better plan. Did you determine the same cap checks out good in the other amp?

Do you mean to open up the other monoblock amp and meassure the same cap in that one? I haven't done that but that sounds like a good idea and my next plan of attack!
Thanks

 

[Doodski]

@Charles_b The golden rule of repair is to locate and fix the problem before doing anything else. Do not attempt a shot-gun re-capping of the amplifier, hoping to fix the hissing/crackling/popping noise. It is most unlikely it is a capacitor and you may cause a more problems.

You need to meticulously find the problem. Start with the speaker relay. Try speakers B and see if the crackling is still there.

Good advice. Diagnose, troubleshoot, repair and then confirm proper operation before doing any other work on the unit is the best approach.

 

[gene_stl]

Wholesale , blanket recapping is likely audiophile snake oil.


If it ain't broke (by measurement) don't fix it.
Don't buy presents for your stereo. It won't notice.

 

[Doodski]

Do you mean to open up the other monoblock amp and meassure the same cap in that one? I haven't done that but that sounds like a good idea and my next plan of attack!
Thanks

You could even take out the apparently bad cap and substitute it with a good cap from the amp that has no issue. Then you save time and don't go down a rabbit hole.

 

[gvl]

Do you mean to open up the other monoblock amp and meassure the same cap in that one? I haven't done that but that sounds like a good idea and my next plan of attack!
Thanks

Yup, it's possible the cap reads bad due to how it's placed in the circuit, if it checks out the same in both amps it is likely a false positive.

 

[Charles_b]

@Charles_b The golden rule of repair is to locate and fix the problem before doing anything else. Do not attempt a shot-gun re-capping of the amplifier, hoping to fix the hissing/crackling/popping noise. It is most unlikely it is a capacitor and you may cause a more problems.

You need to meticulously find the problem. Start with the speaker relay. Try speakers B and see if the crackling is still there.

I have plugged the speaker cables into the B terminals and the noise is still there unfortunately. Could this still be another component and not capacitor related?

I did also record and put it on youtube some months ago although I only managed to capture the squealing and less of the pops and crackes:

Many thanks

 

[restorer-john]

You could even take out the apparently bad cap and substitute it with a good cap from the amp that has no issue.

No. Naughty. Always keep your reference functional amp/channel untouched.

 

[Charles_b]

You could even take out the apparently bad cap and substitute it with a good cap from the amp that has no issue. Then you save time and don't go down a rabbit hole.

and a money saver. Good thinking! Thanks. I'm just waiting for my new soldering iron to arrive in the post.
I actually (believe it or not) have 3 denon 4400a monoblock amplifiers. I was going to sell one one ebay (and I didn't want to sell the dodgy one to someone). If I'm unsuccessful, I can just keep the other good one (although will be a bit out of pocket)

 

[Doodski]

No. Naughty. Always keep your reference functional amp/channel untouched.

I know it's naughty but the guy is a newbie and needs to cut this short.