Polarized capacitors and reverse breakdown

[zaib4tsu]

In many cases the only way to find out (for both issues mentioned in this post) is to try it. Sometimes it works OK, sometimes it does not. The main point is that naive 'upgrades' can sometimes do harm. Be aware that a small amount of signal degradation (e.g. HF peaking falling short of oscillation) may be heard but could be misperceived as an improvement - especially if lots of money has been spent.

Thanks.
I tried it and I claim to hear neither improvement nor degradation - if there is an audible difference it's negligible. The parts are typical panasonic ECWF polyprops, hardly expensive enough to bother fooling myself over. I'm really not in that camp, I wouldn't have posted up a pic of my rookie work if I didn't want to be critiqued / shot down (in the hopes of learning something).

I was actually curious if you had any practical concerns given the circuit (first pic) and before/after photographs (eg. any proximity concerns). I marked (in red) on the schematic the 4 parts (one channel), replicated L/R to make up those 8 brown film caps.

1. No AC mains anywhere near this area, entire power supply and rectifier + caps are miles away and on sep board. There is secondary power filtering before this point too.
2. The 2x 2.2uF/100V caps per channel can't be carrying signal as they are just for filtering (from my understanding), but the DC servo caps (1x 2.2uF/25V, 1x2.2uF/50V) I'm unsure of. To my understanding there is no capacitor coupling in the amp, so wouldn't that make this a non-concern? I may have misunderstood.

One standing flameproof resistor per channel *very* nearby does carry the signal (directly in series with s/p) but if I understood your post correctly, that would be a concern only if a nearby capacitor was also carrying the same signal (at different amplitude)?

I understand from what you say if the circuit was relying on ESR that aspect would be difficult to determine, but I suspect that's unlikely here (seems like bad circuit design to rely on such an inconsistent resistance for resonance damping). I did measure ESR on the original parts from '83 (around 3.2Ω), will measure some new 2.2uF electrolytics soon to check difference.

@MarcelvdG
No voltage regulators here to my knowledge, just old fashioned resistor networks as voltage dividers from what I can see. Good to know that about the LM317 though.

 

[dotneck335]

It's the internet. You are always going to be able to find people with the same crackpot opinions as yourself. From the earth is flat, aliens living next door and changing a capacitor will make your amp sound so sweet regardless of the circuit.

Yes. As well as the belief that circuit design trumps all else---all ICs sound the same (proven by blind tests, according to some) and capacitors of the same value cannot be distinguished from one another. MANY manufacturers adhere to this, and use the cheapest components available.

 

[DF96]

Circuit design is certainly far more important than component brand. Sadly, some people know so little about audio electronics that we have people wanting to swap brands and change the value - and asking about the brand instead of the value change.

 

[silverprout]

Circuit design is certainly far more important than component brand. Sadly, some people know so little about audio electronics that we have people wanting to swap brands and change the value - and asking about the brand instead of the value change.

Perhaps the result is a vast parameters equilibrium and perhaps there is no enough conpetant pople to show the entire chain of parameters (it should be as long as a book)... or not enough competant readers to understand the entire chain of parameters (a book is too long) ?

 

[DF96]

No idea what you mean, so can't comment.

 

[Mark Whitney]

Perhaps the result is a vast parameters equilibrium and perhaps there are not enough competent people to show the entire chain of parameters (it should be as long as a book)... or not enough competent readers to understand the entire chain of parameters (a book is too long)?

Which parameters do you use in choosing a capacitor for the input of an amplifier?

 

[silverprout]

No idea what you mean, so can't comment.

Each components of the whole circuit have its own resistance, capacitance and inductance. Each RLC parameter is dependant of the frequency, the current, the voltage and the temperature.

Nothing of theses parameters are linear and the interaction between them are tricky to predict, moreover the whole circuit is also dependant of the input and the ouput impedance.

 

[silverprout]

Which parameters do you use in choosing a capacitor for the input of an amplifier?

Manufacturers recommandations.

 

[DF96]

Each components of the whole circuit have its own resistance, capacitance and inductance.

True. Most of these will only become relevant at high frequencies.

Each RLC parameter is dependant of the frequency, the current, the voltage and the temperature.

To some extent. Not a big issue if appropriate technologies are used.

Nothing of theses parameters are linear and the interaction between them are tricky to predict

Most are quasi-linear. Interactions can be modelled, althoigh most are too small to bother with for audio.

moreover the whole circuit is also dependant of the input and the ouput impedance.

Maybe you meant to say source and load impedance?

You appear to be trying to argue that audio amps are so complex that the effects of component choice cannot be predicted and therefore cannot be denied. I am not convinced.

Manufacturers recommandations.

Few serious component manufacturers will say in their datasheets that a capacitor is suitable for use as an input coupling capacitor. This is because it is a rather undemanding role: limited bandwidth, low voltage level. One could suggest that such a claim might be a warning to avoid that manufacturer.

 

[silverprout]

True. Most of these will only become relevant at high frequencies.
To some extent. Not a big issue if appropriate technologies are used..

Audio waveforms are very easy to distort, how could we know what is audible or not ?

Most are quasi-linear. Interactions can be modelled, althoigh most are too small to bother with for audio..

When all of pseudo-linear derivations are correlated (they don't look really linear anymore), things appears to me infinitely complex and unpredictable at 100%, there are a lot of compromissions in technology IMHO.

Maybe you meant to say source and load impedance?

You appear to be trying to argue that audio amps are so complex that the effects of component choice cannot be predicted and therefore cannot be denied. I am not convinced.

I've not enough expertise to say what can be predicted or not, simple things are often more complex than they look.

Few serious component manufacturers will say in their datasheets that a capacitor is suitable for use as an input coupling capacitor. This is because it is a rather undemanding role: limited bandwidth, low voltage level. One could suggest that such a claim might be a warning to avoid that manufacturer.

Wima seems reliable to me (and the ratio cost/size/quality seems unbeatable for small audio signals, the MKS02 are smaller than COG SMD and 100 times cheaper.)

 

[DF96]

Audio waveforms are very easy to distort, how could we know what is audible or not ?

Most analogue waveforms are easy to distort. Audio is no different. We know what is audible by doing careful tests of hearing alone. Small low order distortions are not audible.

When all of pseudo-linear derivations are correlated (they don't look really linear anymore), things appears to me infinitely complex and unpredictable at 100%, there are a lot of compromissions in technology IMHO

If you believe that audio circuits are "infinitely complex" and 100% "unpredictable" then audio design and modification is not for you. If true, then recommending component swaps is also a complete waste of time because you cannot know how a component will behave in any particular circuit.

I've not enough expertise to say what can be predicted or not, simple things are often more complex than they look.

True, but simple things are not always as complex as people who don't understand them think they are. "I don't understand it, therefore nobody understands it" is poor logic.

 

[silverprout]

If you believe that audio circuits are "infinitely complex" and 100% "unpredictable" then audio design and modification is not for you. If true, then recommending component swaps is also a complete waste of time because you cannot know how a component will behave in any particular circuit.

True, but simple things are not always as complex as people who don't understand them think they are. "I don't understand it, therefore nobody understands it" is poor logic.

I was suggesting that people who really understand never say that they understand