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Do audio differences exist between capacitors?

post #1 of 60
Thread Starter 

I've heard so many different opinions on other forums regarding recapping vintage gear(replacing old electrolytic capacitators). I've recapped one vintage Harmon Kardon Amp and plan on restoring my Yamaha M-4 amp.

 

I've used Panasonic's low ESR series(FM, M) and Solens but I've heard plenty say to go with "higher" grade  caps like Elna, Rubycon blackgate, Nichicron, etc at about 2x-3x the costs.

Many claim that the different caps have characteristics like very bright or deep bass reproduction......some won't use anything lower than Nichicron claiming how superior these caps costs.

 

The amp/speakers recapped with panasonics sound awesome so far.

post #2 of 60

From what I've read, the capacitor technology has improved, mostly from the materials used today. Mundorf and Duelund capacitors are some of the best but they are very expensive as well.

post #3 of 60
post #4 of 60
Thread Starter 

 

Thanks...

 

But to put it simply.....am I missing out by using Panasonic Low esr series versus "elite" caps in my amplifier? Worth noting the current caps are elite caps(but 30+ years old).

post #5 of 60
Someone might know better than I, but the 30 years might have more of an impact on the sound than the kind.
post #6 of 60

Of course there are differences between capacitors, even of the same listed capacitance, rated voltage, etc., and these can make differences in circuit operation to some degree.  And that's not just by longevity, parameters changing over time.

 

As for magnitude and quality of difference that will make on device performance, depends a whole lot on what it's being used for in the circuit and also a whole host of secondary factors, some of which are not obvious even if you're the designer of the circuit, much less somebody looking with the full schematic in hand and a grasp of everything there, much less somebody without the schematic.  A larger value is not always better, and some parts that look like upgrades may be worse in some other areas.  A power supply bulk capacitor serves a far different role than a DC blocking capacitor, and so on.

 

Most of the auditory descriptions you see about changes are probably not that accurate and indicate larger magnitude of changes than actually exist.  It's not like most people are comparing capacitor A vs. capacitor B side-by-side in a fair blinded scenario.  Usually they know which is which beforehand and furthermore are relying on relatively long-term memory for comparisons.  It's kind of going into the deep end of tweakery.

 

For replacing most old electrolytics in most gear, some kind of decent-quality part like the ones you've been using, should be okay.  I'm not so convinced by the expensive audiophile-approved options.  Is the amplifier really that sensitive to miniscule differences in those capacitors?  When you use electrolytics, you can't really rely on their parameters being exactly accurate out of the box anyway, much less over time.  So if the tolerances were really so tight and it were really such a big deal such that the small differences actually made some kind of perceptible change in the sound, wouldn't you need to be hand-picking the exact capacitors and recapping nonstop?


Edited by mikeaj - 1/6/13 at 11:44pm
post #7 of 60
Thread Starter 
Quote:
Originally Posted by bigshot View Post

Someone might know better than I, but the 30 years might have more of an impact on the sound than the kind.

 

 

You wouldn't believe how many vintage fans suggest "don't touch it! You may replace perfectly good, functional caps with worse ones and worsen the "sound"!" or "if it ain't broke don't fix it!".

 

My favorite "30+ year caps are still good! Don't need replace all of them"

 

 

 

BTW, is it worth replacing smoothing caps??! Mine has some stupidly expensive smoothing caps($40-$60+ each!) THey're still good so I guess they'll be fine.

post #8 of 60

Capacitors probably make the most difference to the sound by being used in ways they should not be (e.g. undersized coupling capacitors, large AC voltage falling on polarized electrolytic capacitors with not enough DC offset on them to prevent "wrong" polarity, very non-linear capacitors used in places where they have a significant effect on the sound (e.g. passive crossovers, equalizers, tone controls), etc.). That is, a good design tries to minimize the effect capacitors can have in the first place, and where they are really needed, it uses ones of the right type and capacitance. Very expensive "audiophile" capacitors are probably mostly snake oil.

 

Other than obviously the frequency response, electrolytic coupling capacitors mostly affect the bass distortion (basically, the larger the AC voltage swing on the capacitor is, the more it distorts, and it has higher impedance at lower frequencies, so the voltage will be higher there when connected serially with a load), however, it is likely that bass roll-off becomes audible sooner than the distortion. There are claims regarding the effect of capacitors on sound stage, dynamics, and other (often vaguely defined) parameters of the sound, but I have not seen these proven or convincingly explained.

 

As a random example, here is the THD vs. frequency and 60+7000 Hz 4:1 intermodulation distortion of a cheap sound card that uses "no name" surface mount 220 uF electrolytic capacitors on its line output. Both were tested at full scale (slightly less than 2 Vrms), and the red trace is the most difficult case, with a total load impedance of only 122 Ω), while the yellow is an easier high impedance line input. I doubt anyone would be able to hear this, and at 20 Hz, where the THD is -84 dB (= 0.0063%), there is already 0.5 dB roll-off; with smaller capacitors and/or lower impedance load, there would be higher distortion, but also more roll-off. At higher frequencies, much of the increased distortion comes from the op-amp buffer driving the line output.

 

700    700

 

Of course, an important parameter of electrolytic capacitors in particular is how long they last. Maybe the cheaper ones can have a real disadvantage here.

 

It would be interesting to do more measurements (especially ones, where, unlike above, the performance of the capacitor is more clearly isolated from the rest of the system), and loopback based ABX tests with various capacitors in different test configurations. However, I think audible differences would only occur with really poor or faulty ones, in "difficult" applications, badly designed circuits, or with a wrong choice of capacitor for the application.


Edited by stv014 - 1/7/13 at 3:13am
post #9 of 60
Quote:
Originally Posted by stv014 View Post

Capacitors probably make the most difference to the sound by being used in ways they should not be (e.g. undersized coupling capacitors, large AC voltage falling on polarized electrolytic capacitors with not enough DC offset on them to prevent "wrong" polarity, very non-linear capacitors used in places where they have a significant effect on the sound (e.g. passive crossovers, equalizers, tone controls), etc.). That is, a good design tries to minimize the effect capacitors can have in the first place, and where they are really needed, it uses ones of the right type and capacitance. Very expensive "audiophile" capacitors are probably mostly snake oil.

 

Other than obviously the frequency response, electrolytic coupling capacitors mostly affect the bass distortion (basically, the larger the AC voltage swing on the capacitor is, the more it distorts, and it has higher impedance at lower frequencies, so the voltage will be higher there when connected serially with a load), however, it is likely that bass roll-off becomes audible sooner than the distortion. There are claims regarding the effect of capacitors on sound stage, dynamics, and other (often vaguely defined) parameters of the sound, but I have not seen these proven or convincingly explained.

 

As a random example, here is the THD vs. frequency and 60+7000 Hz 4:1 intermodulation distortion of a cheap sound card that uses "no name" surface mount 220 uF electrolytic capacitors on its line output. Both were tested at full scale (slightly less than 2 Vrms), and the red trace is the most difficult case, with a total load impedance of only 122 Ω), while the yellow is an easier high impedance line input. I doubt anyone would be able to hear this, and at 20 Hz, where the THD is -84 dB (= 0.0063%), there is already 0.5 dB roll-off; with smaller capacitors and/or lower impedance load, there would be higher distortion, but also more roll-off. At higher frequencies, much of the increased distortion comes from the op-amp buffer driving the line output.

 

700    700

 

Of course, an important parameter of electrolytic capacitors in particular is how long they last. Maybe the cheaper ones can have a real disadvantage here.

 

It would be interesting to do more measurements (especially ones, where, unlike above, the performance of the capacitor is more clearly isolated from the rest of the system), and loopback based ABX tests with various capacitors in different test configurations. However, I think audible differences would only occur with really poor or faulty ones, in "difficult" applications, badly designed circuits, or with a wrong choice of capacitor for the application.

The test you want to do is high level THD at the low corner frequency.  Find the point where LF output drops 3dB then give it all you've got before clipping.  Unfortunately, you've got nothing to compare to, and the sound card will probably clip before you find the THD rise.

 

I went around on this one back when the Jung articles first came out. Actually just a little before that there was something in one of the electronic engineering trade mags about this too.  I was designing a mic preamp at the time, and faced the problem of a rather large value cap in the feedback shunt to ground, or alternatively an output blocking cap.  Without it at high gains you amplify the input offset voltage and end up with a significant DC offset at the output.  The idea was to reduce the gain at DC but not at any audio frequency.  The cap value was quite high because of the impedance around it, so it had to be electrolytic.  I tested a bunch-o-caps and found that THD only rose when three conditions were met: First, I had to use a frequency where the cap was actually acting as part of a filter, rolling off the low end (or high end).  Second, the audio had to be high enough that the peak voltage swing reverse biased the cap to nearly the rated voltage, and third, there was no DC polarizing voltage in the proper polarity on the cap.  Remove any one of those, and THD dropped to nearly that of the test oscillator.  There were several possible fixes.  I could have deliberately introduced a DC polarizing voltage to the cap...not a viable solution.  I could have made sure the value was so huge that no possible audio would ever hit the corner frequency (I sort of did that), but large value electrolytics have more HF issues.  I could have used two caps in series connected in opposite polarity, then polarized the junction between them so they both had a DC voltage on them in their rated polarity.  The downside to that was series caps result in an effective halving of the value, but increasing the HF problems.  I ultimately picked a large value cap, didn't polarize it at all, but made sure that no voltage on it would even come close to its rated voltage in either polarity. I chose a very low ESR and low dielectric absorption unit. Then I used it in the feedback shunt where the voltages it sees are miniscule.  To solve the HF issues it got paralleled with a small value polystyrene.  

 

I'd suggest here that not all vintage gear would benefit from cap "upgrades", it's very dependent on the specific design.  Cap distortion issues were largely unrecognized in the late 1960s and early 1970s, but even though the issue was ignored a lot of designers accidentally got it right.  Of course not many vintage electrolytic capacitors are still capacitors at all at this stage.  Old electrolytic caps without constant polarizing voltage on them to keep the electrolyte formed tend to die younger than ones that are kept constantly formed, and most audio usage of electrolytics barely polarizes caps at all.  So just getting fresh caps with the right value in there after 30 years is a good idea.

post #10 of 60
Quote:
Originally Posted by jaddie View Post

The test you want to do is high level THD at the low corner frequency.  Find the point where LF output drops 3dB then give it all you've got before clipping.  Unfortunately, you've got nothing to compare to, and the sound card will probably clip before you find the THD rise.

 

If the frequency response drops by 3 dB anywhere near the audio range, the capacitor is too small, and the roll-off will be audible anyway.

 

I do not only have a sound card line output, so I can use higher voltages, lower output impedance, and DC output for testing. Also, on the input I can use a voltage divider if necessary, and a differential amplifier. It is possible to compare distortion with and without the capacitor.

post #11 of 60
Quote:
Originally Posted by stv014 View Post

 

If the frequency response drops by 3 dB anywhere near the audio range, the capacitor is too small, and the roll-off will be audible anyway.

 

I do not only have a sound card line output, so I can use higher voltages, lower output impedance, and DC output for testing. Also, on the input I can use a voltage divider if necessary, and a differential amplifier. It is possible to compare distortion with and without the capacitor.

I completely agree that 3dB down in the audio range would be bad, but you need to be at the 3dB down point to see the THD easily. You might find that point below 20Hz somewhere.

 

For the test, if the cap is rated at 10V, you'll need somewhere around 20V peak-to-peak to really see the distortion.  Might see it kick in somewhat below that. 

post #12 of 60
Quote:
Originally Posted by stv014 View Post

 

If the frequency response drops by 3 dB anywhere near the audio range, the capacitor is too small, and the roll-off will be audible anyway.

 

I do not only have a sound card line output, so I can use higher voltages, lower output impedance, and DC output for testing. Also, on the input I can use a voltage divider if necessary, and a differential amplifier. It is possible to compare distortion with and without the capacitor.

I'd really suggest you read the Jung articles.  My example was a very specific case, and the test I cited only covers one type of capacitor distortion.  The article covers the other kinds, and does the job in-depth.  Highly recommended reading.

post #13 of 60
Quote:
Originally Posted by ukon16 View Post

You wouldn't believe how many vintage fans suggest "don't touch it! You may replace perfectly good, functional caps with worse ones and worsen the "sound"!" or "if it ain't broke don't fix it!".

All I know is that a friend of mine who does PA systems for live music shows said that he was testing an old piece of equipment he was refurbishing and decided to change the caps. It made a huge difference, and he didn't even realize it was a problem until he saw the results.
post #14 of 60
Thread Starter 
Quote:
Originally Posted by bigshot View Post


All I know is that a friend of mine who does PA systems for live music shows said that he was testing an old piece of equipment he was refurbishing and decided to change the caps. It made a huge difference, and he didn't even realize it was a problem until he saw the results.

 

 

It's true. Caps drift in values over time....especially cheaper ones. Bad caps can also lead to permanent damage in some cases

 

How much improvement depends on the age and caps used; for example the yamaha M- series amp uses mostly Ceramic, Poly, and Mylar caps in lieu of electrolytic caps(Elec. are the least dependable and degrade) so it actually sounds better or at least equal to my recapped Harmon kardon vintage reciever despite no new caps yet.

 

The Harmon amp improved greatly with new caps. I would say SQ stayed the same but values on everything(treble, bass, etc.) were more disciplined. Bass was not boomy but accurate and focused after new caps. That unit was only 25-28 years old unlike many 40+ year old consoles.

 

Some amps have caps that are have died or way off which would lower sound quality quite a bit I'd imagine. DC offset is another issue the needs to be fixed on some units over time.

 

Plenty of vintage fans don't have the know how to re-cap OR can't afford a repair man($200+ per unit) so they claim recapping is unecessary or ruins the sound. After one recap I realized this was utter BS. 

post #15 of 60

I think that we see here, some people that know the different technical reasons for different capacitors being more suitable for different points in a circuit than other capacitors.  They understand why a given capacitor may be more or less suitable for a given purpose.  They also understand the tests and measurements needed to assure that the capacitor is suitable.

 

But we have others who almost randomly replace capacitors. Then without any tests or measurements,  do a quick listen and make declarations the sound quality of the capacitor.

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