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Capacitors

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discrete badger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote discrete badger Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jan 2012 at 6:40am
Understood about the 20 year spec thing, but this does seem to be an issue with beefy power amps for a few reasons: the electrolytics in the power supplies can be pushed quite hard due to high idle power consumption and raised internal temperatures, and there is quite a lot of "heavy iron" investment in the large transfromers and heavy casework which means less of a temptation to sling it in the bin when the electrolytics have dried out early.

My two power amps (same model, but not very beefy at all and low idle power) are approaching 15 years old, and the one which has never been serviced is showing a bulge on 2 of the 4 power supply caps, corresponding to the right channel. Still sounds as good as the left channel at the moment. The point I guess I'm making is that with well designed equipment that the owner still gets a lot of pleasure out of, 20 years might not be such a long time.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jrhughes Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2012 at 10:22pm
I'm learning so much here. Started to do some reading around following a very informative post by Graham in the "burn-in" thread, where, finally, I am understanding about anodising slit edges... anyway, looking up some details about electrolytic capacitors I saw lifetimes mentioned in hours and was terrified! Thank goodness it's more like 20 years.

Assuming there are electrolytic caps in the PSU1, does the warmth in that equate to much of a lowering of lifetime?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2012 at 6:06am
Originally posted by jrhughes jrhughes wrote:

I'm learning so much here. Started to do some reading around following a very informative post by Graham in the "burn-in" thread, where, finally, I am understanding about anodising slit edges... anyway, looking up some details about electrolytic capacitors I saw lifetimes mentioned in hours and was terrified! Thank goodness it's more like 20 years.

Assuming there are electrolytic caps in the PSU1, does the warmth in that equate to much of a lowering of lifetime?


Capacitor manufacturers play their cards close to their chests so to speak - they declare what they want to declare.

Having said that, comparing a lower temperature range (85 degrees C) the endurance at 40 degrees C is 7 years. The caps in the PSU1 are 105 degrees C so they should run warmer for the same endurance. As temperature falls capacitor endurance increases considerably. The endurance or lifetime is quoted for the capacitor working to specification. After that time it will still be working although it may have started to drift away from its specified performance.
Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jrhughes Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2012 at 11:24am
Thanks Graham - you've answered my next question already: I had been wondering if the lifetime of the caps in the Solo were, say, 20 years, whether it would stop working in 20 years or just perhaps start to sound different. 

Is the sonic effect of caps which have started to drift easy to spot, or so gradual that it's unlikely to be noticed until the whole thing just stops working? I'm thinking of my new Solo/PSU1 and also, potentially soon, a Reflex. Also, thinking about it, my Cyrus stuff is fifteen years old now (Cyrus 3 + PSX-R and dAD3Q + PSX-R)...

Edit: sorry if I'm hijacking a thread... let me know if I should move to a new one.


Edited by jrhughes - 30 Apr 2012 at 11:26am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2012 at 8:43pm
Very informative and helpful thread. Thumbs Up
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DogBox Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2019 at 2:13am
Please Direct Me! 
I thought Here would be a good place to find "Bypassing" with Film Capacitors... but no-one seems to have mentioned it (besides Graham in the Genera notes.)... When I made my crossover for my JBL's it was a suggested thing to do... Costly little things! especially when you buy 10 and realize it wasn't enough to do both channels in 0.01uF AudioCap's from Parts Express in the USA and you're in Oz... 
 I had no idea "bypassing" could be beneficial in other instances too..? I live and learn again!! What a site!! Beats encyclopedia's!! Wink 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2019 at 5:46am
The bypass capacitor could have been yet another Walt Jung idea from his 70s/80s quests for higher fidelity in the US Audio magazine. Then again, it might have been used by RF engineers prior to that (the latter seems more obvious).

It can be a cure or it can be a con.

Adding 0.01uF to a crossover capacitor that's say 0.22uF might be heard as a difference in tone, especially knowing that speaker drive units can resonate all over the place, and if the addition just happens to be in the right/wrong place...

Hi-fi is an opportunist’s paradise so proceed with care.

Remember, a capacitor is also a resistor and inductor; a resistor is also an inductor and capacitor; and an inductor is also a resistor and a capacitor. These are secondary functions known as parasitics, not intended but there because nothing's perfect.

Parasitics can sometimes be benign, and at other times a complete bastard - a destroyer of faith in one's own abilities. I will only discuss the effects in an active electronic circuit here.

Bypassing an electrolytic capacitor with a film cap can often make an amplifier circuit sound different. That difference can be better, or worse in the way it sounds, or measures.

An electrolytic supply decoupling cap can let higher frequencies run amok in high frequency sensitive circuits. This is because it has series inductance (it also has series resistance which we'll come to). At HF the inductance adds resistance which reduces the caps "grip" on supply "stiffness". Placing a 0.1uF film across it is often the cure, as it offers some energy storage at HF, bringing supply "stiffness" back.

But it can also lead to glitches which can upset HF performance. Here you'd draw on paper the electrolytic's circuit which is the capacitor sign in series with an inductor sign in series with a resistor sign; and then you'd draw the film cap in parallel with it, but the film cap also has inductance and resistance, so you'd draw them as well.

Then you need to draw in the values. You know the capacitance but you need an awful lot of information about the components to draw in the inductive and resistive values. Such info should be available from capacitor manufacturers, but it mostly isn't. It's much easier for them to tell you the price...

A good guess for the electrolytic is 0.05 ohms and 50 nH inductance; and for the film cap: 0.005 ohms and 5 nH.

Then all you have to do is use all the LCR formulas you ever knew, or have to learn, to pull out the different excitation frequencies.

Oh, and one more thing: you also have to know the supply series impedance and the load's parallel impedance, to see what effect they have.

Much easier to do a simulation schematic and let the computer do you a frequency plot. Try these folks: https://www.simetrix.co.uk/

Armed with the above you can now turn your attention to the bias cap in the Genera (C9). It doesn't have a bypass, but can it? What does that voltage do? It is the reference voltage against which the op-amp decides what it's doing with the signal.

At high frequencies the PSSR (power supply noise regulation) diminishes, but as it's a resistive split it would only be -6dB to start with. The electrolytic makes it much much better, but can you figure out where it's going at really high frequencies? At some point that reference can be getting a little sloppy.

Once you have your Genera built and run-in a few weeks, tag a 0.1 - 1.0 uF film cap across C9 (under the board) and tell us what you found? Give it a week to bed-in though.

What type of film cap? Something like this should do nicely: https://uk.rs-online.com/web/p/polyester-film-capacitors/1262268/

And don't buy "boutique"!
Not simple enough for Google-Bot to understand...
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