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Laurie
Double Platinum Member
Canada
4854 Posts |
 Posted - 03/20/2008 : 17:52:07
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G'day! Last week I bought a used (2000) MT-2 and as part of the normal maintenance that I do on pedals that come into my rig, I changed all the 1�F electrolytic capacitors to metallised polyester.
This morning I had a few minutes free so I decided to do an "A-B" test between the two different capacitor types. First I played through it with the new metallised polyester caps and found a "distinctive" sound setting (maximum level, minimum distortion, tone flat).
I then pulled it apart and changed the caps back to the electrolytics I removed - took about 5 minutes. I then played it on the same setting and, to my ear, there was very little difference. The only thing that could have been a subtle difference was the "harmonic breakup" (what sounds like the first couple of odd harmonics) may have been a bit nastier - but it's so marginal I wouldn't swear to it.
I then pulled it apart again and swapped the caps all back to the metallised polyesters. I then played it on the same setting and again, to my ear, there was very little difference. And again, the only thing that could have been a subtle difference was the "harmonic breakup" may have been a bit less harsh - but it's hard to tell.
My conclusion from this non-scientific test is that the 8 year old electrolytics are working fine. But I'll be leaving the metallised polyester caps in there.
Laurie.
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Edited by - Laurie on 03/20/2008 17:54:56 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/21/2008 : 04:22:59
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Hi lauries2 & guys
Interesting experiment.
And I'm not surprised at your findings, the Pedal & Caps are not that old.
The effect of aging caps,
would probably be more noticeable 15 to 20+ year old pedals.
After all, there really isn't any heat inside an older Boss pedal,
to contribute the aging effect on the caps.
I have some caps at work that have been sitting in the parts bins, & are now 5+ years old, these (new unused) caps, are showing signs of increasing ESR.
It would be very interesting to know, just how high the ESR has to rise, before it makes an audible difference.
The ESR is more critical, when they are used in SMPS (Switch Mode Power Supplies), especially if it's the start-up cap.
Regards Dr. Bob
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Electrolytic capacitors - take 2
