This is of course much debated, but there are some general rules:
- First of all: remember that electrolytic caps do have a fairly short lifespan (compared to many other types of electronic parts). Some of them needs to be changed in older synths in order for the synths to work properly.
- I think it is fairly common knowlegde now that caps in the power supply and caps for bypassing can be changed without influencing the basic sound. In most cases it will bring back the sparkle in the sound and get rid of various types of problem, so yes: if you do like hum, cracle, noise and various other instabilities in your sound, there is no need to recap. ;-)
- The real culpit is in the caps that are in the direct path of the sound. Often, these components have not been so hard pressed that they malfunction (or are at the border of failure), so they still work even if they are old, and sometimes it doesn´t even matter if they short-circut, because there will still be sound in your synth. Recapping these specific caps might interfere with the sound, but I think the changes are very, very slight nuances - nuances that are ∗less∗ than the natural variances between two equal synthesizers, like two PolySixes or two MS-20s.
- The issue border on a similar discussion regarding op-amps: should you change the old op-amps with better-speced op-amps to get high-quality sound, or should you keep the old ones to maintain the old, "murky" sound, to maintain the original quality of the instrument?
But, yes: it is a good question: do we like the slightly worn-down sound of old instruments? I recalled talking to an old musician, we he states that the old Oberheim SEM modules sound somewhat dull today, while they sounded crisp and fresh when they were new. This could be because when they were new, most other sounds were somewhat mellower, especially the "moog sound" that the SEM was targeted as an extension to. Or it could be that in the years between we have had the digital revolution, and have become accustomed to shiny, highfrequency clinging digital synths, so in comparison an old, original SEM do sound somewhat duller than it used to do. Or it could be his memory, or he could be right that age do dampen some sparkle in electronic instruments, and recapping do return som original sparkle.
I do think a fully recapped PolySix will still sound warm. It is not all caps: it is the analog VCOs, filters and VCAs that makes the sound. And recapping, re-attaching cables and general cleaning really does the trick of getting rid of all kinds of intermittent problems.
Terje Winther
I know this is a tad off topic, but I'm wondering if anyone here has any thoughts about possible sonic negatives to doing this. I think of the recent video interview with the korg engineers who designed the ms-20, which was made and released as promo when the ms20 mini came out... The engineers mention in this interview that they think the ms 20 mini will only sound exactly like an original when it's been a few decades and the capacitors have aged.
So in this light, are we all in love with our aged capacitors? Or would a fully recapped polysix still sound warm?
Im considering doing this for the sake of clearing up stray issues now and in the future. I also am curious if it might even sound.. Better.
Of course it is assumed that recalibrations/tuning etc will then be needed. But couldn't a full scale bath like this be something very effective?