Friday, March 4, 2011

Gotta replace speaker caps this weekend...

I've just decided to take a big plunge (for me).  I've decided I'm going to replace the biggest capacitor inside the Acoustat interface, part of the low pass network that drives the HF transformer (it's a bypass transformer system, with two transformers to get around bandwidth and saturation problems).

That's a 47uF 35V nonpolar electrolytic, now 20-25 years old.  I bought the replacements almost 2 years ago, 600V Solen.

There just seems to be a grundginess I can't get rid of, no matter how I angle the speakers or apply EQ.  Up close, it becomes more annoying, and it's especially bothering me now.  The speakers sound OK on solo voice, etc., but on massed doesn't work anymore, especially up close.

If I were typical DIYAudiophile, I'd have done this 2 years ago.  But it takes me a long time to do soldering especially because I'm klutz and perfectionist and master at procrastination.

But this weekend looks like I will have enough time, and no more excuses.  And I'm very motivated now.   I unplugged the bias before leaving for work.  I've got the manual at hand which gives discharge instructions.

(Also planned to do it when I got back from San Diego in January, left speakers unplugged during my vacation, but lacked motivation when I got back, was really focused on bass problems after hearing my brother-in-law George's system which does have decent sounding bass despite everything.)

Now the original design also has 11uF in 2 polyester film bypasses (10 and 1uF, IIRC).  For the moment, I'm leaving those alone.  Eventually, the tiny one will be teflon, and I'm not sure about the middle one.  These are said by all Acoustat modders to be very critical to the sound, highly subjective, etc.

So for the time being, I'm not messing with the films, they're probably more or less OK, and materially comparable to the Solen I'm adding.  But that pile of dried out aluminum oxide has to go.  It's probably seen more than it's rated voltage many times (especially when I was using the Krell).

George is always saying that bypass capacitor systems are wrong, you should just have one good capacitor.  He's tried all sorts of botique caps, including monsterous teflon, nowadays pretty much uses Solen in all speakers.

I couldn't decide for a few months in 1988, then just decided to take the simplest possible first step.

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