Here we are...the secret is unveiled. These are Sprague Hyrel paper-in-oil capacitors. I have a bunch of these, as well as a bunch of Sprague Vitamin Q caps for future projects. Basically, paper-in-oil capacitors have the reputation of having fantastic tone - warm, detailed, and generally yummy on your ears. So I had to try 'em in our Dynaco preamp.
These things are built like little tanks - they're pretty hefty and are hermetically sealed. The outside shell is covered with an insulating plastic.
Right before I went to put them into the PAS, I got the bright idea of measuring their capacitance too. I figured I'd try to "match" two pairs for the phono and line circuits. I actually have 10 of these puppies, so I got a pair that measured .948 microfarads and a second pair that measure .944. Still within the 10% tolerance after 50 years. That is quality.
So now we have only 2 caps per board that the signal goes through - a Sprague 716P "Orange Drop" poly-and-foil cap, and these Hyrel PIOs. Here's to hoping we get good results.
I went with the red shrink tubing on these cause they're supposed to be so hot!
The difference between the Hyrel's and standard Vitamin Q's is that the Hyrel's have a paper plastic film sandwich for their dielectric structure. I was the Product Manager for both for over 20 yrs.
ReplyDeleteThank you so much for that info!!! Is that Polyester or Polycarbonate film? They are big, but too modestly sized yet for polystyrene, so...
DeleteI couldn't agree with you more. I have been putting Hyrels in my electric guitars for several years now. However, these days they are becoming harder and harder to find. Which is a shame. There's nothing quite like them. Great review.
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