Monday, March 7, 2011

Thoughts on Acoustat capacitors

The three caps in the Acoustat high frequency transformer feed network are 47uF, 10uF, and 0.01uF.  The 0.01uF is a polystyrene.  That 0.01 (or something like that) could be teflon in some future modification.

But perhaps I shoulda got 57uF in one cap.  Actually I think the closest might be 56uF.  That's probably within tolerance.  Actually, IMO, the whole value could be might give better midrange response.  Prior to the "C" version I have (the last one) they used a 220uF electrolytic capacitor with the other two.  They redesigned the network to put less strain on the HF transformer.  So maybe almost as good to have two polyprops, to allow for fine tuning.

(*Will have to look, but IIRC all they changed was the capacitor!  The overlap between the transformers thereby being reduced.  If that's all they did, it suggests there might be some value in experimenting with other values in the range 57-220uF.  Reducing the capacitor from 220uF, I think, reduce the 2000Hz range, where the speaker is quite weak.)

The 10uF cap in there is a high quality (but non-botique) polyprop, though maybe not as good as the Solen I am using.

I've got the caps I got now, so I'm putting them in, no more waiting.  Saturday I drilled holes in the chassis for tie wraps and connections, and got insulators for the leads.  Got a new drill and titanium bits (much better than what I had).  Set up new "drill bench" in kitchen with sorbothane mat, countertops are exactly the right height.  My other drill bench is next to garage door, you have to stand outside to work there.

Now that I think about it, maybe I'll leave just a bit of lead exposed on the capacitor for attaching additional  or alternative capacitance, and this is a good question to ask Andy Szabo (top acoustat tech during the Hafler era) who has a new thread at DIYAudio.

Multiple capacitors can in principle produce lots of weird effects.  That is esp true at supersonic frequencies where the inductances become non-trivial.  However, even a single capacitor might be modeled (or even made) as a series of smaller capacitors in parallel, with series inductance and resistance).  So in my view, this is waay out there in terms of having audible effect, whereas removing 22 year old electrolytic is at the front.

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