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polyester cap in fet to capsule position? Condenser Microphones
Old 24th December 2010
  #1
Lives for gear
 

polyester cap in fet to capsule position?

Hi I ordered some silver mica caps for this duty but unknowingly they were on back order. I want to just use some 1000pf polyester wimas. I will be putting them a pair of apex 185s which are pretty much the same as the mxl 603s.
I would put in polypropalene but I don't have any?

Why do I never hear of anybody using polyesters here? Will it be ok if I use them?
Old 24th December 2010
  #2
Lives for gear
 

Of the plastic film types, polyester isn't so hot, fairly high dielectric effects.

While long there's a lot of good info here:

Capacitor Sound

Polyester is the "PET" type film that in his tests Cyril found to have quite high
measurable distortion, especially with bias, and that is configuration you would
be using the capacitor.
Old 24th December 2010
  #3
Lives for gear
 

Good material there what I got from its try to go polypropylene or polystyrene
but the polyester didn't look bad either and it is talking about harmonic distortion, which sometimes isn't a bad thing. I think I will throw them in there and when I get some polypropylenes replace them or a/b them at least. Thanks.
Old 29th December 2010
  #4
Gear Maniac
 

There's no perfect answer for the job, but polystyrene film works as well as anything - very low leakage and reasonably low microphony. Mica is rather more microphonic. Polyester has a little more leakage and may be detectably noisy, especially if it's a low voltage metallised film type.
Old 29th December 2010
  #5
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tenor39's Avatar
 

I have a ton of 1000pf (.001mf) polypropylene and polystyrene caps. What voltage do you need?
Old 29th December 2010
  #6
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What voltages do you have? I try to stay as High as possible with out breaking a bugdet 63v or 100v would be fine I might be able to use lower and I could defiantly use higher. 1000pf is something I always need but never have in polystyrene or polypropylene.

Just let me know what you can spare and what you want for them. Either though pm or on here doesn't matter to me? Also What brand are they?
Old 29th December 2010
  #7
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tenor39's Avatar
 

I have WIMA PP film/foil in 63, 100, and 630VDC, F-dyne PP film/foil in 600VDC, F-dyne PS in 100VDC, and Mallory PS in 100 and 630VDC. I need to know what size will fit on the board and in the body.
Old 29th December 2010
  #8
Lives for gear
 

I use the 5 mm spacing I think and in body it doesnt matter to much as long as they wouldn't be larger than I would guess 1 cm, most arn't that big I think anyway.
Old 29th December 2010
  #9
Lives for gear
 
tenor39's Avatar
 

I have the WIMA PP, F-dyne PP, and Mallory PS that will fit. I'll send you pairs of each to try. PayPal me $10 to cover the envelope and shipping to: [email protected]. Give me you address in a PM or with the PayPal payment.
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