silver mica cap as input

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dissonantdissident
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silver mica cap as input

Post by dissonantdissident » Sat Aug 31, 2013 1:07 pm

Hey folks,
I know most folks recommend polystyrene for the input know so, connecting the capsule to the PCB. I've seen mention of folks using silver mica. Anyone tried this, and, if so, how would you say they compare?
turn up the pedal steel.

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floid
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Post by floid » Sat Aug 31, 2013 2:06 pm

you might want to price compare, depending on the value - larger value micas are available, but last time I BOM'd an eq I quickly reverted from the $28 micas to the $1.25 films.
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themagicmanmdt
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Post by themagicmanmdt » Mon Sep 02, 2013 9:25 pm

each cap has a different sound. seriously.

i'm not sure if i would personally enjoy a silver mica as the main input cap....

it'll be wideband, and detailed. accentuated top treble.

in non-scientific terms... i'd call micas 'zippy', yet hi-fi.

polypropylene will be a sonic place inbetween polystyrene and silver mica. WIMA's a trusted, great manufacturer.

from gnarly to refined:

ceramic
electrolytic
polystyrene
paper in oil
polyproplene
mica


although a paper in oil is hard to define... smoothed, yet extended... plus, it's completely, completely biodegradable...
we are the village green
preservation society
god bless +6 tape
valves and serviceability

*chief tech and R&D shaman at shadow hills industries*

themagicmanmdt
george martin
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Post by themagicmanmdt » Mon Sep 02, 2013 9:26 pm

each cap has a different sound. seriously.

i'm not sure if i would personally enjoy a silver mica as the main input cap....

it'll be wideband, and detailed. accentuated top treble.

in non-scientific terms... i'd call micas 'zippy', yet hi-fi.

polypropylene will be a sonic place inbetween polystyrene and silver mica. WIMA's a trusted, great manufacturer.

from gnarly to refined:

ceramic
electrolytic
polystyrene
paper in oil
polyproplene
mica


although a paper in oil is hard to define... smoothed, yet extended... plus, it's completely, completely biodegradable...
we are the village green
preservation society
god bless +6 tape
valves and serviceability

*chief tech and R&D shaman at shadow hills industries*

dfuruta
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Post by dfuruta » Tue Sep 03, 2013 9:18 am

This doesn't cover mica caps, but you might find this page of interest: http://www.sg-acoustics.ch/analogue_aud ... index.html.

Polystyrene, polypropylene, and c0g ceramic caps will be essentially perfect (well...polystyrene gets damaged easily during soldering, polypropylene caps are large and thus have potentially higher inductance). Haven't found measurements of mica and ptfe.

Jim Williams
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Post by Jim Williams » Tue Sep 03, 2013 10:26 am

Mica caps are made with pure silver electrodes, a very stable formulation. As for sound, I found them to be a bit smoother and darker than the premium film and foil polystyrene or polypropylene film types. The high voltage poly film caps have a bit more briteness and 'stridency' than the micas. They sound more forward than silver-micas.

All in all, mica caps are a poor choice for the sensitive high impedance nodes of a condenser mic head amp. The reason is microphonics. They will ring like a bell, you can fling them with a fingernail and hear the tones eminating from them. Unless you encapsulate a mica cap, never use one in a high impedance audio coupling configuation.
Jim Williams
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dissonantdissident
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Thanks for all of the responses

Post by dissonantdissident » Wed Sep 04, 2013 3:02 pm

There's a ton of information here to sift through. TapeOp really does have awesome folks on it. So, micas can make sense, but primarily only if insulated from resonanses. Would that mean mica's would be a better option elsewhere in the circuit, such as an eq cap, farther down the circuit?
turn up the pedal steel.

Jim Williams
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Post by Jim Williams » Thu Sep 05, 2013 8:23 am

Mica caps are expensive and rather large compared to their film equivalents. A 1000 pf 630 volt cap is over an inch long. I've tried them in EQ circuits and high end RIAA eq circuits as well. They do not perform as well as the best poly film caps. They do have a sweet sounding top end but sound restrained against more open sounding premium film and foil polypropylene or polystyrene film caps. I found teflon caps to also sound excellent, but those are even more expensive. I do use mica caps for feedback bandwidth control, but those are operating at far above the human hearing range.

One place I do use them for EQ is in all of my tube guitar amps. There is nothing better sounding in those than a silver mica hi EQ cap.
Jim Williams
Audio Upgrades

dissonantdissident
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alrighty

Post by dissonantdissident » Thu Sep 05, 2013 8:52 am

Sounds like I'm better off with skipping the micas. I might get one and a/b with a film, on a high frequency roll off part of the circuit. I've got a mic mod coming up and I'm gonna be needing to take the edge off of a rk67 capsule. Recommended in the position is a 200pf styrene.
turn up the pedal steel.

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