Let's talk caps...

[jbeckva]

First question I have posed to the audio tech gurus... Silver Mica Caps - anything special about them? I need a few 750pF for use in a crossover to rebuild - can't quite get the value I want out of Parts Express for their metal polys they have.

 

[jbeckva]

Put in context.. here is the xover schematic.. (might recognize this one eh?). The silver micas are being used in a bypass type of configuration, right? Isn't there perhaps some sort of consolidation I could be doing here, that also would have the values needed actually be values that solen and the other audio metal poly's come in?

 

[Gepetto]

First question I have posed to the audio tech gurus... Silver Mica Caps - anything special about them? I need a few 750pF for use in a crossover to rebuild - can't quite get the value I want out of Parts Express for their metal polys they have.

Silver mica caps are right on top of my list Jer. Extremely temperature stable, excellent dielectric, usually very precise and are usually very high voltage (again that great dielectric).

I use them on all the small value cap locations, excellent sound qualities. The military used them for all these great qualities.

 

[Gepetto]

Put in context.. here is the xover schematic.. (might recognize this one eh?). The silver micas are being used in a bypass type of configuration, right? Isn't there perhaps some sort of consolidation I could be doing here, that also would have the values needed actually be values that solen and the other audio metal poly's come in?

View attachment 10011

The silver mica values are not critical to this application Jer. They are there to offset the small inductance of the mylar caps at higher frequencies. The values of the Mylar caps are critical to the behavior of your crossover.

 

[jbeckva]

Seen any good metal polys coming in .5uF, Joe? Closest I have seen so far are either .47 or .56.

 

[Gepetto]

Seen any good metal polys coming in .5uF, Joe? Closest I have seen so far are either .47 or .56.

Use 0.47 Jer. 0.5uF is not a standard value.

 

[laatsch55]

Damn, this got deep in a hurry....

 

[Gepetto]

Damn, this got deep in a hurry....

I guess we need to talk about Nav's avatars now

 

[jbeckva]

I guess we need to talk about Nav's avatars now

keeping it semi on topic.. wouldn't mind being the dielectric between some of "em" myself..... haha.. geek joke... (was bad eh?)

 

[laatsch55]

And how would they pertain to crossovers??

 

[laatsch55]

keeping it semi on topic.. wouldn't mind being the dielectric between some of "em" myself..... haha.. geek joke... (was bad eh?)

I thought it was good, keep em comin...

 

[jbeckva]

I can't think no mo.. zzzzzz

 

[laatsch55]

Ok Joe, any improvement to be had here?

 

[NavLinear]

Ok Joe, any improvement to be had here?

Yes there is a potential improvement - too bad you asked though.

 

[Lazarus Short]

There are caps, and there are CAPS.

http://www.electricstuff.co.uk/destructotron.html

 

[laatsch55]

I have a dozen 140,000 uf at 20 volt caps in the garage that I vaporise screwdrivers with. Sometimes all the caps make and sometimes they don't.

 

[Lazarus Short]

I have a dozen 140,000 uf at 20 volt caps in the garage that I vaporise screwdrivers with. Sometimes all the caps make and sometimes they don't.

YIKES!