I have an expensive U67 microphone that uses film caps in the feedback
path of the internal tube preamp.

I have changed the coupling electrolytic that was connected to the
trannie and the sound improved considerably.

I now wonder if the polyester caps have aged or degraded since they
were installed in the mic 40+ years ago.

I want to avoid taking the mic apart as much as possible, since it is
considered a 'vintage' mic and should be kept as 'original' as
possible.

If the caps do age and change sound, though, I will change them
regardless to have the mic as close to factory specs as possible.

anyone know??

As for the film itself, polyester is a stable material. It is affected by
few chemicals and there are no issues with aging. UV degrades it, but that
is a non issue in this application.

There could be other failure/degradation modes I'm not aware of that could
effect the capacitors. Sounds doubtful unless the capacitors were stressed.
John

"maxdm" wrote in message
om...
I have an expensive U67 microphone that uses film caps in the feedback
path of the internal tube preamp.

I have changed the coupling electrolytic that was connected to the
trannie and the sound improved considerably.

I now wonder if the polyester caps have aged or degraded since they
were installed in the mic 40+ years ago.

I want to avoid taking the mic apart as much as possible, since it is
considered a 'vintage' mic and should be kept as 'original' as
possible.

If the caps do age and change sound, though, I will change them
regardless to have the mic as close to factory specs as possible.

anyone know??

jriegle wrote:
As for the film itself, polyester is a stable material. It is
affected by few chemicals and there are no issues with aging. UV
degrades it, but that is a non issue in this application.

There could be other failure/degradation modes I'm not aware of that
could effect the capacitors. Sounds doubtful unless the capacitors
were stressed. John

What is Polyphelelene like ?

geoff