I have a neumann U67 microphone that has some 40 year old wima
polyester foil caps in the feedback path.

Does anyone have any experience regarding degredation of sound in
relationship to ageing in such caps??

The mic is very expensive and I want to solder new ones in only if it
will make a difference in sound.

Max

maxdm wrote:

I have a neumann U67 microphone that has some 40 year old wima
polyester foil caps in the feedback path.

Does anyone have any experience regarding degredation of sound in
relationship to ageing in such caps??

The old caps will work fine - they are sealed.

The mic is very expensive and I want to solder new ones in only if it
will make a difference in sound.

It will probably make a difference in sound, as the new caps are
different from the old ones. But it may not be an improvement.

Best regards,

Mikkel C. Simonsen

Max,

Film caps such as the Wima are designed for severe service. Extended
temperature, high frequency, and abusive currents.

In your application, the caps see none of the above. In fact, they're
loafing!

Physical aging of the plastic dielectric would occur if exposed to UV rays,
extended Temperature, Humidity, and Bias (THB) exposure, etc..

But the Wima has an opaque enclosure against UV rays and It is sealed from
the bottom against THB.

i.e. The cap will last longer than you or I!

Carroll
"maxdm" wrote in message
m...
I have a neumann U67 microphone that has some 40 year old wima
polyester foil caps in the feedback path.

Does anyone have any experience regarding degredation of sound in
relationship to ageing in such caps??

The mic is very expensive and I want to solder new ones in only if it
will make a difference in sound.

Max

(maxdm) said:

I have a neumann U67 microphone that has some 40 year old wima
polyester foil caps in the feedback path.

Does anyone have any experience regarding degredation of sound in
relationship to ageing in such caps??


The mic is very expensive and I want to solder new ones in only if it
will make a difference in sound.

And THAT's probably the last thing you want.
I mean, you bought a Neumann for the sound, not for the name tag,
didn't you?
You can always take the caps out and measure them for capacity and
leakage.
I suspect they'll be allright. Humidity always is the enemy of
electronic components, and one may safely assume that mics like the
U67 were well treated and locked away in their jewel case.

--
Sander deWaal
"SOA of a KT88? Sufficient."

maxdm wrote:
I have a neumann U67 microphone that has some 40 year old wima
polyester foil caps in the feedback path.

First of all cograts. You have a truly fine instrument that will give
you decades of perfect service if well looked after.


The components are all part of the overall design. Any change in kind
(whithin reason even brand) will adversely affect the sound. So, don't
be attempted to alter anything.
The same holds true for the electrolytics. If any fail due to having
dried out, don't be attempted to use modern boutique style caps but use
NOS Wima, Ero (Roederstein), Siemens or Valvo (Philips) only.
Resistors don't fail under normal circumstances. However, id you ever
have to replace one, use only Siemens, Beyschlag or Roederstein carbon
films as they will guarantee the lowest noise floor.


Does anyone have any experience regarding degredation of sound in
relationship to ageing in such caps??

They never fail. They're hermetically epoxy sealed, so don't worry.


The mic is very expensive and I want to solder new ones in only if it
will make a difference in sound.

This is exactly the point. It's an expensive and now rare precision
instrument. You don't want to jeopardize the sound properties of an U67
or any vintage microphone by haphazardly changing any of its components.

Enjoy any and all of your recordings in the future!

/Dieter


Max

The wima caps are early clear plastic/foil types.

I am worried about irregularity between layers as the plastic shrinks
with age due to loss of plasticizer.

they do shrink and crack, as I have seen some that were cracked and
shorted in tube amps.

of course the ones in the mic are in good condition, but plastic will
harden and shrink over the years.

I think what everyone has been saying is this...

Don't screw with it unless it starts screwing up.

HOW will you know?

Trust me, on this mic you WILL know.

In the mean time, enjoy it.

Regards,

Spike


On 28 Jul 2004 12:09:51 -0700, (maxdm) wrote:

The wima caps are early clear plastic/foil types.

I am worried about irregularity between layers as the plastic shrinks
with age due to loss of plasticizer.

they do shrink and crack, as I have seen some that were cracked and
shorted in tube amps.

of course the ones in the mic are in good condition, but plastic will
harden and shrink over the years.