"David Satz" wrote in message
om
Arny Krueger wrote:

http://www.cadmics.com/pdf_files/e100_manual.pdf
the schematic is on page 4.

Thanks for posting the link. The CAD schematic doesn't seem to show
the actual front end of the microphone circuit at all. It shows the
pad switch as a feedback control later on in the circuit. Weird.

I don't find it weird at all. Instead of reducing the input to microphone's
electronics, they reduced its gain.

I'll leave it to David to support his claim... The pad is close to
the input, but not exactly at the input.

Furthermore, I see some advantage to attenuating at the input to the
mic electronics, if clipping in those electronics is the concern.

I agree--in most types of condenser microphone, the capsule can handle
far higher sound pressure levels without audible distortion than the
electronics of the microphone can. When the SPL exceeds the
amplifier's capabilities, a pad at the input of the amplifier is the
right choice.

But that isn't the usual situation, and it's certainly not the case
that the original poster has. He's trying to feed the signal from a
condenser microphone into an input that was designed for a dynamic
microphone, and he's getting input overload.

The external attenuator could work, as could the CAD 100 approach.

The CAD100 approach minimizes distortion inside the microphone's circuits by
reducing the output voltage.

That overload _could_ be avoided by using an attenuator between the
capsule and the microphone's electronics, and the original poster
proposed to do that. OK, it's useful as a test--it shows whether
lower signal levels going into the recorder can solve the problem or
not.

Adding an attenuator between the capsule and the microphone's electronics
shows whether lower signal levels going into the microphones' electroncis
can solve the problem or not.

Since this reduces the output of the microphone's electronics, it also as
you say, shows whether
lower signal levels going into the recorder can solve the problem or not.

But when input overload in the _preamp_ is the problem and the
mike itself isn't anywhere near being overloaded by its capsule, then
that's not a good choice, as compared with a resistive pad in-line at
the preamp input.

I think you've got things reversed.

The point is made however, that using internal and external pads can
have vastly different results when you don't know for sure at the
moment where the clipping is coming from (i.e., the real world).

And we agree completely about that, as we probably ultimately do about
all the other points as well. This message isn't meant as an argument
with you, but just as a way to spell out a thought process for how to
decide what to do in this general type of situation.

My suggestions would be [a] know the maximum SPL that each of your
mikes can handle, and only use their built-in pads when there's a
likelihood of exceeding that range; [b] bring in-line resistive pads
(15 - 25 dB) to all location recordings, and use them at the first
threat of overload; [c] if using the resistive pad doesn't help you,
then maybe the microphone really is being overloaded, in which case
using its built-in attenuator may make sense; [d] if your microphone
seems unable to handle its rated maximum SPL without clipping, check
your phantom power supply (or better yet, do that beforehand ...).

Agreed.

[d] is quite possibly an issue in this case, too. CAD Equiteks
require 8 (!) mA per microphone--an amount of current which falls
just within the IEC standard, and which relatively few phantom power
supplies in my experience can offer. I mean, Schoeps mikes take only
half that much current, and even they run into problems with phantom
supplies at times.

P.S.: The original poster lives in my neighborhood, as it turns out;
we're currently exchanging phone messages and trying to speak and/or
meet in person.