|-----Original Message-----
|From: Timothy Stockman [mailto:[EMAIL PROTECTED]]
|Sent: Monday, July 30, 2001 6:40 AM
|Subject: RE: MD: Recording MDs with microphones...
|
snip
|
|1. Plug-in power for inexpensive, high quality electret microphones.
|2. Reduced number of physical controls through software. (Use a few
rotary
| encoders to replace a lot of potentiometers.)
So you need an LCD display, too, as part of the user interface.
|3. Adjust levels *before* the A/D to prevent overload while maximizing
dynamic
| range. Most modern MD recorders have fixed gain *berfore* the A/D; not
a
| good thing!
Absolutely. So you use the LM1973's you mentioned in a programmable gain
configuration, right? Are these parts quiet enough to work with
microphone-level signals?
|
|One other advantage of one of the Crystal Seminconductor A/D chips I've
|been looking at is that it incorporates a metering circuit that
|gives an accurate
|digital readout in 1 dB steps down to -70 dB. While working on a unrelated
|project a few years ago, I used a 16 character x 2 line LCD as a
|high resoltion
|analog bar-graph meter with software controlled ballistics, as
|well as for its normal
|text display function.
Are referring to the CS5360 or the CS5334 ADCs? I think these chips consume
~350mW. I assume that you mix 6-8 channels of analog down to 2, then
digitize. So with >6 analog channels, each with programmable gain (and
possibly eq), and the other circuitry and microcontroller you're well over
1/2 watt--roughly 20 hrs. with 3-4 AA cells-- is this what you have in mind
for a portable MD system? I guess that's not bad, but I would think that
you would want to use Crystal's CS53L32 for this application, which brings
power consumption down for this system. You lose the peak detect metering,
though.
|
|Since the proposed design would be software controlled, it could adjust the
|channel level trim automatically for optimum performance. The design would
|sort of be like a modern point-and-shoot auto-focus camera.
|
Sorry, I'm not sure what you mean here?
Also, I would think that some MD titling interface built into the mixer
might be a nice feature that would distinguish your mixer from anything else
that's commercially available.
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