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Re: Sony MD Microphone preamp... Design and settings...

Subject: Re: Sony MD Microphone preamp... Design and settings...
From: Walter Knapp <>
Date: Sun, 09 Feb 2003 13:52:23 -0500
Klas Strandberg wrote:
> Evert wrote:
> 
> 
>> [own remark: In both cases this is done by letting the same signal
>> go thru the same opamp, but with 1 resistor more or less in the
>> circuit. So overdriving the opamp will happen at the same SPL no
>> matter the switch position.]
> 
> 
> Hm...? The "1 resistor more or less" is the resistor setting the gain of the
> op amp. The lower value (Ohms)- the higher op-amp gain, the lower headroom
> and the more distortion you get when input goes high. Observe that such "too
> much" never shows on the meter! 

The original webpage referred to shows a difference in headroom between 
the high and low setting that varies from about 11dB to 14dB depending 
on the mic used. So, overdriving will occur at different SPL's depending 
on the switch setting.

This agrees with my own field experience with the MZ-R30 where I usually 
considered the difference to be about 14-15 dB.

If you have a switchable MD and a sonogram program that gives a display 
calibrated in dB, you can easily measure this by switching in the middle 
of a recording and later finding the difference in the sonogram.

Note that this overdriving is in the analog part of the MD. The A/D can 
also be clipped by setting the gain too high. And that clipping is what 
most will notice. The analog part is not near as distinct, a much less 
harsh effect. It will show up as a waveform that does not have flat tops 
on each wave, but does have a overall flat topped appearance.

Walt




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