Older Preamp Nomenclature

[a soBer Newt]

I was talking with my friend over the weekend about old QuadEight mic preamps, he thought because they had labels like -10 -20 -30 for the stepped gain switch that those were pads that could be inserted before the mic preamp, I showed him a schematic and explained how the gain changed on those steps and it was not different pads. I said they probably used this nomenclature because microphones are specified in -dB/pascal and it would be a way to get you up to a good level. Am I right for thinking this?

 

[ruffrecords]

You can lable a mic pre gin control in two ways. One is to simply list the gain; 10, 20, 30, 40dB or you can label the sensitivity which is the input level required for 0dBu output which would be -10, -20, -30, -40 and so on.Cheers

Ian

 

[pucho812]

a lot of older equipment lists the gain so that the level on the stepped switch indicates how far down the level is from giving you a 0 dBu output signal, for example the trident a-range desk at the studio, If I am at -60 on the preamp, it means the input signal is -60dB away from a 0dBu and is actually adding 60dB of gain.

 

[JohnRoberts]

analog consoles are typically organized around a nominal 0VU operating level with X dB of headroom (before clipping) above that nominal 0VU. Digital consoles instead are organized as operating below full scale (clipping or saturation).

The mic preamps gain is easier managed in terms of dB (voltage) gain. Since microphone sensitivity varies between models the gain calibration does not automatically track to console internal operating levels. That's why they use meters.

JR