[R-390] Line Level meter

[2002tii]

Brian wrote:

>OK, I found a pcb for six bucks which runs off a single positive rail supply
>[which I can tap from the filament or pilot lamp circuit] and uses a single
>TL071 op-amp and a handful of diodes and resistors, and presents a line load
>of aboout 100K or better.  Total board size looks be about an inch and a
>half square.

If you're going to put in an op amp, might as well put in two or 
three -- build a precision rectifier, add ballistic and scale 
compensation (the DC meter won't have the same [non]linearity or 
ballistics as a VU meter), and drive the meter with current inside a 
feedback loop.

That said, the original 390/A meters didn't have anything resembling 
VU characteristics, either.

Best regards,

Don