[sdiy] Full wave rectifier for audio

[Seb Francis]

Thanks everyone for the replies.  My reply below..

harrybissell wrote:

>The best way if you want to get averaging as well, is with the
>circuit suggested from PlayHookey.com.  This is a half-wave and
>summing amp. Because the second amp is an inverting summer, you can
>use a cap in the feedback to average.
>
>  
>
Yes, I like the look of this.  I was just using a resistor/cap low pass 
filter to average, but neater to do it in the opamp feedback loop.

>I'd suggest that for a noise gate level detector, you should be looking
>for a peak detecting circuit... NOT a full wave rectifier. I'd use
>an absolute value circuit, followed by a peak detector if you want the
>ultimate in performance.  If not, probably a single (ie half-wave)
>peak detector is good enough.
>
>  
>
I wanted to use full-wave because sometimes analog synths can have 
waveforms that are a bit 'lopsided' so I wanted to make sure I'm looking 
at both halves of the waveform.  As Paul pointed out though precision in 
this application is not really critical.

So perhaps something like the full wave rectifier circuit from 
play-hookey.com, followed by a diode charging a cap (via the attack rate 
pot), with the release rate pot discharging the cap.  Is that what you 
mean by a peak detector .. diode->cap?

Seb