AC signal rectifier design

benidubber · Dec 21, 2010

hi!
I'm playing with a LED-LDR optical compressor circuit to be used in front of a PT2399 digital echo,
with fixed attack, decay, threshold and ratio.
Do you think a typical 4 diodes bridge rectifier (to drive the LED) could be placed in parallel with compressor output without buffering?
output is driven by half 5532 voltage follower.
sorry I don't have any drawing, hope text is sufficiently clear.

sandro

AMZ-FX · Dec 21, 2010

Is this a guitar fx pedal?

I have seen a simple resistor-diode-capacitor rectifier on the output of a compressor design. Look for the Orange Squeezer schematic, for example. The rectifier is half-wave but the LDR response will be slow enough to make this immaterial, especially with the delay blurring the sound.

Not an ideal way to do it, but numerous commercial guitar fx pedals use this method.

regards, Jack

benidubber · Dec 21, 2010

thanks Jack!
yes it is for a stomp box.
this kind of compressor sounds very well if you consider it is made with a few components,
I really like how it sounds even in deep compression.
it is slow attack thou, so I'll add a soft clipper to avoid peaks left there by the optical cell to enter in pt2399 chip.
I'm going to see this kind of rectifier you were about.
bye
sandro

benidubber · Dec 21, 2010

Orange rectifier seems just perfect for my delay.
Why do they use a germanium diode?

AMZ-FX · Dec 21, 2010

benidubber said:
Why do they use a germanium diode?

Because of its low voltage threshold... it takes less voltage for the diode to begin conducting. These days, I would probably prefer a Schottky diode like a 1N5817 because it will be easier to find and cheaper, as well as more uniform in its electrical characteristics.

regards, Jack