My try for an optical

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detonator

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Here’s my try for having a bit of different optical compressor. What I did basically is a redrawn of Mnats Weak Joe compressor. Added a gain reduction meter from the schematic at Kubi’s site, according to Fred Forssells’ schematic. On the front end and the backend, I added a Lundahl transformer. With on the front end a switch for bypassing the iron and have a solid state input stage.

Further ideas for future versions are:
  • Bypass switch for the compressor
  • Sidechain Filter (as designed by Steffen)
  • Input and output LED metering (design by ssltech)
  • Gain Reduction LED metering (design by Fred Forssell)
  • True stereo version, with combined opamps and replaced by TL074 or Burr Brown

My knowledge to electronics is a bit limited and I always like to receive feedback. So I wonder or a circuit like this will work, or is it just another dumb idea?

Thanks in advance
 

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I understand the possibility to choose xfmr or diff amp input, but the output (secondary) of the transformer is shorted by the output of A6b. Ther must be another pole to the switch, or some way of mixing both inputs. As it is, won't really work...
Also, diff amp is wrong (+gain and -gain not same).
C6 & R20 should be much higher (1-10uF & 47k-470k).
R34 & R36 not needed (as they are, they attenuate the output).
You need to add a bypass switch (almost mandatory on a comp).
Not sure about what R23, 24, 25, LED1 are doing...
I think I would not want to always have the 3dB/octave boost in the side-chain; I would have a switch with a linear position.
 
abbey road d enfer said:
I understand the possibility to choose xfmr or diff amp input, but the output (secondary) of the transformer is shorted by the output of A6b. Ther must be another pole to the switch, or some way of mixing both inputs. As it is, won't really work...
It's hooked up according to the spec sheet as Lundahl itself provides. See http://lundahl.se/pdfs/datash/5402.pdf for more info.

abbey road d enfer said:
You need to add a bypass switch (almost mandatory on a comp).
Planned for the v1.2 design, the v1.1 design will include mods from your post

abbey road d enfer said:
Not sure about what R23, 24, 25, LED1 are doing...
The schematic between the transformers and diff amp input stage is a straigh redrawn of Mnats Wea Joe compressor. See, http://mnats.net/what_compressor.html for more info.

abbey road d enfer said:
I think I would not want to always have the 3dB/octave boost in the side-chain; I would have a switch with a linear position.
How about the idea for a sidechain filter?
 
detonator said:
abbey road d enfer said:
I understand the possibility to choose xfmr or diff amp input, but the output (secondary) of the transformer is shorted by the output of A6b. Ther must be another pole to the switch, or some way of mixing both inputs. As it is, won't really work...
It's hooked up according to the spec sheet as Lundahl itself provides. See http://lundahl.se/pdfs/datash/5402.pdf for more info.
What I mean is the output of the xfmr is connected to the output of A6b, which is very low Z. It shorts the output of the tranny.
abbey road d enfer said:
Not sure about what R23, 24, 25, LED1 are doing...
The schematic between the transformers and diff amp input stage is a straigh redrawn of Mnats Wea Joe compressor. See, http://mnats.net/what_compressor.html for more info.
Yes, I can see it's labelled as bias control
abbey road d enfer said:
I think I would not want to always have the 3dB/octave boost in the side-chain; I would have a switch with a linear position.
How about the idea for a sidechain filter?
There are so many possibilities for side-chain filters that I would have the option of a linear position and an insert point. Alternatively, you could have a variable 1st-order hipass, which IMO is all you need.
 
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