Optical tube compressor

analag

Well-known member
Joined
Apr 23, 2005
Messages
1,699
Location
Mars
I have just spiced and built a new version of my optical compressor and it rocks. I think I might just share the schematic
 

soundguy

Well-known member
Joined
Jun 4, 2004
Messages
2,040
Location
NYC, USA
not to spin this completely off topic, but "the anal ag's" would have been an awesome gang in the warriors.

welcome to the lab analag.

dave
 

ciminosound

Well-known member
Joined
Jun 6, 2004
Messages
339
Location
Cape Cod Massachusetts
Might be a farce. After all it's either an optical compressor with tubes for amplification or a tube (vari-mu) type compressor.

If it's for real I'd love to see it.
 

BradAvenson

Well-known member
Joined
Jun 4, 2004
Messages
426
Location
Austin, TX
I thought I had heard about someone making a compressor that changes the tubes gain with a photo cell of some kind. I'll have to look for that refrence somewhere.
 

BradAvenson

Well-known member
Joined
Jun 4, 2004
Messages
426
Location
Austin, TX
Ok it was Oliver Archut over in Klaus Heyne's forum:

the Toshiba modules are active opto coupler, a high intensity LED coupled with a sort of an Solar Cell. They voltage ripple output is depended on the DC input, the nice way that you do not need a DC/DC switching converter that creates switching noise and need filter counter measurements in the audio tree....

The same elements are great for a passive sidechain for a push/push compressor, you just drive them with a buffer resistor of the audio signal and you get enough voltage to direct drive remote cut of tubes....

I wonder if there is a current production model that works that way or if it is just an idea/prototype/concept.
 

bcarso

Well-known member
Joined
Feb 20, 2005
Messages
4,055
Location
San Fernando Valley, Los Angeles
Photovoltaic cell optocouplers have been around for about 20 years or so. They are somewhat intricate, fairly expensive, and somewhat slow. All the ones I've seen have the photodiodes controlling enhancement-mode MOSFETs and haven't provided the d.c. control voltage as an output, but perhaps the Toshiba part mentioned does this.

The current would be very limited, but would be fine for controlling grids.

I remember a more ambitious diode stack for higher power, which had a fiber optic input made for mating with a pretty hefty laser. IIRC it could produce a 100mA or so at useful voltages. The application was powering monitoring electronics on really high-voltage power lines, in the 300kV class.

I was being facetious about the ~6AL7-driven photoconductor, but it shows where this kind of banter can lead =}
 

analag

Well-known member
Joined
Apr 23, 2005
Messages
1,699
Location
Mars
Ok guys I sent the schematic to Kubi and Ian Macgregor to post for me since I cant post off my HD. No trannies are shown, but a 1:2 for input and a 2:1 for output can be used. This is a working compressor in my studio. As my spirit of gererousity increases I might open my treasure chest and showcase some real advances in tube technology, including a very nice B+ regulator and floating heater design that I perfected.
 

analag

Well-known member
Joined
Apr 23, 2005
Messages
1,699
Location
Mars
I see where some of you might want to see a vari mu design, well I have that too, but not before I'm ready and no amount of prodding will make me budge
 

bcarso

Well-known member
Joined
Feb 20, 2005
Messages
4,055
Location
San Fernando Valley, Los Angeles
I see plenty of tubes and one photoemitter symbol (D1) but no photoconductor, hence no variable gain and no compression.

I guess AC1 is supposed to be the signal input, but there is no indication of the output.

??
 

Learner

Well-known member
Joined
Jun 4, 2004
Messages
341
Location
Area 621.xxx
Could it be possible that D1 is coupled with R3 to control the "gain" of the input signal in a feedback configuration, or may be coupled to the 500K grid bias resistor of U2 in a feedforward configuration?

R1 & R2 controls threshold?
 

Latest posts

Top