The Optical Comp Again

[khstudio]

[quote author="dale116dot7"]Once I outfitted a live PA board with an opto in the gain control circuit, with the LED triggered by the overload lamp. Instant opto compression on every channel, no clipping no matter how hard someone (or something?) decided to sing.

-Dale[/quote]

That's a cool idea :thumb:
The LED driver circuit is already there.

 

[living sounds]

Could anyone please point me to a PSU schematics for this project? I haven't found anything in the Meta, and since the G9 PSU would be overkill for this project...

Thanks alot in advance!
Gregor

 

[rafafredd]

it says 241 volts. You could go regulated but I do not see the need. If you filter well, unreg is nice. With a pair of 220:15v transformer you can easilly get 300v rectified and enought voltage for a very good filament regulator. I do it all the time. Just need to calculate the filter Rs values based on circuit consumption. You can use a LM317 for the fillaments, with big caps on output.

 

[Eskiclown]

the vactrol needs to be the dual-LED type with the LED's connected back-to-back

The VTL5C4/2 datasheet indicates that it is a dual LDR controlled by one LED, not two LED's controlling one LDR.

Am I missing something ?

analag,
could you please tell us how you connected your VTL5C4/2 ?
I remember you didn't care about the back-to-back LED's thing when you first posted the schematic. But then why did you use a VTL5C4/2 (and not just a plain VTL5C4) if it is just one LED controlling one LDR ?

Thanks in advance.

 

[skipwave]

If you want to reg, JLM has a nice simple plan:

Different zeners for different output voltages.

 

[analag]

I used an VTL5C4/2 because it has one LED controlling two photoresistors, so one controlling the gain while the other effectively controls the gain reduction meter.

I use a discrete regulator with MOSFet pass device. It sounds like a good tube regulator with much improved ripple rejection.

analag

 

[living sounds]

analag, do you have a schematic for the regulator?

BTW, would it be hard to do a solid-state version of this compressor? What are the sonic advantages of tubes in this circuit?

 

[ChrioN]

Anyone made PCBs for this yet? It's a neat looking compressor.

 

[analag]

[quote author="ChrioN"]Anyone made PCBs for this yet? It's a neat looking compressor.[/quote]

Maybe I should get it done...huh.


analag

 

[Gold]

I would very much like to build one. I've been pouring over the documents but find it a little daunting. I don't know much about tube stuff. Jaakko says it's the bees knees.

 

[ChrioN]

Feels like finaly we got a tubed compressor which doesn't require expensive components. Ok, the PPR vari-mu is out there, but this one looks simpler. Please make some boards Analag.

 

[living sounds]

There is a PCB here somewhere, it's really simple. Will start building now (though my PRR Vari-Mu sadly is not working yet).

 

[adamasd]

I did make a PCB for this way back when, but then I moved and no longer have a computer. I will see if I can find the cd that it is on and get it up here in the next couple of days. It was my first bit of vacuum tube PCB design, but it did seem to go well, everything worked correctlly, no noise problems etc. I liked this compressor quite abit, unfortunatly I did not get time to make a second and a case to put it all in before moving and losing access to space to make such things. Oh I miss having 24 hour access to a a nice big work shop.

adam

 

[ChrioN]

That is truly great.

 

[[silent:arts]]

Analag, do you want to check this PCB for me ?

pm me your email address and I will send you the files for approval.

 

[bernbrue]

Volker,
you did it, wow. :thumb: I tried myself but didn't have the time to finish it. Defenately number 1 on my to do list (after your Dual LA2A, btw, the board is a real pleasure to stuff) :guinness:
Cheers
Bernd

 

[Gwaggin390]

just out of curiosity, how would the sound/characteristics of this optocomp vary from an LA2A copy?

 

[analag]

[quote author="[silent:arts]"]Analag, do you want to check this PCB for me ?
pm me your email address and I will send you the files for approval.[/quote]

You have been PM'ed

analag

 

[ChrioN]

Very slick dual design, and psu included: :thumb:
BTW, I LOVE those white pcb connectors!

 

[[silent:arts]]

ok, I posted the PCB files to Analag and he had a look on it (thanks again):

Looks good...do it

is there any interest in pro made PCBs for this project ?

this PCB version is Dual Channel (with switchable stereo link of course), regulated High Voltage, regulated Heater and another little PSU for Relay ByPass, Meter Lamps etc.
before I contact the PCB manufactor for a quote I would like to have a feeling for the quantity ...

please post here:
http://www.groupdiy.com/index.php?topic=25906&highlight=