Optical Comp

[Viitalahde]

What's the approximate output Z of the 12AU7 stage? Maybe I could get away with less step-down in my short & controlled signal path.

I'm definately going to give this boy a try.

 

[analag]

225 ohms.

It works well without a transformer too. Remember I just put the Edcor in it few weeks ago, yet it's been working for years.

analag

 

[Viitalahde]

Wow, that's low. I'm not a tube expert by any chance but I expected something like 2k5. Very cool! :thumb:

 

[skipwave]

I can't resist the urge to build this. I have everything except the vactrol handy.

Thanks! :grin:

 

[analag]

As soon as one gets built an what I'm saying about it is verified, the others will follow.

 

[Svart]

oh i'm already on it but first I have to finish my class A PRR varimu and my Federal limiters that are sitting on the shelf.. :shock:

I would love to compare your compressor to each of these in the end..

 

[Svart]

so can the Rs be 1/4w or should they be .5w+?

the 500k pot after the first stage, what is it's purpose? not the sidechain 500k..

EDIT:

did you use fullwave or half rectification? Vreg or unreg?

you think 1 amp would be enough for two channels of heaters?

and the cost of two channels without PSU looks around 85$.

looks like under 300$ for everything for two channels. very cool.

 

[tony dB]

I need at least 3 more lives if I want to build all these goodies. :razz:
Thanks for sharing Analag!

What an inspiration men can find overhere!
Can someone mail me the schemo plz?

tony at midasstudios dot com

 

[Svart]

also, what ratings should the .22, 1uf and .1 uf have?

EDIT: Damnit I forgot to order the pots when i ordered my resistors/caps and I left the schemo at work!!

what are the pot values so I can order them over the weekend?

:thumb:

 

[analag]

[quote author="Svart"]also, what ratings should the .22, 1uf and .1 uf have?

EDIT: Damnit I forgot to order the pots when i ordered my resistors/caps and I left the schemo at work!!

what are the pot values so I can order them over the weekend?

:thumb:[/quote]

Use 400-630V caps

[quote author="Svart"]the 500k pot after the first stage, what is it's purpose? not the sidechain 500k.. [/quote]

That's for the gain make up amp. It adds a lot flexibilty to the compressor and the compression characteristics.

 

[Svart]

:thumb:

thanks analag, i'll be ordering the valves shortly.

 

[skipwave]

I ordered the VTL5C4/2 vactrol from Small Bear.Small Bear Opto stuff page.

In case that link doesn't work, because it has some tags merged into the URL, us this Small Bear Opto stuff page. then go to page 3.

In the description it says "dual" so I assume that means this could be used for a dual mono config. Although, I think I want a stereo box. I assume in that case, one cell is used, and signal from both channels is fed into one sidechain.

 

[Svart]

those optos are only 2.49 each at allied...


Allied Stk#: 980-0725
Mfr's part #: VTL5C4/2

 

[skipwave]

[quote author="Svart"]those optos are only 2.49 each at allied...
Allied Stk#: 980-0725
Mfr's part #: VTL5C4/2[/quote]

Good to know. I like to support Small Bear, cuz I think they are a cool little outfit.

 

[Svart]

:thumb:

 

[analag]

[quote author="skipwave"]In the description it says "dual" so I assume that means this could be used for a dual mono config. Although, I think I want a stereo box. I assume in that case, one cell is used, and signal from both channels is fed into one sidechain.[/quote]

The other half is used to run the gain reduction meter, just like in the LA2A.

 

[analag]

I am getting good reviews from the people who built this compressor.

analag

 

[skipwave]

Who has finished their's already? Well done, mystery builder. :thumb:

 

[Svart]

I bought all the passive stufff but never bought the tubes..yet.

 

[sverige_cruz]

I'm pretty sure I'm at least one of the mystery builders. I powered mine up and ran some audio thru just to check that it wouldn't blow up on me. Got jolted once, with the power off, but the caps were at 180 or so still. :green: :guinness: It's because I haven't finalized the soldering of the connections, so I've got all these aligatored wires tangled about. Wanted to check the connections for the pots. Somehow I always get those wired backwards. That, and I was experimenting with resistor values for the power supply. I think by tonight I'll have everything wired up properly. I don't have a real studio setup - just some QEight prees and guitar preamps to play with it... so I'll have to hook up with someone to have a real run thru. I spent barely anything for this project: 1 old steel enclosure from an old magnavox console, 1 power transformer from a wollensak tape rec/player (noticed that someone's starting a thread 'bout that) and some old tubes/parts I had laying around. Oh yeah - haven't implemented the Edcors yet either, so it's running unbalanced, sans transformers. I'll have to pick those up soon. I wonder if they're open on weekends... I'll post more when I clean it up.
Peace out bruthas,
Jesus