"Unison Design" 9K Complete!! Pics Inside!!

Here it is, the 9K "stripped down" with no +48V, no pad, no phase rev. and only 6 position gain switch, ranging from +34 to +46 dB, controlling both channels simultaneously (one pole per channel, "gain A" is fixed). Its purpose is to make up for my summing mixer's -40 dB loss. The paint job went pretty good, but I changed the marker over the one I used in gssl and it wasn't quite comfortable, so the labelling is not really that good compared to my gssl. Sorry for the crappy quality of the photos, too. Oh well:







And a photo with its happy DIY companions   That makes three of them in two month's time (since I registered in the forum)



Here are the resistors I used for the gain switch:

============
6STEPS (34-46dB in 2.5dB steps)

Gain A (Fixed):
Ra 82R 28dB

Gain B:
Rb 294R

            Res.     Gain.   Total Gain.   Actual Resistor
Step1        952R   5.4dB ~34dB       953R
Step2       477R   7.9dB ~36dB         475R
Step3       278R   10.4dB ~39dB       280R
Step4       176R   12.8dB ~41dB       178R
Step5       117R   15.3dB ~43dB       118R
Step6       0       17.8dB  ~46dB
============

And the equivalent drawing:



For a detailed record of my struggle see also:
http://www.groupdiy.com/index.php?topic=4731.msg438100#msg438100


It sounds AWESOME, and I want to thank everyone for advising me to use that particular preamp as gain stage for my passive summing mixer. It is what I wanted, only better!!

Worked on first powerup, too!! Absolutely no troubleshooting was required. No hum , no noise, everythink worked right away. One moment I am checking the voltages, and the other one I find myself mixing with it!   Talk about lucky...

Feel free to add it to the finished projects META if it does qualify

That's very cool. Nice faceplate color too. May I ask one thing? It would be helpful if you edited your post to include links to the threads about your gain mods. AFAIK no one else has done this and it may inspire others to put this nice pre to other uses. Good job!

I would have used a bigger power transformer!  ;D

mitsos said:

That's very cool. Nice faceplate color too. May I ask one thing? It would be helpful if you edited your post to include links to the threads about your gain mods. AFAIK no one else has done this and it may inspire others to put this nice pre to other uses. Good job!

Click to expand...

Thanks, and DONE!


RuudNL, I couldn't find a 30VA transformer, it was out of stock, and I was in a hurry so I got a 50VA one. I know it's huge :-[ :-[
.. But hey, as long as it fits the case and does its job 

Bravo Stefane!
Poly wraia doulia!

;D ;D ;D

well done Stefanos.

Euxaristw V9977!!

Thanks a lot Harpo, and thank you for your awesome advice on the gain switch thing! Having Ra fixed was a great idea!  ;D ;D I even hand-matched the two channel's gainswitch resistors (yeah I went crazy with that for no apparent reason)