CLX-VU Build Thread (DBX 160VU ) UPDATE: REV 3

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Clbraddock

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Good luck! Looking forward to hearing how it goes!
Boo yeah!! It actually worked. The voltage coming off the transformer was a little hot (about 21 volts AC) but I was able to trim it with R100 and R101 to get 15 volts DC across my power rails. That’s as far as I got tonight, but I’m pleased nothing blew up or caught on fire lol.

It was a real ordeal getting the hairball switches into the case from collective cases. One of the slots was too small, so I had to file it to make the opening bigger. Then there is the issue that there is no spacer like on the hair ball kits, so I had to rig a contraption of micro screws and nuts together to get the switch spaced back far enough from the front panel.
So far so good though
 

Clbraddock

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Good news! I finished the build and tested it out tonight. Everything seems to be working. Loving how it sounds with the vintage dbx vca can and rms can. I haven’t done the full calibration yet, so the meter is a bit out of wack, but just dialing things in by ear I really like the sounds I’m getting. I’ve never used a real 160, but have used the UAD and Waves plugins. This has the same overall compression action as those, but has a bit more hair to the sound - maybe a bit livelier than the plugins. Overall I’m pretty pleased.

Edit: Im heading out of town for a week, so won’t be able to finish calibration/testing until I get back. Last night I wasn’t getting an oscilloscope signal from the rms offset as mentioned in the CLX manual. Not sure if it’s because Im using a 207 for RMS instead of a 208/209 or if I was just testing it wrong (im not very handy with an oscilloscope). The 207 RMS does not connect a trim pin according to the service bulletin, so that could also be it. Either way, I found the following service manual that has more detail than the clx manual. I think when I get back I will try these procedures: https://dbxpro.com/en/product_documents/160-161-162-service-manualpdf--3

I think I can get it figured out with some work. It’s definitely compressing and the controls all do what they should. Sounds good. The meter just has little bearing on what’s actually happening right now. (Led lights work though)
 
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Clbraddock

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Ok so I’m down to the final calibration, but might need some ideas. Sound wise everything works perfectly. No distortion, compression action behaves like it should, leds work correctly.

Problem is that the meter is not scaling correctly. It zeros out correctly, but as either the gain going into the unit is reduced or if the threshold is lowered the meter does not scale correctly to the printout I inserted. I’ve tried adjusting R56 and R59 but they make a minimal difference.
I’m using the meter printout posted in post 331. I’m thinking part of the issue is that that printout scales by 5db units whereas the scale in the manual scales by 10db units. I think the solution might be to just edit the numbers on the 331 meter to scale by 10db units, but if there is a different solution I’m all ears. I don’t anticipate doing 40 db of compression ever, so visually the 331 meter scales better to see more precisely what is going on, but maybe it’s not possible to make the actual vu track that way.

Edit: I don’t really understand how VU meters work, but the spec says full deflection at 1 mA. That makes me think maybe it’s possible to halve (or double?) the current going to the VU and thereby make it deflect half (twice?) as much - so then my printout with 5db increments would work. Is that something where I could wire a resistor in line with the VU? If so, what value would I need? Pure speculation, but maybe someone smarter than me can figure out what I’m saying/going for.

Edit 2: So I found a meter printout in post 748 that goes from -40 to +20. Seems like a strange choice of range (who does 40 db of compression?) but after looking at pics of the original 160 again I guess that’s the range they used on their meter. I will print it out tomorrow and give it a try. Fingers crossed
 
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znjamznjam

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Hmm darn. Maybe someone who has built this thing can chime in if they know the answer. I'd hate to connect the wrong pad to the chassis. I've been looking at pics of completed units (see post 567) and still cant figure it out.

Anyways, still really appreciate your help Jman!
Just wire everything as is guide in manuel rev 3 an you will be fine.
 

Clbraddock

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The manual is incomplete and does not mention a ground wiring anywhere. I already resolved that issue by wiring the g pad (between the +15 and -15 pads) to the chassis ground though and that worked fine.
 

Clbraddock

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New meter insert worked well. Meter tracks pretty well after adjusting R56. As far as I can tell everything is now working how it should. Think I’m going to call it complete.
 

Clbraddock

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Hi!

So I finish my unit with original DBX RMS 208 (which is a discrete version, not the same as the one which is on the board (Rev2)) and DBX 200.

And I can't calibrate it... it's working, compressing, everything is ok, but I dont see the same thing on the offset pin when i try to adjust R36, if I put the input signal to -60db, I've got a blured triangle waveform (even if there is not input signal), and if I rise the level, I see something like a square waveform coming through the other one, but if I adjust R36, nothing happen, except at one end, everything go flat and a big hum appears.

I double and triple check everything, try all the trimmers, the original calibration setup, but I can't figure it out... And if I try to continue, I can't have the -11mV a the R79 pins, meter works, but has the level calibrartion isn't ok I can't get all the "0"

Other strange things:

- with the RMS unit on the board, I can't have the below led to work (above seems OK), and without the RMS unit, the below LED works fine
- I can't get ride of a hum (even if the RMS unit is off the board), with low noise mod or not, it seems there is a lot of ripple in the +/-24V rails, is that OK? I change the 1000uF to 2200uF, and it seems to be better but not as expected
- i don't seems to have unity gain when not compressing, something like -10db is lost. But as I can't calibrate it, I'm not sure...

So my question is:

Do you think it's not possible to use DBX RMS 208 and 200 VCA? Do you see anything i can do?

I'm thinking the 208 i've got is an older version than the one you can build on board, maybe it the problem...

I made 2 boards the same, and the 2 are behaving the same, I don't think the RMS or the VCA is dead, cause the unit is working.

Anyone do the same with success?

Abe, any idea?
So I tried building the second board in my dual clx vu unit using a 208 RMS and I am having the same issue you did. If I probe the offset hole on the pcb I get no real signal. If I prob the offset pin or comp pin coming off the 208 can I get a square wave, but R36 doesn’t really affect its shape (except if R36 is turned up too high I go back to getting nothing. I dont currently have the offset pin or comp pin connected to anything on the board, because on the original schematic it says n.l and n.c. for those pins. Wonder if anyone ever got this thing working with a 208 RMS.

I built the first pcb in the dual unit using a 207 RMS which isn’t really original to the dbx 160, but I believe was used on the 165. I believe the difference is that the 207 is pre-trimmed. All the connections from it are the same, except the trim pin is left disconnected. With the 207 everything worked ok. Would be nice to use the 208 like the original model, but wort case I have another 207 available, so I could just ditch the 208 and do what I did in the first board.

Edit: ok, so after spending a bunch of time swapping the 208 for the 207 RMS, things still weren’t working. After going component by component, I apparently accidentally used a 5.49 ohm instead of 5.49k for R69. Oops. I cobbled together a few resistor I had on hand in series and swapped that in and now it’s working. Maybe I will try and swap the 208 back in tomorrow and see if I can get it working now.
 
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matthieu68

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Jul 11, 2017
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Salut tout le monde. Je vais commencer un projet clx (quand mes PCB arriveront). J'ai la procédure en PDF pour V3, ai-je besoin d'autres documents pour l'étalonnage ou est-ce suffisant ? De plus, les liens au début du post il y a 10 ans ne fonctionnent plus, est-ce que quelqu'un a le schéma ainsi que le plan de la face avant ? Merci beaucoup
 

matthieu68

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Jul 11, 2017
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plus personne sur ce forum ? J'ai le schéma de la version 2, donc si vous avez le schéma de la version 3 ? J'ai une question, à quoi sert le 24v ? et je cherche le support pour le Switch, mais pas le support classique le support qui désactive l'autre Switch monté avec (par exemple j'appuie sur 1 qui désactive le switch 2...) merci
 

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