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

[znjamznjam]

Hi, only the mass/shields via Pin 1 of the Input XLR connection to the Input PCB Pad is connected to the Case/Star-Ground for each Board. Thats it. The Output Groundpad on the PCB has no connection. Its only a "Dummy". So there is no chance to generate a Loop.

Thank you for info. I have also connected ground only with pin 1 from XLR input and work great. I was checking because i see other people ask for proper grounding. I think also that gronding only via pin 1 by input is right way of gronding. Thanks for confirmation.

 

[1wildthing]

Hi, I've finished this build. I've built a dual channel version trying to match the components on the 2 boards as much as possible. Unfortunately I'm struggling to calibrate them. TBH it's not that easy. In particular I can't really understand the 1:4 ratio calibration. The manual says to set threshold knob counterclockwise, ratio to 4 and after this to feed the circuit with a "sine wave with no compression" but what does it means?
Could you please explain me in easy words what I need to do to get this process done?

 

[grid_stopper]

Hi, I've finished this build. I've built a dual channel version trying to match the components on the 2 boards as much as possible. Unfortunately I'm struggling to calibrate them. TBH it's not that easy. In particular I can't really understand the 1:4 ratio calibration. The manual says to set threshold knob counterclockwise, ratio to 4 and after this to feed the circuit with a "sine wave with no compression" but what does it means?
Could you please explain me in easy words what I need to do to get this process done?

That is seemingly pretty clear instruction, which part are you struggling with? From what I understand, its asking you to set the threshold so that it is all the way to its highest possible position, so as to avoid the compressor from kicking in. Have you completed the previous 2 steps for level calibration?

 

[JMan]

Does the threshold increase as the knob is turned counterclockwise? I'm not working on this, but that's what would have thrown me off -- I would have intuitively assumed that setting the knob fully ccw would lower the threshold as far as it would go, making it hard to have a signal with no compression. Does that knob function "in reverse" on this unit?

 

[1wildthing]

That is seemingly pretty clear instruction, which part are you struggling with? From what I understand, its asking you to set the threshold so that it is all the way to its highest possible position, so as to avoid the compressor from kicking in. Have you completed the previous 2 steps for level calibration?

Thanks GS, so “sine with no compression “ simply means that with this setting the signal won’t be affected by compression, right?
Actually I’ve stepped back and there’s a few weird things happening that I can’t really explain.
The weirdest happens when I set the input level of the sine. I measure ac voltage between positive and negative xlr’s pins and the same signal gives me 1.228rms on left input and 0,618 on the right. This happens only when the input cable is connected to the board. If I disconnect it from the pcb the measured value is correct (1.228) even on right channel. Moreover the right channel is cracking randomly.
Another freakness , when I push gain pot clockwise the meter goes to the negative side (left) is this normal?
Then, with gain pot fully clockwise I experienced a lot of noise coming in. Could these things be related?

 

[grid_stopper]

Thanks GS, so “sine with no compression “ simply means that with this setting the signal won’t be affected by compression, right?
Actually I’ve stepped back and there’s a few weird things happening that I can’t really explain.
The weirdest happens when I set the input level of the sine. I measure ac voltage between positive and negative xlr’s pins and the same signal gives me 1.228rms on left input and 0,618 on the right. This happens only when the input cable is connected to the board. If I disconnect it from the pcb the measured value is correct (1.228) even on right channel. Moreover the right channel is cracking randomly.
Another freakness , when I push gain pot clockwise the meter goes to the negative side (left) is this normal?
Then, with gain pot fully clockwise I experienced a lot of noise coming in. Could these things be related?

Yes, that should be correct.

In terms of your other questions, it looks like the schematic is no longer accessible through the original website, or the way back machine, so Its hard to speculate. If you have the schematic, it would be handy to post it.

In terms of the meter swing, yes that is normal assuming your meter is set to GR mode. Meter swings left to indicate the amount of gain reduction being preformed.

 

[1wildthing]

Ok I solved a problem caused by an inverted wiring in the input of the 2nd board. I’m still having problems with 1:4 ratio calibration. I’ve applied a -30db 100hz sine wave measured at input xlr (0.028v rms), threshold knob counterclockwise and compression knob at 4. When I step up sine wave volume on input, the output level decrease instead of increasing. I’m getting mad over this process. Any help would be really appreciated!

 

[grid_stopper]

Check that you didnt wire your threshold knob backwards.

 

[SmokeyJoe]

Hey folks. I'm interested in this build but none of the links in the first post seem to be working, anyone know anything about that?

Does anyone have a source for PCBs? Cheers!

 

[JMan]

Dan at Collective Cases sells the PCBs now.

https://collectivecases.com/?product=clx-vu-pcbs

 

[SmokeyJoe]

Great, thanks. Do you know if there is a UK/Europe source for them?

 

[JMan]

Not as far as I know, except checking the used market. My understanding is that Dan is now the exclusive seller of Abe's projects.

 

[1wildthing]

Hi all, I'm still fighting with this build. Finally I solved the problem of crackling on output that was caused by a faulty pot. Unfortunately now I have another problem related to leds.
I've already read about this problem in the thread but I didn't find the solution.
In just one board, sending an 1.228VRMS on input, the above led is always turned on don't matter threshold or ratio settings. Consequently I can't get the off position for both leds. Only if I send a lower input signal I can get that result.
The other board instead works correctly. I've tried to replace or swap all the ICs but nothing changed.
Does anyone has solved this problem or has ideas on what could be the cause?

 

[1wildthing]

I discovered that the problem with leds was due to the calibration process not completed successfully.
I've also realized that I didn't soldered c1 and c4 in the PSU section.

Can be this fact the source of my problems in calibration? However I'd like to stress out that my power rails have correct values .

May I use ceramic caps in replacement of Filmcaps for c1 and c4?

 

[Jase_Sanderson]

Apart from it looking a bit odd and out of place, does anyone have an opinion if it matters or not to use a 'can' lm301 instead of a 'dip' one? If I just maybe bend the legs to the right socket. I know @HerbertR mentioned not getting the cheapo chinese ones, but the NOS search is proving difficult, yet I have a few of these can ones laying around. Guessing it should be fine but wanted to check.

Also, @HerbertR Do you have a part number for those heat syncs you have for the LM317 & LM337, didn't see them in the bom but figure that's a good idea.

Cheers crew.

Jase

 

[Clbraddock]

I'm not an expert, so just relaying my experience. I have used dip and can ICs interchangeably when necessary. As long as I get the correct leg to the correct pcb hole it has worked for me.

 

[Jase_Sanderson]

I'm not an expert, so just relaying my experience. I have used dip and can ICs interchangeably when necessary. As long as I get the correct leg to the correct pcb hole it has worked for me.

That's good to hear. Cheers @Clbraddock . By the way did you ever get the 208RMS installed, I know you mentioned you finally sorted the your issue with the 207 installed and resistor correction, but just following up, did you swap it back out for the 208? I'm hopefully building mine from some 200vca & 208rms that I've taken from an incredably cheap deal on a 154.

 

[Clbraddock]

Trying to remember back, lol. I think in the end I have a 207 RMS on one side and a 208 RMS on the other side. So, in the end I got the 208 working and must have been happy with it. I know I bought another 208 can afterwards and planned to replace the 207 with it eventually, but haven't gotten around to it.

I haven't used the CLX in awhile (long story short, had first child this year and have had no time), but my recollection is that both the 207 and 208 sounded good. I think the low end response was slightly different between them, but that is probably more due to an error in calibration than anything else.

Like I said, I bought another 208 can after I finished the CLX, so I must have wanted to replace the remaining 207 with it. So, I think you are good with 208 cans if you have them.

Edit: If you are using vintage cans, I would look at the original DBX schematic. I think I posted it somewhere in this thread. There are a few values that are different than the CLX schematic. I think I also posted somewhere all or most of the different values I found between them FYI.

 

[HerbertR]

Apart from it looking a bit odd and out of place, does anyone have an opinion if it matters or not to use a 'can' lm301 instead of a 'dip' one? If I just maybe bend the legs to the right socket. I know @HerbertR mentioned not getting the cheapo chinese ones, but the NOS search is proving difficult, yet I have a few of these can ones laying around. Guessing it should be fine but wanted to check.

Also, @HerbertR Do you have a part number for those heat syncs you have for the LM317 & LM337, didn't see them in the bom but figure that's a good idea.

Cheers crew.

Jase

Hi Jason, the Heatsink is nothing special. Instead of mounting it upright I used this heatsink sideward while covering the backside of the two regulators and drilled a second hole to fix both. It is absolutely necessary to use mendatory insulators or you will get a shortage between the 317/337 regulators. It is really easy to kill a transformer this way, believe me. It was not my first homicide I ve killed a Power TX ....
As for the LM301 - try them, why not. If they get hot in a few seconds you also have these China ones and you can dispose them. The DIP8 LM301 ones are nearly gone everywhere from this earthball. I think as for an option you can try the SOIC-8 version with an SOIC+8 to DIP8 replacement socket board for a few cents. The availability of these SOIC-8 version is much better and cheaper. But I do not know if they will work, never used them.....

 

[Jase_Sanderson]

Hi Jason, the Heatsink is nothing special. Instead of mounting it upright I used this heatsink sideward while covering the backside of the two regulators and drilled a second hole to fix both. It is absolutely necessary to use mendatory insulators or you will get a shortage between the 317/337 regulators. It is really easy to kill a transformer this way, believe me. It was not my first homicide I ve killed a Power TX ....
As for the LM301 - try them, why not. If they get hot in a few seconds you also have these China ones and you can dispose them. The DIP8 LM301 ones are nearly gone everywhere from this earthball. I think as for an option you can try the SOIC-8 version with an SOIC+8 to DIP8 replacement socket board for a few cents. The availability of these SOIC-8 version is much better and cheaper. But I do not know if they will work, never used them.....

Thank you Jedi Master, much appreciated haha