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

[Spencerleehorton]

I agree with you, the set instructions in the pdf are confusing, there are some points i dont have a clue about what they are talking about?
would be great to have a clear and up to date guide on setup.

Spence.

 

[critterkllr]

Well, even though I can't get through all of the calibration, I did try it. Seems like calibration is more for the meters? If so, I don't really care that much. I might be more happy with this compressor build than any of the other so far. It's exactly what I was looking for on kick and snare. I'm very glad I built this.

 

[Bowie]

Well, even though I can't get through all of the calibration, I did try it. Seems like calibration is more for the meters? If so, I don't really care that much. I might be more happy with this compressor build than any of the other so far. It's exactly what I was looking for on kick and snare. I'm very glad I built this.

I still haven't done proper calibration on mine.  Just got it "close enough for rock n roll" and it's fantastic.  Really knocks on kick and snare as well as other things.

 

[Spencerleehorton]

1. Calibrate RMS - insert -60db (whats -60db when measuring output with MM) 100hz sine wave on input, probe offset pin, adjust R36 until waveform is symmetrical.
2. RMS Symmetry - get right mark audioanalyzer software or distortion meter, set test tone to 100hz, start playback, adjust unit so its compressing 20db
adjust r34 until lowest distortion achieved.
3. Level Calibration - set tone to 100hz @ 1.228RMS (i set my MM to AC and adjust sine wave output to 1.228) set meter to input & turn R63 until voltage on end of R79 is -0.011 VDC.
4. Threshold Knob Adjustment - with 1.228VRMS on input turn threshold knob so both lights off, put knob on so it reads 1.2V
5. 1:4 Ratio Calibration - Adjust ratio to 4 and threshold CCW, input with -30db 100hz with no compression, adjust output for convenient reading on external VU meter (-30db) step up output of oscillator to +10db, output of clx-vu should be only 10db louder, adjust R43 until this is true.
6. Meter Calibration - confirm R109 disconnected, adjust R124 until meter reads 0, once done connect R109.
7. GR & Input Calibration - oscillator to 100hz @ 1.228VRMS, set threshold CW, Ratio CCW set meter to GR, adjust R51 until 0 on meter, Set meter to IN adjust R62 until 0 on meter, repeats until both set to 0.
8. Output Knob Adjustment - with 1.228VRMS on input set to output, adjust gain control so meter reads 0, attach output knob so it points to zero.

 

[critterkllr]

The threshold and output knob adjustments are to adjust the actual knob (that you use), to set to the number out on the faceplate. You just loosen it and make sure it's exactly at the right marker. Seems kinda silly to include in a DIY version, but makes sense they would want to have them pointing correctly at the factory.

 

[Spencerleehorton]

getting weird oscillation from one of my units, think the 2181C is shot, there doesnt seem to much info on how to trim this 2181VCA, also im a little confused on the options of what resistors to use omit in both types.
On the resistor choice is it the ones on the left that you use if your using the 2181 or do you use the ones on the right?

regards

Spence.

 

[critterkllr]

Use the ones on the right. The (T) is for THAT.

 

[Spencerleehorton]

Thanks, I need to change a few resistors then!

Spence.

 

[Spencerleehorton]

I get it now with knob adjustment, the output knob is set in the middle so it's -/+ 20, i thought it started from 0.

Spence.

 

[Spencerleehorton]

Now have correct resistors in units working much better, I still think that something is wrong with one 2181 as I'm not getting output but may be lm301 or tl081, will swap the IC about to find problem.
Hopefully they will both setup ok now.

Spence.

 

[critterkllr]

If you check the schematic on page 1 (original is easier to read), the signal path is pretty short. You could send a sine wave through it with your oscillator and measure AC voltages at different points. The input on the 2181 is pin 1 and the output is pin 8. That will help you pinpoint where it's stopping so you're not going at it blind.

 

[Spencerleehorton]

after blowing a couple of 1n4007 diodes on the AC i've got the troubled unit back working again, it totally fried a TL071, loads of secret smoke coming out!! it blew some of the track at this point and ive had to rebuild it?
i have no idea why this happened as the voltages now to the IC socket check out fine?
when i put a new TL071 in it has dodgy voltages on pins 7 and 8?
i'm not getting any audio on the output?
the now strange thing on the working unit is that the Meter now seems to work backwards? the unit seems to setup fine but i cant quite work out why it works backwards, as reversing the leads to it results in no change, i suppose reversing the +/- of the diodes would. but the strange thing is it worked fine?
would anyone be able to help please?

regards

Spence.

 

[critterkllr]

I would take all of the ICs out and remeasure voltages. The voltages in the PSU are high enough to fry any of the ICs if it was powered up before calibrating to +/-15V. TL071 supply pins are 4 and 7 and has a max voltage of +/-18V. When in doubt, Google the IC number along with "pinout" or "datasheet". The supply pins will be labeled as -Vcc and +Vcc.

Quadruple check your wiring, solder joints and orientations (diodes, electrolytics). If you haven't cleaned your board with some rubbing alcohol, do it before moving on. Make sure there is at lease 1K ohms resistance between your power rails. Some clear pictures of both sides of the pcb along with the wiring would help.

 

[Spencerleehorton]

yes voltages are +/- 15v, i will give it a nice clean and look for any bad solder joints then post some pictures.
when i last built my other stereo unit i had some trouble but not like this!!!

Spence.

 

[Patrick from Davis]

Ilfuengo also had a CA 3083 IC go bad in his build, caused trouble with the calibration. Never read why it went bad, but something to think about.

 

[Spencerleehorton]

I'd just like to understand how the meter is working backwards but the unit is functioning fine.
In GR rather than the meter swing to left it swings to right, when switching to input the needle goes to the right and when I give it input the needle moves to the left?

Spence.

 

[Spencerleehorton]

well in changing over a few of the input and output IC's along with the NE5534 i have sorted both units now and they setup fine.
phew!!!

regards

Spence.

 

[critterkllr]

Just in case anybody is looking for knobs for the CLX-VU. I used EH71-1C2S for the Threshold and Gain. EH71-2C2S for the Ratio. They are very high quality and look a lot like the originals.

http://www.newark.com/ehc-electronic-hardware/eh71-1c2s/round-knob-with-line-indicator/dp/95F6988

http://www.newark.com/ehc-electronic-hardware/eh71-2c2s/round-knob-with-line-indicator/dp/95F7000

 

[EmptyMusicBox1]

hello everyone !!!

i'm now determinate to fix my problem on my CLx comp but i need you please
The problem is :
I don't have sound on the Pin 3 of the PCB

i use a transfer function with smaart to follow the audio on the board point after point... and i have check that :

After the LM301output i have 0db and positive phase ok for the pin2 correct ?

after C21 i have -6db and a positive phase

Before R83(10k) i have the -6db but after i have -15db and after R92(22.1K) i lost the signal for finish to my pin3 output....

i don't uderstand the process of the balanced signal and where is the problem ...

can you help me please

hello

i don't find the solution for my Unbalanced Output problem ...

i have 0,35v on R83 when i use 0,75v on input and after R92 to the output i have 0v ... no sound on pin3

but on R89 i have 0,75v !!!!!!! pin2

it's normal ?

i can split the audio signal at C25 more a resitance R22 for my pin 3

thanks for your help !

i add a schamtic with voltage test point :


about C32 why it's not wire on the Schema ? it's neccesary ?

thanks for your help

Hi,
The way the circuit works is my understanding you don't see signal on pin 3 but it is still fully balanced....I think I read somewhere even better then fully balanced as it has some sort of "compensation" circuity in the output stage.

C32 should be connected to that line its close to, also cr14 isn't connected. weird. But its right on the pcb.

thanks abechap024 for your help, i try to find my problem....

if somene have a solution to testing i'm ready !!!!! )))

thanks

 

[G-Sun]

The FMR RNLA didn't work out so well for me,
so I maybe return to this project.

Checking out some the Stillwell Major Tom. RMS and Feedforward? Or Feedback?