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

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AW

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Just found this link on how to calibrate a dbx160
https://dbxpro.com/en/products/160
 

BerndVP

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Yes, correct, I have these too, and it's not helping much more.

So it's more like the calibration of the 4:1 ratio that's not willing to work great...

I'm having problems with the LEDs too, where 'Roel' doesn't have these problems
 

AW

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I just ordered the parts today, had trouble finding the NTE929 was lucky to find one on amazon.
Is there a substitute for the  THAT2180CL08-U, mouser, digikey, and newark are all out of stock. The THAT2181CL08-U seems to have the same specs for the exception of pin 4 SYM ADJ for the 2181.
 

BerndVP

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yeah, you need another circuit to make it work then.

I gonna try it tomorrow again to get it calibrated, I went thru the whole topic again and saw most are saying the 4:1 cal is almost doing nothing for them
 

AW

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Where did you get the info on the calibration
 

AW

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Hi Ken
Thanks for the reply, but the CLX VU build docs I downloaded shows a page with some waveform pics with no text Is this what you are referring to? I know the person that created the pcb boards is no longer in business, the build docs I downloaded was called clx_manual_rev3-2.pdf, and it seems like there are parts in the manual that aren't complete. Is this the only build documents available?

Thanks Tony
 

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JMan

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Oh wild.  Where did you get your docs from?

I tried attaching the clean copy of the build manual to this post, but it kept giving me an upload error.  If you want to send me a message with your email address, I can get that to you.
 

AW

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I Just finished stuffing the PCB, and connecting the transformer, panel pots, and switches on one channel. I left out all opamps,Ic's,meter,LED's and transistors. I am not using the vca cans just the that 2180.
I plugged it in (120vac), and started checking DC voltages. At first I checked the -/+ 15v rails and they were above 15v, I adjusted R100,and 101 and got it to 15v, but the +/-24v rails and not reading right. The +24 is reading 16.6v, and the -24v is reading -39.8v in respect to ground. I am reading 6.2v at the VU output, and 16.6v at the VU LED output. I did use the correct resistor for the hairball 1ma meter. I was checking all supply voltages to the opamps/Ic's and they are all +/-15v, the only one that is off is LM301 near the that circuit, -v(pin4) is (-)33.8v, and +v(pin7) is +10.8v.
I am not getting any readings at the nte929 socket.
I also noticed LM337 gets very hot, while Lm317 stays warm. I feel like I am working in the dark, there is no full schematic of this project.
Any help would be greatly appreciated. I don't want to start installing the opamps, Ic's, and transistors with these voltage readings.
 

AW

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I found the problem, The secondary AC center tap was not grounded, the center tap etching on the bottom of the pcb is not connected to ground, the top etching is, So when you solder the AC input 3pin molex to the pcb the center tap is not going to ground, I had to run a separate wire from the center tap to ground. The other pcb has the same issue.
Has anyone experienced this?
 

AW

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Is there anyone currently building the CLX-VU ?
 

JMan

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AW said:
Is there anyone currently building the CLX-VU ?

My boards are stuffed, and I keep saying I'm going to get back to this project, but it keeps getting bumped further down the priority list.

Regarding your penultimate post, why would the pin from your header not be connected to the path just because of which side the trace is on, given that this is a double-sided thru-hole board?  Maybe you simply had a bad solder joint...?  Or perhaps I just didn't understand your description correctly.
 

AW

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Hi JMan

The center pin from the bottom header on both of my boards are definitely not connected to ground, the top is. I would check yours to make sure you don't have that issue. It drove me crazy I thought also it could be a cold solder.
Anyway I installed heat sinks on the regulators and accidentally they touch and shorted out some IC's. I will update my build as I proceed when I get my replacement IC's
Tony
 

JMan

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AW said:
Hi JMan

The center pin from the bottom header on both of my boards are definitely not connected to ground, the top is. I would check yours to make sure you don't have that issue. It drove me crazy I thought also it could be a cold solder.
Anyway I installed heat sinks on the regulators and accidentally they touch and shorted out some IC's. I will update my build as I proceed when I get my replacement IC's
Tony

Huh, I haven't looked at the board in awhile, I'll have to dig it out and take a look at that.

Anyway, thanks for posting your progress here as you go.  Maybe you will inspire me to get back to this build!
 

AW

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I got one channel built, and working :) I want to calibrate it but it looks really confusing from the post here. I got the meter to sit at -40 for input and output mode, but zero is at +10 on GR mode.
I have a scope, signal generator, and digital voltmeter. If anyone has done a calibration on these please let me know what you did. I don't have a distortion meter.
 

AW

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Looks like Spencerleehorton post on calibration worked, the only thing I couldn't do is
2. RMS Symmetry I don't have a distortion meter or software, everything else calibrated fine.  I will install it in my rack and run some kick or snare through it. Will post later to comment.
 

AW

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I inserted the compressor on my bass track, sounded distorted, trimmed the that2181 until distortion was gone.
Sounds great!!!!
Channel 2 next up
 

yvus

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Hello guys, and thank you again for this great circuit and this gret tread.

I Just finished building one CLX board, it is not calibrated yet. I have the audio passing through and getting compressed, but only from the output (+) of the xlr (pin 2 i guess), I have no signal from the output (-) (pin 3). Is this normal ? With an audio probe, I can hear the signal is lost between R92 and C35.
Thank you in advance.
 

AW

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Did you adjust the two trimmer pots R100, and R101 to +/- 15vdc power rails before you inserted the IC's, also you should check to see if you are getting +/-24vdc
 

yvus

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Yes, I get all the correct values for the power rails, I adjusted the power supply circuit before inserting ICs (even if I didn't mention it, sorry!).
 

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