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

[matthieu68]

thank you for your answer. Precisely, my needle goes up during compression, it also goes up on in and out when I lower the signal and goes down when I increase the signal. I think I was wrong, my vu puts the sifam al19wf is an AC vu meter and not DC as mentioned in the documentation. I think the problem comes from there.

 

[HerbertR]

I also used the Sifam AL19 WF which I bought from Don Audio in Germany and almost all other successful manufacturers used these Sifam too. They work fine. Then there is another problem.

As always - check Polarisation of Caps, Diodes/ wrong direction, bad solder joints, cable connections correct. Op-amps, heat dissipation of the ICs, Voltages on the ICs are correct...? You could post some detailed pictures. Regards

 

[matthieu68]

I will post more precise images if necessary. I don't think it's a soldering error, it would be very unlikely that this would have happened on both units. The ICs are of the respective type for each location, I should in theory not have any inversion problem on this side... thank you

 

[matthieu68]

From what I understand, the VU meter is controlled by the TL082 chip and the TL071 chip, nothing else should influence the VU meter (am I right?) The two chips are visibly inverting input... hum

 

[matthieu68]

now that I think about it, at the start of the tests when r109 was not yet connected, my VU meter was going to crash all the way to the right, I tell myself that logically it should remain completely on the left, that was how at your place?

 

[matthieu68]

I think what I don't really understand is the "Meter emulation" calibration
In the doc it mentions putting the needle on 0 while the resistor r109 is removed, without signal I therefore have the needle which goes from 0 and not completely to the left.

How did you go about this step?

THANKS

 

[HerbertR]

Hi, this is very easy to explain. The original VU meter from the DBX160 had a different VU meter that always had the zero point / pointer fixed at around 1pm / 30 degrees.... / ...5min after 12pm... without a Signal connected. In order to simulate this in Abe's CLX160 and to be able to emulate it with the Sifam AL19 WF..., you need this emulation circuit. You must first calibrate this "5 minutes after 12pm..." zero point to "0" with the trimmer R124 as stated in Abe's CLX 160 instructions on page 32, firstly with the new scale and not with the old Sifam scale, and secondly - by first removing the resistor R109 completely or at least one foot of it / not soldering it in! Only after you have trimmed/calibrated to "0" can you put/solder/insert R109 back onto the board. I hope this is clear.

 

[matthieu68]

This is the procedure that I did, as indicated in the manual, except that once r109 is connected, my needle remains on 0 even in IN or OUT mode.
I watched a video on YouTube from ABE and in IN and OUT mode the signal raises the needle, but when there is no signal it remains completely to the left.
There is only in GR mode where the needle goes to 0 when no signal is applied.

 

[matthieu68]

With the sifam did you put the resistance of 10k or 1K? (although I don't think this should play a role in my problem)

 

[matthieu68]

Ok I found my problem, the r124 multiturn can be turned even further, this brings the vu meter back to the left and starts to raise it up to 0 again. I guess it plays once on the negative and once on the positive.
Now it works correctly.

I remain confused about certain calibrations, for example, when I adjust R34 and I obtain the lowest distortion, I go to the next step and by moving R63 this has a relationship with R34, and even R62. And R63 moves the distortion for me.

This means that even when I adjust R62, if I then measure the 0.011v on R79 I no longer obtain them.

R62,R34,and R63 are related.