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

[ilfungo]

I finished 2 x 160
I had several problems
2 x TL071 dead
1 x TL082 dead

I can not calibrate R63 (I can not get .011 vdc)
Someone has done it?
if I try to use a larger value trimmer?
thanks

 

[tfp]

Hi Ilfungo,

I also cannot reach the -0.011DC. Changing the trimmer would not help I think because in my sitiuation the trimm is full open i.e. 0Ohm. so a different value it is the same situation??

How far off are you? Mine is at 0.002 VDC at the moment!
And what is your THD %?

all the best

RJ

 

[jplebre]

guys, for that adjustement, don't forget to change the meter to i/p!
It's obtainable. Check if your i/p signal meet the specs

 

[tfp]

I tried it again with input switched in (good tip) but I do not get the value. With lots of trying I do know that had has someting to do with r107 and which risistor you have in place. With 10k I can do -0.011VDC, but I have a 0.1 amp meter and use a 1.5k resistor (I want to see a lot of movement on the meter, max -db is now -20db not -40db, for me better to see gainreduction) and lowest possible is now +0.004 VDC. With a risistor of 3k for example I got 0.000 VDC.

I do not know what exactly is adjusted (level calibration) with the -0.011DCV and if this is really a problem?

 

[jplebre]

it's located in the GR section and I had the feeling it had to do with level to the treshold section bit thingy

but hey what do I know

 

[plektra]

Hi,

I'm also having problems with the initial meter calibration and level calibration. I guess both TL071 chips are dead (identical results as what eparg had, both chips are heating quite a lot). Also with the level calibration, the lowest voltage on R79 with the kit components is about +62mV, which is still far from -11mV.

The unit is passing signal though, THD is 0.135% and noise level -94.5 dBA (using RME Babyface).

I'll fetch new TL071s and try with those, but do you have any suggestions on how to proceed debugging the level calibration issue?

 

[tfp]

Hi Guys,

Just for sharing, my custom scale for max -20db gainreduction.

all the best!

RJ

 

[Winetree]

RJ, Thanks for the Meter Scale.
Took file to Staples, it prints out real small.
Because it's a PDF file, the only way they could change the size was to adjust
the margins. It's a guessing game, so i have to take an orginal scale down to size it.
Any other advise?

 

[tfp]

Hi Winetree,

The scale fits the hairball 8027-WF 1mA Meter and will measure around the 4.2 centimetres wide when printed. Is this correct or is it smaller? What meter do you use?

 

[Winetree]

I'm using same Hairball meter.
Prints on my b&w printer (orginal fit) at the right size.
However, I want it on heavier gloss stock with the blue print.
I have that on the other unit with the needles painted black.
Staples didn't know what they were doing. I'll find somewhere else.
Thanks

 

[tfp]

OK good! I attached a new version, I think it is nicer!

 

[berkleystudios]

I received these v regs

http://www.mouser.com/Search/m_ProductDetail.aspx?Texas-Instruments/LM317LCLPRE3/&qs=/ha2pyFadujltRttC1l4fmJT%252blEhQxqXcZt81pi8RQV4Nl2H%252bbAl7A==


They are in different housing that the  lm337 ie look like a typical transistor... Will they work or should I reorder?

 

[ilfungo]

after several days of testing I discovered some things ...
on one of the channels I could not have the symmetry (R36 calibrtion)
the problem is related to IC CA3083 (exchanged between them can adjust it)

Same problem with R63, changing CA3083, I can get-11mV.

There is one thing I do not understand

I had problems with 2 x TL071 (dead)
1 x TL082 (dead)
1xCA3083 (not working properly)
Why?
I do not understand


After having calibrated the compressor, however at high compressions the waveform I get is not symmetric
Has anyone noticed the same thing?
is this normal?
thanks

 

[abechap024]

I received these v regs

http://www.mouser.com/Search/m_ProductDetail.aspx?Texas-Instruments/LM317LCLPRE3/&qs=/ha2pyFadujltRttC1l4fmJT%252blEhQxqXcZt81pi8RQV4Nl2H%252bbAl7A==


They are in different housing that the  lm337 ie look like a typical transistor... Will they work or should I reorder?

Well the ones you ordered are only rated for 100ma....I would be on the safe side and just reorder the lm317 it can handle up to 1.5A

 

[abechap024]

after several days of testing I discovered some things ...
on one of the channels I could not have the symmetry (R36 calibrtion)
the problem is related to IC CA3083 (exchanged between them can adjust it)

Same problem with R63, changing CA3083, I can get-11mV.

There is one thing I do not understand

I had problems with 2 x TL071 (dead)
1 x TL082 (dead)
1xCA3083 (not working properly)
Why?
I do not understand


After having calibrated the compressor, however at high compressions the waveform I get is not symmetric
Has anyone noticed the same thing?
is this normal?
thanks

Were the ICs inserted the wrong way round? Were some of them inserted before the voltages were adjusted to safe levels (+/-15v) also how were they handled? In the technical papers, sometimes they say to use static protection wristbands and stuff, usually with digital ICs but also some opamps/transistors. Could've been bad chips, or more likely could've been fried during installation/handling.

 

[ilfungo]

thanks ABE
I was paying attention to everything ....
However, I am very happy with the sound
Great project!

Last question:
"After having calibrated the compressor, however at high compressions the waveform I get is not symmetric
Has anyone noticed the same thing?
is this normal?§"
thanks

 

[abechap024]

thanks ABE
I was paying attention to everything ....
However, I am very happy with the sound
Great project!

Last question:
"After having calibrated the compressor, however at high compressions the waveform I get is not symmetric
Has anyone noticed the same thing?
is this normal?§"
thanks

Glad you got it going!
Yes, I've noticed if you change the gain of the waveform it becomes unsymmetrical. I haven't tried to compress a ton and see if it becomes unsymmetrical. I'll look at it with this next units I build, I wouldn't think it would be a problem though, as the symmetrical calibration is just to get all the units operating in the same window of range.

 

[ilfungo]

Have any of you managed to get a compression reading correct?
I can not get proper tracking ...
Hairball 1ma meter with 3k3 resistor
Thanks

 

[tfp]

Hi Ilfungo,

Interresting about the ca IC and reaching the -0.011VDC, I am going to order some to see if I can manage the -0.011VDC! Now I am at -0.004VDC.

For about the right amount of compression on the meter did you also calibrate the unit with trim R43 and did the last step mentioned in the official DBX calibration guide:

8. INPUT TRACKING
8.1 Place "METER" switch to "INPUT and step oscillator to -3ODB. Adjust R56
for a reading of precisely -30 on the DBX 160/161 meter.


Two more questions for Abe:

Is THD of 0.38% in the right ballpark;
Is it a big problem if you are a little bit of the -0.011VDC, -0.004VDC?

Thanx!

 

[abechap024]

Two more questions for Abe:

Is THD of 0.38% in the right ballpark;
Is it a big problem if you are a little bit of the -0.011VDC, -0.004VDC?

Thanx!

Hi!
The THD question is a little ambiguous...is that with no compression? Also are you still using a silver can VCA? Either way that reading seems pretty high for a THAT build unless your doing some serious GR.

No, don't get too hung up on these little tweaky calibrations guys, I've gotten the meters and readings and everything to track beautifully, it takes a little time and patience when setting up the meter but very possible. But really, who needs to know when they are slamming 30db compression if they are +/- a db or two?

Put your soldering irons down and go make some music ;D ;D