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

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Hi Guys, i'm finishing mine to, with dan's collective case,
and i'm struggling to install the boards inide the case,
wich seems to small for m ,
can somebody post pics of an inside build unit ?
thanks in advance,
francois
 
warpie said:
Thanks Abe,

It'll be interesting to see how hot your regulators are.  I'll try with the switches once I get them. Opamps and chips seem to be OK at the moment (not hot at all).

Is there any chance this is cause from the high voltage I get in the 24V rails (I measure +/-28V)?
In fact, is it normal/OK to have 28V in these rails?

I was thinking of using a relay connected to the +/-24V for bypassing the signal but I don't know if that's a good idea.

Thanks
Mike

Hi Mike
I checked some regulators today and they don't get too hot to the touch. I'm using 20v secondaries which comes to about 26v on the output section. So I wouldn't worry to much about it. Yes 28v is fine for the output. I think I used a 25v secondary transformer for my first build and that gave me upwards of 30v and its still running today.

24V relays should work fine with the 24v taps.

pacemaker said:
Hi Guys, i'm finishing mine to, with dan's collective case,
and i'm struggling to install the boards inide the case,
wich seems to small for m ,
can somebody post pics of an inside build unit ?
thanks in advance,
francois

Hi Francois,
Yes the boards are a bit hard to fit once the switches are in there. The best way I found was to mount one board in between the meter switches slightly under one of the meters, and the second board mount above the second set of switches. I found that using 2" spacers with 2.5" screws worked great.
I'll look for a pic around somewhere.

Abe
Cheers!
 
yeah that's what i thought,
it's tricky !
maybe we shouls warn dan about this, so as he can provide deeper cases to future buyers ,
i think i will try a deeper ,
as i hate sneaking to mount PSU transformers, AC wiring to power switch etc...
but would love to see some pics of your build ;-)
thanks again for this boards,
regards,
Francois
 
Hey guys easy solution.  Just let me know you want it 11" and I will send one when you order instead of the standard 9" deep. 

BTW, just mixed a record last week.  I used the CLX on all the perc and random stuff.  Sounded amazing plus it was awesome watching the LEDs bounce! 
 
I know, sorry.  I have mine in a 9" and I know Abe has made a bunch in 9" cases.  So we thought 9" would be fine with everyone.  Would it help to see some pics of how they fit in 9" cases?
 
Hello Everybody,

I'm on my way to finish my stereo CLX-VU, with DBX200 VCA and DBX208 RMS detector.
Everything isn't finish right now but I've got a question about Q7 (Rev2 board)

in the manual, it's said:

THE EXTERNAL
TRANSISTOR BC560C MUST BE SELECTED
ATER THE 200 SERIES VCA IS
INSTALLED/BUILT. HOW TO EXACTLY
SELECT THESE TRANSISTORS AND OPTIMIZE
THE DISCRETE VCA IS OUT OF THE
SCOPE OF THIS MANUAL


I can't find any information to choose the transistor, does anyone succeed in building the CLX-VU with DBX200 VCA?
Any information to help me?

Thanks!
 
Mirouf said:
Hello Everybody,

I'm on my way to finish my stereo CLX-VU, with DBX200 VCA and DBX208 RMS detector.
Everything isn't finish right now but I've got a question about Q7 (Rev2 board)

in the manual, it's said:

THE EXTERNAL
TRANSISTOR BC560C MUST BE SELECTED
ATER THE 200 SERIES VCA IS
INSTALLED/BUILT. HOW TO EXACTLY
SELECT THESE TRANSISTORS AND OPTIMIZE
THE DISCRETE VCA IS OUT OF THE
SCOPE OF THIS MANUAL


I can't find any information to choose the transistor, does anyone succeed in building the CLX-VU with DBX200 VCA?
Any information to help me?

Thanks!


Nope!
But I am getting ready to start on a pair with original DBX Cans. What I would do is just measure out a couple transistors, measure by HFE. Choose some various values. And Put some sockets in that spot and put a middle of the road value in, and power it up and see how it sounds, then replace that transistor and see how it sounds.

From theory I have no idea what that transistor is supposed to do, and really I imagine there is a good chance it will work just fine with any transistor in there, I don't think its a matter of working or not working.

Go for it!
Abe


PS Maybe (hopefully) someone else more knowledgeable can shed some light on this? Cause I would also love to know what it does and how to choose it.
 
Ok!

I was on my way to do the same, match some pairs and test... I let you know if I found something about it!
 
Hi Abe/guys,

My unit is almost done! I'll post some photos soon.  :)

However, I have one (hopefully) last question. Checking with my scope it looks like the output sums the signal (i.e both pin2 and pin3 on the XLR have the same polarity. Is this normal? I would expect same amplitude but different polarity between pin 2 and 3 for a balanced output...

thanks
w.
 
warpie said:
Hi Abe/guys,

My unit is almost done! I'll post some photos soon.  :)

However, I have one (hopefully) last question. Checking with my scope it looks like the output sums the signal (i.e both pin2 and pin3 on the XLR have the same polarity. Is this normal? I would expect same amplitude but different polarity between pin 2 and 3 for a balanced output...

thanks
w.


Yea I had to look at the schematic to be sure, but looks like the output signal doesn't get its polarity flipped for either Pin 2 or 3. Must be a type of impedance balance, would be my guess...anyone?
 
So that means there's nothing unusual with my unit right?

FWIW, I checked (with the scope) the TL082's pin2 and 3 (inverting inputA and non-inverting input A) and both signals have the same polarity.  I'm talking about the input TL082 (TL082a1 in abe's PCB).

If I disconnect the TL082 from the PCB,  the scope shows inverting and non-inverting signal (as in the input).

any clue? is this normal?

 
warpie said:
So that means there's nothing unusual with my unit right?

FWIW, I checked (with the scope) the TL082's pin2 and 3 (inverting inputA and non-inverting input A) and both signals have the same polarity.  I'm talking about the input TL082 (TL082a1 in abe's PCB).

If I disconnect the TL082 from the PCB,  the scope shows inverting and non-inverting signal (as in the input).

any clue? is this normal?
Yes that's normal. Think about the feedback going into the negative input, wich is the same polarity as the positive input. That is not happening while the chip is disconnected.
 
Yes that's normal. Think about the feedback going into the negative input, wich is the same polarity as the positive input. That is not happening while the chip is disconnected.
[/quote]

OK I see, that makes sense..  ::)
Thanks for that.

Still trying to figure out why the output the sums hot and cold signal though...
 
warpie said:
Yes that's normal. Think about the feedback going into the negative input, wich is the same polarity as the positive input. That is not happening while the chip is disconnected.
[/quote]
OK I see, that makes sense..  ::)
Thanks for that.

Still trying to figure out why the output the sums hot and cold signal though...
[/quote]


Well I admit I don't understand completely how it does this, but the engineers at DBX no doubt knew what they were doing. I can understand when 2 signals are out of phase and then summed how that gets rid of noise, but the 160VU is doing something different...

Wait I remember reading something in an original 160vu manual that the output circuitry is different and "noise sensing" or something and counter acts for noise is the line somehow (opamp feedback loop?) at the very least don't worry about it, but I am curious too how it exactly works, must be pretty simple. I see if I can dig of that manual.
 
Yes, it's quite odd indeed... I'd be very interested to know (purely for educational reasons) why DBX engineers did it that way.

In fact, what I get on the output is  the sum of both signals on pin2 (like they're added with the same polarity) and nothing on pin3. This is clear on the scope but when I use my soundcard's I/O the unit seems to be at unity gain with the gain pot at 0db, which seems correct.
 
abechap024 said:
Wait I remember reading something in an original 160vu manual that the output circuitry is different and "noise sensing" or something and counter acts for noise is the line somehow (opamp feedback loop?) at the very least don't worry about it, but I am curious too how it exactly works, must be pretty simple. I see if I can dig of that manual.
Since I wonder, too (Even though I do not build the unit, or own it, only the humble dbx 117, which I like a lot), I had a look at the manual and the schematics.
The manual states hum suppression with that circuit and the way I see how it could work, I might be wrong though, is:
R92, R83, R84 and R33 are all 1% resistors, the first two are going to pin3, the latter building the feedback network. So, if any hum gets into the compressor through the output, it will be the same amplitude on pin2 and 3. On Pin2 it will travel the feedback network to the negative input of the 301 the same amount of hum should enter the positive input of the 301 through R92. It will be canceled at the ouput of the opamp.
R93 and R103 are obviously simulating the output impedance at pin2, so you have an impedance balanced output and also the noise entering through Pin2 and 3 sees the same impedance on both lines.
So DBX did not rely on the following device (It might be unbalanced anyway) to cancel any noise, but built a circuit do do it in the 160 itself. Seems clever to me.
 
Got everything soldered up, all connected and ready for testing. When powered up on the power rails I am getting the  + or- 15V within spec. The 24V rails are showing +16V and -41V which seems way out. Are there any obvious cuplrits causing this before I start desldering components?!
Regards
Steve
 
redmojosteve said:
Got everything soldered up, all connected and ready for testing. When powered up on the power rails I am getting the  + or- 15V within spec. The 24V rails are showing +16V and -41V which seems way out. Are there any obvious cuplrits causing this before I start desldering components?!
Regards
Steve

Hmmm....Are you sure you are measuring correctly? If so, you must have your transformer hooked up on correctly would be the only solution  I could think of. Because if you look at the 160vu schematic it goes:

Transformer -> Diodes -> smoothing caps --> +/-24 tap

So maybe you have the center tap of your secondaries hooked in the wrong spot (it should be the center pin of the power TX input on the PCB)
 
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