G1176LN TOO MUCH VOLUME

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Mar 18, 2005
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3
Hi guys,
I have build my first DIY project,it's a G1176LN.The output trafo is reversed.
Good news,it works!!!!!!! :grin:
The sound is good,no humm or distorsion.
The problem is that,I can't open a lot the input pot & it compress very quickly.
Is it a problem or is it due to the calibration?
If someone got some suggestion,many thanks.
James
 
The 1176's have very high gain as-is. Can you compare to a "real" 1176 - or have you tried working with one?

To get the compression right, you need to perform the adjustment procedure.

Jakob E.
 
...and what's your input source? If your input level is very high, then it will begin compressing at lower levels of the input pot.

And as Jakob said, if you haven't set the Q-bias correctly, the point at which compression begins will be wrong.

Mark
 
How fast is your attack setting as well... with fast attacks, it will jump on transients with very little input gain.
 
I have made the calibration procedure.It seems to be ok but what level must I apply for the 1Khz signal for the BIAS adjustment?
I have made the BIAS calibration with a 1Khz at 0 db and I have opened the In & Out pots equal (approx 3 o'clock) to see +1db on the Vu meter and I have turned the bias pot til I read 0 db on the Vu, not like in the original 1176 manual where it's wrote that the Out pot must be full clockwise.
Is it ok? Am I wrong?
Jam
 
With the unit in bypass?
If I bypass the unit,the Vu meter doesn't move.
I have made it with the unit in VU mode.
How can I bypass the unit without using the bypass mode?
Jam
 
Hi Jam,

Right- this is your problem!

When setting the Q-bias the unit needs to be in "Bypass" mode (i.e. meter switch in first position) This disables the sidechain from affecting the bias level of the FET. Therefore you can set the Q-bias to move the FET into the beginning of it's gain reduction region.

To set it you need an external meter to monitor the signal at the Output XLR. This can be another VU meter, or a console or DAW meter. Just use the external meter to set the level. You'll notice as you adjust the Q-bias pot that at one extreme there is full signal, and at the other extreme no signal output. Set the pot so that the output signal is -1dB the input signal level.

Get this set up and you'll be compressing fine!

:thumb:

Mark
 
I'm revisiting some of my 1176 calibration procedures now that I have the G1176 out of the rack for other investigations.

I've always had the same complaint as "Beginner" here.. I only turn my input pot like 1 or 2 hours (imagine the dial as a clock) from CCW and I'm deep into compression, I don't have alot of play on the Input.

I've calibrated it before and I'm going thru the steps again tonight... I use protools and send in a -1dB signal, adjust input until I see 0db (can't see +1 in protools) and then adjust Qbias until protools sees -1 dB.

I can't imagine that this 1dB is screwing me up.

Any advice on this problem?

thanks !
 
Hi bradb !

Just wanted to second what u r saying about the compression kicking in at a low input level.

My g1176 behaves exactly as u describe!

The sound quality is better than many of the real 1176s I've used...hats off to Jakob (and mnats for the nu layout). :thumb:

For the record , I calibrated mine using the oscillator on my soundcraft 2400,with standard VU's,and also using a dmm to check the levels in terms of mV. I'm pretty certain I have the calibration correct .

I also tried a bunch of fets,albeit from the same batch ; this didn't seem to make much difference in my unit.

IMHO the g1176 is as good as, if not better,than the original . The only slight quirk is not having much leeway with that input control .

I wonder if (like the gssl thresh mod) some kinda added resistor , or different value pot may open things up a bit? ..or am I out of my depth suggesting such things??!

BTW I do all my testing at the channel insert point on my desk, with quite average signal levels. The soundcraft patchbay is unbalanced , so I always double check with the 1176 in the middle of a balanced chain,just to confirm.

cheers!
 
My unit doesn't seem to behave this way. I often get my G1176 in the 11 to 1 o' clock positions often.

Are you using Linear or Log pots for the input control?
 
Hi greg !

Hmm that's interesting!...that's certainly more like the typical place I'd be setting a urei.. nice to hear from someone who doesn't have this issue!

Unfortunately I am already using a log pot on the input , so that aint the answer for me...

Very good point tho' !

Anyone else experiencing this?

Cheers Greg

nEon.
 
I've thought about the log / linear pot issue. I'm pretty sure I have the right pots in there, but I'll double check tonight.

thanks guys,
 
Ive built two units. One with electronic balanced inputs and the other with an OEP transformer input.

Both units seem the most useable with the input pot between 9:00 and 12:00 straight up. That just seems to be where my threshold works the best for my use. This is comming directly from a +4 tape deck into the compressors, and not an insert point. When using my -10 insert points my input knob can go even higher. My output pot always seems to be around 1:00-3:00 or so, using OEP outputs.

It seems now that I have used real 1176's and the G version, mine work pretty much the same as the real ones. The units are very fast too.

I got to say, the ones I built sound marvalious! I have a slew of compressors in my studio, and these get used every session. That and my GSSL I just finished. Both absolutely quality gear.

Joe
 
Hey

I have/had the same problem, and was convinced I had made a mistake somewhere. After 2 days of double checking and FET swaping I couldn't find any construction or calibration proceedure errors. I rewired my input the way UREI did it on the transformer balanced input revisions A-E, F being a slight exception with the way the attenuator is grounded. I found this to give a much more usual input response. I'm curious to know why this is happening to so many poeple though. It still seems different than my other 1176s. I'm at about 9 and 3 on input and output for my usual operating and GR levels. It does sound quite good though, it's a really useful 1176 flavor for what I do. thanks Jakob.
 
I have an Mnats board, for what its worth, i usually have my input all the way down and my output pretty much cranked up to the max.

I've got lundhals on the input and output.
 
could you give some details Al?

In the meantime im going to order some more FETs, perhaps 2 lower gain matched ones would be better.
 
Hey Brad,

There's one 1176 manual on the internet somewhere that has schematics for all the revisions. If you look at the rev < F schemaitics you will see how UREI wired the inputs on the transformer balanced versions. You will need a dual ganged pot, and 2 620 ohm resistors. I actually don't know what the value of the pot is suppoesed to be. I had some routing modules from a UA console that had pots in it that physiaclly looked the same as the one used in the revision D. It also had the 2 620 ohm resistors wired across terminals that agreed with the schematic, I i decided to give it a shot. There are probably some impedance experts here who could hazard a guess on what the value of that pot should be. The transformer I used was a hammond 850G which is a really common 600:600/150:250 line transformer. It was the closest thing to the original UTC O-12 which was wired as 500:200. Mine is wire 600:150. I'm also going to try a new batch of FETs...this rewire got me close, but i'm still not %100 happy.
 
The problem here - if I understand it correctly - not that the gain is too high, but that the threshold is too low.

The place to fix this would probably be selection of the FET's for higher cut-off voltage.

Jakob E.
 
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