kdawg

Calibrating G1176
« on: June 16, 2004, 03:37:33 AM »
I'm trying to calibrate the G1176, but I'm a little confused about the volts versus dB info. If it asks for 1 kHz at 0 dB, does this mean a 1 volt peak to peak on my scope hooked up to the signal generator? And +1 dB = ? volts p-p?

And when hooking up the signal generator to the XLR in, should this be between ground (3) and pin 2 since it's unbalanced? Same with the output?

I already seem to have some weird oscillation on the output, but I just turned it on today and haven't begun to measure the voltages. At least the meter driver is OK!

Thanks... should have some build pics up this weekend, getting panels laser engraved.

-kdawg


kdawg

Calibrating G1176
« Reply #1 on: June 17, 2004, 12:28:15 PM »
bump

Michael Krusch

Calibrating G1176
« Reply #2 on: June 17, 2004, 05:17:01 PM »
If you planning to use this box in your studio only, absolute level is not a real issue. If you run your studio unbalanced, connect the generator unbalanced (3-2). If your studio is balanced try (1-2).
It's importend to adjust that 1dB gain reduction and the metering, but the level inside the box also depends on the input and the output pot.
It's not the answer for all of your questions, but I hope it helps a little bit.

Calibrating G1176
« Reply #3 on: June 17, 2004, 08:37:18 PM »
Quote
If it asks for 1 kHz at 0 dB, does this mean a 1 volt peak to peak on my scope hooked up to the signal generator? And +1 dB = ? volts p-p?


Okay, in this case, 0db = .775Vrms. That is your reference voltage.

.775 X 1.414 X 2 = peak to peak volts on the scope.

To find what voltage corresponds to +1db, use the formula:

db = 20[log(V1/V2)]

I'd just start plugging in values for V1, using .775V for V2, until you get the correct db result (+1). Or you could rearrange the above equation to solve exclusively for V1. :roll:

Don't forget to convert to P-P if you're using the scope to measure levels.

The Sifam VU or equivalent reads 1.23Vrms at 0db rather than .775Vrms because it is referenced to +4db, which is what you'll get if you plug 1.23V and .775V into the above equation.

To recap, .775Vrms is the 0db reference for all calibration procedures on the 1176.

Dean

FrankSL

Calibrating G1176
« Reply #4 on: June 18, 2004, 02:07:14 AM »
Shouldn't ground be pin 1 on the xlr?
Frank

bubba_b

Calibrating G1176
« Reply #5 on: May 31, 2005, 01:56:51 PM »
I'm having some trouble calibrating my 1176. I don't have an oscope. I have a multimeter and am using my DAW to generate a 1kHz tone (0dB) to use for my signal source. I did everything gyraf said for the bias adjustment (even did it by the urei manual as well), but no matter what I do with the bias trimmer, my meter never moves from dead position. I have no problems adjusting the GR meter to read 0dB, however and the GR trck trimmer works, too. Here's what I'm doing:
    input=full ccw
    output=full cw
    ratio=20:1
    meter=VU pos.
    attack=full ccw
    release=full cw

    sending a 0dB, 1kHz tone to the input
    meter reads: full left, no reading or you could say -20dB
    complete ccw to cw adjustment of bias trimmer does nothing to meter reading.


What am I doing wrong here?

yan_b

Calibrating G1176
« Reply #6 on: May 31, 2005, 03:38:37 PM »
Quote
I did everything gyraf said for the bias adjustment (even did it by the urei manual as well), but no matter what I do with the bias trimmer, my meter never moves from dead position


since its done in bypass mode it should not move, you should measure the in/out voltage, or "bypass" the bypass switch section of the meter, note that the original 1176 bypass is different, hence the manual comfusion.
I love the smell of burned electrolyte in the morrning.

soundguy

Calibrating G1176
« Reply #7 on: May 31, 2005, 04:30:27 PM »
dean-

if you were installing an 1176 into a +4 referenced system, wouldnt you want to calibrate it referenced to 1.23v?  Is there a reason to calibrate it at .775V if you are planning to use it in a +4 environment?

I hope this isnt a silly question.

dave

chips are good with dip...

gyraf

Calibrating G1176
« Reply #8 on: June 01, 2005, 03:01:25 AM »
Dave,

that calibration procedure is just a way of setting the FET, not anything to do with absolute working levels..

Jakob E.
..note to self: don't let Harman run your company..

soundguy

Calibrating G1176
« Reply #9 on: June 01, 2005, 12:06:08 PM »
cool, thanks jakob!

dave

chips are good with dip...


Calibrating G1176
« Reply #10 on: June 02, 2005, 12:51:22 AM »
Dave,

On the G1176 page at Jakob's site, you can download the original manual..
http://www.gyraf.dk/gy_pd/1176/1176.htm

Look at the bottom of page 2 for the statement regarding reference levels.

 Actually, page 2 really cleared up a lot of mysteries and brought this project full circle for me. It now makes sense to reverse the output transformer for correct output level AND headroom. The Threshold vs. Output Level chart lets you verify that the comressor has the correct sensitivity and gain at various settings...if you feel like studying the lingo a bit and doing the test.

Dean

soundguy

Calibrating G1176
« Reply #11 on: June 02, 2005, 01:43:47 AM »
wow, thanks for the heads up on that link, I hadnt noticed that the last few times I visited jakobs site.  thats awesome, printing it now.

dave

chips are good with dip...

Mrosso

1176 Fubar in the final stretch
« Reply #12 on: January 11, 2006, 04:13:21 PM »
Hey everyone. I have my mnat's/Gyraf 1176 built and calibrated up to the final tracking adjustment for the GR meter. No matter what I do, the meter does not move off of 0dB. I can turn the trimpot hard CW to hard CCW and the meter doesn't move. Please Help!

radiance

Calibrating G1176
« Reply #13 on: January 11, 2006, 06:34:29 PM »
Mrosso: your meter does not move? even not when you put in the required 1kHz 50mV test signal?

I found out the "GR meter Zero" and the "GR meter Trck" trimmers do influence eachother in a way.
Try setting the "GR meter Zero" fully CW. Now fiddle with the "GR meter Trck"....still no movement?

than try setting the "GR meter Zero" fully CCW. Now fiddle with the "GR meter Trck"....
"Knowing that you are dreaming, however, does not automatically guarantee full rationality.
Then again, being awake doesn't ensure good thinking, either." -  Lynne Levitan

white noise

1176: the effects of the calibration
« Reply #14 on: January 29, 2006, 10:05:42 AM »
Hi,

I have almost finished my 1176LN, but I am still waiting for the Sifam AL20 meter, and I heard it is going to take at least three weeks or so, before I have it. I found a temporary meter in the cellar and I am doing some tests. The Input and the Output of the 1176 seem to work. If I switch to VU, the meter moves considerably, I hope this is correct? But the release, attack and compression ratio don't to seem to do anything with the sound. My question is: are these (release, attack and ratio) only going to be heard when the 1176 is properly calibrated with the correct meter, or should I hear at least some effects when I turn the knobs, although I might be using a wrong meter? Thanks in advance!


All the best, David.

radiance

Calibrating G1176
« Reply #15 on: January 29, 2006, 12:29:10 PM »
You should definitely hear some changes when turning the attack and release pots, even when the unit is uncalibrated and with no meter attached.
Just disconnect your meter and listen again. I don't think the meter can have any effect on the sound but just in case...
"Knowing that you are dreaming, however, does not automatically guarantee full rationality.
Then again, being awake doesn't ensure good thinking, either." -  Lynne Levitan

white noise

Calibrating G1176
« Reply #16 on: January 30, 2006, 06:39:20 AM »
Hi Radiance,

Thank you for the info. :thumb: I will try what you suggested.


All the best, David.

Mbira

Calibrating G1176
« Reply #17 on: February 01, 2006, 12:32:53 PM »
Is the 50 mV used to do the calibration RMS or P2P?

Thanks.
Joel
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

white noise

Calibrating G1176
« Reply #18 on: February 16, 2006, 06:13:58 AM »
Hi,

I have almost finished my 1176, but I am still waiting for a Sifam meter, so I haven't calibrated it yet.  When I switch between the different compression ratio's I notice that the higher ones, 1:20 for instance, sound somewhat more quiet than 1:4 compression. Is this ok, or is something wrong? I haven't got a hardware compressor so I am not that familiar with its subtle effects. Thanks in advance!


All the best, David.

dissonantstring

Calibrating G1176
« Reply #19 on: February 16, 2006, 06:17:26 PM »
hi david,
if you think about it your compressor is working as it should.
1:20 ratio of compression is squashing down the level much more than 1:4 ratio of compression so your level will be audibly less.
use your output pot to bring levels back up.
regards,
grant


 

Related Topics

  Subject / Started by Replies Last post
0 Replies
1067 Views
Last post January 30, 2006, 06:13:20 PM
by Mbira
13 Replies
3965 Views
Last post March 11, 2006, 05:43:53 PM
by NewYorkDave
150 Replies
57390 Views
Last post November 13, 2015, 01:35:39 PM
by okdaniel
2 Replies
1289 Views
Last post May 10, 2012, 10:04:50 PM
by Mbira