All things G1176 - the new "repost" thread.

[dale116dot7]

Yes, the 'PIN 1' spot is left unconnected. The NE5532 input stage will not be used - its output goes nowhere if you put in those parts - you can eliminate the NE5532 and all of its support components.

 

[Zee1usa]

Thanks Guys!

That was one of the last things I needed to get figured out as I
am finishing this thing up. I went ahead and have done the 1:2
Mod on the output transfo for the extra 12db of gain. which was
fairly simple.. 4 cuts with my carbide cutting wheel/ dremel
and solder 4 jumper wires. easy enough.

Another couple questions I have are:

1) is there anything else I need to do with the transfo
as far as the mod is concearned.

2) I am wondering if I should connect that extra ground wire
to the bottom of the PCB for less hum or just in case there may be
some hum cause I would rather do it now than take the board out
10 times to add finishing touches as I am hoping this thing will
work the first time up and just need calibrating(fingers crossed)

QUTOE FROM FUM:

I also took some 14 guage solid copper and soldered it around the perimeter of the ground plane on the bottom of the board, as suggested in a few threads. the output traffo is also wired as per the Chef suggestion, for increased gain.

No hum at all from these units.

ju

QUOTE FROM FALLOUT:

I've got Labs' Gyraf 1176 PCBs... Has anyone built these yet? I'm curious if the ground around the circuit needs to be fixed as I remember people having noise/hum problems with the current layout due to the ground not being thick enough? If so, did you just scrape the solder mask off of the GND and solder a thicker piece of wire around it?

-Jay

QUOTE FROM GYRAF:

In stead of scraping off the solder mask - which would look ugly - simply run a good piece of wire around the board, and solder it to the points where components meets ground, that is, at the ground pads..

Jakob E.


This answers my question about the extra Ground for reduced hum.
(talking to myself again ...kinda like OWEL does=)

Thank-you

 

[kdawg]

I figured I'd try reposting my problem in this thread...

Input gain - I have some heavy limiting (-6 to -10 db) occuring starting at around 1-2 on the dial with a balanced or unbalanced input at all ratios. Think this is strictly Q bias adjustment (I did the procedures like 3 times) or more? It's unusable this way because I get barely any output gain.

Also - The ratios seem to be backwards. I checked the wiring, but both channels I built react the same way. What could cause this? My markings are fully CCW to CW: 1:4, 1:8, 1:12, 1:20. Meter showing more GR reduction with 1:4 than with 1:20.

Measuring voltage at point 22 to GND:
with 1:20 ratio = -6.3V, approx 90k to GND
with 1:4 ratio = -2.08V, approx 47k to GND

If I decide to do the output transformer flip for more gain, that is going to make the VU meter mode not accurate to 0dbu = +4dB right?


Pic of my 2nd board waiting for assembly (minus a BD245 that I forgot):
http://www.jnd.com/kdawg/kd_1176_board.jpg

thanks

 

[gyraf]

Hi kdawg,

Are you using the right BF245 A-version FET's? If so, try interchanging the audio and meter fets.

Check that you have around 1x gain from input to input level pot top. A wrong resistor in the input amplifier could mess up things here.

Ratio switching is probably fine - it also change threshold setting when changing ratio. So the higher gain reduction at low ratios is not an effect of higher ratio, but of a lower threshold.

Flipping the output transformer won't affect meter precision, as the meter is simply hooked across the output.

Jakob E.

 

[Greg]

kdawg - I've read that you should probably put a small heat sink on your voltage regulator. I haven't powered up a G-1176, so I'm not sure how hot the regulator gets without a heat sink, but I just thought I'd mention it since I'd read it on Gyraf's site.

 

[dale116dot7]

I had the same problem (low gain) and I looked at the FETs I soldered in, they were BF245C. Obviously wrong - I didn't check the suffix. I didn't have any BF245A FET's but I used 2SK170's which have a 1.5V threshold voltage, and they worked - it calibrated up just fine.

My voltage regulator gets warm without a heatsink, but not overly hot. I will install one.

 

[fum]

Okay, I'm not out of the woods yet, but first, to Nick:

If you've got the board out still, I'd add the extra ground plane reinforcement. But that's just me =).

One of my units is complete and running. The other, I fixed the voltage problems, but managed to bugger the metering ( which was fine). In troubleshooting the voltage problem, I at one point smelled smoke(didn't see it), and the metering hasn't been correct since then.

Here's what it does:

The VU rises maybe halfway, and then sinks back to zero, over and over. If I meter vu output, the voltage ramps from 0-6V, and then drops to zero again.

Somethings gotta be cooked, just need to figure out what.

As per usual, any pointers/advice appreciated.

Regards

ju

 

[gyraf]

Fum,

The meter circuit is the two trimmers, the meter fet, and the TL071. Try changing the meter fet and the TL071..

 

[fum]

Thanks Jakob,

Did try swapping the TL071 already ( as it's socketed, and was easy), will try the fet next.

ju

 

[kdawg]

Thanks for the info guys...

>>Are you using the right BF245 A-version FET's? If so, try interchanging the audio and meter fets.

I have two complete boards hooked up and they both react exactly the same. The FETs are marked BF2 45A.

>>kdawg - I've read that you should probably put a small heat sink on your voltage regulator.

I do have heatsinks, just not in that pic

I have a different batch of FETs I can try and I'll check that 1x gain at the input pot.

Do BC107's have to be BC107B or are BC107 ok?

 

[deanp920]

kdawg,

Input gain - I have some heavy limiting (-6 to -10 db) occuring starting at around 1-2 on the dial with a balanced or unbalanced input at all ratios. Think this is strictly Q bias adjustment (I did the procedures like 3 times) or more? It's unusable this way because I get barely any output gain.

Also - The ratios seem to be backwards. I checked the wiring, but both channels I built react the same way. What could cause this? My markings are fully CCW to CW: 1:4, 1:8, 1:12, 1:20. Meter showing more GR reduction with 1:4 than with 1:20.

Measuring voltage at point 22 to GND:
with 1:20 ratio = -6.3V, approx 90k to GND
with 1:4 ratio = -2.08V, approx 47k to GND

Here is some info that I feel is of great G1176 significance, but is probably overlooked by most:

Near the bottom of page 2 in the UREI 1176LN manual, you'll find a little chart titled "Threshhold vs. Output Level".

Using this chart will let one know very easily if the compressor is working within spec at the various ratio settings.

It is important to remember that the chart is written with the assumption that the output transformer is wired 1:2, so adjust your numbers depending on how you have the OPT set up(stock=2:1, Chef=1:1 Dean=1:2).

The 10db output gain reserve note is basically just turning down the output so one can read the results on the VU meter without pegging it.

Maybe someone knows how and is willing to cut and paste this info and post it here.

Dean

 

[Klaus Mogensen]

kdawg, when you adjusted the Q-bias, did you remember to turn the q-bias trimmer fully counter clockwise, before turning up the input control. This is not mentioned on the Gyraf site, but mentioned in the manual. If you forget this you will end up with the problem you describe.

Klaus Mogensen

 

[kdawg]

Ok... I've built 4 channels of 1176s, and they all act the same way. I can't turn the input pot above 2-3 or the signal just gets slammed too much. Can someone tell me if this Q bias calibration seems correct?

Q Bias
Release: Fully CW (Fast)
Attack: Fully CW (Fast)
Input: Fully CCW (off)
Output: Fully CW
Ratio: 1:4
Meter: Bypass
Q bias: fully CCW

Signal Generator: 0.245 V (AC) sine wave 250 Hz
Measuring across input pins 2 and 1 & 3 for ground

1. Turn up input control until I get 0.100 V AC, measuring across output pins 2 and 1 & 3 for ground

2. Rotate Q Bias until reduced to 0.089 V AC across output. [ 1 dB = 20 log (0.100 / 0.089) ]

GR Meter:
Release: Fully CW (Fast)
Attack: Fully CW (Fast)
Input: 12 o'clock
Output: Fully CCW (off)
Ratio: 1:20
Meter: Bypass

Signal Generator: 0.050 V (AC) sine wave 250 Hz
Measuring across input pins 2 and 1 & 3 for ground

1. Switch to GR meter, with no input, set meter zero adj so dial reads 0 db.

2. Switch back to bypass.

3. Adjust Output knob till 0.050 V AC measuring across output pins 2 and 1 & 3 for ground (unity gain)

4. Turn on GR metering.

5. Turn up signal generator voltage till 1/2 input V = output V.

6. Set GR meter adj so meter reads -6 db

7. Remove signal. Re-set zero if necessary, plug signal back, set GR meter adj so still get -6 db. Repeat if necessary.

---

I did Chef's mod for the output, much beter! So if I can nail this input reduction, they are finally done!

 

[deanp920]

I can't turn the input pot above 2-3 or the signal just gets slammed too much. Can someone tell me if this Q bias calibration seems correct?

If you are sending a very hot signal in , this will happen. It sounds like you set the Qbias correctly.

I'll just repeat what I suggested in my last post: Go to the bottom of page 2(specifications) in the UREI manual where it says 'Input vs. Threshold', and check your unit against their numbers.

I thought the threshold was way low on mine as well(more sensitive at 4:1 vs 20:1 etc.), but it turns out that it is right on the money. This thing goes into compression very easily.

Anyway, check it out and see what you get.

Dean

 

[orson whitfield]

Hi all. Well I gotta say my G'76 is really working very nicely. Thank you Dean and Jakob! It's a very good compressor and much smoother than I anticipated. Calibration finally seems to be correct. BUT I am having a buzz noise kinda like a ground loop. Actually I am pretty sure it is a ground loop. I can have nothing plugged into the input xlr and still get the buzz/humm from the output xlr. The funny thing is it wasn't there before. I am listening to the first recordings I made with my G'76 and there was no humm/buzz. Could this be due to unshielded cable? I did solder a thick wire around the PCB ground as Jakob recommended. I even took the compressor to a diffferent location to see if it was my electrical source but the humm/buzz was still there. No matter what I do to the pots or controls of the unit, it still buzzez/humms at the same level. Question number two is I have a 1/4 watt resistor on the Ratio switch(the 10Mohm), is that ok?

TIA,

Ors

 

[gyraf]

1/4W resistors are OK, but for the 1K1 regulator adjustment resistor.

Your hum may come from your PSU - try measuring ripple voltage on the -10 and the +30V.

If it worked perfectly earlier, it may be something like addition of the meter light that strains the PSU and makes excess ripple? Try removing meter light and recheck..

If this is the problem, you may need to feed your meter lights directly from transformer secondary AC, or use a light with less current draw..

Jakob E.

 

[Klaus Mogensen]

I made some attack and release time measurements on my unit to check that it is working as expected. There was a fairly good agreement with the values from the manual.

I have posted some graphs and the resulting times on the following site:

http://medlem.jubii.dk/klausdiy/experiences.html

Sorry for the all the damn commercials on this page, but it was for free.

Best regards, Klaus

 

[gyraf]

Thanks Klaus,

These are good measurements to have and refer to (I hope you'll keep them on your page for a while..)

About the actual timing, remember that this is a feedback-sidechain construction, and will thus have somewhat different timing at different ratio settings. Higher ratios > faster timing

Jakob E.

 

[orson whitfield]

[quote author="gyraf"]Your hum may come from your PSU - try measuring ripple voltage on the -10 and the +30V. [/quote]Ok I'll do that once I read up on how to do this. By the way, I disconnected the output xlr wires to the pcb and the hum was still there. Then I disconnected the power supply from the pcb and the humm/buzz was still there! I kept the star ground connected though. So to recap, I had the #1 pins from both input and output xlr's connected and joined at the star ground nut near teh power IEC. Ofcourse, the ground from the IEC was connected to these aswell.

[quote author="gyraf"]If it worked perfectly earlier, it may be something like addition of the meter light that strains the PSU and makes excess ripple? Try removing meter light and recheck. [/quote] I tried removing the light and it was still present. Besides I had the light working before when the humm/buzz was no present. The buzzing sound cyclical, if this helps. Actually there is the cyclical buzz accompanied by a lower pitch humm.

 

[Zee1usa]

Calibration problems!
I am trying to follow this procedure below:




[quote author="kdawg"]Ok... I've built 4 channels of 1176s, and they all act the same way. I can't turn the input pot above 2-3 or the signal just gets slammed too much. Can someone tell me if this Q bias calibration seems correct?

Q Bias
Release: Fully CW (Fast)
Attack: Fully CW (Fast)
Input: Fully CCW (off)
Output: Fully CW
Ratio: 1:4
Meter: Bypass
Q bias: fully CCW

Signal Generator: 0.245 V (AC) sine wave 250 Hz
Measuring across input pins 2 and 1 & 3 for ground

1. Turn up input control until I get 0.100 V AC, measuring across output pins 2 and 1 & 3 for ground

2. Rotate Q Bias until reduced to 0.089 V AC across output. [ 1 dB = 20 log (0.100 / 0.089) ]

GR Meter:
Release: Fully CW (Fast)
Attack: Fully CW (Fast)
Input: 12 o'clock
Output: Fully CCW (off)
Ratio: 1:20
Meter: Bypass

Signal Generator: 0.050 V (AC) sine wave 250 Hz
Measuring across input pins 2 and 1 & 3 for ground

1. Switch to GR meter, with no input, set meter zero adj so dial reads 0 db.

2. Switch back to bypass.

3. Adjust Output knob till 0.050 V AC measuring across output pins 2 and 1 & 3 for ground (unity gain)

4. Turn on GR metering.

5. Turn up signal generator voltage till 1/2 input V = output V.

6. Set GR meter adj so meter reads -6 db

7. Remove signal. Re-set zero if necessary, plug signal back, set GR meter adj so still get -6 db. Repeat if necessary.

---

I did Chef's mod for the output, much beter! So if I can nail this input reduction, they are finally done![/quote]

I have gotten to step 1 , but I get no increase or decrease
when I adjust the input control. I have the 250hz/.245 V AC
on input pin 2 and 1 (do i need to jumper pin 1&3?)
As far as I know I got my pots and XLR's wired correct.

:?


Here are some of my measurments:

Q2
E .536
B 1.034
C 2.195

Q3
E 1.595
B 2.194
C 12.57

Q4
E 11.98
B 12.57
C 30.44

Q5
E 4.37
B 4.81
C 28.73

Q6
E 29.23
B 28.66
C 14.30

Q7
E 29.88
B 29.25
C 14.32

Q8
E 13.72
B 14.33
C 30.42

Q9
E 13.66
B 13.0
C 0


Q12
E 3.911
B 4.45
C 15.13

Q13
E 14.5
B 15.3
C 30.42

Q14
E 2.9
B 3.4
C 16.9

Q15
E 16.3
B 16.9
C 30.37


The Measurments seem ok :?: