All things G1176 - the new "repost" thread.

[gswan]

1. Have you checked the DC bias conditions?
2. Have you attempted to calibrate the unit?
3. Have you measured the gain through each stage?

 

[sedit1]

Edit....My bad 

 

[late]

Anyone have pushbutton wiring picture for 1176 Rev J board?

Like this
http://www.diy.ine-kpro.com/1176/images/check/wireCheck3.jpg

 

[audiophreak]

Hi All,

  Not sure if this can be done (  after lying out project , front panel Laser engraved and machined )  :-\

  I'm trying to use Hairballs Push Button Meter switch assy and the stock Rev.J  Rotary Ratio Switch PCB with "Slam" mode.

  I have used the switch recomeded and wired as instructed on mnats 1176 page and assembled  to the stock Ratio Rotary PCBs  - Also installed Hairballs Meter Push button assy with his push button PCB ...

    Confused on two connection designations - the BLK and GRN  designations on Hairballs Meter switch PCBs are connections made from his Ratio PCBs that I dont have and are not using.

  They go to the outer terminals for the GR Bypass switch with the pad 22 from the main board going to the COMM pole of that switch. 

  In reading some of this thread , I have read the Pad 22 to ground will put the unit in GR Bypass ..

so my questions are ,  were should I take signal ground from to the switch for GR Bypass, and  what wire connection to the other side of this switch for " GR IN " or Normal comp operation  ?


  I do apologizes if this has been covered, when I search for " Push button " or " Rotary "  I get all for one or the other, but not this combination. 

Thanks ,
              Chip
   

 

[audiophreak]

OK ... after looking closer at the schematic and the PCBs -  I think I can take the Shield / Ground from the outPut Pot to the BLK pad on the PushButton PCB to ground pad 22 for GR Bypass  -  and pad 4 from the Rotarty PCB to the GRN Pad on the PushButton PCB for the return from the PushButton Switch  -  is this correct ?  .... anyone ?  ... Please  ;D

 

[audiophreak]

wow ... way to kill a thread .... sorry  :-\

 

[audiophreak]

Hellooooo  ;D

  I've figured most of the stuff out , it passes signal, checked all transistor voltages - all good, I'm on to the Calibration now.
    I've performed the "Q" Bias Adjustment and I"m on to the Grain Reduction Meter Tracking  using the calibration instructions here

http://www.axtsystems.com/images/stories/1176LN/1176ln-setup.pdf

I set the controls as stated in the spreed sheet type area , but when I got to step #5 - it states to "Turn the output level control CW until the meter reads 0VU."  ... but the Output level control is already full CW as stated in the above instructions ??? 

Help .. Please    ...  what am I missing ??     

 

[gswan]

It's a typo, start with the output control ccw and then increase it (cw) until you get the reading.

 

[audiophreak]

It's a typo, start with the output control ccw and then increase it (cw) until you get the reading.

  Thank you so much !!!
                              I am using the SEARCH function and am reading the results now  ;D

 

[Chrome Heart]

I remember reading somewhere in the thread that a 100K trimpot can be used to help reduce the sensitivity of the input pot. Can this be done on a Rev J board with a rotary ratio? Im also using the 5532 input.

 

[mrcase]

hey guys!

I was fiddling with my 1176 and wanted to try to reverse my OEP input so that it is 2:1 on the mnats board.
so far so good but the strange thing is that by doing so I have a heavy HF rolloff starting at 5kHz?
the threshold is much more usable though, but the whole comp not ;-)
before I had a perfectly flat frequency response. Should I remove the R* resistors?

thanks as always
M

 

[Babas]

Hi all!

I recently finished my Mnats 1176 rev J unit, and I’m struggling to get it to work correctly.
It’s passing signal and so on, the meter switch seems to be working (bypass, GR and VU),
as is the VU meter. But I’m not getting any good/strong compression out of it, and both the
attack and release switches results (if any, maybe I’m imagining) are VERY subtle
(the attack in particular).

I have checked gain reduction at the output and it seems to be quite low.

I have also done a signal trace following the instructions presented on this page:

http://www.axtsystems.com/index.php?option=com_content&view=article&id=57:1176lnproblems&catid=34:1176ln&Itemid=62

The only signal I’m having problem in reading (maybe due to an old oscilloscope(?))
is the signal at the D3/D4 junction. All the rest are good and correspond well with those presented
on the above web page. The diodes seems to be fine when checked, as is the signal level on the anode
of the diodes. If I lift the cathode I have a fair signal there as well. But if I solder them down to the pcb
again, I’m not really seeing anything (but then again, this could be my scope). I have checked my ratio
board for shorts, solder blobs, and so on but I can’t find anything.

One interesting thing is that if I’m following the calibration procedure that Mnats presents in video form
on his page (http://mnats.net/1176_revision_d.html), I can get along with the Q Bias adjustment,
which gives me zero on the VU meter and +4 at the output. The next step is to calibrate the GR meter
tracking adjustment. I zero the VU meter in GR-mode, then lifting the ground from the GR circuit as in
the video, the meter falls short of the -10db mark. Mnats then says to increase (CW) the input control
to allow the meter to reach -10db, I can’t do that. If I increase (CW) the input the meter rises again
towards zero. I have to turn it down (CCW) to get the meter towards -10db and that’s is the other way
around compared to what is shown in the video (the input pot is wired correctly). Any ideas on this?
Seems like I’m not going “up” in gain reduction. Could my bias adjustment be off somehow?
Or am I short of signal level? The resistor network on the GR switch/ratio board seems to be fine.

ANY ideas greatly appreciated as I am out of them 

Thanks!

/Babas

 

[Spendor]

Hi all. Just wondering how calibrating the G1176 can be achieved correctly with the different builds? I have made 2 units both with active input, one with OEP 2:1 output tx and one with 1:2. If the calibrating process involves using the output amp stage (with output pot on full) then surely the procedure should be different for each build style?
I have real trouble with the input - it starts squashing way too early on both versions. This is mentioned as a problem for several people, but not a problem at all for others. How can there be such inconsistencies when people are using the same circuit and pcb's!
Both my versions sound good but they don't feel like I'm using an 1176.
Any pointers very much appreciated!

 

[gswan]

Calibration is simply a matter of setting the bias point for the GR FET such that it is into conduction at an output level of +1dBu. It does not matter what is in between, since you are starting with a 0dBu input level and adjusting the input control until you get +1dBu at the output with GR off.

The input level controls where the gain reduction threshold comes into effect (ie fixed threshold but with variable input level). If you find gain reduction starting too early, the simple fix is to drive it with a lower signal (attenuate your input). Then you can turn up the input level further before the gain reduction threshold is reached.

 

[audiophreak]

Hello All ,
          I have been putting this off for as long as I could ... I have searched and searched, read , tested , checked and rechecked to no avail ..  :'(

  I am trying to put together a Dual mnats  Rev.J's .  I have used the switch recommended on mnats page for the " Slam " mode for ratio with mnats ratio PCBs and Hairball push button Meter switches and PCBs.  I have connected "22" to the "22" pad on the Meter PCBs and "4" from the Ratio PCB to the "GRN" on the Meter PCB ( as thats one of the poles from the Ratio PCB ) and ran a Jumper from "28"( which is Ground) Pad on the Meter PCB to the "BLK" Pad on the Meter PCB  to short "22" to " Ground" for "GR Bypass"  ...  am I correct so far ?

    I have checked all the voltages listed here -

http://www.axtsystems.com/index.php?option=com_content&view=article&id=57:1176lnproblems&catid=34:1176ln&Itemid=62

.. and all voltages are close to spot on - only ( B of Q12 is +4.504vdc - was listed as +4.47vdc )  on one PCB  and ( E of Q9 is +13.58vdc - its listed as +13.1vdc  ) on the other  ... are these readings too far off ?

all other voltages are almost spot on -

PCB #1  TL071        PCB #2 TL071
pin 1 = -9.91            pin 1 = -9.91
pin 2 = -0.813          pin 2 = -0.825
pin 3 = -0.813          pin 3 = -o.825
pin 4 = -10.06          pin 4 = -10.05
pin 5 = -9.91            pin 5 = -9.91
pin 6 = 1.573          pin 6 = 1.572
pin 7 = 16.55          pin 7 = 16.70
pin 8 = 0.00            pin 8 = 0.00

    PCB #1
  - Q1  -  G= -1.519    S = 0.00    D = 0.00
  - Q10  - G=  -1.343  S =  -0.812  D = 16.56

  PCB #2
  - Q1  -  G= -1.436    S = 0.00    D = 0.00
  - Q10  - G=  -1.290  S =  -0.829  D = 16.7


  I have been able to set the " Q Bias "  properly ( or so i think )  when I get to the Gain Reduction Meter Tracking , I am able to  "2. With no signal applied, adjust VR55 so that the meter reads 0VU."
... and also -" 3. Apply a 0.245Vrms (-10dB) 1kHz sine wave signal to the input.
4. Switch the meter mode to +4dB.
5. Turn the output level control CW until the meter reads 0VU." 

.. but when I get to - "6. Turn the attack control ON (CW) and observe the drop in the meter reading."  I dont get a Drop in the Meter ????  no mater what i do  - I have then turned the " Input down " to see a -10dB on the Meter , then when I put it back in to " GR Bypass"  the Meter doesn't
move off of -10dB and when I max the " Output " pot all the way up the meter only climbs to about -5dB or so - ( eventhought I know its not right )  the Same in Both PCBs  ... and thats as far as I have gotten  :-[


  Both channels pass good clean audio, I can hear compression happening  , I am using a signal gen 1k at 0dB and -10dB for the calibrations verified with DMM.


  From reading I think my problem is in the GR Meter Driver Amp ?    but where to Start ?

    Thank you in advance for any and all help / suggestions

  Thanks ,
                Chip 

 

[gswan]

.. but when I get to - "6. Turn the attack control ON (CW) and observe the drop in the meter reading."  I dont get a Drop in the Meter ????  no mater what i do  - I have then turned the " Input down " to see a -10dB on the Meter , then when I put it back in to " GR Bypass"  the Meter doesn't
move off of -10dB and when I max the " Output " pot all the way up the meter only climbs to about -5dB or so - ( eventhought I know its not right )  the Same in Both PCBs  ... and thats as far as I have gotten  :-[

This step ONLY applies if you have the GR enable switch on the attack pot, as in the original version. If you have it on a separate switch then leave the attack control alone, it will do nothing for you.

 

[audiophreak]

Thank you gswan ,
                          I do realize this , so when the instructions say " attack control ON (CW) / or OFF ( CCW)  - I take that as Engaging or Disengaging the GR .. is this correct  ? 

  The Hairball switches are interlocking , so I start this calibration with the " GR Bypass " and "VU" buttons press IN at the same time , then press the "VU" button so the " GR Bypass" button pops out to " Engage GR "  is this correct ?

 

[gswan]

That's right. "Attack control OFF" means bypass the GR amp, and "Attack control ON" means engage the GR amp. Simply modify the knob/button operations to achieve this to suit your own situation.

 

[audiophreak]

GREAT !!  .. so at least I have that correct  ;D

  so I guess that means when I think I'm " engaging GR amp " were I should be seeing the meter drop ( and it isn't )  would indicate that either GR Amp is NOT engaging OR not working OR I have a problem somewhere else ?

 

[audiophreak]

... or Maybe the " GR Meter Driver Amp "  as its the Meter I'm Calibrating Right ? 

                                    ... oh I'm so confused