All things G1176 - the new "repost" thread.

[Soeren_DK]

INPUT TRANNY FOR G1176

I have bought the ED transformer C-3837-1 from Hairball.
I have read from Mnats page that PPR suggested that you change the input ratio to 2:1.

Is it possible with the G1176 board? And how should I wire this up?

Cheers
Søren

 

[schrobbelbop]

Anybody help!

My meter reads -0.5dB when its just turned on
when on for 'bout 15 min it goes to +0.5dB.
I've single turn cheapass trimmpots, this might be the issue?

Also the total sound is a bit dull, i expected the unit to be a bit brighter
compared to my api2500 it has a lot less highfreq's. (air). My Gssl is much
more brighter then both.

Hairball Kit (input/output trafo's)
Mnats REV J

mayby caps wich have insane voltage ratings (huge ass wimas...)
cheap ass, ceramics? or is it just the input/output trafo sound?

 

[mac]

Hey Schrobbelbop,
my meters tend to do that too. It seems to take a while for them to settle from a cold start. I cant remember, but I think it might have been Geoff who mentioned this previously and I dont think this is a problem - but normal behaviour.

Sometimes different times of the day (minor variations in your mains supply) can affect this meter calibration also.

I dont think it is anything to be worried about - just calibrate for the "hot" state (when the unit has been on for 20mins or so).

In terms of "brightness" - my GSSL has more sparkle than my J board G1176's but it isnt very noticable or concerning for me (I have switchable Op Amp and Lundahl inputs and Ed Anderson outputs from Mike at Hairball). Pehaps this has more to do with the input trafos?? anyone else with ideas here??

Mac

 

[skal1]

Hi lads


i have just swept my 1176 from 1khz 40khz and this is my result . ic input  oep o/p A262A2E

i/p full cw

o/p full cw


I  ave a 7db drop between 1khz and 10khz  is this natural for project, or i am doing something wrong, any suggestions welcome.


skal1

 

[gswan]

Something wrong there. It should be flat all the way through the audible range.
Try performing the sweep through different sections of your circuit to see where the problem is.

Hopefully you weren't running the compressor into clipping when you did the sweep or all kinds of harmonics will stuff up your response curve. You should also be sweeping with compression OFF.

 

[skal1]

Hi


yes it was in bypass  ,i also took out the fets , one  thing i did notice is that if i turn i/p and o/p pots at 12 oclock the signal looks ok , but it has the 10khz  slope off to 20khz  even  with  the 2k4 mnats suggested  for R84 .

I will try  what you mention above , all voltages or ok so it might be a cap problem.

i will also sweep the amp with out the tx in circuit and i will post findings later.

thanks

skal1

 

[skal1]

OK  so i have follow the method on this page for checking the amp stages of the 1176 {http://www.axtsystems.com/index.php?option=com_content&view=article&id=57:1176lnproblems&catid=34:1176ln&Itemid=62}.


I reach Q5 and the base was alright , it was not until i probe Q6 base i found a problem.


Here is a pic of Q6  base

 

[Soeren_DK]

Stereo Link
Anybody tried the Hairball stereo link with luck? Any experience? Where did you take the 30VDC?

Cheers
Søren

 

[Echo North]

Stereo Link
Anybody tried the Hairball stereo link with luck? Any experience? Where did you take the 30VDC?
Cheers
Søren

I take it from the 30V rail.  Just attach a wire to the 30V test point.

 

[Soeren_DK]

Stereo Link
Anybody tried the Hairball stereo link with luck? Any experience? Where did you take the 30VDC?
Cheers
Søren

I take it from the 30V rail.  Just attach a wire to the 30V test point.

Where are the test point located? It would not give any noise on the 30V rail?

Cheers
Søren

 

[Echo North]

It's indicated on the board.

It's the same link method used in the PA MC77.

 

[rooster21]

Sorry it's taken me so long to reply, but I've had a really hard time trying to make sure that the GR FET is not conducting. I've taken some time to attempt to understand Vgs a little better. If I'm not mistaken, I should have the negative probe of my DMM on the gate of the FET, and the positive probe on the source, and when I change the trimmer for Qbias the result on the DMM (V ac) should change, correct? No matter what I change I get a fixed .012 Vac.

Yep, you are mistaken.
You should be measuring a DC voltage from the gate to GND. It should range from about -2.5V up to 0V.
When it is most -ve, it should be past the pinchoff voltage and not conducting.

Alrighty then, so it seems that gain stage 1 is giving me 10.5 dB, and gain stage 2 is giving 11 dB. Does this make sense?

 

[gswan]

Not really.
The first stage should give you about 26dB.

 

[rooster21]

I redid the test for the first stage and got 24.7 dB, I don`t know what i did differently but I`m happier with this result. What would the next step be?

 

[Janus Audio]

Hi ragazi,

after fitting my mnats 1176 with an OEP input transfor, I have some trouble getting it calibrated or compressing in general, I don't know. I repeated the precedure a couple of times but in the end there is always none or little differenc in the output level when I change the ratio settings.

Is there a quick way to check if there are problems with my ratio switch or any other things I can check - voltages or so?

For calibration I used a sine out of my DAW 0.775 Volt and so on. Is it supposed to + to 0 or + to -? I tried both and neither worked. The output signal was measured at the output jack (also tried both variants).

I know there are other people who had similar problems, but I really didn't find a solution using search und this thread like 150 pages ;-)

So thanks for some hints, where to look...

Sebastian

 

[Janus Audio]

hey. no idea anyone?

or is there another 1176 help thread or something i can post my into?

 

[MrShhh]

Purely out of theoretical interest, what would happen if I used a 10k log output pot instead of a 100k log output pot? Would it just make the output control more sensitive? I'm betting there's more to it than that.

Cheers

 

[Chrome Heart]

Hey Schrobbelbop,
my meters tend to do that too. It seems to take a while for them to settle from a cold start. I cant remember, but I think it might have been Geoff who mentioned this previously and I dont think this is a problem - but normal behaviour.

Sometimes different times of the day (minor variations in your mains supply) can affect this meter calibration also.

I dont think it is anything to be worried about - just calibrate for the "hot" state (when the unit has been on for 20mins or so).

In terms of "brightness" - my GSSL has more sparkle than my J board G1176's but it isnt very noticable or concerning for me (I have switchable Op Amp and Lundahl inputs and Ed Anderson outputs from Mike at Hairball). Pehaps this has more to do with the input trafos?? anyone else with ideas here??

Mac

I have not used the trafo input on either of my 1176 builds, just a Lundahl on the output, and I dont notice any high end drop in either. Perhaps its the character of the input transformer?

 

[gswan]

Purely out of theoretical interest, what would happen if I used a 10k log output pot instead of a 100k log output pot? Would it just make the output control more sensitive? I'm betting there's more to it than that.

It would have no effect on sensitivity, it would still be ratiometrically tapping the voltage from the preceeding output stage. It would load the preceeding output stage by a factor of 10 and move the pole from C9.

 

[gswan]

after fitting my mnats 1176 with an OEP input transfor, I have some trouble getting it calibrated or compressing in general, I don't know. I repeated the precedure a couple of times but in the end there is always none or little differenc in the output level when I change the ratio settings.

Is there a quick way to check if there are problems with my ratio switch or any other things I can check - voltages or so?

For calibration I used a sine out of my DAW 0.775 Volt and so on. Is it supposed to + to 0 or + to -? I tried both and neither worked. The output signal was measured at the output jack (also tried both variants).

If it worked before you fitted the transformer then that should give you a clue as to where to look.

What procedures did you use?
- Check DC bias conditions.
- Check stage gains
- Perform Qbias calibration
- Perform metering calibration
- Check compression ratios