[BUILD] 1176LN Rev D DIY

[Regi]

Hey guys,

I've just finished making my 1176 Rev D and I couldn’t find an answer for my problem, so if someone already asked this I apologize.
So, PSU checking shows 27,7V. Is that alright? (I’m asking that ‘cause the tolerance is allowed by 5%)

Furthermore, during the calibration I’m stuck at the first stage because, in some weird way, as soon as I connect 1kHZ, 0.775 V
to the compressor, on the inside XLR connector it shows 0,273 V (this measured voltage is across PIN 2 and 3).
Where does that drop-off in the voltage come from?

BTW voltage on the input XLR across PIN 1 and PIN 3 is 0,133V and on the output XLR the voltage is 0,315V.

Any help is much appreciated

Regi

 

[Echo North]

Hey guys,

I've just finished making my 1176 Rev D and I couldn’t find an answer for my problem, so if someone already asked this I apologize.
So, PSU checking shows 27,7V. Is that alright? (I’m asking that ‘cause the tolerance is allowed by 5%)

Furthermore, during the calibration I’m stuck at the first stage because, in some weird way, as soon as I connect 1kHZ, 0.775 V
to the compressor, on the inside XLR connector it shows 0,273 V (this measured voltage is across PIN 2 and 3).
Where does that drop-off in the voltage come from?

That power supply is a little low.

Impedance  loss is explained in the calibrations section.

http://www.hairballaudio.com/blog/resources/post/calibration

Mike

BTW voltage on the input XLR across PIN 1 and PIN 3 is 0,133V and on the output XLR the voltage is 0,315V.

Any help is much appreciated

Regi

 

[Regi]

Hey guys,

I've just finished making my 1176 Rev D and I couldn’t find an answer for my problem, so if someone already asked this I apologize.
So, PSU checking shows 27,7V. Is that alright? (I’m asking that ‘cause the tolerance is allowed by 5%)

Furthermore, during the calibration I’m stuck at the first stage because, in some weird way, as soon as I connect 1kHZ, 0.775 V
to the compressor, on the inside XLR connector it shows 0,273 V (this measured voltage is across PIN 2 and 3).
Where does that drop-off in the voltage come from?

That power supply is a little low.

Impedance  loss is explained in the calibrations section.

http://www.hairballaudio.com/blog/resources/post/calibration

Mike

BTW voltage on the input XLR across PIN 1 and PIN 3 is 0,133V and on the output XLR the voltage is 0,315V.

Any help is much appreciated

Regi

Thanks for a quick reply Mike, your service was quick as well when I ordered these parts. 
But what could be wrong (on what should I pay attention) with the PSU?
And why, when I measure the test-voltage (1kHZ) from my DAW, multimeter shows 0,775 across PIN2 and PIN3, but as soon as I plug it in the compressor, the voltage lowers to 0,273?

 

[Echo North]

Hey guys,

I've just finished making my 1176 Rev D and I couldn’t find an answer for my problem, so if someone already asked this I apologize.
So, PSU checking shows 27,7V. Is that alright? (I’m asking that ‘cause the tolerance is allowed by 5%)

Furthermore, during the calibration I’m stuck at the first stage because, in some weird way, as soon as I connect 1kHZ, 0.775 V
to the compressor, on the inside XLR connector it shows 0,273 V (this measured voltage is across PIN 2 and 3).
Where does that drop-off in the voltage come from?

That power supply is a little low.

Impedance  loss is explained in the calibrations section.

http://www.hairballaudio.com/blog/resources/post/calibration

Mike

BTW voltage on the input XLR across PIN 1 and PIN 3 is 0,133V and on the output XLR the voltage is 0,315V.

Any help is much appreciated

Regi

Thanks for a quick reply Mike, your service was quick as well when I ordered these parts. 
But what could be wrong (on what should I pay attention) with the PSU?
And why, when I measure the test-voltage (1kHZ) from my DAW, multimeter shows 0,775 across PIN2 and PIN3, but as soon as I plug it in the compressor, the voltage lowers to 0,273?

Voltage will drop when it's loaded, especially with a similar impedance.

Did you build and test your power supply before stuffing the rest of the board? What did it test then?

Mike

 

[junkface]

having an issue with my q bias circuit I believe, that is keeping me from calibrating this rev D up. aren't all these voltages supposed to be positive?
1. What is your DC V on either side of R35.        -9.5 V    -2.9V
2. What is your DC V on either side of R60.        -2.9V      0V
3. What is your highest and lowest DC V at pad 18 when you rotate the Qbias trimmer.  -2.9      0V

 

[Echo North]

having an issue with my q bias circuit I believe, that is keeping me from calibrating this rev D up. aren't all these voltages supposed to be positive?
1. What is your DC V on either side of R35.        -9.5 V    -2.9V
2. What is your DC V on either side of R60.        -2.9V      0V
3. What is your highest and lowest DC V at pad 18 when you rotate the Qbias trimmer.  -2.9      0V

Looks good to me.

Locate the GATE on your FET, when you turn the QBIAS does that DC voltage do?

 

[junkface]

It starts at -2.3 V fully CCW, goes to almost 0 V fully CW

Looks good to me.

Locate the GATE on your FET, when you turn the QBIAS does that DC voltage do?

 

[Echo North]

It starts at -2.3 V fully CCW, goes to almost 0 V fully CW

Looks good to me.

Locate the GATE on your FET, when you turn the QBIAS does that DC voltage do?

Are you able to get +11 dBu at your output per the calibration steps? Can you get a 1dB drop?

Start the calibration so the gate it at the -2.3V DC setting.

Mike

 

[junkface]

ya I can get the +11 signal all right, but turning the trimmer isn't giving me the 1db drop. CCW or CW fully, it's just not dumping like it's supposed to. I did start fully CCW like usual tho fwiw

 

[Echo North]

ya I can get the +11 signal all right, but turning the trimmer isn't giving me the 1db drop. CCW or CW fully, it's just not dumping like it's supposed to. I did start fully CCW like usual tho fwiw

FET must have died.

Send us an email, we'll send you a new set.

Mike

 

[junkface]

Well I got that new pair of 2n5457s you sent (thx!) and swapped them in, but I'm still not getting any gain to dump when I'm setting the Q bias.  readings are much the same now except the gate of Q1 now reads:
-5 V dc at Q bias full CCW
-2.88 dc at Q bias full CW

 

[babaorum]

HELPPPP  :'(

With a friend, we have verified input stage and output (Amp part)  and it seems like ok.
but there is a big pb in the Preamp or Drive meter parts because when I have a 1000 Hz signal in input , it seems like the compression is always present and at the output I have less 2/3 dB than the input ...
I have done voltages mesures but I can't adjust the qbias because this pb.
Could you help me to debug my pcb please ?
Thanks very much

Baba

 

[Echo North]

Well I got that new pair of 2n5457s you sent (thx!) and swapped them in, but I'm still not getting any gain to dump when I'm setting the Q bias.  readings are much the same now except the gate of Q1 now reads:
-5 V dc at Q bias full CCW
-2.88 dc at Q bias full CW

That's too high. Ideally the gate voltage would go up to 0V DC and the FET would be dumping a lot of gain. What is you DC voltage at that R35/R60 junction now?

Make sure you don't have your attack/release wiring swapped, or your release output pots swapped.

Mike

 

[Echo North]

HELPPPP  :'(

With a friend, we have verified input stage and output (Amp part)  and it seems like ok.
but there is a big pb in the Preamp or Drive meter parts because when I have a 1000 Hz signal in input , it seems like the compression is always present and at the output I have less 2/3 dB than the input ...
I have done voltages mesures but I can't adjust the qbias because this pb.
Could you help me to debug my pcb please ?
Thanks very much

Can you get +11dB at the output as described in step 1 of the calibration?

Baba

 

[junkface]

ya i was wondering why the heck the gate voltage would have been so different with the new FETs. figured it out. had pads 19 and 21 reversed, musta not been paying enough attention when I went back and reseated all the screw terminals during the original diagnosis. you're the best mike!

That's too high. Ideally the gate voltage would go up to 0V DC and the FET would be dumping a lot of gain. What is you DC voltage at that R35/R60 junction now?

Make sure you don't have your attack/release wiring swapped, or your release output pots swapped.

Mike

 

[babaorum]

HELPPPP  :'(

With a friend, we have verified input stage and output (Amp part)  and it seems like ok.
but there is a big pb in the Preamp or Drive meter parts because when I have a 1000 Hz signal in input , it seems like the compression is always present and at the output I have less 2/3 dB than the input ...
I have done voltages mesures but I can't adjust the qbias because this pb.
Could you help me to debug my pcb please ?
Thanks very much

Can you get +11dB at the output as described in step 1 of the calibration?

Baba

No impossible, when I have 0dB in input I can to maximum obtain a -10 dB !!! (output knob at max)

 

[felix1988]

Hi everybody,

I went through the whole thread and also found similar cases which helped me a bit to narrow my search but i'm still not able to solve my problem.

I'm troubleshooting a hairball rev d a friend of mine built. I can't complete the first calibration step - I'm not able to get a volume drop via the bias control.

the unit is passing audio in full bandwidth and I can get about 42 dB of gain with both pots at max. GR meter doesn't move to zero and I don't get any compression.

Power rails are in the 10% margin.
also my voltages are only about 10% off max from the mnats schem so I assume they are fine?

at pin 19 on the pcb I get 0 VDC and it doesn't change when turning the pcb bias trim. same for G at Q1 and Q11.

I reheated all the solderpoints and redid the wiring - all seems correct to me.

could it be that Q1 or Q11 are dead?
or maybe the bias-trim pot?

How could I find out which of the two is the culprit? the trimpot being stuck would explain the q-bias not changing but not being non-existant, right?

or maybe something else is the problem? but i assume somewhere in the GR control circiut?

I would appreciate any help or hints!

thanks!

felix

 

[Echo North]

Hi everybody,

I went through the whole thread and also found similar cases which helped me a bit to narrow my search but i'm still not able to solve my problem.

I'm troubleshooting a hairball rev d a friend of mine built. I can't complete the first calibration step - I'm not able to get a volume drop via the bias control.

the unit is passing audio in full bandwidth and I can get about 42 dB of gain with both pots at max. GR meter doesn't move to zero and I don't get any compression.

Power rails are in the 10% margin.
also my voltages are only about 10% off max from the mnats schem so I assume they are fine?

at pin 19 on the pcb I get 0 VDC and it doesn't change when turning the pcb bias trim. same for G at Q1 and Q11.

I reheated all the solderpoints and redid the wiring - all seems correct to me.

could it be that Q1 or Q11 are dead?
or maybe the bias-trim pot?

How could I find out which of the two is the culprit? the trimpot being stuck would explain the q-bias not changing but not being non-existant, right?

or maybe something else is the problem? but i assume somewhere in the GR control circiut?

I would appreciate any help or hints!

thanks!

felix

I would be suspect of the attack/release/ratio PCB wiring.

 

[kerrymckenna14]

Hi guys,

I'm having a problem with my 1176 Rev D build. 
I've completed the build and began calibrating, I can get .775VAC reading in the input, but when I set me compressor up like how it is suggested in the MNAT's guide, and I bring up the input gain the needle doesn't move at all, I tried using other dials too but it won't budge.  When I switch the compressor to GR mode, the needle pegs to the right. 
I've tried turning the trimpot both directions in hope that it would move a little but no luck.

I don't seem to be getting a reading out my output when I bring up both the input and output. 

Does anyone have any ideas as to what could be wrong?


Any replies greatly appreciated,
Kerry McKenna

 

[Echo North]

Hi guys,

I'm having a problem with my 1176 Rev D build. 
I've completed the build and began calibrating, I can get .775VAC reading in the input, but when I set me compressor up like how it is suggested in the MNAT's guide, and I bring up the input gain the needle doesn't move at all, I tried using other dials too but it won't budge.  When I switch the compressor to GR mode, the needle pegs to the right. 
I've tried turning the trimpot both directions in hope that it would move a little but no luck.

I don't seem to be getting a reading out my output when I bring up both the input and output. 

Does anyone have any ideas as to what could be wrong?


Any replies greatly appreciated,
Kerry McKenna

You need to measure some DC voltages with your compressor on, no signal needed. 

What is your DC at pad 19 and what happens to it when you turn the qbias trimmer? What is the highest and lowest you can get it. Use the CT/0V pad as your reference/common.

Mike