[BUILD] 1176LN Rev D DIY

[weiss]

after a week of working with my new revD from hairball i am wondering:

is it normal that i can't  compress with more than 2db of GR on bass guitar without distortion when using a release time faster than 1 o'clock?

what type of distortion? you shouldn't hear much difference in the type of tone when changing the release time

 

[craigmorris74]

Hi folks,

Just purchased a Rev D that is passing signal but not compressing.  I've confirmed this by measuring the AC at the XLR out between between pins 2 and 3.  I've read this thread and have taken note of the suggested test for this problem.  Here's what I've measured (when feeding a signal, I only have resolution to a tenth of a volt AC, so I'm reading .8V AC on input pins 2 and 3):

Pad 22+ground (AC):
20: 1.8V
12: 1.2V
8:    0.7V
4:    0.4V
Pad 21 and ground (DC)
20:  -6.71V
12:  -3.68V
8:    -2.55V
4:    -1.60V
Pad 19 and ground (DC)
20:  -.32V
12:  -.32V
8:    -.32V
4:    -.32V

With no signal:
R64:  -9.75 and -6.71 DC
R63:  -6.72 and -3.67 DC
Pad 21:  -1.60DC

With a signal:
R78:  2.9V and 2.2V AC
Pad 21:  0V AC

Any help would be greatly appreciated.

Thanks,
Craig

 

[useme2305]

after a week of working with my new revD from hairball i am wondering:

is it normal that i can't  compress with more than 2db of GR on bass guitar without distortion when using a release time faster than 1 o'clock?

what type of distortion? you shouldn't hear much difference in the type of tone when changing the release time

the tone doesn't really change. but there is distortion on especially the low notes when i turn the release over 1 o'clock when compressing. it's weird and i have no idea if this is normal.

it behaves exactly as shown here: https://www.youtube.com/watch?v=Otd05vTBlfg

 

[craigmorris74]

the tone doesn't really change. but there is distortion on especially the low notes when i turn the release over 1 o'clock when compressing. it's weird and i have no idea if this is normal.

it behaves exactly as shown here: https://www.youtube.com/watch?v=Otd05vTBlfg

That's typical 1176 behavior. 

 

[craigmorris74]

Hi folks,

Just purchased a Rev D that is passing signal but not compressing.  I've confirmed this by measuring the AC at the XLR out between between pins 2 and 3.  I've read this thread and have taken note of the suggested test for this problem.  Here's what I've measured (when feeding a signal, I only have resolution to a tenth of a volt AC, so I'm reading .8V AC on input pins 2 and 3):

Pad 22+ground (AC):
20: 1.8V
12: 1.2V
8:    0.7V
4:    0.4V
Pad 21 and ground (DC)
20:  -6.71V
12:  -3.68V
8:    -2.55V
4:    -1.60V
Pad 19 and ground (DC)
20:  -.32V
12:  -.32V
8:    -.32V
4:    -.32V

With no signal:
R64:  -9.75 and -6.71 DC
R63:  -6.72 and -3.67 DC
Pad 21:  -1.60DC

With a signal:
R78:  2.9V and 2.2V AC
Pad 21:  0V AC

Any help would be greatly appreciated.

Thanks,
Craig

Just bumping to see if these numbers point out any red flags.

Thanks,
Craig

 

[Echo North]

I think you have something messed up/fried in your GR Control Amp section.

Measure the AC at C19 (- pad) the same as you did with pad 22.

Mike

 

[craigmorris74]

I think you have something messed up/fried in your GR Control Amp section.

Measure the AC at C19 (- pad) the same as you did with pad 22.

Mike

Thanks for your reply!  I get 0V AC at all ratios.

 

[Echo North]

All that AC at pad 22 should be amplified there. You have something bad in that GR Amp area.

Check those voltages against the schematic with voltages on the MNATS.net page.

Mike

 

[craigmorris74]

I'm not sure how to measure the voltages per the mnat's schematic (it says no input, and I don't get any voltage with no input), but when I input the 1K tone, I get 1.8V at pad 22, but nothing after Q7.

 

[Echo North]

I'm not sure how to measure the voltages per the mnat's schematic (it says no input, and I don't get any voltage with no input), but when I input the 1K tone, I get 1.8V at pad 22, but nothing after Q7.

Measure the DC at each transistor leg.

 

[craigmorris74]

I get less than a volt on the pins of Q10, and nothing on the other transistors.

 

[Echo North]

I get less than a volt on the pins of Q10, and nothing on the other transistors.

Check your resistors. That part of circuit has 4.7k, 47k, and 470k resistors.  Make sure you don't have them mixed up.

Mike

 

[craigmorris74]

I get less than a volt on the pins of Q10, and nothing on the other transistors.

Check your resistors. That part of circuit has 4.7k, 47k, and 470k resistors.  Make sure you don't have them mixed up.

Mike

I don't see anything mixed up.

 

[Echo North]

I get less than a volt on the pins of Q10, and nothing on the other transistors.

Check your resistors. That part of circuit has 4.7k, 47k, and 470k resistors.  Make sure you don't have them mixed up.

Mike

I don't see anything mixed up.

Something is up in there.

Look at the DC voltages here:
http://mnats.net/files/1176REVD_VOLTS.pdf

And reference these pinouts for the 3707 (3708) resistors:
http://library.hairballaudio.com/images/2013/09/14.jpg

If you look at the schematic with voltages, the collector of Q10 is attached directly to the 30V DC rail. If you don't have 30V DC there that's a big issue. Maybe that transistor shorted?

If you remove the transistor does the voltage appear at Q7?

Mike

 

[craigmorris74]

Mike,

Thanks so much for your patience!  I re-flowed and checked the soldering around Q10, and now I have gain reduction!

All your tips let me hone in on the problem area and get it working.  I've got it calibrated and ready to rack!

Thanks again,

Craig

 

[craigmorris74]

I spoke too soon!  After I calibrated the unit, I hooked it up and ran some drums through the unit, and it's distorting badly.  It's an ugly splatty hard distortion (I'm familiar with the the typical 1176 saturation sound as I have a UA reissue in the studio right now).  It doesn't matter what setting I use, even with the attack know turned off.  I've tried low input, higher output and higher input, lower output and still get the same results.  It almost sounds like when I turn the output less than halfway up, the problem get worse as I turn it down more.
Any more help would be greatly appreciated.

Craig

 

[JingleDjango]

http://www.hairballaudio.com/catalog/fet-rack/bare-bones-kit-builder#tab-132
Dead link on the new Hairball page here.
The substitution guide link (http://library.hairballaudio.com/docs/SubGuide.pdf) redirects to home.
Original document available here: https://web.archive.org/web/20120523012619/http://hairballaudio.com/docs/SubGuide.pdf

 

[craigmorris74]

I spoke too soon!  After I calibrated the unit, I hooked it up and ran some drums through the unit, and it's distorting badly.  It's an ugly splatty hard distortion (I'm familiar with the the typical 1176 saturation sound as I have a UA reissue in the studio right now).  It doesn't matter what setting I use, even with the attack know turned off.  I've tried low input, higher output and higher input, lower output and still get the same results.  It almost sounds like when I turn the output less than halfway up, the problem get worse as I turn it down more.
Any more help would be greatly appreciated.

EDIT:  R86 is a 5K trimpot instead of 100.  Could this be the problem?

R86 being 5K was the problem.  It was set way too high and causing the distortion.  I dialed it way back and now it sounds awesome. 

Mike-thanks so much for walking me through this!
Craig

 

[mgalimbe]

I forgot to mention that I have .278vav at the input pad on the  main pcb

Check all of your components in the box labeled "Signal Preamp".  Make sure you have the R values right, like you don't have a 56K or 560K mixed up.  Check everything super close.

Check the DC V in that section against these values:
http://mnats.net/files/1176REVD_VOLTS.pdf

Mike

Mike

All of my resistors are of the correct value. Where should I go from here.  I forgot to mention that I should probably know how to do this but I'm not too sure how or where to check the DC voltage. ex what pins should I be testing and do I need the unit plugged in or just run a signal through it. Thanks

 

[cfleming1989]

Hey guys! First time post  ;D Nice to e-meet yall!!

So I'm having a problem with output level. I've completed my build, and all of my calibration/tests - which all went immaculately. (Those distant sounds you all probably heard were my gigantic sighs of relief.)

I tried passing some vocals through my box, and my output level seems to be really low, so I have to push the level in my DAW window to get any sound. The sound I do get is still pretty low, distorted and has a ton of hiss. I've gone through my board and all of my solder points are solid (I think!), and my tests all went well, so this is my confused face:  :-\

Haalllpp!!!!!