[BUILD] 1176LN Rev D DIY

[andyfromdenver]

so that's where it stands now : (I took some pictures to make it easier )

1) the 28.1V is the AC power of input 2 ( one gets the same power)
2)the 34.7V is the DC power on the leg of the R87 (1.1k resistor) , this is the problematic value (suppose to be 30V) 
3)the -9.8V is the DC power on the leg of the CR6 Diode (which is a correct value )
4)the  12.12V is the DC power on the legs of the 220 ohm resistor (R89)
5) the 37V is the DC power on the leg of the CR7 Diode .

6) only that you'll see that everything else is ready except the PCB 

so my guess is that the problem is on the AC power that the PCB gets, I think it suppose to be 25V AC for each input .
i also think that the Diode (CR7 ) should be 35V DC  (you can't see it on the MNATS schematics but on the original schematics
on the dot between the C25 and CR7 )
what do you think guys? if you agree maybe i can drop it somehow with a resistor ! (before the PCB)
and dmnieto , thank you for the help , really, I'm hopeless!

the links for the pictures: (direct links to Dropbox)
https://dl.dropboxusercontent.com/u/83599022/1176/picture01.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture02.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture03.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture04.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture05.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture06.JPG

In one pic vr1 looks backwards.  Just confirm, is the metal backing plate towards the large filter cap (c25)?

 

[dmnieto]

In one pic vr1 looks backwards.  Just confirm, is the metal backing plate towards the large filter cap (c25)?

My thoughts exactly, I cannot think or other reason for its circuit than reverse biasing the LDO... But he claims he checked that.

 

[dbonin]

so that's where it stands now : (I took some pictures to make it easier )

1) the 28.1V is the AC power of input 2 ( one gets the same power)
2)the 34.7V is the DC power on the leg of the R87 (1.1k resistor) , this is the problematic value (suppose to be 30V) 
3)the -9.8V is the DC power on the leg of the CR6 Diode (which is a correct value )
4)the  12.12V is the DC power on the legs of the 220 ohm resistor (R89)
5) the 37V is the DC power on the leg of the CR7 Diode .

6) only that you'll see that everything else is ready except the PCB 

so my guess is that the problem is on the AC power that the PCB gets, I think it suppose to be 25V AC for each input .
i also think that the Diode (CR7 ) should be 35V DC  (you can't see it on the MNATS schematics but on the original schematics
on the dot between the C25 and CR7 )
what do you think guys? if you agree maybe i can drop it somehow with a resistor ! (before the PCB)
and dmnieto , thank you for the help , really, I'm hopeless!

the links for the pictures: (direct links to Dropbox)
https://dl.dropboxusercontent.com/u/83599022/1176/picture01.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture02.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture03.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture04.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture05.JPG
https://dl.dropboxusercontent.com/u/83599022/1176/picture06.JPG

In one pic vr1 looks backwards.  Just confirm, is the metal backing plate towards the large filter cap (c25)?

Bingo!  Pics were helpful!

 

[omribgr]

hahahaha !!!!! working !!!
thank you all i thought the info suppose to be in the line side
I really appreciate your help !

 

[thomasdepa]

Hi everybody,

a few months ago I build a 1176 rev A with great result! Sounds great so I started with building a rev D. With this project I have some problems for which I can't seem to find the solution.
These are my problems: I have very low input gain and if I put my meter to GR the meter doesn't do anything.
I triplechecked all the wiring and everything seems to be fine. I checked voltages and they all seem fine except for Q11 and Q12.
Q11:
G: 0,4
S: -0,3
D: -0,27

Q12:
G: -0,10
S: 0,43
D: 0?75

Does anybody have tips for solving the problem?

Thanks a lot in advance!
Greets,
Thomas

 

[dbonin]

Hi everybody,

a few months ago I build a 1176 rev A with great result! Sounds great so I started with building a rev D. With this project I have some problems for which I can't seem to find the solution.
These are my problems: I have very low input gain and if I put my meter to GR the meter doesn't do anything.
I triplechecked all the wiring and everything seems to be fine. I checked voltages and they all seem fine except for Q11 and Q12.
Q11:
G: 0,4
S: -0,3
D: -0,27

Q12:
G: -0,10
S: 0,43
D: 0?75

Does anybody have tips for solving the problem?

Thanks a lot in advance!
Greets,
Thomas

How far did you get in the calibration?  The baseline voltages are from a calibrated unit.  Did you verify that the unit is compressing regardless of what the meter is telling you?

 

[andyfromdenver]

@thomasdepa,

Is it in the black powder coated chassis?  Is your inpt tran board well grounded/ all well grounded?

 

[dmnieto]

I believe I need to share some tips and hilarious events that happened while I was building my rev D. ( I already had built a rev F). I let you imagine the results of each of my "mistakes"

1. Do not trust your memory, just because you have built a device of a different revision. Check the new schematic, ESPECIALLY IF YOU PUT A HEADER THAT COVERS THE SILKSCREEN MARKINGS
For example.
+ In rev F, the connector to the output pot in the PCB has pins: 15 16 17 (output pre, ground, input line).
+ In rev D, the same connector has pin-out: 16 15 17 (ground, output pre, input line).
Do it the wrong way, and you have fun debugging it.

I have to ask @mnats, you did in purpose to punish the idiots that don't check the overlay, correct?

2. Almost the same as above, always check the schematic! If you believe that RED is hot and BLUE is cold you are in for a surprise. The schematic says, BLUE=>PIN 2 (HOT), RED=> PIN 3 (COLD).
You end up inverting the phase. If you think that is not a problem... think again.

If you feed a differential signal to the input, but you measure with a single ended measuring device (for example an old dynamic audio analyzer), which you ground to chassis... Well enjoy your afternoon. You will be chasing an oscillation in the circuit that only happens when the output pot is close to zero (counter-clockwise max).

On the bright side, it sound amazing!

 

[thomasdepa]

Hi,
thanks for the quick reply!
@andyfromdenver: Yes, it is the black powder coated chassis. I double checked grounding and it is ok.
@dbonin: since my input is that low I didn't start calibrating yet. By now I tried it but the q-bias trim pot doesn't seem to affect the VU-meter. I checked whether the unit is compressing regardless of what the meter tells me. It seems to me that I don't hear compression working (maybe because I don't reach the treshold level because my input is too low). When I put the input level pot to the max and lower output level pot so the output doesn't clip I do hear some saturation (sounds like hitting the input tran too hard).

Any suggestions?

 

[dbonin]

Hi,
thanks for the quick reply!
@andyfromdenver: Yes, it is the black powder coated chassis. I double checked grounding and it is ok.
@dbonin: since my input is that low I didn't start calibrating yet. By now I tried it but the q-bias trim pot doesn't seem to affect the VU-meter. I checked whether the unit is compressing regardless of what the meter tells me. It seems to me that I don't hear compression working (maybe because I don't reach the treshold level because my input is too low). When I put the input level pot to the max and lower output level pot so the output doesn't clip I do hear some saturation (sounds like hitting the input tran too hard).

Any suggestions?

Use a DMM to measure AC volts on the output - your ears may not detect what you need to measure:

START WITH THESE SETTINGS:

• Input = "24" mid rotation
• Output = "24" mid rotation
• Attack = full CW (fully on)
• Release = full CW
• Compression ratio = 20:1
• Meter mode = "GR"

Then TEST using these steps:
1. Apply a signal (1 KHz, 0db).
2. Set output control for 0db (0.775 VAC) as read on an external meter measuring AC volts across output XLR pin 2 and 3
3. Set attack full CCW (off position). 
4. Set input control for +10db (2.44VAC) as read on an external meter, measuring AC volts across output XLR pin 2 and 3
5. Turn the attack control OFF (CCW) and readjust the output level control for "0" if necessary.
6.  Repeat 4 & 5 until the output drops 10dB (2.44V to 0.775V) whenever the attack control is turned ON.

If you can do this, your unit is compressing.

 

[mnats]

These are my problems: I have very low input gain and if I put my meter to GR the meter doesn't do anything.
I triplechecked all the wiring and everything seems to be fine. I checked voltages and they all seem fine except for Q11 and Q12.
Q11:
G: 0,4
S: -0,3
D: -0,27

Q12:
G: -0,10
S: 0,43
D: 0?75

Does anybody have tips for solving the problem?

The tips are on my FAQ which you must have already glanced at. You probably have at least two problems.

1. Build and use a signal tracer to find where the gain drops.

2. Test as advised on my page around the transistors that are giving the incorrect voltages.

BTW, bipolar transistors like Q12 do not have a Gate, Drain or Source. Find the data sheet for the transistor you used to get the correct pinout.

 

[Echo North]

Hello,

Not sure if this is the right place to ask.
But I'd like to buy the hairball audio 1176 kit ($595) and make the compressor, but I'm afraid I can't or get stuck on issues.
It would be my first self build project.

I mean I'm not even sure if I can apply 1 KHz O dBu signal to the input, how do I hook this up?
I got a Rode K2 -> Focusrite Isa One Digital -> mbox -> PC.

Making the compressor looks kind of simple with the provided guide on the hairball audio website, I'm more worried about the calibration part since I've seen people having troubles with the 2k trim pots, and 3rd part of calibration..

Hope that some one could help me.

All advice is welcome

TreyDay

Your DAW should have a signal generator in the inserts section (protools does for sure).  Open a track and insert the signal generator, set the output to your interface output and plug that into the 1176 input.  You'll see some impedance loss, so measure across pin 2 and 3 of the input for VAC and adjust the sig generator level so you see 0.775VAC (0dB) across the input.

Mike

 

[TreyDay]

Hello,

Not sure if this is the right place to ask.
But I'd like to buy the hairball audio 1176 kit ($595) and make the compressor, but I'm afraid I can't or get stuck on issues.
It would be my first self build project.

I mean I'm not even sure if I can apply 1 KHz O dBu signal to the input, how do I hook this up?
I got a Rode K2 -> Focusrite Isa One Digital -> mbox -> PC.

Making the compressor looks kind of simple with the provided guide on the hairball audio website, I'm more worried about the calibration part since I've seen people having troubles with the 2k trim pots, and 3rd part of calibration..

Hope that some one could help me.

All advice is welcome

TreyDay

Your DAW should have a signal generator in the inserts section (protools does for sure).  Open a track and insert the signal generator, set the output to your interface output and plug that into the 1176 input.  You'll see some impedance loss, so measure across pin 2 and 3 of the input for VAC and adjust the sig generator level so you see 0.775VAC (0dB) across the input.

Mike

Appreciate your answer! Thank you!
Do you have any idea when the kit will be available again? Can't wait to try this project.

TreyDay

 

[Echo North]

About a week.

 

[dbonin]

Not sure if this is the right place to ask.
But I'd like to buy the hairball audio 1176 kit ($595) and make the compressor, but I'm afraid I can't or get stuck on issues.
It would be my first self build project.

TreyDay

You will do fine - you'll need a good soldering iron, careful attention to detail and patients.  If you are building a rev D, spend some time up front (while you wait for the kit)  to read through this entire thread.  You will learn loads and there are plenty of us online to offer any help we can if you run into issues.  Mike and Mnats are here regularly, so you will be successful!

My two cents:
1.) Read through all the guides several times before even starting the project.  The more you know up front the easier it'll be when you have a bench full of parts staring back at you. 
2.) read this entire thread before starting
3.) build the kit step by step, carefully following the guides (their advise is proven to be best practice, follow it closely)
4.) test when possible before moving on to a new section/area of the kit

My best advise to anyone starting this project (aside from reading EVERYTHING several times)  is to test as you go when ever possible - there are lots of small tests you can do as you assemble the kit, from stuffing the PCB's (main, ratio, meter) to testing wiring continuity that can save you time later if/when problems surface.

Good Luck,  and welcome to DIY!

 

[mnats]

It would be my first self build project.

I wouldn't recommend this as your first DIY electronics project. If I wanted to get into construction would I start by making myself a house?

If you decide to ignore this advice please don't ignore the warnings about the high voltage AC wiring. Despite what some might think, they do apply to everyone and they aren't there for my protection, but for the safety of the builder.

As an aside, could we please keep all discussion of commercial transactions to the White Market?

 

[quinncmusic]

Hello DIY friends!

I just finished my 1176 build. This is my second DIY project, the first being a pair of VP26 pre's from classic API.

The build went smooth until I got into the calibration and thats where I first found my problem. Calibrating the first steps was fine but when it came to the gain reduction circuit I could not get the voltage anywhere close to 0 and I cannot get the needle to 0 either (the closest I can get it is around +1 and I run out of room on the Q control. I think the main problem is that there is NO gain reduction at all! Even with the GR needle calibrated close to zero with the 1k 0db sine wave and the input cranked I do not see any GR movement.

With the calibration as close as I could get it I took the 1176 into my studio and hooked it up with a vocal mic to see if I could hear any gain reduction to narrow down if it was just a metering problem (sm58->avedis pre ->1176->Ua Apollo). The unit passes audio just fine until I turn the input any further than around 24 and I start to hear audible clipping/distortion. Also, I do not HEAR any gain reduction either.

Has anyone had similar problems or could point me in a direction of things to check first?


Thanks so much for your help in advance!

Also, if it is easier and one of you would be willing to get on a Skype conversation to help troubleshoot, I would be more than willing to pay you for your time.

 

[dbonin]

Hello DIY friends!

I just finished my 1176 build. This is my second DIY project, the first being a pair of VP26 pre's from classic API.

The build went smooth until I got into the calibration and thats where I first found my problem. Calibrating the first steps was fine but when it came to the gain reduction circuit I could not get the voltage anywhere close to 0 and I cannot get the needle to 0 either (the closest I can get it is around +1 and I run out of room on the Q control. I think the main problem is that there is NO gain reduction at all! Even with the GR needle calibrated close to zero with the 1k 0db sine wave and the input cranked I do not see any GR movement.

With the calibration as close as I could get it I took the 1176 into my studio and hooked it up with a vocal mic to see if I could hear any gain reduction to narrow down if it was just a metering problem (sm58->avedis pre ->1176->Ua Apollo). The unit passes audio just fine until I turn the input any further than around 24 and I start to hear audible clipping/distortion. Also, I do not HEAR any gain reduction either.

Has anyone had similar problems or could point me in a direction of things to check first?


Thanks so much for your help in advance!

Also, if it is easier and one of you would be willing to get on a Skype conversation to help troubleshoot, I would be more than willing to pay you for your time.

Do these as best you can:
- complete a visual inspection (caps and transistors are seated correctly?)  Check that C7 is seated correctly.  Polarity is extremenly important and it's easy to miss. 
- visually check EVERY solder joint on the back of the board, point by point.  I just completed a rev A that had some weird behavior and I traced it back to two resistors that I had soldered the leg on only ONE side - it happens, check for the SIMPLE stuff FIRST!  Make sure there are no solder bridges or cold joints.

- voltage tests - get the rev D DC voltages reference PDF from mnats site and check your power section and transistor voltages

Forget about the second and third calibration at this stage until you can work through the issues you are having - those calibrations have NO IMPACT on the sonic performance or compression behavior of the unit.

Do a search through this forum and see what others have done to correct similar issues. 

Hopefully I'll talk to you tonight.
-Don

 

[dmnieto]

Hello DIY friends!

I just finished my 1176 build. This is my second DIY project, the first being a pair of VP26 pre's from classic API.

The build went smooth until I got into the calibration and thats where I first found my problem. Calibrating the first steps was fine but when it came to the gain reduction circuit I could not get the voltage anywhere close to 0 and I cannot get the needle to 0 either (the closest I can get it is around +1 and I run out of room on the Q control. I think the main problem is that there is NO gain reduction at all! Even with the GR needle calibrated close to zero with the 1k 0db sine wave and the input cranked I do not see any GR movement.

With the calibration as close as I could get it I took the 1176 into my studio and hooked it up with a vocal mic to see if I could hear any gain reduction to narrow down if it was just a metering problem (sm58->avedis pre ->1176->Ua Apollo). The unit passes audio just fine until I turn the input any further than around 24 and I start to hear audible clipping/distortion. Also, I do not HEAR any gain reduction either.

Has anyone had similar problems or could point me in a direction of things to check first?


Thanks so much for your help in advance!

Also, if it is easier and one of you would be willing to get on a Skype conversation to help troubleshoot, I would be more than willing to pay you for your time.

+ Well, could you try to get some high quality pictures of your pcb (both top and bottom) so we can spot any clear issues?
+ Having distortion at input 24 depends on a lot of things, specially if your GR circuit does not work, you may be just saturating the pre-amp or the output amp
+ Did you measure your transistors on the GR path to verify that:
  a) The transistors on the meter are closely matched.
  b) The hfe of all your GR transistors > 250.
+ Check that your Q-bias is correct. There is a very simple way to do that.
  a) Connect your 1176 to pro tools.
  b) Using the signal generator in pro tools, send a 1Khz sinusoid to the 1176 (-10dB).
  c) Set the output pot to "24" and put the input pot so you get a 0dBu signal in the +4 meter.
  d) put a frequency analyser plugin in the return aux track from the 1176.
  e) If q-bias is set, you should see the fundamental at 1kHz and then both the 2nd and 3rd harmonics (2k and 3k) should be visible with the second and third harmonic roughly of the same power.
  f) If you only have 3rd harmonic, your FET is NOT conducting and your q-bias is wrong.
+ If your qbias is set, then check the cabling to the push-buttons of the ratio, and check that you have correctly wired the attack pot switch, you may have wired it the wrong way and shorted the input to the GR circuit.
+ Check that the voltages at the transistors of the GR path are ok. http://mnats.net/files/1176REVD_VOLTS.pdf

 

[Pkj07]

Hello,

This question may not be relevant here, but is it really necessary to remove powder from the XLR and I/O transformer mounting holes as instructed on step 3 of the build?