[BUILD] 1176LN Rev D DIY

[evanbradford]

That did the trick, accidentally mixed up the release and output pots. Thanks so much for the quick response!

make sure your release pot it the 5M pot...

First post, so first and foremost, thanks to Hairball and the DIY community for making all these projects available!

I finished my first 1176 rev D yesterday, and it is being used on a vocal, along side a couple of vintage UREIs, as I'm typing this. Sounds phenomenal! The reason for this post is that the only problem is that the release knob is not working. I know 1176s are never super slow, but this one is definitely only functioning with what seems to be the fastest release time and not changing at all when turning the knob. I double checked the wiring and resistor soldered to the pot and it looks correct.  I searched and can't find any info or anyone else that's encountered this, so I was wondering if anyone might have ideas as to what would be causing this.

Thanks!

-Evan Bradford

 

[dalmaproductions]

Hi,
Having an issue finishing off my REV A. Unit passes audio, and compresses nicely in all ratios Except 4:1

I resoldered the joints, measured resistance of the switch in all positions and that seems to be ok. However, I tried a test that I read about on the thread, measuring DC at pad 21, and AC at pad 22.

With the DC at pad 21, the voltage behaves normally, going down in value when going from 20, 12, 8, and then when I  get to 4:1 there is no change(same as 8:1)
With the AC at pad 22, the voltage also goes down normally from 20, 12, 8, and then at 4:1 I get 0V AC.

Any ideas on what to check?

Thanks

 

[dalmaproductions]

One more piece of info, I noticed that when in 4:1 mode I'm now getting a pinned meter (to the left in GR mode), and low output also. The other ratios continue normal!

 

[Echo North]

One more piece of info, I noticed that when in 4:1 mode I'm now getting a pinned meter (to the left in GR mode), and low output also. The other ratios continue normal!

That's either a bad trace on either side of R21 or that 4:1 switch is bad.  Check with a continuity tester to see if it's the ratio PCB trace or the switch itself.

Mike

 

[dalmaproductions]

Hi Mike thanks, I found a trace that seemed to be bad, right next to R21! I put a quick jumper over it and things have changed slightly, but still not 100%. This is really strange but the symptoms are:

- 4:1 now compresses, but only when previously coming from 12:1
- If i'm on 20:1, and change to 4:1. I will get meter at 0 Gain Reduction on meter and and a un-compressed ouput.
- If i'm on 8:1, and change to 4:1, I will get a pinned meter to the Left(Gain reduction) and low output.

I going to keep checking these traces on the switch, but maybe this last symptom is familiar?

Miguel

 

[hymentoptera]

Miguel,
That has got to be a bad switch.. I haven't heard of this problem yet. It shouldn't matter what ratio you're coming from. Pressing any switch by itself should trip the other three. 

 

[Echo North]

Hi Mike thanks, I found a trace that seemed to be bad, right next to R21! I put a quick jumper over it and things have changed slightly, but still not 100%. This is really strange but the symptoms are:

- 4:1 now compresses, but only when previously coming from 12:1
- If i'm on 20:1, and change to 4:1. I will get meter at 0 Gain Reduction on meter and and a un-compressed ouput.
- If i'm on 8:1, and change to 4:1, I will get a pinned meter to the Left(Gain reduction) and low output.

I going to keep checking these traces on the switch, but maybe this last symptom is familiar?

Miguel

Ya send me an email.  [email protected].

You should probably get a new switch and PCB

 

[leitrim_lad]

Hi all thanks for the help so far.. So i switched the output and release pots and that seems to have worked with my release time issue. However im still getting no compression on ratios 4 and 8.. It seems to be compressing perfect on 12 and 20.. Also i thought i had an issue with a noisy pot on my original output pot (which ended up should have been the release pot). However when i switched them round im still getting a noise when i turn the output pot and not the release pot. This would lead me to believe its not the pots and a separate issue on the output as iv been getting this noise on the output with the 2 different pots.. Any help or ideas would be greatly appreciated..

Thanks a million

 

[hymentoptera]

Hi all thanks for the help so far.. So i switched the output and release pots and that seems to have worked with my release time issue. However im still getting no compression on ratios 4 and 8.. It seems to be compressing perfect on 12 and 20.. Also i thought i had an issue with a noisy pot on my original output pot (which ended up should have been the release pot). However when i switched them round im still getting a noise when i turn the output pot and not the release pot. This would lead me to believe its not the pots and a separate issue on the output as iv been getting this noise on the output with the 2 different pots.. Any help or ideas would be greatly appreciated..

Thanks a million

I post 4194, you said 4:1 and 8:1 were intermittent? Are they still? Perhaps a bad batch of switches got out...

I'm guess the noise is the hum you mentioned on the previous page? Is it typical 50Hz  hum? I think this will likely be unrelated to the 4:1/8:1 problem, but I should ask, have you tied PCB ground to chassis? What I mean is did you run a wire from the negative side of one of the PSU filter caps out to your star ground or anywhere?

 

[rosestudios]

Hi all, first post here,

I've already searched through here and on the internet, but I'm having trouble with the last step of calibration.  I am using the complete Hairball 1176 Rev D kit and as such I was only given two FETs which I were to assume were matched by hairball.  All other transistors have been tested for appropriate hFEs and the meter transistors are within 5% of each other.

I have already successfully performed the Q-bias and Null set, and I can pass audio through and have audible compression.

Can you do this for me please and confirm what readings you get:

1.) Apply a 1 KHz, 0dBu signal, confirmed with your DMM at pin 2 and 3 of the input XLR (0.775 VAC).
2.) Move your DMM to pin 2 and 3 of the output XLR.
3.) Set output control for 0dBu (0.775 VAC) at the output.        <----      (My input sits now at 24 and my ouput at the dot between 48 & 36)
4.) Set attack full CCW (off position) set release to 7 or full CW for fast release. Set the Meter to GR mode.
5.) Set input control for +10dBu (2.44 VAC) at your output XLR.        <---------------- NOTE THAT NOW THE ATTACK IS OFF!! (My input sits now at the dot between 24 & 18, and my ouput knob sits between 48 & 36) (Measuring 2.44VAC on my DMM on the output xlr, pins 2/3)

6.) Turn the attack control ON (full CW) and observer the voltage drop at each of the ratio settings

For each of the ratios, on a rev D, you should be seeing something close to this, shown with attack on:
Ratio:
20 (Att On .788VAC)
12 (Att On .679VAC
8 (Att On .642VAC)
4 (Att on .585VAC)

Hey so I've done an official test here, an analysis would be helpful.  My unit is compressing but I have to pull the output down quite far to get the gain properly for my API 3124s, also there's a bit of noise but not sure if this is the normal level.  I looked through the forum and found that in response to the extreme output trimming, it's meant to act as a makeup gain control so it's ok and someone found noise earlier by using a signal tracer (how would I go about doing this if I were to proceed down this route?  I know how to use a signal tracer but not to find noise).

My results of dbonin's test:

My output is at 48 to get .775 at the output.  My input is at a little above 12 to get 2.44 VAC at the output.

Ratio Results-
20 = .383 VAC
12 = .340 VAC
8 = .333 VAC
4 = .330 VAC

These results appear to be very different from your's, clarification would be great.

Thank you again all, it's been very helpful.

Hi sorry, any update on this, particularly from dbonin or hairball?  Why are my ratio output voltages so far off from dbonins?

 

[the groke]

Hi. I just completed a build of the Hairball rev D, and I'm having some issues with the Q bias.

I have a 1k tone set for .775V at the input. I power on with the input and output at 24, attack off, release fully CW, 1:20 ratio, and the meter on GR. My trimmer is CCW (not sure how many times to turn to get it to go all the way since it has no physical end point - but I think it's 12 turns)

With the ratio at 24 I'm reading .005V between output pins 2/3. When I turn up the output all the way, I get .044V. This obviously is far below the target reading.

I measured the voltages and they seem to basically match what is on the mmats site (except in the meter driver section - though I can make the readings look correct by jumping ahead and adjusting the 0 set pot).

I checked my wiring and it seems fine. Can anyone point me in the next direction for debugging?

I should mention that my kit was an earlier one (2010) so some of the pots are different from what is shipping now, I believe.

Thanks in advance.

 

[leitrim_lad]

Hey there, thanks for the reply.. No i havent got the 4:1 and 8:1 ratio sorted.. Im kinda stuck on it pulling my hair out to be honest!! :-( No the noise isnt a hum, its a noise when i move the output pot. its not the pot thats causing it tho as original i had mixed up the output and release pots and was getting this noise on the output pot, however when i switched the pots round i was still getting it on the output pot which was my original release pot. here is a recording of the noise

https://www.dropbox.com/s/eco3q5gwthrzumx/1176%20noise.mp3

any help would be greatly appreciated..

Hi all thanks for the help so far.. So i switched the output and release pots and that seems to have worked with my release time issue. However im still getting no compression on ratios 4 and 8.. It seems to be compressing perfect on 12 and 20.. Also i thought i had an issue with a noisy pot on my original output pot (which ended up should have been the release pot). However when i switched them round im still getting a noise when i turn the output pot and not the release pot. This would lead me to believe its not the pots and a separate issue on the output as iv been getting this noise on the output with the 2 different pots.. Any help or ideas would be greatly appreciated..

Thanks a million

I post 4194, you said 4:1 and 8:1 were intermittent? Are they still? Perhaps a bad batch of switches got out...

I'm guess the noise is the hum you mentioned on the previous page? Is it typical 50Hz  hum? I think this will likely be unrelated to the 4:1/8:1 problem, but I should ask, have you tied PCB ground to chassis? What I mean is did you run a wire from the negative side of one of the PSU filter caps out to your star ground or anywhere?

 

[leitrim_lad]

Some thing else i noticed is that whenever i switch ratios the level of the output seems to drop and then gradually get louder.. is this normal?

Hey there, thanks for the reply.. No i havent got the 4:1 and 8:1 ratio sorted.. Im kinda stuck on it pulling my hair out to be honest!! :-( No the noise isnt a hum, its a noise when i move the output pot. its not the pot thats causing it tho as original i had mixed up the output and release pots and was getting this noise on the output pot, however when i switched the pots round i was still getting it on the output pot which was my original release pot. here is a recording of the noise

https://www.dropbox.com/s/eco3q5gwthrzumx/1176%20noise.mp3

any help would be greatly appreciated..

Hi all thanks for the help so far.. So i switched the output and release pots and that seems to have worked with my release time issue. However im still getting no compression on ratios 4 and 8.. It seems to be compressing perfect on 12 and 20.. Also i thought i had an issue with a noisy pot on my original output pot (which ended up should have been the release pot). However when i switched them round im still getting a noise when i turn the output pot and not the release pot. This would lead me to believe its not the pots and a separate issue on the output as iv been getting this noise on the output with the 2 different pots.. Any help or ideas would be greatly appreciated..

Thanks a million

I post 4194, you said 4:1 and 8:1 were intermittent? Are they still? Perhaps a bad batch of switches got out...

I'm guess the noise is the hum you mentioned on the previous page? Is it typical 50Hz  hum? I think this will likely be unrelated to the 4:1/8:1 problem, but I should ask, have you tied PCB ground to chassis? What I mean is did you run a wire from the negative side of one of the PSU filter caps out to your star ground or anywhere?

 

[dbonin]

Hi sorry, any update on this, particularly from dbonin or hairball?  Why are my ratio output voltages so far off from dbonins?

Judging from your readings, it appears that your unit is over compressing.

• Have you done a complete voltage comparison as per the "schematic with voltages"  guide?
• Tripple check that you have all the transistors in the correct positions and seated correctly.
• Input transformer is seated correctly.
• output pot and release pot are not swapped (rels should be 5M)

 

[dbonin]

check out this short video - if your VU meter is working this can help assure you that you are starting the qbias with the trimmer turned the right way.
http://www.youtube.com/watch?v=9yECKyklD0o

If your VU meter isn't working or you can't reproduce the steps as shown in my video, you can do all of your measurements with a DMM on the output xlr pins 2/3.  Mike described those steps in an earlier post - I'll post a link to that shortly.


Here Mike talks about setting qbias by using your meter on the output XLR:
http://groupdiy.com/index.php?topic=20058.msg675018#msg675018

Hi. I just completed a build of the Hairball rev D, and I'm having some issues with the Q bias.

I have a 1k tone set for .775V at the input. I power on with the input and output at 24, attack off, release fully CW, 1:20 ratio, and the meter on GR. My trimmer is CCW (not sure how many times to turn to get it to go all the way since it has no physical end point - but I think it's 12 turns)

With the ratio at 24 I'm reading .005V between output pins 2/3. When I turn up the output all the way, I get .044V. This obviously is far below the target reading.

I measured the voltages and they seem to basically match what is on the mmats site (except in the meter driver section - though I can make the readings look correct by jumping ahead and adjusting the 0 set pot).

I checked my wiring and it seems fine. Can anyone point me in the next direction for debugging?

I should mention that my kit was an earlier one (2010) so some of the pots are different from what is shipping now, I believe.

Thanks in advance.

 

[hymentoptera]

Hey there, thanks for the reply.. No i havent got the 4:1 and 8:1 ratio sorted.. Im kinda stuck on it pulling my hair out to be honest!! :-( No the noise isnt a hum, its a noise when i move the output pot. its not the pot thats causing it tho as original i had mixed up the output and release pots and was getting this noise on the output pot, however when i switched the pots round i was still getting it on the output pot which was my original release pot. here is a recording of the noise

https://www.dropbox.com/s/eco3q5gwthrzumx/1176%20noise.mp3

any help would be greatly appreciated..

I listened to the mp3 and it sounds like normal pot noise at VERY high gain. It shouldn't be making that much noise, and certainly not without any signal going through it.

Some thing else i noticed is that whenever i switch ratios the level of the output seems to drop and then gradually get louder.. is this normal?

I'm stumped here. I'm looking at the schematic and I can't think of what could be causing this. Hopefully some can make a recommendation about what to check to help narrow it down.

You have checked all your DC voltages, correct?

 

[the groke]

Hi Dbonin,

Thanks very much for your reply. I actually did try the procedure in your video earlier. My Q bias trim pot requires full CCW rotation to be off.  If I crank my output all the way to 0 and put my meter on +8, then I can read -9 on the meter. Rotating the Q bias CW, I can obtain a 1db (or more) drop, but again, it is at the extreme low end of the meter, and this is with the output cranked, which is very different from what is seen in your video.

I'm not quite clear as to whether or not I can proceed with such results or if I need to check for an issue with output level in the circuit.

Thanks - D

 

[galloni21]

This is my first compressor build (i've built several class A preamps from SCA before this) and I'm trying to do the Q bias calibration. I send a 1k 0db signal to the compressor with all the settings per the q bias instructions (input at 0, output knob about 3/4 turn, release fully clockwise, attack fully counter clockwise, and pin 22 of the gr pcb grounded). I then turn the input knob til I get a meter reading of +1db. Here's where I have the problem. When I start turning R59 q bias adj resistor the meter reading doesn't change at all, and I'm trying to reduce it 1 dB so it reads 0 db.

Any ideas on what my problem may be?

Any help would be greatly appreciated in troubleshooting. I double checked the build and am pretty damn sure things are hooked up correctly. I measured all resistors before installing, etc. Thank you!

 

[leitrim_lad]

Hey there, i was having the same problem only lately when i was doing the q-bias.. its right at the very end of the pot turning cw ul get the drop. took me awhile to get it as i was afraid of turning it to far and breaking the pot. its a slight change right at the very end..

Hope it helps

This is my first compressor build (i've built several class A preamps from SCA before this) and I'm trying to do the Q bias calibration. I send a 1k 0db signal to the compressor with all the settings per the q bias instructions (input at 0, output knob about 3/4 turn, release fully clockwise, attack fully counter clockwise, and pin 22 of the gr pcb grounded). I then turn the input knob til I get a meter reading of +1db. Here's where I have the problem. When I start turning R59 q bias adj resistor the meter reading doesn't change at all, and I'm trying to reduce it 1 dB so it reads 0 db.

Any ideas on what my problem may be?

Any help would be greatly appreciated in troubleshooting. I double checked the build and am pretty damn sure things are hooked up correctly. I measured all resistors before installing, etc. Thank you!

 

[leitrim_lad]

Hey there, no one any ideas on what my issues could be with noisy pot and no compression on ratios 4 and 8? Beginning to pull my hair out with this one.. any help would be greatly appreciated..

thanks a million