[BUILD] 1176LN Rev D DIY

[jplebre]

Enjoy, great souinding guy, still trying to get my attack working properly.
Should be close!

 

[Dvaughn]

I just want to say thanks to mnats and mike for making my 1176 possible.  It sounds AWESOME! The plethora of info on this thread and mnats site made my build smooth.  Only had a few hitches along the way but she calibrated all the way through and I ran drums, and some bass thru it and turned knobs for about an hour and am very satisfied with this build.  Fun and rewarding!!  Next up is a stereo blue stripe, or stereo rev D!!


Thanks guys!!! ;D

 

[Dvaughn]

Ok, after using the compressor a few times I'm noticing a few things that I think need to be sorted.

I did all of the calibrations in the videos on mnats site, i've yet to do the distortion adjustment (this could be the culprit?) but, what seems to be happening is, I'm hearing some distortion of the signal when compression is occuring, but I only seem to hear it when I have the attack and release settings at their fastest speed (fully clockwise) Either if both are fast or even if just the release is fast and attack medium, but it's really apparent when both are set to fastest.  It also seems to get worse/more apparent when the ratio is increased.  The output is not near maxed out, and even if the input is fairly low, as long as I compress something with the attack and release both fast I hear distortion.  When I back both pots off just a bit (to about 3 o'clock) it goes away and sounds clean again.  I don't hear distortion when unit is bypassed, GR off mode, and I don't hear it when attack and release are set medium to slow even if a lot of compression is occuring.  At first I thought it was the amount of compression that I was hearing, but like I said if I have attack and release at medium settings with 10db of compression it sounds clean (no distortion).  The distortion sounds like a fuzz pedal (maybe not that bad but, not crackling just overdriven sound) and ONLY when compression is occuring

I checked all the voltages on the mainboard and all are within .5V (is that good enough?)  I could post the differences if it would help.  Also I checked the DC Voltages on pad 21 like I saw on a post earlier that sounded similar and those all were dead on.

I didn't notice the distortion at first because I was doing a lot of transient stuff (drums) but the second i put some bass/keyboard thru it I noticed right away

Everything else seems to work correctly and if I can get to the bottom of this it might help out some of my future builds

-the only other thing I wanted to ask about was a "skratchy" sounding input pot.  If no signal is present i don't hear the pot, but if there is audio going thru, i hear noise when the input pot is turned.  Any ideas?

Thanks so much for any help!!

Dylan

 

[jplebre]

I did all of the calibrations in the videos on mnats site, i've yet to do the distortion adjustment (this could be the culprit?) but, what seems to be happening is, I'm hearing some distortion of the signal when compression is occuring, but I only seem to hear it when I have the attack and release settings at their fastest speed (fully clockwise) Either if both are fast or even if just the release is fast and attack medium, but it's really apparent when both are set to fastest.  It also seems to get worse/more apparent when the ratio is increased. 

There is a fair amount of this in the original units. you think you are above the mild fuzz you can pull from them on stuff like bass?

Scratch in the pot: what's your source? eg could you have some DC bleed?

 

[Dvaughn]

I think it sounds excessive, and like i said it's not like i'm smashing the input and bringing the output way down.  It seems to distort based on the attack and release settings (if i have them both fast).  That's what made it seem more like a problem to me.  But I don't have an original unit to a/b with, so i don't really know 

I've had the unit connected to my digi003 rack (out and back in) and also i had a bass going in thru an external pre and then into 1176 ->003 and i still heard the scratchyness of the input pot, only when sound is happening, especially noticeable on sustained sounds. 

I'll see if i can record some of the distortion to see if it's something normal/abnormal

 

[jplebre]

that could help.

Check the input wiring again, specially the shield http://mnats.net/1176_reva-d_hairball_wiring_input.html
I saw you did that bit for the transformer but couldn't see under the input T attenuator if it was touching.

Seems the problem should be between your signal source and the transformer as the transformer should be blocking DC

Maybe Mike (Echo North) or someone else will pitch in on how to clean the pots if at all possible. Could be you got a dodgy pot. But also could be DC.

Did you insert the transformer correctly on the PCB (ie the ground bit right side around, there's a mark).

Would be nice to hear it. I can definitely pull some distortion (and can get quite nasty very quickly on faster settings) on our 76 and 78's

Feel free to correct if any of the above is not right

 

[Dvaughn]

You know,

I think i'm just bugging out on something that is normal.  I was reading thru the manual and it says.  "Extremely short release times may even introduce harmonic distortion if the gain reduction changes between cycles" also in the troubleshooting section it says if distortion is the problem select slower attack and release times as a solution.  I could record some of the distortion i'm hearing but I would feel dumb if it was just the normal thang. 

 

[jplebre]

"Extremely short release times may even introduce harmonic distortion if the gain reduction changes between cycles"

some people love it. Last week this guy I worked with used it to get some distortion out of the bass and worked pretty nice in the overall mix.
There is some, but it's not fuzz face like or gritty, if you know what I mean

Scratchy pot shouldn't be there though keep us posted

 

[Dvaughn]

Hey I made a video of my issues.  It's only 2 min long and shows what i've been rambling about.  Let me know what you guys think.  The audio got mp3'd by youtube but I still think you will be able to hear the difference.  I also demonstrate the "scratchy" sounding input pot at the start.  Any ideas?

here's the link:  http://www.youtube.com/watch?v=Otd05vTBlfg&feature=youtu.be



sorry for the mundane non-musical sound sample but i needed some control to demonstrate

Thanks for checkin it out!

Dylan

 

[mitsos]

@dvaughn,  I'd start by looking at your input/preamp section first, starting from the XLR all the way to the output pot.  The noise getting compressed more with each setting, tells me it's there from the beginning.  I'd start by trying to rule out the output section. If you disconnect the output pot wiper from pin 17 (IIRC that's where the wiper goes) and then inject a signal to that pad, you will be going through the output section only and can rule out the output section if there is no noise.  Proceed to cut the circuit down to parts and test each separately until you find the problem.  Good luck, you'll find it.


Now, I've also got a weird issue with a dual 1176.  At my house, the thing works fine, sounds great, compresses, calibrates, etc. All good. The VU needles rest at zero in GR mode.  But when I tested it at my friend's studio, the first thing we noticed was that the needles seem to like to float vertically.  I say float, cuz that's what they look like, they move slightly, but very smoothly, back and forth.  Both needles move more or less together, and this is in dual mono, not linked. 

On first test, my friend thought they were more aggresive.  He said he'd likely not use them on drums (he's got purples, distressors and has used Ureis, so I know he knows the 1176 sound).  Anyway I left him using it for a few days now, last time he used it was on a vocal I think.. 

(btw, the meters on the Purples don't do this, they sit at zero.)

I am going to meet up with him sometime next couple of days, and I'm going to recalibrate the thing at his place, to rule out any issues from moving them(?).  But the way the needles moved was weird, they never stayed still...

Now, we did find some 60 and 120Hz on his system, but didn't have time to check if it's coming from the 1176 or something else. Will check that as well. 

Anyone seen PSU ripple cause something like this? My gut says yes, can anyone confirm? IIRC I used 4700uF filter caps in the original Mnat's PSU to power this thing. 

thanks in advance!

 

[Echo North]

(btw, the meters on the Purples don't do this, they sit at zero.)

The Purple is a completely different meter circuit.  Modern and IC based.

The MNATs versions (A and D) use the original discrete circuit.

Let us know what you find!

Mike

 

[Idiophonic]

Hello to everyone on the forum, long-time lurker here! Apologies in advance for the long post.

I recently completed a REV D build and everything went smoothly, I just want to thank Mnats and Hairball for making this as straight-forward as it was.

I do have an issue I'd like to get some feedback on:  After calibrating, and then double checking my calibration,  the threshold on my compressor seems to be lower than on both original and UA 1176 re-issues.

When running a 0 VU tone into a UREI, UA, and my Hairball,  the Hairball goes into GR with my input knob around 48, IOW, the input is almost turned down all the way.  The UA is closer to 9 o'clock, the UREI around 10 or 11 o'clock.

I measured the total amount of gain available in my unit.  With GR switched off and the input and output dimed, I have approx. 44 dB of gain through the unit, which I understand to be normal.  (40 db was my understanding.)

The result is I am unable to turn down far enough to get light amounts of GR on a particularly hot signal.  The sound of the unit is comparable to the other units otherwise, just my input knob must be nearly all the way down to match the behavior of the other units.

I have checked and re-checked the Q-bias adjustment.  I thought I may have been sending the unit the wrong level of tone during this step, but I cannot find anything I am misreading.  I don't understand why the exact level of tone and position of the input knob during this step would not have an effect on where the threshold ends up, but that is what is stated in the Mnats Q-bias video.

I am also suffering from a scratchy input pot, which I did not expect from a sealed Bourns pot.  But this is less of a concern than the threshold issue.

Again, I am happy with the sound of the unit, but I am hoping to fix these last two little bugs.  Does anyone out there have a similar experience or a suggestion?  How can I increase the threshold to get more room to work the input knob?  Any suggestions on the scratchy input?

Thanks to all of you for contributing your knowledge to this board and LONG LIVE DIY!

 

[Echo North]

Hello to everyone on the forum, long-time lurker here! Apologies in advance for the long post.

I recently completed a REV D build and everything went smoothly, I just want to thank Mnats and Hairball for making this as straight-forward as it was.

I do have an issue I'd like to get some feedback on:  After calibrating, and then double checking my calibration,  the threshold on my compressor seems to be lower than on both original and UA 1176 re-issues.

When running a 0 VU tone into a UREI, UA, and my Hairball,  the Hairball goes into GR with my input knob around 48, IOW, the input is almost turned down all the way.  The UA is closer to 9 o'clock, the UREI around 10 or 11 o'clock.

I measured the total amount of gain available in my unit.  With GR switched off and the input and output dimed, I have approx. 44 dB of gain through the unit, which I understand to be normal.  (40 db was my understanding.)

The result is I am unable to turn down far enough to get light amounts of GR on a particularly hot signal.  The sound of the unit is comparable to the other units otherwise, just my input knob must be nearly all the way down to match the behavior of the other units.

I have checked and re-checked the Q-bias adjustment.  I thought I may have been sending the unit the wrong level of tone during this step, but I cannot find anything I am misreading.  I don't understand why the exact level of tone and position of the input knob during this step would not have an effect on where the threshold ends up, but that is what is stated in the Mnats Q-bias video.

I am also suffering from a scratchy input pot, which I did not expect from a sealed Bourns pot.  But this is less of a concern than the threshold issue.

Again, I am happy with the sound of the unit, but I am hoping to fix these last two little bugs.  Does anyone out there have a similar experience or a suggestion?  How can I increase the threshold to get more room to work the input knob?  Any suggestions on the scratchy input?

Thanks to all of you for contributing your knowledge to this board and LONG LIVE DIY!

The threshold is set by S4(b).  You can see in the schematic it feeds a negative voltage to that point between R52/R53.  One of two things might be happening.  This voltage may be too negative, or the signal coming from S4(a) might be too weak.

I'd check all the resistors on the ratio board and you transistor voltages in the GR control amp. 

Also what is your Qbias voltage?

The input section of the 1176 is sensitive to any noise in the pot.  It doesn't take much to get some noise there.  A new t-pad would probably fix that.  Email me about that.

Mike

 

[mitsos]

(btw, the meters on the Purples don't do this, they sit at zero.)

The Purple is a completely different meter circuit.  Modern and IC based.

The MNATs versions (A and D) use the original discrete circuit.

Let us know what you find!

Mike

hmm, did not know that purple used an IC meter circuit.  Anyway, I've never seen meters do what mine do, it's very weird, and even weirder that it doesn't do it at my house!  I think my bud's using it on a mix today, I hope to pass by there in a few hours and do some tests and post back. 

 

[Echo North]

(btw, the meters on the Purples don't do this, they sit at zero.)

The Purple is a completely different meter circuit.  Modern and IC based.

The MNATs versions (A and D) use the original discrete circuit.

Let us know what you find!

Mike

hmm, did not know that purple used an IC meter circuit.  Anyway, I've never seen meters do what mine do, it's very weird, and even weirder that it doesn't do it at my house!  I think my bud's using it on a mix today, I hope to pass by there in a few hours and do some tests and post back.

You're right it doesn't use the IC circuit.  I thought it did but it doesn't according to the posted schematic.  It just has a IC buffer.

My bad.

 

[jplebre]

Idiophonic, in my unit the threshold is slightly higher than the urei sisters. (when the UREI is 12o'clock, mine is at 15 (dot).

My 20:1 voltages are fine, but the others are off.

I've just received some parts and will work on it a bit more, but please let us know if you find your issue will definetly help me with mine.

 

[mitsos]

(btw, the meters on the Purples don't do this, they sit at zero.)

The Purple is a completely different meter circuit.  Modern and IC based.

The MNATs versions (A and D) use the original discrete circuit.

Let us know what you find!

Mike

hmm, did not know that purple used an IC meter circuit.  Anyway, I've never seen meters do what mine do, it's very weird, and even weirder that it doesn't do it at my house!  I think my bud's using it on a mix today, I hope to pass by there in a few hours and do some tests and post back.

You're right it doesn't use the IC circuit.  I thought it did but it doesn't according to the posted schematic.  It just has a IC buffer.

My bad.

I haven't looked at their schemo in ages, I was always under the impression they copied the Rev C/D schems to the letter.  Not that the meter circuit should make a difference in sound, but...

Afraid I didn't get to do too much checking on the 1176s last night, but I did find out the 60Hz is coming from his Portico compressor(60Hz, 180Hz, 300Hz on this channel, weird since it runs on DC, which I didn't think of at the time, getting behind the rack was a pita yesterday).

Now the 1176 had no 60Hz on it, but it did have a peak at 120Hz (at -81dB or so).  So insufficient filtering... Funny, I used 4700uF filter caps thinking they'd be more than enough for 2 channels (they should be, right?) but once more, the shitty brasilian power grid has trumped my judgment. Anyway, the 1176 is going to stay at my friend's for a month before I see it again (holidays and all that) at which point I'll try either adding another set of 4700uFs (might not fit, it's cramped in there) or a CRC with 2200 or 3300uF caps. 

I wonder if this ripple is finding it's way to the sidechain and meter circuits and causing the needle weirdness. 

I'm still confused why these symptoms occured there and not at my place.  Anyway, happy holidays to everyone, thanks mike, I'll let you guys know how this ends up when I get back to my friends place in january.

 

[Idiophonic]

The threshold is set by S4(b).  You can see in the schematic it feeds a negative voltage to that point between R52/R53.  One of two things might be happening.  This voltage may be too negative, or the signal coming from S4(a) might be too weak.

I'd check all the resistors on the ratio board and you transistor voltages in the GR control amp. 

Also what is your Qbias voltage?

The input section of the 1176 is sensitive to any noise in the pot.  It doesn't take much to get some noise there.  A new t-pad would probably fix that.  Email me about that.

Mike

Thanks for the reply.

I checked continuity on the ratio board and everything seems ok.  I measured voltages as suggested, they are as follows:

Q7  GATE - 4.54  SOURCE - 14.79  DRAIN - 3.99

Q8  GATE - 14.8  SOURCE - 29.9    DRAIN - 14.16

Q9  GATE - 3.45  SOURCE - 17.32  DRAIN - 2.89

Q10 GATE - 17.31  SOURCE - 29.9  DRAIN - 16.75


I also measured the voltage at the point between R52 and R 53 at all four ratio settings.  They are as follows:

4:1  -- -1.69 V
8:1 --  -2.62 V
12:1 --  -3.73 V
20:1 -- -6.69 V

By q-bias voltage, I assumed you mean the voltage at the gate of Q1, which measured -1.01 V.
(The voltages at Q1 Drain and Source were zero, obviously, I had no input signal applied.)

The voltage coming from the attack and release pots into Pad 7 on the board measures -1.18.

Is it possible I simply have a bad 2N5457  @ Q1?  All the voltages seem to be reasonably close to the ones provided by mnats on his schematic, but there were no voltages listed for the different rato settings, or voltages around Q1.

I am not exactly sure what this all means, any help would be appreciated.

Thanks!

 

[sage]

Finally finished this build today - the calibration process it is a bit strange on the videos - someone i have a easier time with a step by step as instructed by Mike at Hairball and also you can find in several places on these threads...

ONE IMPORTANT SUGGESTION : if you are using the Cinemag trafos it is a good idea I think to change the resistor value of R4 to 10k.

We noticed a pretty drastic frequency cut of several dbs from 10 to 20 kHz but that goes away with this simple resistor replacement.

David at Cinemag had me do that on the REV A but he said there was no need on the REV D, well indeed it seems to be wise to change that values or do 4.6K on each side of the input.

We will be posting some pics tomorrow with Marson -

 

[jplebre]

Idiophonic, Q7 Q8 Q9 and Q10 are NPN BJT. The legs are collector, base and emitter (top to bottom, when reading the schematic).
If you can confirm you simply swapped the names (which seems to be the case) then your voltages are on the ballpark http://mnats.net/files/1176REVD_VOLTS.pdf

Funny, I just built a second PCB and the threshold is pretty much where you described, around 7-8 o'clock.