[BUILD] 1176LN Rev D DIY

[Sillen]

Okey! Thank you 

 

[Sillen]

It's calibrated now.. But when I turn the attack knob ON the sound loses alot of frequencies at the low end and sounds very hollow. When it's Off it sounds fat like you would expect and seems to be compressing the audio the way it should also (According to my ears at least). I'll post photos soon.. Anyone have any idea what may be wrong already?

 

[dbonin]

When the attack knob is in the OFF position it is in bypass mode and no compression should be occurring.  This is interesting! 
It's good that a signal is passing through the unit.
Double check your transistors - the correct values are seated correctly in the GR section of the board?

Did all of the calibration steps pass without any issues?
Do a search to see if anyone else has experienced something similar.

It's calibrated now.. But when I turn the attack knob ON the sound loses alot of frequencies at the low end and sounds very hollow. When it's Off it sounds fat like you would expect and seems to be compressing the audio the way it should also (According to my ears at least). I'll post photos soon.. Anyone have any idea what may be wrong already?

 

[fluxofpinkindians]

Just wanted to update. The source of my problem was a cold solder joint on two of the pins of the t pad attenuator. It was attenuating but not nearly enough!!!

many thanks to Mike and others for your help.

best wishes

flux

You've got an issue in your GR meter section.  Bad trimmer, R value, or pad 28/29 wiring.  Keep in mind when you're in +4 your by passing all of that.

I'm not sure you have an issue with your compressor, other than your GR metering.  I could be wrong.  If you're compressor is not passing/compressing signal properly it most likely NOT related to the GR metering issue unless you have the pad 28/29 wiring mixed with something else.  They would be separate.

Have a look at the meter PCB and follow where 28 and 29 come in and test continuity for a broken trace.  Keep in ming those 2 resistors are not in the circuit in GR so don't worry about them. 

That's all I think of right now.  Are you passing clean audio?  The Qbias when well?

Mike, thanks so much for your continued patience with this. I am summarizing things here below as things are getting a bit spread out over the various posts. I am determined to fix this.

• Unit passes clean audio and compresses
• Q bias set but strange (see below), Discrete Meter set, GR meter tracking adjust set
• The Meter is tracking ok and seems to be representing correctly the voltage drops that I see between the input and output when compressing.
• Visual inspection of wiring correct. Trimers checked. R values of meter driver section ok. Continuity of pad 28/29/meter board pcb checked.
• All voltages ok except collector of Q13 which is negative (-1.56 )in +4U mode. Not sure if this is normal.

Problem: In +4VU mode, IN BYPASS, If I apply 0.775VAC to the input, to get 0.775VAC at the output, I need to fully rotate the input CCW (full attenuation) and rotate the OUTPUT CCW to -50 (huge attenuation)

It is as though the signal preamp is amplifying way too much. Or the input attenuator is not attenuating enough. This is what made setting the q bias "strange"

With compression engaged, it is pushing the signal into the "threshold" very early and thus compressing far too much.

I am a bit at a loss as to what to do next!

with best wishes,

Flux

 

[DDay]

Hi,

I've just completed my first 1176 Rev D.

Unfortunately (before any calibration) there is a big hum on the output and the VU meter is not responding..
The light comes on and the needle jumps when you turn it on but then doesn't move from the -20 position on any setting.

The power rails are fine BTW.

Please help!

 

[schepbo]

I'm sure you already checked this, but for the record...

make sure all your polarized caps are positioned the right way, transistors are seated correctly and the right transistor values are where they need to be.

High freg oscillation?  All your wiring is shielded and or twisted as it should be, routed around the board?  did you check to make sure chassis ground is good all around the case?

Hey! I just finished my build of the rev D 1176. It turns on and passes audio fine, but when i turn the output knob to about 1/4 the meter pins straight to the right. When the output knob is almost open, the needle drops to zero again. I have an oscilloscope and i can see a high frequent signal coming out when the meter pins to the right, even when no input is present. I also listened, and i can't hear any kind of compression, regardless of the settings.
I checked the wiring, and everything is connected as it should be. Soldering joints are all very neat. Voltages from the power supply are perfect and stable.
I'm very confused right now.. I hope there is someone who can help me!

Bart

P.s.: Sorry for my bad English.

Checked everything twice and everything is as it should be.. Very confusing..

 

[DDay]

.. The nasty hum/noise is completely dependant on the output pot position (0=no hum).

Music does go through the unit but sounds pretty tinny/distorted and I can't hear any compression.

The way I've managed to move the VU meter is with the release pot nearly fully clockwise. This seems ridiculous and it doesn't even recognise the output at all, just stays static in relation to the release pot, q bias, trimmers etc.

If someone can point me in the right direction for trying to remedy these issues I'd be extremely grateful!

 

[mnats]

If someone can point me in the right direction for trying to remedy these issues I'd be extremely grateful!

The first line of the first post of this thread?

 

[DDay]

Thanks, I've sifted through a ton of pages!

All the transistor voltages are more or less correct, I've tried balanced/non-balanced cables, different output / input sources and power leads / terminals, removing & reattaching the pin 1-chassis grounding, checked continuity for each wiring section (including the PCB grounding), and even removing completely the red&black wires from the output XLR to meter.

The unit does pass audio and compress but the output-dependant Hum is very loud even with no input .. Could this be a bad output transformer? Voltages at each wiring point with no input are: violet 0v, grey 0v, black 29.4v, white/red 2v, white/black 2v, brown 26.9v.

The release pot still moves the meter a great deal and now the needle seems to jump around of it's own accord.. Could this be dodgy CR2 & CR3 diodes? I get a -7.24v reading at the anode and -1.74v at the cathode of each for a ratio of 20.

Sorry to have to post but I'm really stumped! Could anyone shed any light?

 

[mnats]

Music does go through the unit but sounds pretty tinny/distorted and I can't hear any compression.

The unit does pass audio and compress but the output-dependant Hum is very loud even with no input .. Could this be a bad output transformer? .

What changed between your earlier post and the next?

As mentioned in the FAQ it is unlikely that there is a faulty component and unlikely that the output transformer is causing hum.

It seems like the perfect candidate for signal tracing. Find out which stage is tinny/distorted and concentrate your efforts there. If the hum is still present after that you can also signal trace to find out where it starts.

The release pot still moves the meter a great deal and now the needle seems to jump around of it's own accord.. Could this be dodgy CR2 & CR3 diodes?

Intermittent problems are often caused by poor or shorting solder joints. Poking around with an insulated blunt instrument like a chopstick might be one way to isolate the fault. Got a pic of your soldering skill?

 

[wimmy7986]

Hello everyone - I'm in need of some help with my build...

I've built 5 of these so far, and have never had a problem like this.  I'll do my best to explain.

This unit has been functioning perfectly for about 2 months.  All voltages were spot on, and the calibration was exact.  It never left my studio.  Now, I'm getting this weird, constant, crackling hiss coming from the output.  The level of hiss and crackle changes with the output pot position, and then disappears when it is fully clockwise.  I cannot for the life of me figure out where this is coming from.  I've poked around inside of the unit for hours, and cannot isolate the issue.  I've rerouted wires, resoldered EVERY pad, and reground everything, and nothing has changed.  It also never changes with movement of the input pot. 

The weird part is that the unit works as it should, just with this overpowering crackling.  All compression is there, and the meter is reacting like normal. 

Any thoughts??  Thanks!

 

[DDay]

What changed between your earlier post and the next?

[/quote]

Yes, I jumped the gun a bit with the first post! I only had a dodgy old turntable and preamp to test the input at first, once I got it into the studio with the right levels etc it kicked in fine.

My soldering is ok but there's always room for improvement.. thanks for the pointers, I'll redo some soldering in GR meter sections and do some signal tracing to track down the hum.

 

[COLLEYK2]

I am having trouble with Step 3 of the Calibration. After moving the jumper and putting the Tracking Adjustment trimmer back in circuit, I set the compressor to GR and 20:1 with no input signal. I then go to adjust the meter to 0 with the zero set pot but with no luck I can only get the needle to get upt o -2 b before running out of turn on the pot. I have repeated the first two steps multiple times and this is always the result. What do you think? Should I replace the 2k Zero Adjust Pot with a 5K? Thanks for your help. This is my first post and so far the Hairball Audio 1176 Rev D Kit has been loads of fun and great experience.

 

[Echo North]

The tracking adjustment is a play between the 0 adjust and tracking trimmer.  If your 0 is making out put in in the center and try to move it the other way with the tracking trimmer.

 

[Spadehead]

Hi All,

I haven't been around here for a while so apologies if this has been covered somewhere in the last 100 pages - I have searched but can't find anything pertaining to this:

I have 2 Rev D units and 1 Rev A. All builds went smoothly and calibration, although not the easiest, seemed to go okay. 

My question is: what are people finding their unity gain points to be? In the original 1176 manual it suggests both input and output at midday - around the -24 mark on the pots, however this for me is way too loud on the return path.

I have the same issue on all three units which work out to all be working in the same area of -36 for both input and output to be showing unity gain. Did I do something wrong in calibration? I would ideally like the unity point to be higher so I can be a bit more precise with the controls - also with hot material sometimes the input pot is way down and still showing compression. Is this possible with this design? Anyone managing to get unity at -24 on both pots?

I seem to remember (it was a while ago - forgive me) that I needed to crank/turn down the tones to get them in a manageable area for the units and that also my pots tended to be different from the videos so maybe I should try to calibrate again?

Any ideas anyone?

Best wishes

 

[wimmy7986]

Hello,

I'm still having trouble finding where this noise is coming from.  It sounds like someone blowing air into a microphone...  Does anyone have any recommendations on where to start??  I've never had a problem with these builds and LOVE how they sound!  This one, however, is not playing nice....

Thanks

 

[dbonin]

Hello,

I'm still having trouble finding where this noise is coming from.  It sounds like someone blowing air into a microphone...  Does anyone have any recommendations on where to start??  I've never had a problem with these builds and LOVE how they sound!  This one, however, is not playing nice....

Thanks

Try to trace a signal, by probing and listening to it and see if you can narrow down where the noise is introduced.  Start from the input transformer and work your way to the output. 

 

[mnats]

I'm still having trouble finding where this noise is coming from.  It sounds like someone blowing air into a microphone...  Does anyone have any recommendations on where to start??  I've never had a problem with these builds and LOVE how they sound!  This one, however, is not playing nice....

Is it different to the problem described in the troubleshooting FAQ?

 

[wimmy7986]

Thanks for the replies!  Yes it appears to be different from the one in the FAQ.  The meter isn't pegging or anything, its just noise.  It doesn't seem to affect anything - the controls/meter operate normally. 

I've tried rerouting every wire to make sure its not oscillation, and the noise isn't changing...  Also the noise isn't changing when I unplug the input cable. 

I'm going to try Mark Burnley's signal tracer and see what I can find.  Thanks

 

[wimmy7986]

I finally found the problem!!  Of course, the day I make another post is the day i figure it out...  It appeared to be a cold solder joint in the "signal line amp" section.  Thanks to that signal tracer I was able to isolate the noise. Once I re-hit those solder pads, the noise was gone.  Thanks again everyone!