[BUILD] 1176 Rev A - Back to the beginning...

[orangerec]

uhhhmm, guys, what part of it responds just like the real thing did you miss. It's the design. The blue stripes are "spongy" with the metering, for lack of better words. 

 

[structuredloud]

Finished building my Rev. A with pushbutton a few days ago. Had a minor issue with intermittent sound, double checked all my solder joints etc. and things are cool. So I've gotten the thing to where it passes signal clean, no buzz, hum. Full bandwidth etc. The VU responds in both VU and GR settings. It is tracking reasonably like the 1176's I use at work with regards to the attack and release settings during compression. I have quadruple checked all the wiring from the main board to the front panel knobs and ratio boards. Here's the problem:

No audible compression, no change in output volume despite the meter suggesting up to 20db compression. It's like the gain control amp just isn't getting the message to turn down.

I can't get though the "Q bias" because I can't get the control amp to raise or lower the signal at all.

So again, the meter is responding to changes in compression just like a fully functional unit in the studio, the amp is just missing the "cue" and I can't for the life of me figure out why it's not responding.

I'll take a fresh look tomorrow, and if I still can't work it out I'll post photos. Just wanted to see if anyone has a similar problem.

 

[structuredloud]

Okay, got that fixed. The q bias pot was not connected well enough, now the compression is kicking in and I passed calibration step 1. Now for the null adjustment I can't seem to drop the r74 voltage to 0.

Anybody have this problem? I've jumped R44 properly (to take the tracking out of circuit) no matter where I move R75 to I can't get below .84V (I tested r75 and it's behaving how it should in terms of resistance measurements). I've managed to properly calibrate my meter and even shot the unit out against a real 1176 and it performed nearly identically. The amount of compression, needle behavior, overall sound was similar (maybe even a bit better  ) only difference was slightly different overall gain due to transformer differences I imagine.

 

[Rob Flinn]

This meter circuit sucks big time.  WHat you could do is go back through this thread.  There are some points where people suggest changing SOME of these meter presets for 5K from 2K.  It gives you a bit more range to play with. 

Did you match the fets ??????    I had a problem with not gettting the meter scaling right.  I wound up swapping out the fets.  Despite matching them prior to installation, I think the meter fet had been damaged. 

 

[Neeno]

Hi guys !
First of all I'll say thank you to mako for this project.
I finished my first blue stripe, after matching the fets and the transistors (I've found some 2N3707 with 250-360hfe) I've got it calibrated.

At the moment I didn't set the tracking adjust properly (but it looks like it measures just one dB off)

Now, It looks like this version of the 1176 has a way more gain than the rev D.
Anyone figured it out yet ?
If i turn the input knob 1/4 the compressor kicks in.

I calibrated it exactly like the rev D.
Anyone noticed the same behaviour ?

 

[phatmateo]

yeah, my rev A exhibits the same behavior.  I never set my input past 12:00 with most sources

 

[ethervalve]

me three.

 

[Rob Flinn]

Actually I will look into the pops when I get free with my limited knowledge. But will be another week until I am free.

Doesn't effect me actually cause I rarely use that effect...

John

I'm just wondering whether it has been confirmed that this is normal behaviour ??

 

[Rob Flinn]

Bump

 

[edanderson]

download a copy of the jbl/urei 1176 manual, which includes a list of all the changes between the different revs; looking at the schematics might provide some insight to the sensitivity issue as well...

not sure about the plosive problem.

just a note to say that part of the behavior you are seeing is "how it is supposed to be" -- the rev A had IIRC about 6db lower threshold for onset of compression than the later revisions, due to higher gain in the first amp stage.  this is part of why people think they sound so different from the rev D, etc.  people who know the rev D would set the knobs on the rev A the same, and the rev A would compress at lower input levels.

your solution will work, but you might consider instead looking at the schematic where the pickoff to the sidechain starts (at the top of the output pot, R23) and putting an attenuator there or possibly right at the input to the sidechain (C17).  that way you don't have to attenuate your audio all the time to get the threshold in the range you want.

ed

 

[Rob Flinn]

Ed thanks for the response.

It would still be useful to know whether the clicking/popping happens on the originals !  ANyone ??

Also I am experiencing low frequency oscillation on one of the blue stripes I built.  The Woofers on the speakers are pulsating slowly.  Has anyone experienced this phenomenom or know of the likely cause in this circuit ?

 

[stitch-o]

i've try to draw a wiring guide for REV A with on off position on switch and without gr disable,

i checked all the 1176 topic to know and modified the rev D wiring guide v3, i think it's good but no sure cause i'm beginer.

Let me knows if thereis some wrong link.
thank you

Hey kats,
I was wondering if this diagram has been confirmed to be correct?
Why the difference between this and Skylar's Rev D diagram?

Cheers!

Upon examination of this wiring and the Hairball instructions (Im doing the pushbutton version), the only connection I'm not sure about is the GRN off the Ratio board.
In the hairball diagrams, GRN from the ratio board gets tied to the SPST Attack pot switch, not 22 on the board as per this 'Rev A' diagram above  ???

There is no 22 on the meter board so I assume that the 'Rev D' version need not apply to this...

Cheers!

 

[Rob Flinn]

Ed

What thread is the quote you made below from ?
I can't seem to find it, & it looks like it might have some usful info in it I haven't seen.

download a copy of the jbl/urei 1176 manual, which includes a list of all the changes between the different revs; looking at the schematics might provide some insight to the sensitivity issue as well...

not sure about the plosive problem.

just a note to say that part of the behavior you are seeing is "how it is supposed to be" -- the rev A had IIRC about 6db lower threshold for onset of compression than the later revisions, due to higher gain in the first amp stage.  this is part of why people think they sound so different from the rev D, etc.  people who know the rev D would set the knobs on the rev A the same, and the rev A would compress at lower input levels.

your solution will work, but you might consider instead looking at the schematic where the pickoff to the sidechain starts (at the top of the output pot, R23) and putting an attenuator there or possibly right at the input to the sidechain (C17).  that way you don't have to attenuate your audio all the time to get the threshold in the range you want.

ed

 

[edanderson]

rob,

you can click on the link where it says "Quote from: edanderson on May 29, 2009, 09:15:14 am" and it will take you to the thread.

ed

 

[Rob Flinn]

Is anyone else experiencing a weird LF oscillation/thumping when in "all in" slam mode ?I know that these older versions are supposed to be less stable than the later revsions but is this normal ??

 

[orangerec]

Rob,
I'm not experiencing the low freq. osc. on any of my 1176s but there is a plosive issue documented earlier in this thread. I came to realize that this is normal for a revA.

 

[Rob Flinn]

Orange

I'm only getting this with all the buttons in at certain settings.  Would it be possible for you to try this out So I can see if it's jut me ?

 

[Neeno]

Guys... yesterday I spent some time reading the schematics on the JBL manual.
As far as I understand, Mako schematics is exactly the same as the first schemo on the manual.
The second schemo is marked as revision A.
In fact there are some discrepancies.

Looking at the SN log on the schematic Mako used it looks like only 24 pieces where built in this way.
Probably Sir Putnam noticed something wrong with the first units...

Then they changed the ratio board resistors, the feedback on the preamp stage (R16 = 100k instead of 47k and the C6 has been removed) and a couple resistor values here and there, if I recall R11 and R12.
I would like to try stuffing the board following the JBL REV A schematic but R11 is unreadable there.
Anyone has a better scan of the schemo please ?

Now the question is... am I the only one ? Am I getting too old for DIY ? 

Mako: which schematic diagram did you followed for the DIY 1176 Rev A and why ?

 

[Neeno]

BUMP !

 

[ilfungo]

Ciao
My rev A is ready but i Have some problems...
the meter ( hairball) work on +4 and +8 but not in GR mode ???  I have checked all resistor and are OK
some problems with 20:1 ratio and nuke mode...
all the trimpots don't do nothing...
some ideas?
Thanks and sorry for my english...