[BUILD] 1176LN Rev D DIY

[Bri]

Thanks Patrick. :thumb:

I'm definitely getting too much out.

When sending a 1khz .775VAC signal into the unit, .002VAC is getting to the main board when input control is fully CCW, and output control is fully CCW.

This seems correct.

But when I turn the ouput control fully CW(input control still full CCW), it's turning into .775VAC....measured at the output XLR.

I don't know enough to determine how or why.....yet.

--Brian

 

[wmb]

I'm trying to find a power transformer for a 2x1176 setup. I've seen a few mentioned here but I'm only having limited luck. My only successful hit is a Hammond 546-182K30 which mouser has in stock. The $52 price seems kind of high. Can anyone suggest a more affordable alternative and where to get it or is that the going rate for a 30-0-30 toroid?

Thanks, wm.

 

[kazper]

http://www.avellindberg.com/

Price break is on 2 transformers so order at least 2....

35VA 30-0-30 was $23 in April
50VA 30-0-30 was $25 in April

That's the one price, can't remember what they were priced at 2.

I ordered 25-0-25 for mine seems to do ok without a load (1176 not finished) P/N: Y236106 Price was 2 for $17.85 Each

Check these guys out for all your mounting needs
http://www.toroid.com/mounting_hardware/mounting_hardware.htm

Kevin

 

[wmb]

Thanks for the suggestions! That price seems much more friendly.

How did you get in touch with Avel Lindberg? I sent them an email at the beginning of the week but haven't heard anything. I will give them through the weekend and try calling next week.

Cheers, wm.

 

[dissonantstring]

hi wmb,
just call avel-lindberg. i've had good experiences with them and i usually just call my order in - no problem.

@kazper,
kevin, thanks for that lead on the mounting hardware! i was searching for that very same thing last week and could not find someone who sold just the mounting disk! you rock!

regards,
grant

 

[Bri]

So,
My GR tracking adjustments would not take, so to speak.
My problem was that the effect of the meter adjustments would never eventually change.

I was following the 1176 calibration procedures on pgs 39-40, from JBL.
I Set levels for -10db of gain reduction...no R44.
After I adjust R75 for -10, and then turn Gr mode off, needle moves back up to only -6VU.
I then would readjust R71 for 0VU on the meter.
I'd turn GR mode on, and needle moves left, only to -2VU.
So I readjust back down to -10VU, etc., etc.
This repeats many many times, without even the slightest change.
R71 is eventually fully CW, and I have to stop, of course.

Although fets and transistors were matched, I changed them out.
I verified all resistors, components, wiring, and meter.
I had normal voltages(relative to the data I could find).

After a couple weeks of troubleshooting this, last night, I decided to see what would change if I put R44 in.
I put R44 in and I was shocked to see the meter suddenly tracking almost perfect.
I repeated the calibration procedure with R44 in, making some minor adjustments, and now everything is fine.

Can someone explain why this is...or what it indicates.
I'm happy that everything is finally functioning, but I'd feel better knowing why.

Thanks,
Brian

 

[mnats]

[quote author="Bri"]Can someone explain why this is...or what it indicates.
I'm happy that everything is finally functioning, but I'd feel better knowing why.[/quote]
It seems to indicate that you did not follow the "Meter Calibration 1176 With Discrete Components in Meter Circuit" instructions before doing the gain reduction meter tracking adjustment :wink:

 

[Bri]

Ah, I think I see.
Adjust for -10VU and 0VU just once, and then stick R44 back in.
And THEN the repetitive adjustments.

Well, the bright side to all that unnecessary troubleshooting is that I learned a lot more than I would have...that is for sure.

And I was really trying hard to avoid that infamous, humiliating, obvious oversight.

Thanks mnats...it's a great project.
If I could get a hold of another board and an output transformer I'd build another one ASAP. :sam: :guinness:

Cheers,
Brian

 

[mnats]

[quote author="Bri"]Ah, I think I see.
Adjust for -10VU and 0VU just once, and then stick R44 back in.
And THEN the repetitive adjustments.[/quote]
No. Why not just read the page I referred to? Its title is just what I wrote in the quotes.

In short, you want to:

1) Null the meter circuit itself first, then...

2) Calibrate the meter circuit to the compressor.

The former requires that you remove R44 and the latter requires that R44 is in circuit. Step 1 is listed as A and B in the page referenced. From there you can skip to one of the other calibration pages to do step 2 above.

As I've stated a few times now it can't be written much clearer than in the original manual. However, you must pay attention to the fact that most of the instructions I've seen refer to later revisions of the 1176 and the trimmer designations are different. Where they refer to R54, this is R44 on my Rev D where I have substituted a trim pot instead of a fixed, selected resistor to make calibration easier. It's labeled "TRACKING ADJ", the name it is given in later revisions (F and on).

 

[Bri]

Hi mnats.

I was following the discreet meter adjustment page, actually.
I just got a little confused at part C.
I was trying to adjust tracking before I had put in R44.
And that of course was my embarrassing blunder.
It's clear now.

Cheers,
Brian

 

[mnats]

[quote author="Bri"]Thank you for clearing that up.
I had become a bit confused, for the various reasons.[/quote]
Me too. What you wrote above is essentially correct - R44 has to be installed before you can adjust the meter circuit to the rest of the compressor and you have to set the input control until the compressor shows a 10dB drop in gain.

But I want to make sure that everyone knows you have to set the meter circuit null before calibrating it to the compressor.

 

[Bri]

:thumb:

Aside from my troubles(being my first major DIY)...
the unit sounds awesome!

Thanks mants, and everyone else!

Now I gotta go and make it pretty.

Cheers,
Brian

 

[JdJ]

Hey all-

Got my dual 1176 all tied up and it sounds great. I am having a hard time properly calibrating it however.

I have followed the JBL/1176 manual instructions as closely as possible- let me review:

I started with R44 out of the circuit- set the Null and Zero Adjust so there is .00 volts across r74.

I then put R44 back into the circuit- followed the directions for Q bias. (Interestingly, after I put R44 in- even with no signal the meter dropped to around -20 on the internal VU with no signal- however this was before I calibrated the meter to the compressor, so I forged ahead.) The Q bias went with no problems.

Here's where things go awry- I have cross referenced all of the revisions for resistor names and functions just so I could be sure I know what the directions are referring to (Meter Null Calibration and Meter Gain Reduction Calibration refer to different revisions in the 1176 instructions resistor wise...)

I get a 10db swing no problem switching from GR Bypass to GR, but when I set the Zero adjust to register 0 on the Meter with no input signal (I set this up with rotary style knobs), I can't get the R44 Tracking adjust to bring the needle above -20 with -10db reduction on my external meter?! So I end up stuck here- right around step #20 on the JBL site instructions.

Other observations:

When I switch to GR Bypass mode I get nothing on the meter in any situation- ie no signal- lots o' signal- I'm not sure if this is normal, or if the Meter should go back to 0...

When I switch the ratio switch, the needle swings quite a bit with no signal present...

I will say that other than the meter tracking, the unit sounds killer, and all other functions seem to be working properly.

Any help is most greatly appreciated!

Thanks,

Josh

 

[Bri]

Hi Josh.

Hopefully mnats or others will chime in here.
It's a bit more difficult for me to give you some good answers, because I don't know the circuit backwards and forwards.

However, what I can tell you is, yes, the meter needle will jump when switching ratios.

In GR bypass mode, the meter needle will be at rest...all the way to the left.

For the various reasons, without a lot of seemingly trivial detail, it's not always easy to get a truly accurate idea of another's procedures and methods...

So if this is the case don't mind me, however, you have to adjust for the -10db swing before you put R44 in circuit.
So take R44 out, readjust your "zero set and "null adjust" appropriately whilst getting the zero voltage across R74.
Then inject the .775vac 1khz tone, appropriately adjusting input and output controls for the 10db GR.
Then put R44 back in, and hopefully the meter will now properly adjust.


--Brian

 

[Stagefright13]

You have to set the bias FIRST. Turn the trimmer up till the meter Stops climbing and a little more if ya want. And wait a few to make sure it is maxed. Then set the zero at +1 THEN turn the trimmer down to achieve 0VU (1db drop) And make sure it has been on half hour at least to warm up. And don't touch any transistors. I hear you can blow on them (Humid air) and effect their performance. But I may just be paranoid

THEN go on to adjust for the other steps such as the 0 volts. Ya have to do it in order for it to work properly. I used the Urie document except I used a dimm on the resistor "Purple Doc style" cause I kinda got loopy at that point lol. Then went back to the Urie instructions.

Make sure your using the discrete components directions.

And set R44 for 1k before ya reinstall it cause it will be at least close at that point.

 

[JdJ]

So just to clarify:

1. Null adjust
2. Q bias
3. 10db swing
4. Then R44?

In the Urei/JBL cal instructions it refers to adjusting R54=R44 Tracking Adj on step 17 right after readjusting the meter to read 0 in step 15. So before R44 goes back in- the meter will be at zero and there should still be 0 volts across R75 right?

Turn the trimmer up till the meter Stops climbing and a little more if ya want.

So this is what they mean by turning the Q Bias all the way counter clockwise, you are just going about it a different way, right?

Thanks for the responses! This will be attempt #3. It's a real PITA to desolder R44 when the boards are in the case...

Cheers

:guinness:

Josh

 

[Bri]

I hear ya. I had to destroy my R44 to get it out.
I then put in a socket.

Well, in regards to the order, it may not really matter whether you do the null or the Q-bias first, but I would take John's advice and do the Q-bias first.

I've seen a few different bias methods described, but yes, with a signal injected, you're essentially turning the bias trimmer(CCW?) until the fet is out of it's conductive range...voltage increases...turn until it stops increasing...and a bit beyond, so you're obviously sure.
They are touchy/sensitive...so always adjust carefully.

I mostly used a couple DMMs to calibrate, so I didn't have to rely on the the unit's meter.
So now that the fet is out of it's conductive range, I still have my .775v signal coming in, and I readjusted the input and output controls to get a nice round 11db(2.7484v) coming out...measured with a DMM at the output XLR.
Now, all ya have to do is carefully turn the bias trimmer CW(?) until you read a 1db drop...i.e, my output would now read a steady 10db(2.4495v).

Not to add more decision and confusion, but FWIW, I have seen info regarding the fact that biasing even further, say, 2db or more, may allow for a "smoother" compression given the nature of the fet within this particular circuit.

So now you're set to do the rest of the calibration.

And yes, before R44 goes back in, the meter needle will be at 0VU(in "GR mode"), and it should read zero volts across "R74"(because of your null adjustments).

To clarify:
Q-bias.
Null adjust.
10db swing.
R44 in.
Tracking adjust.

--Brian

 

[JdJ]

Thanks for the in depth post Brian- I really appreciate it!

:guinness: :guinness:
-Josh

 

[Bri]

No problem....hope it helps. :sam:

-Brian

 

[JdJ]

Uggg-

I feel really stupid at this point... I have attempted to calibrate this thing at least 5 times now. Now I have R44 socketed so I can go back easily.

1. I start by Q biasing with ratio set to 20:1 & input signal of .775v (0db) I get the 1db drop on my DMM & PT metering, but the internal meter reads more than a 1db drop?! After setting as Stagefright13 recommended above. (Both channels are Sifam AL19s)

2. I set the null adjust/ Meter 0 with no input signal

3. Get a 10db swing confirmed by DMM and meters in PT as described in the Urei calibration instructions w/ ratio set to 20:1

4. Make sure with no input signal I'm still at 0 on internal meter and 0.00v across R75

5. Plug in R44 after setting it to approx 1kOhms and immediately my meter drops to -10 in GR mode WITH NO INPUT SIGNAL PRESENT! If I try to adjust it so I get the correct reding on the internal meter, I run out of range on the Tracking Adjuster. End of story.

Maybe I wired something wrong? I have X & Y connected to pins 2 & 3 respectively. The Red & Blue wires coming off of the OT are also connected to 2 & 3.


Anyone have any ideas? I'm stumped for the time being... Both channels of my dual are behaving this way. I have double checked all of the connections between the motherboards and the ratio/meter boards.

Thanks for spoon feeding me...
:sad:

Josh