BaZZZZZ

Re: All things G1176 - the new "repost" thread.
« Reply #3800 on: June 27, 2016, 01:46:51 PM »
Yeah! :o I solved the problem! The ratio switch was broken and the signal not went to pin 22... Now i must understand - Can I use that inclusion of meter (through the diode)... Its correct? And how to set a compressor with an oscilloscope and generator by measuring voltages... It is now fully working, all switches, compress as it should... But I would like to configure it correctly... I did not understand what the initial position of the BIAS... In video on youtube from the resulting minimal gain... I set up opposite from the high resulting gain...

And what about VU meter. How must it work? If I take alone UV meter with diode bridge without resistors and conect to 0  db generator,  What should it show? 0 db?

My transformer is 1:1 it means my meter must show 0 dB if signal 0.775 V?
« Last Edit: June 28, 2016, 06:32:45 PM by BaZZZZZ »


Re: All things G1176 - the new "repost" thread. (too much gain at input)?
« Reply #3801 on: August 30, 2016, 03:56:04 AM »
Hey folks.

I have this problem on just one of my 1176 builds (the MNATS RevJ board with IC input stage).
Basically input level is a long way off on this one. (too high)

I've built a few but this is the first time I experienced this issue.
I've triple checked in case I used any different components or wiring from the last one I built (working fine) to this one, but I can't find the problem).. 

Where usually I would have the input knob at say "24" (top centre) on my other unit, on this problem unit I get the same level coming in dialled right back down to "48" (ie. approx. 7 o'clock kinda position, almost off).

I've seen this problem mentioned quite a few times in relation to this build (mostly circa 2006/2007) and a few threads suggesting some thins to look at, but nothing really conclusive..

eg.  this ref thread:
http://groupdiy.com/index.php?topic=14234

Everything else on my units are working the same in terms of compression amount and threshold operating point, but I have to have the problem unit dialled way back down at the input to get that same operating level. 
I feel like I'm possibly hearing a bit of additional background noise which may be accompanying this too, but not sure at this point.

From what I have deduced across these various posts, it's looking like the change of R1A in the IC input stage (from 10k ohms to 3.7k ohms) is probably the most likely to sort out this issue on my unit, but wanted to ask if anyone worked out any other things that I really ought to check first?

Thanks!
Evan

Re: All things G1176 - the new "repost" thread.
« Reply #3802 on: August 30, 2016, 09:51:18 PM »

UPDATE:  Tried swapping R1A to 3.7k ohms, to decrease input level.
I think it "helped" a bit, but not that much.  I suspect it's not the best way to properly fix my issue here.
I guess I could try an even lower value, say, 1.5k ohms .. but i suspect increased background noise will become more of a problem.

gswan

Re: All things G1176 - the new "repost" thread.
« Reply #3803 on: August 31, 2016, 07:27:48 PM »
Did you perform any measurements for the gain of each stage?
This should be part of the final test after assembly, so you know each section is performing as it is supposed to.
With gain-reduction switched off, the first amplifier stage should be about 26dB gain, and the line driver amplifier about 10dB gain.
More post-build troubleshooting info here:
https://axtsystems.com/joomla31/index.php/projects/11-cat-1176ln-audio-compressor/15-art-1176ln-troubleshooting

- Geoff

Re: All things G1176 - the new "repost" thread.
« Reply #3804 on: August 31, 2016, 10:12:37 PM »
Did you perform any measurements for the gain of each stage?

Thanks Geoff!

I didn't do that yet. 
Thanks for the suggestion.
Do I need a probe to do this? / signal trace?

I'll look into it..  I hadn't found that page on your site before.  Looks very good.

gswan

Re: All things G1176 - the new "repost" thread.
« Reply #3805 on: August 31, 2016, 10:34:12 PM »
You will need at the least a known signal to inject into the input, and a means to measure its value at each point in the signal chain.
A signal generator can be used to inject a signal (say 1kHz), and an AC millivoltmeter or scope to measure the RMS signal level at each stage. Then calculate the gain of each stage as dB.

Re: All things G1176 - the new "repost" thread.
« Reply #3806 on: September 01, 2016, 01:21:29 AM »
ok, i think i get it.  CHEERS!
Shall try it and see how it go. 
Thanks again.
Evan

JW

Re: All things G1176 - the new "repost" thread.
« Reply #3807 on: January 11, 2017, 05:09:00 PM »
Guys,

I need a schematic for the Mnats G1176 REV J transformer input (same as the Gyraf G1176) with the 2:1 step down input, usually the Lundhall.
The problem is, the Gyraf schematic on his site is for the IC Rev G/J input with no other schematic for the input transformer version. And Mako, I don't think I've ever seen a schematic for your original Gyraf (REVJ) board?

What I'm trying to do is wire up a Cinemag CMOQ-2S for the input. http://cinemag.biz/output/PDF/CMOQ-2.pdf
This Cinemag is an output transformer with four windings. It's probably gonna saturate too fast, but I thought I'd try.

I think to use this for a 2:1 input I would reverse it like so:

Input: 
Connect Blue and Violet together.
Connect + to Green
Connect - to Grey

Output:
Use only one of the pairs.
i.e.

Brown goes to +
Red goes to ground
Leave the other pair unconnected.

Is this correct?

Anyway, same concept as the Lundahl but I'm trying to use a Cinemag.

I'm trying to figure out which pins of the input transformer footprint I should be going into.  And if I should be damping the transformer secondaries at all. I'll probably email Cinemag about that, but I'd like to have an actual schematic reference for this input transformer and input pot, (all the way up to the the first transistor)

It's not like any of the UREI units with the T pads.

I'd be quite happy with a hand drawing.
???

« Last Edit: January 11, 2017, 05:13:30 PM by JW »

Whoops

Re: All things G1176 - the new "repost" thread.
« Reply #3808 on: January 11, 2017, 06:55:05 PM »
The problem is, the Gyraf schematic on his site is for the IC Rev G/J input with no other schematic for the input transformer version. And Mako, I don't think I've ever seen a schematic for your original Gyraf (REVJ) board?

Yes you've seen it it the Gyraf Schematic. LOLOLOL
It's the same thing.

Well the G1176 is a project that uses an IC for the input , or Lundhall transformer or OEP transformer. Thats the Project.
PCB's have silkcreen on the transformer mounting positions.

You are really making your life difficult without a reason.  Why not just using what's supposed and build the unit?
Also by sticking to the project if you have any problems with your build people can help you out, if you want to go another way and do your own invention then you will be alone also during troubleshooting as people will not be able to help you out.

using the cinemag line output as an input transformer? really bad idea

If you want to see how a transformer is implemented on the 1176  input, check the 1176 manual and compare the differences of the REV G input to the REV F and REV D:

http://www.jblproservice.com/pdf/vintage%20jbl-urei%20electronics/urei-1176lnmanual.pdf


« Last Edit: January 11, 2017, 10:17:19 PM by Whoops »

JW

Re: All things G1176 - the new "repost" thread.
« Reply #3809 on: January 11, 2017, 07:54:28 PM »
Okay,

Sorry.  Some confusion here. I was asking for a schematic of only the transformer input for this project. I figured it out by pulling the boards again and looking underneath. Took awhile but I figured out how to connect the input Xformer secondaries.

!!!!! Edit: I just realized that the project uses an actual input transformer in the case of the lundahl. I must have been under the impression with all this transformer flipping that they were actually the same transformer for both input and output. Just reversed. Doh.

Anyway, I did  give the cinemag a shot to see how it sounded . It sounds pretty good. I don't know if it beats the IC input though. Which is what I'm trying to do.

I know that the Gyraf schematic is the SAME project, but he never actually bothered putting the input transformer section in any schematic that I can find. And neither did Mnats. That I can find anyway.

The way this transformer is wired up with regards to the input pot is unlike any revision of a UREI 1176. All theirs with Xformer input, use a T pad, up through REV F.

« Last Edit: January 11, 2017, 08:15:11 PM by JW »


JW

Re: All things G1176 - the new "repost" thread.
« Reply #3810 on: January 11, 2017, 08:03:08 PM »
BTW,

There must be a reason UREI made that input with the UTC transformer and T pad like they did.  and never changed it until IC input. I imagine Putnam (or somebody) must have thought to configure it like Gyraf did with the input transformer.

I haven't searched for that discussion yet.

Whoops

Re: All things G1176 - the new "repost" thread.
« Reply #3811 on: January 11, 2017, 08:40:59 PM »
What I'm trying to do is wire up a Cinemag CMOQ-2S for the input. http://cinemag.biz/output/PDF/CMOQ-2.pdf
This Cinemag is an output transformer with four windings. It's probably gonna saturate too fast, but I thought I'd try.

I don't know how BAD this idea is, because the input footprints are for Lundahl and OEP OUTPUT transformers. Using the Cinemag output in this fashion is the same concept, and it certainly CAN'T distort before the OEP did. Or maybe it will. I haven't looked at the specs yet. I just thought I'd give it a shot and see how it sounded . It sounds pretty good. I don't know if it beats the IC input though.

I don't know where did you get the idea that the G1176 used output transformers for the input.

Inputs are:

LUNDAHL LL1540 - "LL1540 is a high impedance, high level line input transformer."

OEP A262A2E - "Each transformer is constructed with dual windings on the primary and secondary providing a wide range of impedance matching ratios to suit many input, interstage and output applications."

In the case of the OEP A262A2E as described it can have different uses.

If you want to have fun or disappointment with your Cinemag CMOQ-2S, connect it  as 2:1 stepdown as you described
 http://mnats.net/1176_revision_j.html

Input:
Connect Blue and Violet together.
Connect + to Green
Connect - to Grey

Output:
Use only one of the pairs.
i.e.

Brown goes to +
Red goes to ground
Leave the other pair unconnected.


reference to the Schematics page 54 and 55
http://www.jblproservice.com/pdf/vintage%20jbl-urei%20electronics/urei-1176lnmanual.pdf

From Mnats G1176 FAQ:

"Q: Which components can I eliminate if I want to use the optional OEP or Lundahl input transformer on my Rev J 1176?

A: From the schematic or screen layer of my boards: IC 2; R1-A, B, C, D, E; R3; R4; C*4 (C35); C30; C31; C32; C33; C34; C100; C101. On the newer Rev J boards these components are contained within a line border to facilitate their identification. "





Whoops

Re: All things G1176 - the new "repost" thread.
« Reply #3812 on: January 11, 2017, 08:52:03 PM »
BTW,

There must be a reason UREI made that input with the UTC transformer and T pad like they did.  and never changed it until IC input. I imagine Putnam (or somebody) must have thought to configure it like Gyraf did with the input transformer.

I haven't searched for that discussion yet.

Imagine at one point UREI was able to buy 1 million UTC 012 for 1 cent each,  it was take it or leave it.
They decided it was a long term investment, so they got them and built compressors with it.
After a while they changed the circuit, but there were still 500.000 UTC 012 units in stock, let's use them.
New revision, still 250.000 in stock.
It gets to the fith revision and the 1 million 012's are gone.
Ok let's buy more transformers, but the price now is 50 cents each, bad news. But there's something called an IC that costs 1 cent now.  Great , dont even need to change the Project Cost scheme.

Bottom line, this is purely fiction, but can also be true
LOL

JW

Re: All things G1176 - the new "repost" thread.
« Reply #3813 on: January 11, 2017, 09:35:52 PM »
Yeah,

You quoted me while I was editing it. Hope that doesn't cause confusion. NO, there is not a Lundahl output being used for the input. My ridiculous error. Sorry everybody.

Whoops

Re: All things G1176 - the new "repost" thread.
« Reply #3814 on: January 11, 2017, 10:19:16 PM »
No worries,
the same OEP is used for both input and output just wired differently so the confusion came from there.

Spencerleehorton

Re: All things G1176 - the new "repost" thread.
« Reply #3815 on: January 27, 2017, 01:53:58 AM »
This may well have been covered so feel free to put me right on this:
I have 3  X G1176 without transformers in and after getting my 1176 blue stripe functioning I would like to change the G1176 to sound either more rev A or rev D.
Rev D seems the better way to go as a fair bit of the circuit is the same.
Needs R4 - 270R on input, C9 to 1uf then the Signal Line amp section needs redoing and GR meter driver is different but hopefully the Gain meter driver will still work?
Using T-pad and input transformer, change line amp and put in output transformer.
Anyone done this?

I feel its worth giving a go to my 1U unit to see how it pans out, i can wind the input and output transformers, just waiting on some t-pads.

any thoughts?
« Last Edit: January 27, 2017, 07:54:11 AM by Spencerleehorton »
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: All things G1176 - the new "repost" thread.
« Reply #3816 on: January 28, 2017, 06:08:08 AM »
I don't quite know what it is but have check all my G1176 versions and all seem to distort in a very fluffy way with the bottom end, which to my ears is not very nice, the 1176 blue stripe doesn't do this, so this is my thinking of changing them as i really want to be able to use them all and if it makes a sound i don't like its just taking up space in my rack.
Does anyone else have this same sound? its difficult to describe but it must be the ICs distorting in a very un musical way compared to the transformers which distort in a more music way?

Any thoughts?
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

gswan

Re: All things G1176 - the new "repost" thread.
« Reply #3817 on: January 28, 2017, 06:13:37 AM »
I don't quite know what it is but have check all my G1176 versions and all seem to distort in a very fluffy way with the bottom end, which to my ears is not very nice, the 1176 blue stripe doesn't do this, so this is my thinking of changing them as i really want to be able to use them all and if it makes a sound i don't like its just taking up space in my rack.
Does anyone else have this same sound? its difficult to describe but it must be the ICs distorting in a very un musical way compared to the transformers which distort in a more music way?

Highly unlikely. If you think there is a problem then you need to perform measurements to quantify it. Once the problem is properly understood then the solution may be simple. This is called engineering :)




Spencerleehorton

Re: All things G1176 - the new "repost" thread.
« Reply #3818 on: January 28, 2017, 07:43:19 AM »
thanks for the insight :)

but does seem weird that all 3 different units makes the same sound.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

gswan

Re: All things G1176 - the new "repost" thread.
« Reply #3819 on: January 28, 2017, 05:06:25 PM »
thanks for the insight :)

but does seem weird that all 3 different units makes the same sound.

Yes. It could be all 3 units, or it could be a common factor external to all 3 units.


 

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