All things G1176 - the new "repost" thread.

[EvLoutonian]

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]

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.

 

[EvLoutonian]

ok, i think i get it.  CHEERS!
Shall try it and see how it go. 
Thanks again.
Evan

 

[JW]

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.
???

 

[Whoops]

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

 

[JW]

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.

 

[JW]

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]

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]

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]

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]

No worries,
the same OEP is used for both input and output just wired differently so the confusion came from there.

 

[Spencerleehorton]

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?

 

[Spencerleehorton]

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?

 

[gswan]

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]

thanks for the insight

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

 

[gswan]

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.

 

[Whoops]

I never had that problem with my G1176 or any of the other versions I built.

I would follow gwan advice, do measurements or at least record audio of the problem you're having

 

[Spencerleehorton]

I will check all voltages and setup and see how far it's all out, then record some audio and let you guys listen to what I'm hearing.

 

[JW]

Does the 470uF output cap need to be 35V? (Original had a 40V rating) I have a nice 25V bipolar, but not sure I should use it.

Also, what is the function of C10? From UREI revision F to G this changed from a .15uF to 1uF.

 

[Mzrt]

Thanks so much for this great thread! One question though that I didn't find the answer for.

Has somebody a working 1176 open right now and can tell me the voltage readings at Ratio 1:20 on pin 19 and 21, e.g. before and after the FDH333 diodes? It would help me a lot to find the mistake mine has. I triple checked the voltages on the transistors, the values of resistors, caps directions, everything seems correct but the voltage difference before (-6.54V) and after (-0.84V) the diodes is 5.7V but the signal coming from the GR control amp is about 1V (AC) so the FDH333 diode can't rectify the signal. Or am I misunderstanding the construction? Another thing, is it normal that the LL1540 Input Transformer only gives out 0.5V of the 0.75V input signal?

Any advice would be more than appreciated!
Greets, Moritz