Modding UA 1176 w/ Cinemag input to UTC

[kakumei47]

I have a couple reissue 1176s, and one of mine had the Cinemag transformer (a big run in the middle of production has this as the input pot was unavailable for a while). I wasn't as into that one as the other reissue with Magnetica input transformer, so I modded the input section with a vintage input pot and UTC 0-12.

The results are fantastic. Clear difference especially when pushing the input even over the reissue with the more original style transformer (more forward with better presence and clarity in the high mids...my reissue just sounded a little dull and veiled in comparison). These are two separate units, so I can't scientifically claim it's because of the mods alone, but for $200 in parts a worthwhile mod at least if you have the version with Cinemag input without the dual-ganged input pot.

It's not too hard to do this, but I thought I'd post how to do it to save other people time if you want to try this (and I get so many good ideas from this forum but don't post a lot myself!). I didn't have schematics for the reissue version, but I do owe a big thanks to UA's support team, who were very helpful and gave me some really useful wiring info to get started with this.

Sorry if this seems too basic, but I know we have people with a huge range of experience here.

Pictures and steps to follow.

Parts needed:
UTC 0-12 transformer
Mu metal shield UTC 0-17
Mounting bracket for above
1 270ohm resistor
T-bridge input pot. I used a vintage one but you can get them from studio electronics (http://www.studioelectronics.biz/sunshop/index.php?l=product_detail&p=1151)
You'll also need a foot or so of console or mic cable.

 

[kakumei47]

Here's the version I'm talking about modding: See the Cinemag input pot and the single-gang pot on the input:

 

[kakumei47]

and input pot:

 

[kakumei47]

Remove R89, R90, R91, R92, and the input transformer.
You don't have to jumper those resistors or anything...you're just not going to use that section.

Change R4 (originally 15k) to a 270 ohm resistor.

You can also desolder the wires at points 36/37 and 2/3 and the wire for the transformer shield (right near R4). You should just completely pull the cable that goes to 2/3 because it's too short to reuse, but 36/37 is plenty long enough to reach your new transformer. You don't need the transformer shield cable.

 

[kakumei47]

Mounted the input pot and a bracket for the transformer (side of chassis).

To connect to the pot from the inputs:
Wire a piece of console cable to the barrier strip where the wire to points 2/3 was. If you're facing from the front of the unit, the hot side of this goes to the first tier of the pot on the right-side resistor, and the cold goes to the lug with no resistors.

To connect pot to IPT:
Connect the lug with the resistor on the left (1st tier of pot) to pin 1 on the input transformer. The lug with no resistors gets connected to pin 5 of the transformer.

I copied the grounding from the other reissue, which was different from the cinemag reissue. I connected the shields at the pot side, but not the terminal strip or IPT side. Don't think that matters a ton though.

 

[kakumei47]

Then I hooked up pin 6 of the 0-12 input transformer to pin 8 of the old transformer on the pcb, and pin 8 of the 0-12 to pin 2 of the pcb.

That's it...pretty simple and a nice change for $200 or so...
I'll post some A/B clips if I get a chance...