UA 6176 - 610MkII Output Transformers

[dirtyhanfri]

Hi

A friend of mine has both UA 6176 and 610 MkII channel strips and wants to use the preamp section of them to bring up the stereo mix coming from a passive summing mixer. The problem is the 6176 is around 6db´s lower in the same setting. He brought them to me to compare thinking it was a failure in the 6176, but after tracing the signal I found the loss comes from the output transformer on the 6176. 610MkII uses a Cinemag CM 2810 (9,6K:600r) and 6176 uses an unknown (at least for me) output transformer. You can see it here

Googling EIA606 MS 1335 I found this web http://www.unclespot.com/transformerEIAcodes.html and it looks like it´s a Woodward - Schumacher transformer, but I can´t find anything relevant.

ASSuming the preamp circuitry is the same (more or less, in the construction there are huge differences, like the use of SMD components in the 610MkII) the output transformer should be swappable right? Because I´m thinking in buy a Cinemag CM2810 for the 6176, expecting to have the same level at the preamp output, should it be ok?


EDIT: I keep thinking about it, I recall the output transformer in the 610MkII is soldered to the pcb, but has visible pins, maybe I can get the signal from the preamp output of the 6176 (before the output transformer), put it into the preamp output transformer in the 610MkII and measure the output (with 610MkII unpowered), maybe that way I could try if it works, I´m a bit scared to damage something, nothing to worry about if I just test the transformer with no power in the unit right?

 

[joaquins]

A schematic would help us to help you, best practice would be take both transformers out and make the swap, but first you need to know something about the output stage at least, if there is any DC current on the OT and if there is how much, before testing anything so you don't have troubles.

JS

 

[dirtyhanfri]

Thanks for the answer.

I din´t found any universal audio schematic, but I´ve found some 610 schematics which looks similar to the preamp in 6176, not so sure about 610mkII actually, anyway I will measure DC at both preamps output transformer before testing anything

 

[radardoug]

Using two different preamps on your stereo bus is not a good idea. Especially when you don't know how close they are to each other. On the other hand, if you want to produce really bad recordings with phase problems between channels, go right ahead!

 

[dirtyhanfri]

Using two different preamps on your stereo bus is not a good idea. Especially when you don't know how close they are to each other. On the other hand, if you want to produce really bad recordings with phase problems between channels, go right ahead!

Actually, if you could read the first post in this thread would know it's not my deal, anyway, thanks for the helpful post, you made my day...

Any other useful bit of wisdom?

 

[radardoug]

Never step in front of a moving train.......

 

[ruairioflaherty]

Doug's advice could have been stated with a little more charm but I think he's right, using two different preamps could lead to phase issues.  It might sound ok (ish) in stereo but it could be very bad in mono.  Or it could be fine.

Based on what I've heard of the UA channel strips there's no way I'd use them for a summing amp but that's personal opinion.

Could you offer to help your buddy build a nice summing amp?  Maybe something based an the Classic API ACA?

Ruairi

P.S. if your friend is determined to use the UA strips why not just level match using tones and bump the gain control on the quieter unit?

 

[dirtyhanfri]

Of course he is right, I know

I would never run a mix through a pair of different preamps, and I wouldn't use these kind of preamps for summing amps neither.

I told him about build a summing amp, something nice and useful, but he told me he likes that way, I'm not a "technical police" so he can do whatever he wants with his mixes, I won't suffer.

P.S. if your friend is determined to use the UA strips why not just level match using tones and bump the gain control on the quieter unit?

That was my first advice but he says doing that gets different "character" from the preamps.

I'm gonna explain him that even with the same transformer and giving the same level probably the differences will be still there.