Understanding UTC transformer

[SteveM]

I was wondering if anyone could help me understand this UTC transformer I have. I think it's supposed to be a 600 ohms to line level but it seems just as loud with it as it does without it. What I'm trying to do is go from a preamp balanced out into a line level -10 input on the mixer. I have a UTC ha 101 transformer. If you look at this http://www.clarisonus.com/Archives/Trans/UTC_conn.pdf it shows how it's supposed to be hooked up. So primary is 6 and secondary is 31 and chart F shows the set up.

So I have 1 and 6 going to the balanced out and 3 and 4 tied together. Then I have 7 going to hot on the rca out and 10 on the ground wire, 8 and 9 are tied together.

I don't know what the "single grid" "two grids " means nor "CT"

But what exactly so the terms primary and secondary indicate? Is this considered and output transformer?

What exactly is "grid" though and does it matter which terminal the hot pin from the xlr is hooked up to? I'm just trying to get a better overall understanding of these.

 

[dementedchord]

if i read that right... this is not an impedence matching transformer you got there... it's an ultralinear output tranny for a tube amp... it's used in a special type of pentode amp... popular with hi-fi types... used in old sunn and ampeg gear...

 

[SteveM]

if i read that right... this is not an impedence matching transformer you got there... it's an ultralinear output tranny for a tube amp... it's used in a special type of pentode amp... popular with hi-fi types... used in old sunn and ampeg gear...

Thanks for answering DC. What exactly does that mean though? Does that mean it does not change voltage output and is only for going from balanced to unbalanced?

I got this with a Concertone reel to reel and preamp. Never understood what it was for but it came with an rca jack soldered on the secondary side.

 

[Blue Jinn]

http://www.bunkerofdoom.com/xfm/UTC_1955_WEB/027.jpg

This appears to be a mic input **step up** transformer. It isn't an output transformer but an input transformer with a 1:14 *gain* (sqrt of 120000/600) (but it says split, so maybe it is 1:7 gain) as it is apparently designed to drive two tubes if I'm interpreting P-P grids. (Push Pull?) That part is confusing to me.

Grid refers to tube grid. This is 50-600 ohms input to 120,000 ohms outpput split. I'm not sure what it is you're trying to do, but I'm assuming you want to go from a +4dB balanced output to a -10dB unbalanced input. In that case you want a 4:1 step down transformer, not a step up transformer like this one.

An ultralinear output transformer would be something like 6,000 ohms to 8 ohms.

AFAICT this xfrmr is desingned for an input on a mic preamp, which would make sense given the source.

 

[SteveM]

Thanks Blue Jinn. That is what I wanted to do, go to -10 input from +4 output of preamp but it sounds like this is not the thing to use. I'll probably just get another LA 40 when I find one, I tried the one I have today with and it works great. But I'd still like to understand what this is for. I still don't really get it. Which side would the mic hook up to and what kind of mic I wonder? The preamp has a hi z input.

 

[Dr ZEE]

.. to -10 input from +4 output of preamp ....

you can do this with A-20 (if you really want to, that is .. ) , you can find those on eBay from time to time, but don't buy them for more than something like 40 bucks or so.

I had few of those., but no more...sold them all. Those are great transformers for audio, but I figured that they don't do a thing , besides "transforming" , isolating, bal/unbal interfacing (which they do GREAT ...), but non of the above I really practically need ... so they are gone
*************
as for HA-101:

"two grids" configuration is for Push-Pull type amplifier, so 7 and 10 are connected to grids of the tubes (one positive the other negative swings), while 9+8 are "c.t." - center tap (zero volts) ...

..Which side would the mic hook up ....

The mic connected to one of the available impedance "configurations" as per primary #6 in that pdf

*******
P.S.
Steve, you are asking for unnecessary headache

 

[SteveM]

you can do this with A-20 (if you really want to, that is .. ) , you can find those on eBay from time to time, but don't buy them for more than something like 40 bucks or so.

I had few of those., but no more...sold them all. Those are great transformers for audio, but I figured that they don't do a thing , besides "transforming" , isolating, bal/unbal interfacing (which they do GREAT ...), but non of the above I really practically need ... so they are gone
*************
as for HA-101:

*******
P.S.
Steve, you are asking for unnecessary headache

As usual. haha

I know we talked about this thing before. I don't think I showed you the chart though. Thanks Mike. CT = center tap, that's right. So what I thought was the unbalanced side goes to grid?

I probably won't need it for this but it's still good to know what it is. I might try it sometime.

 

[dementedchord]

my bad....

 

[Blue Jinn]

Thanks Blue Jinn. That is what I wanted to do, go to -10 input from +4 output of preamp but it sounds like this is not the thing to use. I'll probably just get another LA 40 when I find one, I tried the one I have today with and it works great. But I'd still like to understand what this is for. I still don't really get it. Which side would the mic hook up to and what kind of mic I wonder? The preamp has a hi z input.

As I said before, you can do this, but you need a 4:1 transformer, probably somehting like a 10kohm to 600ohm transformer. This one won't work even if you wire it backwards the voltage drop would be too much. As also said the mic would hookup to the variable impedence side and the secondary to a tube input stage. If you peruse the jensen transformer site, you'll find many schematics and datasheets that explain a lot of this.

Also, if you peruse the diy forums at prodigy-pro you'll find information on how input transformers work.

 

[SteveM]

Thanks Blue Jinn.

Would I be foolish to sell this one? I just saw one go on ebay for $120. I bought the whole concertone preamp and reel with UTC for $10

 

[Dr ZEE]

Steve, you can try using it as LoZ mic input for concertone into "HI IMP. INPUT" and see how it works (or, say, how it "sounds").
See the diagram attached. While there you also can try different inmpedance option on primary side as per #6 in pdf, (if you feel like experimenting ).
Turn the level pot down first when trying this, then turn up slowly.

So if you find this to be a "sexy" input configuration, then you can actually install HA-101 into Concertone and add XLR mic input. Also you'll have to deal a bit with how to place the transformer the best way and connect it and screen/ground all the connecting leads correctly etc. You know how it is there...heh heh , if don't pay attention you get a "mystery buzz" or something

Generally speaking, as I understand, if you do this, you pretty much get what you already have when using your adaptor. But hey, you never know. Maybe you get some "meat" there.
From my experience, I didn't hear any extra beef, but instead, the transformers just were "perfectly" passing the signal. So it's cool, but nothing speacial, really. I may be wrong, though

 

[SteveM]

Mike, Thanks for the diagram!

What about the terminal input screws in back? Can't I use those instead of the high z input? I don't think I've tried this. (but I'm not sure)

Also I don't understand "the green jumper" Isn't the screen connected to 3&4, 8&10, respectively? Or that's is what you mean, indicating green jumpers on UTC in diagram?

This could be good if I'm using the phantom power box.

 

[Dr ZEE]

Steve, "green-jumpers" have nothing to do with cables screens ...I just 'placed' that note there under the black connector "wire" that connects screens of the cables. The green jumpers are just the connections between pins of the transformer as shown.
Pin "1" of XLR connected to the screen of the mic cable and to the screen of the short cable from transformer secondary to 1/4" plug, and connected to the sleeve of the plug as well. I've made this diagram specifically as for your situation.
**********
I am not sure what would happen if you connect secondary of the HA-101 with "Line Input Bridging" terminals, but you can try it too, it would not hurt. If you do that, than instead of 1/4" plug, simply use very short wires and connect: "7" to left terminal and "10" to right terminal. Do not connect anything to C.T. terminal. For that you don't really need a screened cable, just make the wires very short , 2inch or so, so the transformer is sitting right next to the bridging input. It should be fine for the experiment.
Also the screen of the mic cable, then should be connected to the Concertone's chassis - ground, that is.
Now, here's why I've said that you are asking for a "headache"...heh heh heh ...
You see, now you need to check again, is the C.T. terminal of that bridging input connected to the chassis? It should not be for the "experiment above". But it should, if you would use it as "designed" for line level balanced input.

OK. The most important thing for you to keep in mind, that if you use that bridging input (instead of Hi IMP 1/4"), then the signal does not go through the first V1 stage, but instead "goes" via bridging transformer to "mix point" ( see concertone_preamp_signal_path.jpg diargam, if you still have it, that I've made back then... follow the green signal path there) and from there to the "split-stage".
Soooooooooooooo.... to cut it short, I think that you will not get enough if any gain for the mic signal this way. Well, I can't guess for sure. Try and see what you get that way.
Also, what ever you get, this is NOT a right way to do it, that's for sure ..huh huh

In theory there are at least two more different ways (that I can think of) of how to impliment this transformer as LoZ mic input into this specific system, but this would mean modifing it again and in rather "drammatic' way, I must say. It may turn out for better or may not. It would turn the preamp into diffrent "type". Well, Steve, honestly, I don't think you want to go through this. Even if you get something diffrent, you will lose what you have now...so, what's the point?, You know what I mean.

arghhhhhhhhh, good luck.
drop a note how is going

 

[EvLoutonian]

UTC project

Hi Steve,

How did your experiments with this transformer go?

Did you end up concluding if the secondary is 120k or 60 k ohms? (x2?)
Or either possible?

I'm just learning, but I reckon I need to find a mic input transformer - something like this one - for resurrecting an old PRESTO RECORDING CORP pre module (circa 1940's I reckon!)

Pri: 50 / 500 ohms
Sec: 60k ohms

Seems to be what's indicated on the schematic.

Does that look like what you have?

Thanks!
Evan (first post on Home Recording!)

Mike, Thanks for the diagram!

What about the terminal input screws in back? Can't I use those instead of the high z input? I don't think I've tried this. (but I'm not sure)

Also I don't understand "the green jumper" Isn't the screen connected to 3&4, 8&10, respectively? Or that's is what you mean, indicating green jumpers on UTC in diagram?

This could be good if I'm using the phantom power box.

 

[SteveM]

Hi Evan,

I didn't go far at all with it. I didn't really have a use for it and never got much further into it. After input from Zee and the others I think I concluded it was for tube amplification but my knowledge is so limited on it I didn't completely grasp or retain it.

I think it must have been used to go to an amplifier from the reel preamp. That was my guess. But as far as the inner specs on it I have no idea. I actually just sold this one too.