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[ajcamlet]

As far as balancing output transformers go, can you describe the personalities of the differnt manufacturers of transformers- jensen/sowter/carnhill/lundahl....

do these companies have a signautre personality in their products?

[zmix]

Here is a good place to start:

http://www.jlmaudio.com/Neve%20transformer%20info.htm

[volki]

zmix, interesting link! now that's what i call practical info.

ajcamlet, the link is about different substitutes of input xformers, but the same principle applies to output xformers, of course =) i couldn't describe the differences of every single brand , since i mostly have gear using german made stuff (haufe, pikatron), but maybe some thoughts help, too:

just like that link revealed different behaviour of different xformers with the same circuit, the same xformer will not exhibit the same personality with different circuits, either. if i'm not completely nut's i'd say that e.g. the infamous neve o/p circuit using the lo1066 receives it's special sonic character due the dc-bias of the xformer's primary winding. also, some o/p xformers are 1:1, some others may have different ratio's, some may just be inserted at the unbal. out without any damping network at the secondary, others will exhibit ringing or overshoot if with network omitted.

the german telefunken/tab/neumann solid state stuff using pikatron and haufe xformes is mostly pretty clean, or "neutral" if you will (just my 2 cents, and just regarding the very xformers, anyway). jensen and lundahl are also brands which seem to receive those attributes... low distortion, wide freq. range. i have a few cadac modules with marinair i/p xformers which definitely exhibit some colour with a decent amount of LF signal applied  

gonna stop babbling, hope that helps you at all?

[ajcamlet]

Certainly does help.  This is all new to me and i, as a novice am trying to educate myself.

Reason:

I have an Amek Angela console from circa 1985.  The main outs are unbalanced.  I'm toying with the idea of balancing them with transformers and am in the "gathering of information mode"  I'm not all that interested in the Xformers being too transparant per se, and am looking actually for some slight color.  90% of my work is rock music so, i'm not afraid to commiting to a colored sound....

thanks very much for you  reply.....

[volki]

do you know what the o/p impedance of your console is? unbalanced *consumer* stuff usually has a pretty high Z's, although i would expect something like an amek to have a fairly low Z.out. - the thing is, transformer distortion increases with source resistance - which equals the console's o/p Z in this case. the "colour" you're after is mostly due to the trannie's nonlinear distortion in the LF region, but you wanna be able to control it, and not end up with a trannie distorting too much for your liking, because it was not designed for your desk's o/p Z.

max. source Z is one of the things that should be mentioned in a trannie's datasheet, though.

[ajcamlet]

Specs on the Angela outs are "less than 100 ohms"

[Geoff_T]

ajcamlet wrote on Wed, 17 November 2004 09:09

Specs on the Angela outs are "less than 100 ohms"

Hi

That still sounds pretty high and suspiciously like there are protection resistors in series with the output.

A circuit diagram would be handy to resolve that!

[ajcamlet]

Hi Geoff....

thanks for your reply and interest.....i'll scan the Schematic for the Master module and post.......

thanks again for your interest and help!
alan camlet

[bluemuse]

I'll post this for Alan.

[Geoff_T]

bluemuse wrote on Thu, 18 November 2004 16:13

I'll post this for Alan.

Hi

That was handy and, as suspected, there's 47 ohm protection resistors (which also work like a small inductor) in the outputs of the 5534.... you'd have to remove them. I note that the coupling cap has been upped to 220uF from 100uF and it wouldn't do any harm using 470uF if you are going to hang a transformer on that.

Neve drove 5534's into step up transformers on the outputs of the 54 range of consoles. In your case I'd use a 1:1 output transformer to keep levels consistant. Neve used to have a sexy toroidal output transformer that they used on BBC consoles and that crept into their later music consoles. Perhaps some brokers may have a few kicking around?

[tom eaton]

Hey Alan-

I actually had a long conversation with Bill Isenberg at Jensen about the best way to interface that console with balanced gear, which led to the installation of the 47ohm resistors at the outputs of the console between the negative and ground poles of the main buss patch points.  This is typically called "impedance balanced" and gives you the benefit of common mode cancellation without any additional color.  If I had done it really well, I would have made a home run balanced cable run to the master module and put the additional resistors there, as close to the original 47ohm output resistors as possible.

With that particular board, if you're looking for more color, I'd look into un-doing some of Jim William's work, as his approach when he did the master section was to make it as transparent as possible.  I'd certainly get Jim's opinion about what transformer he'd hang on the end of the 2 mix and how it would interact with his circuit when considering trying to get a more colored output.

Hope the board is doing you well!

-tom

[tom eaton]

Any hey...that schematic is copyrighted to Jim.  He gave it to me because I paid him for it.  You got it 'cause you bought the board from me.  Not really sure it's for public consumption.

-tom

[ajcamlet]

Hey Tom!

Yes, I'm digging the Angela!  And the mastersection is indeed Nice work.  Its super quiet.  The routing options on the A10 modules have my head swimming at times....we traced the toggle that Rob Mounsey had placed on the A10's and found that its a post fader send to the busses....

With regard to the transformers on the out- it seems like an interesting project and i contacted Jim to get his opinion - we'll see what he says....

aha----correct...schematic removed...

[tom eaton]

Hey Alan-

Good detective work!  Yeah, that board is damn quiet.  

Let us know what you end up with and the sonic results-

Take care-

tom

[Geoff_T]

TER wrote on Fri, 19 November 2004 08:28

Hey Alan- I actually had a long conversation with Bill Isenberg at Jensen about the best way to interface that console with balanced gear, which led to the installation of the 47ohm resistors at the outputs of the console between the negative and ground poles of the main buss patch points.  This is typically called "impedance balanced" and gives you the benefit of common mode cancellation without any additional color.  -tom

Hi

That's an interesting concept... how you can get good common mode rejection by adding two resistors to an unbalanced output.

We used to measure CMRR by putting two precision matched resistors across a balanced output, connected together, and the level measured between the junction of the two resistors and the 0v.

I wonder what rejection ratio that system obtained?



PS A similar concept is used on the quazi balanced virtual earth bussing on the 51 and V series Neve consoles but that's to do with splitting the input and output 0v to the mix amp.