Polarity reverse in a balanced to unbalanced input

[thakava]

Hi gang!

Building a line in console that will be unbalanced, but would like to have a polarity reverse at the input. Would putting a input transformer like this make that possible?

Best/
Tom

 

[JohnRoberts]

That seems like an expensive way to accomplish that. A simple inverting op amp stage can generate a polarity inversion inexpensively.

JR

 

[john12ax7]

You can just flip the hot and cold at the input stage, would work whether it's an electronic stage or a transformer.

 

[Bo Deadly]

You can just flip the hot and cold at the input stage, would work whether it's an electronic stage or a transformer.

Not if it's unbalanced out to unbalanced in. Then 0V reference have to be connected together.

If it's a transformer then yes, the hot and cold could be swapped.

But you could do the same with a THAT 1206 IC and it would be a lot cheaper.

 

[john12ax7]

The OP specifically stated balanced to unbalanced input.

 

[pucho812]

The OP specifically stated balanced to unbalanced input.

I don’t see where he did…

 

[scott2000]

It's in the title

 

[pucho812]

It's in the title

Yes but in the op he says
Building a line in console that will be unbalanced, but would like to have a polarity reverse at the input
See my cornfusion.

 

[john12ax7]

I got it from the title. But maybe we need some clarification of the details.

 

[thakava]

Thanks!
I mean:
the inputs are (could be) balanced, from there-> the signal travelling inside is unbalanced eqs, auxes, then into a summing amp Neumann 475.

Best/
Tom

 

[Stack]

Hi gang!

Building a line in console that will be unbalanced, but would like to have a polarity reverse at the input. Would putting a input transformer like this make that possible?

Best/
Tom

Transformers by the nature of their design will definitely colour the quality of sound and provide isolation from outside RF anomolies. I’ve built a 32 channel +4 line level mixer that was basically a passive monitor mixer. Simple enough. Buss wire to each channel using a ten k iso resistor for each potentiometer. We had custom Claropots, plastic conductive, expensive to have them made. Many large frame consoles cheapen out on the pots. Many use carbon pots and those tend to become noisey and aggrivating. We spent the extra money buying the pots and switches ( all gold contact ).
It still works today ( 5534s) on all bussing outputs, the two mix too.
In hindsight, I should have added a buffered fader amps and pan pots on all of them. Gain stages were set safely below zero on a vu meter. Typical positioning on each fader gain stage was around 1-2pm. A buffering amp would bring it into a safe zone in terms of fader linearity & response. Not a huge negative, just a wish.
When I began engineering albums, most consoles were hybrid builds by people holding aerospace tech jobs. They needed a hobby
SpectraSonics was the buzz word floating around Hollywood Studios.

 

[Stack]

I wouldn’t get cute adding a bunch of redundant opamps into any console. Class A construction can get very pricey. AD, the chip manufacturer, has newer, faster slews, better performing opamps today but that ole 5534 has been in the channels mixing many great albums and recordings for a long time. Give it enough voltage & current and it’ll sound great for most things. A patch point will ideally require a buffering stage, as well.

 

[JohnRoberts]

I wouldn’t get cute adding a bunch of redundant opamps into any console. Class A construction can get very pricey. AD, the chip manufacturer, has newer, faster slews, better performing opamps today but that ole 5534 has been in the channels mixing many great albums and recordings for a long time. Give it enough voltage & current and it’ll sound great for most things. A patch point will ideally require a buffering stage, as well.

I would add an op amp before adding a transformer just to realize a polarity inversion.

I don't recall seeing many (any?) class A consoles, while everything was class A if you go back far enough.

JR

PS; Yes the 5534 is an old soldier that has performed well over the decades, at least since the 70s.

 

[pucho812]

polarity reversal can be as simple as using a dpdt push button switch and wiring it so that in one position it’s in polarity and in a second position it’s out of polarity. The rest from there can be achieved in many forms, if it were me I would use that chips.

 

[Stack]

I would add an op amp before adding a transformer just to realize a polarity inversion.

I don't recall seeing many (any?) class A consoles, while everything was class A if you go back far enough.

JR

PS; Yes the 5534 is an old soldier that has performed well over the decades, at least since the 70s.

I'm pretty sure all consoles are single ended inside. The cost of manufacturing requires the IC amp route. I'd consider being lucky if a bipolar voyage supply was the power system used....then you could retrofit with a quicker performing amp into any console.
Neve made a console so full of heat generating opamps, it was like working over a hot oven all the time...I believe it was called the, Neve VR....Ugggg....Not a great sounding mixer either. Wasn't an SSL fan either. They fixed it with the 9000.

 

[Bo Deadly]

I'm pretty sure all consoles are single ended inside.

You're confusing single-ended with unbalanced which is not the same thing. A single-ended amplifier is one where the active device is only sinking or sourcing current but not both. An op amp circuit is not single-ended but it is unbalanced in that there is one signal line relative to 0V.

 

[Stack]

Probably so…. I’m confused over a lot of things most times. I do recall some consoles requiring bipolar supplies and some only + & -. The bipolar aspect’s also an API construct. The MCI416 lifted a few conceptual ideas too. Dave Harrison designed that first inline console.

 

[JohnRoberts]

How about a proper welcome, hi and welcome.

There seems to be some conflating unbalanced, with singled ended, with class A......

It is the nature of internet conversations to veer off all over the place.

Time to focus on preparing to have a happy new year, we can sort out the classes and balance later.

JR

 

[thakava]

Hi gang,
Thanks for all replies.
As a reference: I had an early Trident B-range a while ago, that was unbalanced, except for the mic input (Zutt transformer) it only had a polarity reverse on mic input, not the line.
I was told back then that if I wanted that feature a line transformer would have to be added. Never did that.
It was frustrating not to have that feature. So here I’m thinking I’ll add it to my console build.

Best//
Tom

 

[gyraf]

If you're building from scratch, I'd go with JR's suggestion in post1: Inverting opamp

pol_inverse.gif shows two channels
Calrec PQ1347_input_polarity.JPG shows calrec's implementation with 5532 opamp

esp pages on this: Phase Inversion Switch

/Jakob E.