Balancing DOA output

[hejsan]

So, I've been looking at various methods of acheiving balanced line output.
The ones I found being used where 3
1) Use 2 opamps to do the job as in the gssl output circuit
2) Use an integrated Balanced Line Driver such as Analog Devises' SSM2142
3) Use a transformer

For my purposes, In an all discrete circuit I would not want to send the audio suddenly through a chip just to acheive balance. So that rules out contestant number 2 and 1 as well unless the opamps are descrete.
But using 2 DOA's just to balance a line seems like overkill.

For my purposes where I have to make quite a few of this circuit, I must also rule out contestant number 3, the transformer on account of price.

So what I am looking for is some simple transistor based circuit that has the abillity to receive an unbalanced signal and send out two signals out of fase with each other.

So I ask you wise people of this counsil: Could I somehow use a supermatched transistor pair or quads to acheive this in a way that it does'nt alter the signal to any great extent and would also have some drive for the line and keep it simple?

The prospects are:
SSM2210 - Audio Dual Matched NPN Transistor
MAT02 - Low Noise, Matched Dual Monolithic Transistor
MAT04 - Matched Monolithic Quad Transistor
LM394BH - You know the guy
And I read somewhere on the forum about matched npn/pnp pairs being available.

Does such a circuit exist or does anyone feel that it could easily be made?

hejsan

 

[cuelist]

[quote author="hejsan"]Does such a circuit exist or does anyone feel that it could easily be made? hejsan[/quote]

Balanced outputs is much more than two signal of opposite polarity. Making two complementary outputs would not require matched transistors anyway.

You suggest you read up on balanced line technology, I am pretty sure there are some 'whitepapers' on the subject from those who make the SSM and THAT chips. It may be IC's (that you don't like) but the same principles apply.

Or just use a transformer...

 

[bcarso]

Agree with Mats---you don't need specific tightly-matched transistors.

Check out some of the papers on the Jensen Transformers site as well.

 

[Svart]

Producing DOAs in large numbers is cheaper than you think. remember that you'll be buying in bulk and that usually makes things considerably cheaper. I built about 24 of Gainbloaks for less than 100$