Splitting preamp output with LL5402, impedance matching etc. Help needed :)

[ln76d]

Hi Guys!

I need some advice/help.
I want to make direct output from console preamp module.
I want to use LL5402 for it.

http://www.lundahl.se/wp-content/uploads/datasheets/5402.pdf

Simplified circuit attached (sorry for quality).
It's only output stage. Marked on red is audio path for microphone preamp (it is also for stereo line "B"channel).
Yellow - reference point "BIAS 2".
Let say i want to connect transformer after phase switch and before channel selection switch.
Since the LL5402 needs very low source impedance how should i connect it to the high impedance output?
Output level at this point is -6dB.
What ratio i should use  for better  and simplified work - 2:1, 1:1, 1:2?
Should i connect in parallel with R96(R97) 22k  other resistor to lower the impedance?
How this could affect on standard working with balancing output drivers - for stereo line as example?
I have stuck on that

 

[ln76d]

Is Anybody Out There?  ???

 

[radardoug]

It looks like that circuit is using single ended supplies, and so the point you picked could have d.c. on it. You need to add a buffer to drive the transformer.

 

[RuudNL]

It looks like that circuit is using single ended supplies

I don't think so! The non-inverting input of the OpAmp is tied to ground, so the output of IC11A should be (close to) zero volts.
If you want to use a 1:2 transformer ratio, the drive capabilty of a 5534 may be (too) low, especially if you are loading the transformer with a relative low impedance.
A 1:1 ratio would give less problems, a 5534 should be capable to drive 600 ohms.
It may be an idea to choose a higher value for C84, to improve the LF response with low impedance loads.

 

[ln76d]

Thanks Guys!

It looks like that circuit is using single ended supplies, and so the point you picked could have d.c. on it. You need to add a buffer to drive the transformer.

Yes, it's a single ended supply. 
I picked that point, cause the "BIAS2" is reference for the output balancing drivers also.
There are coupling caps (C84 and C69) before those points also.
Ajjj... a buffer you say... I was hoping that would be much simpler  :-\

It looks like that circuit is using single ended supplies

I don't think so! The non-inverting input of the OpAmp is tied to ground, so the output of IC11A should be (close to) zero volts.
If you want to use a 1:2 transformer ratio, the drive capabilty of a 5534 may be (too) low, especially if you are loading the transformer with a relative low impedance.
A 1:1 ratio would give less problems, a 5534 should be capable to drive 600 ohms.
It may be an idea to choose a higher value for C84, to improve the LF response with low impedance loads.

In attachment is the rest of the circuit. The big "rectangle"  section on this schematic is that part from the previous.
The IC11 is only gain trim stage - if that info is usefull somehow.

Sorry, i had to edit that crap...

 

[RuudNL]

OK, I overlooked the Bias 2, I thought the non-inverting input was connected to ground.
In that case you MUST use a blocking capacitor!

 

[ln76d]

Let say it would be connected to the soundcard input with the impedance higher than 5kΩ

I had to edit this post, becuase i found some answers and overall it was really emberassing  ;D
I left the only passage referring to PRR question

 

[PRR]

Why do you need a transformer, an exotic transformer, to drive a sound card?

 

[ln76d]

Why do you need a transformer, an exotic transformer, to drive a sound card?

Thank you PRR for your interest in the topic, I really appreciate

I would like to make extra balanced direct outputs from preamps and because i have  enough LL5402 transformers to make it.

Sorry for so many edits, some had to be done