Balance to unbalance problem

[simonsez]

Hi guys, may be you can help me. I build this balancer circuit below for my SSL9K, but when i connect it to unbalanced output (- connect to ground) then the opamp 5532 became very hot. :-X

Should i put the output cap there?

Many thanks,

Simon

 

[Samuel Groner]

I'd need to look in detail at the circuit, but likely if you short the inverting output to ground the corresponding opamp dumps a lot of current into ground.

Samuel

 

[s2udio]

Why use the balancer circuit if your using unbalanced.........use a seperate output jack
For unbalanced and the XLR  for balanced operation ,the jack socket (switching type) can be used,
To connect the Input to the balancer board when unbalanced is not being used.

 

[simonsez]

So, is there a simple solution for that circuit to make it accept both balanced or unbalanced connection? (without adding extra unbalanced jack like s2udio mention).


Simon

 

[abbey road d enfer]

Hi guys, may be you can help me. I build this balancer circuit below for my SSL9K, but when i connect it to unbalanced output (- connect to ground) then the opamp 5532 became very hot. :-X

Should i put the output cap there?

Many thanks,

Simon

Your schemo is wrong. You must try to simulate it.
What you need is resistors in the outputs. Output caps are not theoretically necessary, but practically, you need them to fight DC offsets.

 

[simonsez]

That circuit was from grace mic pre output balancer, it's fine when connected to balanced load. I will try to put 75 ohms resistor in the output, and see .... Many thanks...


Simon

 

[abbey road d enfer]

I think you got the schemo wrong. The simulations show that it works correctly only when both legs are not heavily loaded. Grounding any of the outputs gives incorrect signals.

 

[JohnRoberts]

I agree with Abbey, that schematic looks like it is incomplete/incorrect..  Look for a different version to copy, preferably one with some buildout resistors, etc.

perhaps like this one... 

http://sound.westhost.com/balance.htm

I have not checked out this actual circuit but it looks a lot better, en passant.  I think I typically put 6dB of gain in such stages to take full advantage of 2x signal swing, but unity gain will work, especially if you anticipate driving unbalanced loads.

JR

 

[simonsez]

How about this one? Sorry, i can't use the circuit simulator.. :-[ :-[


Many thanks,

Simon

 

[JohnRoberts]

What about it?

Looks a little scary to me, If you like it why don't you build it up and see what it does?

JR

 

[abbey road d enfer]

How about this one? Sorry, i can't use the circuit simulator.. :-[ :-[


Many thanks,

Simon

It does work; it's not perfect, in particular the voltages on both legs are not equal, neither th e impedances, but it provides good real-life performance.

 

[Junction]

Just dont connect - to ground, leave it floating, take your unbalanced feed from + and ground.

 

[Dr_J]

Hi,

just as a little hint, check out JLM-Audio

http://www.jlmaudio.com/forum/viewtopic.php?f=2&t=164&sid=f60a89c912be6139c2f01d7ab36a080e

Cheers!