balanced to unbalanced circuit?

[brad]

I made a post in the Lounge about some problems I'm having with hum in a DIY magnetic pickup bracket I made for my upright bass.  The suggestion was raised that I may be able to fix the hum by running the pickup wires on a balanced line and then converting it to an unballanced line.  Now, I've searched the net and have found plenty of passive designs and active unbalanced to balanced designs...but nothing that actively converts balaned to unbalanced (I suppose no one really wants that).

I figured I'd field the question here since more people read this board;  Does anyone have a schematic for a circuit that converts ballanced to unballanced without a transformer?

This is the original thread:
http://diystompboxes.com/sboxforum/viewtopic.php?t=30659

[Paul Perry (Frostwave)]

http://www.nrgkits.com/workshop/balanced_to_unbalanced_audio_converter_and_vice_versa.htm
is a start.

[brad]

That looks perfect!  Thanks Paul  

I was aiming to keep my pickup system entirely passive (to keep with the theme of it being for an accoustic instrument), but I doubt I'd be able to find the appropriate transformers easily in Australia.  For example, Jenson publish this simple circuit for converting balanced to unbalanced: http://www.jensen-transformers.com/as/as089.pdf

I've always wondered what the big cylinder hanging below the "Stringcharger" pickup was...but now I'm beginning to think it's a transformer to battle the same problem I'm facing!
http://www.stringcharger.com/

[onboard]

Yessir, there's a transformer on the Stringcharger. Neat-o, unless you're trying to build one and can't get a transformer...

For the record - the thought of a balanced/unbalanced solution was born more from imagination than reality. I could imagine isolating the signal from ground at the source, and thought "hey, wouldn't that be balanced?"

It is sort of going backwards though, eh? Isn't the usual arangement to convert unbalanced to balanced :?

Can someone else please chime here? What about all those magnetic soundhole pickups for acoustic guitar that don't need a preamp and are fairly quiet?  

Brad, I apologize for maybe setting you in the wrong direction by guessing about things.

[12afael]

check the ina134 and drv134 from texas instruments you can get samples.
I think is the best way to get high CMRR. this chip have laser trim resistors for a perfect match .