simple unbal to bal converters

Useually when testing DIY stuff i take it down to my studio (1 door further then my workshop), rip some cables out of stuff and plug it in. Then when i have to change things, rip the cables out, go back to workshop, solder that better cap in, go back to the studio, pluginn the cables etc..
I thought this was a bit to much work and so i was thinking off using my terratec producer usb soundcard to do this with a set of simple speakers and stuff, will save me a lot of time and keeps my studio more tidy.  ;D
The only thing is that the soundcard has only unbalanced outputs (phono plugs) and so i want to build a simple unbal/bal converter and also the other way around (for the input of the card for tests).
I was thinking of doing a veroboard with a 5532 converter but then i came up to the ssl9k pre amp balanced board based on a ssm2142 line driver (http://www.studio21.ch/diy/neeno/ssl9k/DIY_9k_Preamp.pdf last page). I have these baords and parts laying around here so i thought of using these for the soundcard outputs. Will this be a good option or will a 5532 type be a bit better? Not familiar with ssm2142 drivers at all.. ordered them for my crussh and blend but ended up using 5532's as in living notes version.
I will just build it in a simple box with some plugs just for testing so nothing really fancy.. as long as it's balanced and working without to much problems.

I would go for the ssm2142...less work and a step up from the 5532 option...

Or choose for the THAT 1646.
http://www.profusionplc.com/pro/gex/manuftable?imanuf=THAT&itypes=Balanced%20Line%20Driver#

Willem.

OK, will do that, have the 2142's 'in stock' so it's just a matter of stuffing the board and drilling holes in a box and done!  ;D
It doesn't have to be like a real pro box because the it''s going to drive a 200 euro soundcard (bought it for a live performance some time a go) anyway but at least it's not going to add more noise then the card itself, that is always a good thing.  8)
I also have some ssm2141's here, maybe i'll figure something out for going the other way around > balanced to unbalanced so that i can use that, good to know what these things are doing anyway.

Just checking about the ssm2141:
To me it looks like it''s just plain + and - input driving (no input caps or resistors, just the straigth signal), some bypass caps, + and - 18v and maybe a resistor and cap at the output and i'm done with the balanced to unbalanced converter, am i right or do i miss something here?



BTW: happy new year to all!  ;D

Or maybe try a pseudo balanced aproach....

http://www.groupdiy.com/index.php?topic=5941.msg70549;topicseen#msg70549

Nah.. was also thinking about that but i like the idea of a line driver better and since i have the 2141's laying around here i go for the official bal2unbal approach instead.
As far as i can see i just need a cap and maybe a resistor at the output and i'm done.

2 x unbalanced-to balanced & 2 x balanced-to-unbalanced converters on one pcb:

http://audioxxx.googlepages.com/bal_card_block_diagram.pdf
http://audioxxx.googlepages.com/bal_card_schematic.pdf
http://audioxxx.googlepages.com/bal_card_layout_designations.pdf
http://audioxxx.googlepages.com/bal_card_layout_values.pdf

Hey nice little I/O board, Veli  Doing that in SMD atm...I see you take two opamps for debalancing, is there something that makes that better than just sticking the other line into the + input of one opamp?

livingnote said:

I see you take two opamps for debalancing, is there something that makes that better than just sticking the other line into the + input of one opamp?

Click to expand...

Gain is adjustable by changing only one resistor instead of two (and not affecting CMRR).

If I get that right, in the one-opamp version that would be the feedback r and the r to ground in the + input, and in yours just the second feedback r?

How does that affect CMRR? I'm kinda new to all the details of opampery...

OK, just wondering about the ssm2141 for going from balanced to unbalanced.
I made test version with the 2141 but i have really distorted, way to loud sound with just the 2141, some decoupling and a 51r and alsso tried 10k at the output.
Is it better to have something like 10k at the + and - (pin 2 and 3) inputs? or maybe a resistor to ground?
Or is there something i should do with the ref and sense outputs?
I'd like to have something like unity gain.
http://www.datasheetcatalog.org/datasheet/analogdevices/12157751ssm2141.pdf

ok.... think i found it.. pin 1 (reference) to ground and pin 5 (sense) to the output.
Am i correct here?

yep

radiance said:

yep

Click to expand...

And it's working  ;D

Now i only have to get my phase26 terratec card to work in RMAA.. grrr.. doesn't work properly in some kind of way... and not just in RMAA but not like really stable in windows vista at all 

Well.. at least i have a nice clean box now for balancing and debalancing for testing stuff which was the purpose of this thread.  8)

Actually, I would shy away from the SSM2141.  It doesn't handle induced line noise nearly as well as the INA137 or the THAT 12xx series.  I saw a demo of the THAT chips at AES last year, and the difference in noise handling is staggering.  I use the INA137 chips in my summing mixers, which is also what is used in the Dangerous 2-Bus units.  I am in the process of redesigning my unbalancing input circuits to utilize the THAT chips for my next product design.

In any case, any of these chips will provide a much better solution to an NE5532 or the likes version of an unbalancing circuit.  The THAT chips have a bootstrap circuit built into it that compensates for voltage differentials in the + and - inputs automatically that provides improved CMRR performance over the other two chips.  Still, the other two hips have trimmed resistors on the inputs which maximize the CMRR capabilities and will be far superior to any dual opamp solution used by ht elikes of the NE5532 unless you hand match all your resistors down to negligible tolerances in the unbalanced circuit inputs.

You know, this would be a valuable project for someone to take on as a kit.  Many computers come with quite capable sound cards built-in.  They even provide input and output headers on the motherboard to connect to front panel jacks on the case.  Unfortunately, these are lousy, unbalanced I/O. 
I have often wished for a simple device that would plug into the header on the motherboard and provide a balanced line in and a balanced line out.  (I guess a phantom powered mic jack would be asking for too much.)
It would be a simple thing, then, to mount the connectors on an empty expansion bay cover and have a low-cost machine with balanced pro-level inputs and outputs.  There's 12v and 5v supply sources in abundance.  How hard could it be?

Well what I will be doing later this week is to make a little I/O board thingy in SMD, I consider it handy in general to have one of those for general in-outing. You know, fits on a postage stamp and does balancing duty, maybe mountable to a print XLR directly or hijack it and stick it into your 'puter as mentioned.

I'll see if I can track down the audio header specs for motherboards.  I know Intel set some standards that most folks follow.

Yah, maybe find out what all pinouts there could be and just make one for each kind. 5532s and OPAs come to mind - anything else?