connecting balanced to unbalanced

[chrispbass]

Hi guys, I have a small active computer speaker which I intend to use to test my projects through and wondered what the best way was to connect a balanced output into this. It is mainly to get an obvious 'thumbs up' that its working, i.e connecting a mic into my g9 into this monitor etc, but wondered if it is simply a case of making the correct lead, or is there more to it?

I've checked this out on the rane website...

http://www.rane.com/note110.html

and lead 5b would seem to fit the bill, however it also shows lead 3 for non tx balanced outputs. Am I heading in the right direction with this?

cheers

Chris

 

[JohnRoberts]

As the RANE note implies there are numerous output topologies and input topologies, so to mentally determine a best path you need to determine what you are dealing with.

It is generally easier to make a best guess, try that, then empirically adjust from there.

JR

 

[okgb]

the quick & easy thing is to have the connector open and leave the  - or cold line floating
unconnected and jumper it to ground in the cases where you need that , which should cover
many scenarios ,  and not being a permanent install , reasonable but no one size fits all here

 

[sodderboy]

My first choice for something like this is to wire + to hot and - to sleeve leaving the shield unconnected.  If you have a spare 10 or 50K pot around you should use it as a simple attenuator to account for the +4 to -10 signal level difference issue.  Without some sort of attenuation you will probably always distort the input stage of the speaker causing an otherwise correct build to sound like something distorted and incorrect.
Mike

 

[chrispbass]

Thanks for your replies guys, most useful. Mike, is it a case of just wiring the pot inline with the hot lead or should I connect across the 'ground'?

Signal levels aside and not using a pot, Is this also the correct method for connecting a scope to the output?

Cheers

Chris

 

[sodderboy]

Hot to CW, cold to CCW for the input, hot to Wiper, shield to CCW for the output.  As for a scope yes it is the way to measure, but you want to be aware if the scope chassis is connected to "ground" same as the chassis under test you will short the cold.  Better to measure one leg at a time or use a high quality iso transformer.
Mike

 

[chrispbass]

Hot to CW, cold to CCW for the input, hot to Wiper, shield to CCW for the output.  As for a scope yes it is the way to measure, but you want to be aware if the scope chassis is connected to "ground" same as the chassis under test you will short the cold.  Better to measure one leg at a time or use a high quality iso transformer.
Mike

Thanks again Mike
Chris

 

[Brian Roth]

12+ years ago, I was working as a "liaison" between a company that was pioneering live streaming video to the internet and another company which supplied a LARGE television mobile, like used for NFL football games, etc.  I was there to 'keep an eye' on any problems getting the video and audio from the truck through the dedicated T-1 line to the 'edge server' for the live stream.

(Keep in mind the time frame...Now Ancient History...lol).

Anyway, the wise/grizzled "Chief" who ran the truck had an ground/buzz problem feeding audio back into some PA/foldbacks supplied by the venue (which wasn't my specific problem, but the Chief and I had become friends).

He dug around in his Box O' Tricks, and pulled out one of these, but with the RCA's cut off, and XLR'S installed:

http://www.radioshack.com/product/index.jsp?productId=2062214

Buzz Be Gone  lol.  Simple/cheap solution.

Since then, I've always carried one of those Rat Shack items in my tool box, and have quickly solved various interconnect probs.  In fact, at a couple studios that have hired me to solve probs, those Rat Shacks live to this day as a problem solver between the output of a desk and the (unbalanced) inputs of Crown power amps used for a passive headphone cue system.  I OFFERED to make a better solution, but the studio owners tell me the "sound is just fine, the buzz is gone...leave it alone!"  LOL

Inside of the plastic can is merely a pair of 1:1 iso transformers.  They actually test semi OK on the bench, but then again, a 1:1 "ain't rocket surgery".    <g> 

No, Rat Shack isn't selling a pair of Jensens or UTC's.  BUT, for Chrispbass and his "small active computer speakers", they can provide a cheap balanced input for simple testing purposes, and with decent performance.

Bri

 

[chrispbass]

Another take on this...cheers Bri.

Yes, the computer spkr is only for a 'rough and ready test' in my lab, but will be good enough for hopefully hearing a project spring to life! Didn't want to risk using my studio spkrs and found this little active spkr in the shed...knew there was a reason not to chuck it! 

Chris

 

[sodderboy]

I've also used them for decades, and NY Dave spec'ed them in one of his builds.  The quality has gone down a bit over the years from the metal to plastic cans in the physical size of the core and laminations, but they are still quite good enough to keep in the bag of tricks.
Cheers crisp
Mike

 

[RuudNL]

As long as you drive them from a low impedance, everything works fine.
But you will loose some LF when driven from a higher impendance. (R-L filter)

(By the way: did you ever measure the transformer distortion when driven from a high impedance, even at higher frequencies? You may be surprised!)