Balanced/unbalanced out on GSSL

[jeroddumas]

This is a stupid question, but I just want to make sure. :? . If i wire up balanced outs with trs jacks, can I just plug in an unbalanced cable to do unbalanced out?

 

[Svart]

technically yes, but you have to make sure you aren't shorting the -(cold) output to ground. this would make the IC very unhappy.

grounding the -(cold) on the input is perfectly fine and necessary for running unbalanced into the GSSL.

PS: all my HDDs on the studio computer are named after DBZ entities.. :green:

 

[emtee]

[quote author="Svart"]technically yes, but you have to make sure you aren't shorting the -(cold) output to ground. this would make the IC very unhappy.[/quote]

Really? My 95% finished GSSL's have only been tested using unbalanced connections with the -ve grounded on in & outs and have performed perfectly... :?

 

[Steffen]

NE5532/34 have build in short circuit protection. no problem ;-)

steff

 

[hejsan]

I thought that it was "industry standard", at least in modern gear, to assume that the cold goes to ground if someone plugs in an unbalanced cable, am I right?

Do most common opamps have this kind of protection, and are they working optimally even if they have detected a short circuit?

 

[MrZpliff]

I thought that it was "industry standard", at least in modern gear, to assume that the cold goes to ground if someone plugs in an unbalanced cable, am I right?

Mee too :shock:
I've been running it like this for over a year and no problemo :?

 

[gyraf]

It WILL work, but it's not good practice on electronically-balanced outputs..

Jakob E.

 

[Svart]

shorting the -input to ground is necessary on any balanced input. for trafos this gives it a reference, for sandstate inputs this will drop your noise and boost about 6db if your input jack does not already short it to ground.

I agree with Jakob, shorting the -output to ground is NOT a good idea nor is it good practice. IF the designers for some reason did not decide to design for this and their opamps are not designed to have short protection, thenyou are going to be driving a dead short. this = unhappy opamps.

It is never a good idea to depend on the opamp's short protection to make up for any other inadequacy, it wasn't designed for that. i say just make up special cables for them. all my inserts are unbalanced so i just wired everything up for unbalanced cables.

 

[hejsan]

[quote author="gyraf"]It WILL work, but it's not good practice on electronically-balanced outputs..[/quote]

Do you mean "Not good practice" as in it could damage something or as in theoretically bad practice?

Actually I now remember that the other day I was working on some even*t monitors that were explicitly marked "balanced" but where connected with an unbalanced cable, and it had a constant, pretty loud high pitch tone coming out. It dissapeared when I used a balanced cable..

 

[MrZpliff]

[quote author="Svart"].... i say just make up special cables for them. all my inserts are unbalanced so i just wired everything up for unbalanced cables.[/quote]

I thought that was making cables with "Cold (-) shorted to ground" :?
Maybe I shold use some trafos then ? Would 600/600 ohm do ?

 

[gyraf]

I mean "Not good practice" in the sense that it will run the risk of sounding less-than-desireable in some (unpredictable) cases.

Jakob E.

 

[idylldon]

So it's best just to leave the output (-) disconnected when using the GSSL unbalanced, which means just connecting tip (+) and ground? This is the way I connected the GSSL to my Neotek and it seems to work fine.

Cheers,
--
Don

 

[gyraf]

which means just connecting tip (+) and ground

Yes...

 

[bcarso]

Grounding an op amp output in this situation will produce a variety of unwanted effects, among them pumping a lot of current into the ground and pulling at least as much from the power supplies. As well if the amp is part of a dual the chip heating with signal will contaminate the adjacent chip unless it is completely immune to temp swings, which they never are.

Worth the trouble to avoid.

 

[MrZpliff]

Ok. Ok ! :wink:
I'm convinced !

I'll disconnect the - (cold) and just use the + (hot) and ground for the
8-bus send/returns....

...seems you learn something everyday :thumb: :guinness:

Is there a situation when theres any advantage to connect - (cold) to ground :?:

 

[idylldon]

I just pulled my GSSL out of the rack to install the sidechain filter setup and realized that I had put a switch on the back to choose between balanced and unbalanced output.

Sheesh! After building six 1176, one GSSL (another on the way), numerous guitar amps, and an LA2A I'm having trouble keeping it all straight. Perhaps it's time to keep a file in Info Select for all of this data and relieve the stress on my short-term memory (it ain't what is used to be!).

Cheers,
--
Don

 

[ulysses]

[quote author="MrZpliff"]Is there a situation when theres any advantage to connect - (cold) to ground?[/quote]

It depends on the circuits you're connecting. In this particular case, it's never going to be a good idea because you will always be grounding the output of an opamp that doesn't want to be grounded. In some electronically balanced output circuits, the outputs are cross-coupled which produces a more transformer-like floating output that works fine with one of its legs grounded. And of course if you have a real transformer with a real floating output, then you HAVE to ground one leg in order to get signal into an unbalanced load. The trick is to know what kind of circuits you're connecting, and know what connection scheme is most appropriate for those circuits.

 

[hejsan]

[quote author="gyraf"]..but it's not good practice on electronically-balanced outputs..[/quote]
Just to be sure..
What if the output is balanced via a transformer, like the LL1539, is it then ok to short the -neg side?
Thanks

 

[SSLtech]

[quote author="hejsan"][quote author="gyraf"]What if the output is balanced via a transformer, like the LL1539, is it then ok to short the -neg side?
Thanks[/quote]
Not only is it OK, it's essential. Otherwise you're only connecting one end of a piece of wire (the secondary) and nothing happens without both ends connected!

Keith

 

[owel]

The second SSL I built, I used some old MCI416 transformers. (Bought from one of the members here, forgot who!)

I like it with transformers... it helps with ground isolation because it's like having a built-in ground loop eliminator.

http://www.fivefish.net/diy/SSL4000Compressor/default.htm