Unbalanced from balanced.
 

On the odd occasion when I've been forced to feed an electronically
balanced output into an unbalanced input, I've normally done this by going
across Pin 1 (ground), and Pin 2 (+) But I've just come across an
electronically balanced device that seems to also short 1&3. Thought that
was bad practice or is it ok these days?

Other odd thing is the spec of this balanced output - it says output
impedance 200k ohms. Is that likely a misprint? The balanced input for the
same device says 50k ohms impedance.

Basically, it has both XLR and TRS jacks for output and reckons you can
simply use a 'mono' jack for unbalanced and shows that shorting 1&3.

--
*How much deeper would the oceans be without sponges? *

Dave Plowman London SW
To e-mail, change noise into sound.

Unbalanced from balanced.
 

In article , Dave Plowman (News)
wrote:
On the odd occasion when I've been forced to feed an electronically
balanced output into an unbalanced input, I've normally done this by
going across Pin 1 (ground), and Pin 2 (+) But I've just come across an
electronically balanced device that seems to also short 1&3. Thought
that was bad practice or is it ok these days?

I'd been wondering about this recently because of experimenting with USB
Audio input/capture devices. Nearly all the ones for 'musicians' have
balanced inputs. But often have 'combination' XLR+TRS connectors.

However experiment and discussion indicate that using them balanced is OK.

I've been using the Focsrite Scarlett 2i2 by plugging TS ('mono') 1/4"
jacks into the connectors. This shorts 'cold' to ground. Works fine.

In fact I think one of the comments in this month's 'Sound on Sound' is
about this and says that unbalanced is fine provided you don't have a
grounding / interference problem that makes balanced help.


Other odd thing is the spec of this balanced output - it says output
impedance 200k ohms. Is that likely a misprint? The balanced input for
the same device says 50k ohms impedance.

Pass.

Basically, it has both XLR and TRS jacks for output and reckons you can
simply use a 'mono' jack for unbalanced and shows that shorting 1&3.

That's what I'm doing. Works here on the 2i2 and a Behringer UMC202. I'd
try other devices but makers cannae be bothered to tell me if they work
with Linux or comply with the USB audio class standards.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Unbalanced from balanced.
 

In article , Jim Lesurf
wrote:
In article , Dave Plowman (News)
wrote:
On the odd occasion when I've been forced to feed an electronically
balanced output into an unbalanced input, I've normally done this by
going across Pin 1 (ground), and Pin 2 (+) But I've just come across
an electronically balanced device that seems to also short 1&3.
Thought that was bad practice or is it ok these days?

I'd been wondering about this recently because of experimenting with USB
Audio input/capture devices. Nearly all the ones for 'musicians' have
balanced inputs. But often have 'combination' XLR+TRS connectors.

However experiment and discussion indicate that using them balanced is
OK.

Sorry, typo, that should be "unbalanced". I'm actually using TS jack - RCA
adaptors.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Unbalanced from balanced.
 

On 04/03/2014 14:41, Bob Latham wrote:

I would have thought that shorting one side of a balanced input to ground
and using the other for signal would usually be fine and cause no harm. I
would not do the same with a balanced output though unless it was
transformer coupled with no ground on the centre tap. Surely you could
blow up the cold side driver if its not a transformer?

I assume that balanced outputs have sufficient output impedance
that they are short circuit proof, as part of the design spec.

--
Eiron.

Unbalanced from balanced.
 

In article ,
Bob Latham wrote:
In article ,
Jim Lesurf wrote:
In article , Dave Plowman (News)
wrote:

On the odd occasion when I've been forced to feed an electronically
balanced output into an unbalanced input, I've normally done this by
going across Pin 1 (ground), and Pin 2 (+) But I've just come across
an electronically balanced device that seems to also short 1&3.
Thought that was bad practice or is it ok these days?

I'd been wondering about this recently because of experimenting with
USB Audio input/capture devices. Nearly all the ones for 'musicians'
have balanced inputs. But often have 'combination' XLR+TRS connectors.

However experiment and discussion indicate that using them balanced is
OK.

I've been using the Focsrite Scarlett 2i2 by plugging TS ('mono') 1/4"
jacks into the connectors. This shorts 'cold' to ground. Works fine.

Forgive me for jumping in on your conversation but I am intrigued by
this.

It was posted for discussion as well as answers. ;-)

I would have thought that shorting one side of a balanced input to ground
and using the other for signal would usually be fine and cause no harm. I
would not do the same with a balanced output though unless it was
transformer coupled with no ground on the centre tap. Surely you could
blow up the cold side driver if its not a transformer?

That's what I'd always thought - from the early days of electronic
balancing, at least. Of course you could add series resistors to each leg
to limit the short circuit current. Which is why I was querying the quoted
output impedance.

Apologies if I'm misreading this.

No - if you Google balanced to unbalanced most seem to say not to short
Pins 1&3 with electronic balanced. But this device clearly shows that you
can use a mono jack into the TRS socket which shorts the ground to the -
leg. On both the back panel and instructions.

I'm actually interested in getting the best possible signal to noise
connection. And did wonder if it would make any difference.


Bob.

--
*Why isn't 11 pronounced onety one? *

Dave Plowman London SW
To e-mail, change noise into sound.

Unbalanced from balanced.
 

In article , Bob Latham
wrote:
In article , Jim Lesurf
wrote:
In article , Dave Plowman (News)
wrote:


Forgive me for jumping in on your conversation but I am intrigued by
this.

I would have thought that shorting one side of a balanced input to
ground and using the other for signal would usually be fine and cause no
harm. I would not do the same with a balanced output though unless it
was transformer coupled with no ground on the centre tap. Surely you
could blow up the cold side driver if its not a transformer?

FWIW my comments (and tests) so far are just using the balanced *inputs* to
the devices. However you are right to suspect there is a potential pun
problem here.

This has two aspects. One is if the inputs/outputs 'float' so don't
actually care what the specific potentials are, just the difference. The
other is what actually happens to the 'cold' if clamped to ground.

In addition, there may well be differences between serious studio equipment
and the circa 100 quid boxes for 'prosumer / home studio' which I'm
personally trying out at present.

I'd welcome info from someone familiar with this kit. Alas makers seem to
ignore such questions when I've emailed them to ask about these matters. It
has been something I've been wary about since my experience is with home
audio (unbalanced) not studio (balanced) equipment.

As things stand, when I *do* experiment with the outputs I plan first to
see if simply 'hot' versus ground will drive an output signal OK with
nothing connected to 'cold'. i.e. use a TRS jack but leave the R
unconnected. I *suspect* that the outputs may be happy to connect R to S.
But I really don't know as yet. Although the user handbook for the Scarlett
2i2 does say either TRS or TS can be used under the diagram and details of
the back of the unit showing the output sockets.

These units also tend to have a headphone output which is stereo unbalanced
using a standard headphone TRS.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Unbalanced from balanced.
 

In article ,
Jim Lesurf wrote:
These units also tend to have a headphone output which is stereo
unbalanced using a standard headphone TRS.

Think you'll find the balanced TRS connector is identical to the headphone
one. Not like in the UK where balanced jacks are usually of the PO type.
Or were in my day. ;-)

--
*Sorry, I don't date outside my species.

Dave Plowman London SW
To e-mail, change noise into sound.

Unbalanced from balanced.
 

In article , Eiron
wrote:
On 04/03/2014 14:41, Bob Latham wrote:

I would have thought that shorting one side of a balanced input to
ground and using the other for signal would usually be fine and cause
no harm. I would not do the same with a balanced output though unless
it was transformer coupled with no ground on the centre tap. Surely
you could blow up the cold side driver if its not a transformer?

I assume that balanced outputs have sufficient output impedance that
they are short circuit proof, as part of the design spec.

I'm hoping you are correct. But I'm also wary that although 'safe' in terms
of not failing, shorting one output might affect performance. e.g. degrade
the distortion performance. So I'm planning to test this for the devices I
have when I get a chance.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Unbalanced from balanced.
 

In article , Dave Plowman (News)
wrote:


I'm actually interested in getting the best possible signal to noise
connection. And did wonder if it would make any difference.

I suspect this is an "it depends..." question.

*if* the circuit is well balanced and designed to reject common mode then
it should not care if you are grounding one input. Indeed. giving it a zero
resistance link to ground might help with any uncorrelated current noise on
the cold side.

You obviously sacrifice being able to use balancing to reject noise from
loops or common-mode pickup. Beyond that it will depend on the actual amp
design. Again this is something I plan to check sometime for the devices I
have. But since my main interest is use with unbalanced home audio kit, its
a matter of curiosity rather than need for me.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Unbalanced from balanced.
 

Arising from this I've been having real problems trying to connect this
balanced output device to an unbalanced amp.

It works ok apart from a low level buzz. Not mains hum - more like I'd
describe as an open circuit buzz.

The amp is a home made device with a 47k input impedance which is via a
cap. The input connector a phono. Been used with lots of other stuff with
no problems.

I've tried every combination of mains ground/no mains ground, screen/no
screen I can think of. It even buzzes with the balanced device switched
off and the mains lead to it unplugged. Remove the lead between them total
silence.

Only thing which does work is an audio isolating transformer.

--
*If I agreed with you, we'd both be wrong.

Dave Plowman London SW
To e-mail, change noise into sound.