Using balanced outputs on mic preamp

[HiC]

I've got a Studio Projects VTB-1 mic pre. I've never used the balanced
outs on it. Have always gone out from the 1/4" jacks to a sound card.
What are some examples of gear the balanced outs would go into? I
gather the balanced output is "better" - what differences would be
noticed using the balanced outs compared to the 1/4" outputs?

Are there sound cards with balanced in's that this could go into?

Thanks

[Arny Krueger]

"HiC" > wrote in message
oups.com

> I've got a Studio Projects VTB-1 mic pre. I've never used
> the balanced outs on it.

No big deal.

> Have always gone out from the 1/4" jacks to a sound card. What are some
> examples of
> gear the balanced outs would go into?

Sound cards with balanced inputs. ;-)

> I gather the
> balanced output is "better" - what differences would be
> noticed using the balanced outs compared to the 1/4"
> outputs?

Theorectically better dynamic range. Practical advantages are less likely.

> Are there sound cards with balanced in's that this could
> go into?

Sure - consider the M-Audio Delta 24192.

[DeeAa]

"HiC" > wrote in message
oups.com...
> I've got a Studio Projects VTB-1 mic pre. I've never used the balanced
> outs on it. Have always gone out from the 1/4" jacks to a sound card.
> What are some examples of gear the balanced outs would go into? I
> gather the balanced output is "better" - what differences would be
> noticed using the balanced outs compared to the 1/4" outputs?
>
> Are there sound cards with balanced in's that this could go into?
>
Balanced cables keep the noiselevel down.
http://en.wikipedia.org/wiki/Balanced_audio

It will be a huge difference if you wire a whole project studio with all
balanced versus all unbalanced cabling. Or even live; unbalanced is fine for
short cables and instruments etc. however that is one of the functions a D/I
box is used for; to change instrument lines into balanced lines before
they're run off stage for longer distances.

[RD Jones]

On Feb 5, 8:54 pm, "HiC" > wrote:

> I've got a Studio Projects VTB-1 mic pre. I've never used the balanced
> outs on it. Have always gone out from the 1/4" jacks to a sound card.
> What are some examples of gear the balanced outs would go into?
> I gather the balanced output is "better" - what differences would be
> noticed using the balanced outs compared to the 1/4" outputs?

How far are you going ?
Into what type of input, transformer or electronically balanced ?
Is the output on the VTB-1 transformer balanced or electronic
(differential) ?
What type of noise environment ?

Most modern equipment with 1/4" TRS or XLR line inputs will be
balanced due to virtually all audio IC opamps having differential
inputs. So it's become a trivial matter of using a proper TRS jack
and wiring it for balanaced operation. The expense of a transformer
at the input is now reserved for higher end gear.
The line inputs on almost all of my outboard gear are balanced:
effects, compressors, line (cue) mixer, power amp. There are a
few exceptions on older pieces. All the line ins on my Soundcraft
console are balanced.

Balanced lines over long distances are much less suseptable
to noise. Ground loops (hum) can be eliminated.

Transformers can change the sound a bit, cheap ones sound
worse than good ones.

I'm not familiar with the circuit of the VTB-1. Is it a transformer
output ?

> Are there sound cards with balanced in's that this could go into?

Echo Mia's 1/4" inputs and the add-on A/D cards for my RME
with 1/4" ins are balanced.

rd

[HiC]

On Feb 6, 2:19 am, "RD Jones" > wrote:
> On Feb 5, 8:54 pm, "HiC" > wrote:
> > I gather the balanced output is "better" - what differences would be
> > noticed using the balanced outs compared to the 1/4" outputs?
>
> How far are you going ?

I have 35' of patch cord from each output to the input on the sound
card, one 25' with another 10ft section using an RCA connector. The
sound booth and computer are in different rooms.

> Into what type of input, transformer or electronically balanced ?

Not sure. The options at the moment are into either the Line2 or Aux2
jacks on the breakout box on an Audigy Platinum EX. There's also
optical, SPDIF, Firewire, but these aren't under consideration at the
moment.

> Is the output on the VTB-1 transformer balanced or electronic
> (differential) ?

According to the VTB-1 manual:

Output impedance: Male-XLR Balanced Output: 100 ohms (50 ohms each
leg)
TRS Line Out: 300 ohms (Impedance Balanced)

I'm not versed in electronics, so not really sure what this means.

> What type of noise environment ?


Homemade sound booth - approx 7x9x10, sheetrock over 2x4 frame, R13
insulation throughout, Armstrong fibrous acoustic panels from Home
Depot covering the inside to kill ambient reverb. It's inside a spare
bedroom in a residential neighborhood. Also have a barrier made of
2x4's with acoustic panels, filled with foam, set into the window in
the room.


> Most modern equipment with 1/4" TRS or XLR line inputs will be
> balanced due to virtually all audio IC opamps having differential
> inputs.
> So it's become a trivial matter of using a proper TRS jack
> and wiring it for balanaced operation. The expense of a transformer
> at the input is now reserved for higher end gear.


Over my head technically. Any way to explain/summarize what this
means?


> Balanced lines over long distances are much less suseptable
> to noise.


What distance is long enough to make a difference?


> I'm not familiar with the circuit of the VTB-1. Is it a transformer
> output ?


Is this covered by my answer above re: the output impedance?


> > Are there sound cards with balanced in's that this could go into?
>
> Echo Mia's 1/4" inputs and the add-on A/D cards for my RME
> with 1/4" ins are balanced.

So, a jack doesn't have to be XLR to be balanced? You mention TRS
1/4". I get that this stands for tip/ring/sleeve. I was under the
impression that a TRS jack has 3 segments. The ends of 1/4" cables I
have coming out of the amp are the kind with 2 segments - the little
mushroom shaped tip, a plastic insulator, and the rest of the shaft of
the insert, and RCA connectors on the other end from the jacks labeled
"line out". I assume I'm using the right kind of patch cable for them.
There are separate jacks labeled Insert with "Tip=send" "Rign=Return"
which are for effects units. It's my understanding these are TRS jacks
and are configured differently than the line out jacks.

[Richard Crowley]

> "HiC" wrote ...
>> I've got a Studio Projects VTB-1 mic pre. I've never
>> used the balanced outs on it. Have always gone out
>> from the 1/4" jacks to a sound card.
>> What are some examples of gear the balanced outs
>> would go into?

Typically a mixer or other gear with balanced inputs.

>> I gather the balanced output is "better" - what differences
>> would be noticed using the balanced outs compared to the
>> 1/4" outputs?

In the absense of a problem, you would likely notice no
difference at all. If it ain't broke, don't attempt to "fix" it.

>> Are there sound cards with balanced in's that this could go into?

Sound cards and lots of other equipment, too.

"DeeAa" wrote ...
> Balanced cables keep the noiselevel down.
> http://en.wikipedia.org/wiki/Balanced_audio

The technical competence of Wikipedia aside, balanced
interconnections by themselves do not "keep the noiselevel
down". They are good for rejecting external interference
especially for low-levels like microphone, and/or long
distances. But for short, line-level interconnections in an
otherwise problem-free environment, there is no inherent
advantage. Note that this exactly the situation that "HiC"
is asking about.

I have used equipment that had MORE noise using the
balanced inputs than using the unbalanced. Universal
pronouncements are not valid here.

> It will be a huge difference if you wire a whole project
> studio with all balanced versus all unbalanced cabling.

I seriously dispute this. Balanced cabling certainly has
its place. But it not a magic cure-all. Nor is it needed
everywhere.

> Or even live; unbalanced is fine for short cables and
> instruments etc. however that is one of the functions
> a D/I box is used for; to change instrument lines into
> balanced lines before they're run off stage for longer
> distances.

Certainly live venues are a more difficult environment
and balanced lines make it easier to cope with whatever
situations you encounter.

[Mike Rivers]

On Feb 6, 7:54 am, "HiC" > wrote:

> I have 35' of patch cord from each output to the input on the sound
> card, one 25' with another 10ft section using an RCA connector. The
> sound booth and computer are in different rooms.

> The options at the moment are into either the Line2 or Aux2
> jacks on the breakout box on an Audigy Platinum EX.

Those appear to be unbalanced, from the photos I could quickly find of
your card.

> Output impedance: Male-XLR Balanced Output: 100 ohms (50 ohms each
> leg) TRS Line Out: 300 ohms (Impedance Balanced)

This is an electrically balanced output, but not transformer or
electronically balanced. It is the least expensive way to make a
balanced output and it is the simplest to interface to either balanced
or unbalanced inputs. No surprise that this is what Studio Projects
used on their $100 mic preamp. There's nothing really wrong with it,
by the way. It's one of those tricks that's cheap but it works pretty
well in most circumstances. It's a popular output configuration.

> > What type of noise environment ?
> Homemade sound booth - approx 7x9x10, sheetrock over 2x4 frame, R13
> insulation throughout . . . .

The question really referred to electrical noise. Computers and
monitors, cordless phones, cellular phones or wireless computer
networking, dehumidifier or room air conditioner, fluorescent lights,
SCR light dimmers, shop machinery, refrigerators, etc. Those are
things that generate electrical noise that can be picked up by the
long cables and injected directly into your mic preamp.

> > Most modern equipment with 1/4" TRS or XLR line inputs will be
> > balanced due to virtually all audio IC opamps having differential
> > inputs.
> > So it's become a trivial matter of using a proper TRS jack
> > and wiring it for balanaced operation. The expense of a transformer
> > at the input is now reserved for higher end gear.

> Over my head technically. Any way to explain/summarize what this
> means?

The summary is right there: It's a trivial matter to use the right
kind of connectors and cables. The problem is that the inputs of your
Soundblaster card are unbalanced, so you don't really have the option
of using balanced cables between balanced outputs and inputs. You're
doing the best you can with what you have and how you have it
installed.

If you aren't having problems with hum or hash-like noise, then don't
worry about it. If you are having such problems, before rushing out
and buying another interface, consider rearranging the cables. You can
perform a simple test by bringing the preamp into the room with the
computer, connecting them with a short cable, and listening to a test
recording (even if you don't have a long mic cable and have to use the
mic in the same room - bury it under a pillow) to determine if you've
reduced the noise. If so, then make this your permanent setup. It may
be convenient to have the preamp gain control in the same room as the
mic and sound source, but you'll find that after a while there are
just a few ballpark settings that you can use that will work just
about all the time. You can use the exercise.

> What distance is long enough to make a difference?

Whatever distance noise begins to be a problem. First you need to
determine if you have a problem at all. There is no assurance that you
will have a problem if you use unbalanced connections, it's just more
likely given the lack of care taken with most installations these
days.

> So, a jack doesn't have to be XLR to be balanced? You mention TRS
> 1/4". I get that this stands for tip/ring/sleeve.

Correct. The signal is carries on two wires connected to the tip and
ring of the 1/4" plug or pins 2 and 3 of the XLR connector. The sleeve
or pin 1 is connected to a shield that covers the two wires, but does
not carry the audio signal. With an unbalanced connection, there is
only one wire (connected to the tip of the 1/4" plug) and the shield
is used as the second wire to complete the audio circuit.

With a balanced connection, the shield (hopefully) only goes between
the chassis of the two pieces of equipment that you're connecting and
any noise that gets picked up by the shield doesn't go where it can do
any harm. But when the shield carries the signal current, even though
it's connected to chassis ground, any noise that's picked up by the
shield or the center conductor in the cable gets added to the audio.

Also, with a balanced input, the voltage that does the work is the
difference between the voltage on the two wires, like the two
terminals of a battery, that go to an input transformer or a
differential amplifier. Any noise that gets through the shield will
(approximately) be coupled to both wires equally. When you take the
difference between two numbers that are the same, you get zero, so any
"common mode" noise picked up by the cable gets canceled.

> There are separate jacks labeled Insert with "Tip=send" "Rign=Return"
> which are for effects units. It's my understanding these are TRS jacks
> and are configured differently than the line out jacks.

They are. An Insert jack has both an output (send) and an input
(return) on a single connector. Because there's only one wire for each
(with the shield available to complete the circuit) they're
necessarily unbalanced. You cannot use an Insert jack as a balanced
output or input, but it can be used as either an unbalanced output, an
unbalanced input, or both.

[DeeAa]

"Richard Crowley" > wrote in message
...
>> It will be a huge difference if you wire a whole project studio with all
>> balanced versus all unbalanced cabling.
>
> I seriously dispute this. Balanced cabling certainly has
> its place. But it not a magic cure-all. Nor is it needed
> everywhere.
>
That's of course true. While at it, why not just forget about decent
groundings and power sources, they are also quite indifferent in home
studios :-9

Seriously, I'm not saying it will _cure_ anything, I'm just saying that if
you build a project studio especially around computer equipment, it'd be
silly not to wire stuff balanced. Much better for all kinds of interference
issues etc. There's no reason not to use it, anyway.

I used to have an all-unbalanced setup, but ditched that and now it's been
all balanced for a long while, except on the listening side. It certainly
made my recordings much better, but that is also due to getting better
equipment in the first place.

Simply rebuilding the FX/amp rack with all balanced cabling and tossing the
unbalanced compressors etc. had an indeed huge effect on the overall sound
quality. That's no bull.

Hell, I know this guy who is so allergic to noise and such that he even
converts his guitars and basses into having balanced outputs right from the
start up - now that's overdoing it perhaps...

[Richard Crowley]

"DeeAa" wrote ...
> Seriously, I'm not saying it will _cure_ anything, I'm just saying
> that if you build a project studio especially around computer
> equipment, it'd be silly not to wire stuff balanced. Much better for
> all kinds of interference issues etc. There's no reason not to use it,
> anyway.

Sure there are good reasons not to use it. Particularly
where the equipment doesn't have balanced inputs and/
or outputs. Duh.

> I used to have an all-unbalanced setup, but ditched that and now it's
> been all balanced for a long while, except on the listening side. It
> certainly made my recordings much better, but that is also due to
> getting better equipment in the first place.
>
> Simply rebuilding the FX/amp rack with all balanced cabling and
> tossing the unbalanced compressors etc. had an indeed huge effect on
> the overall sound quality. That's no bull.

As you said yourself, you didn't just replace your original
(unbalanced) equipment with balanced versions of exactly
the same thing. It wasn't the balanced connections that
improved the sound.

> Hell, I know this guy who is so allergic to noise and such that he
> even converts his guitars and basses into having balanced outputs
> right from the start up - now that's overdoing it perhaps...

If it ain't broke, don't atempt to "fix" it. Sounds like
someone with way too much time on their hands.

[Arny Krueger]

"Richard Crowley" > wrote in message

>> "HiC" wrote ...
>>> I've got a Studio Projects VTB-1 mic pre. I've never
>>> used the balanced outs on it. Have always gone out
>>> from the 1/4" jacks to a sound card.
>>> What are some examples of gear the balanced outs
>>> would go into?

> Typically a mixer or other gear with balanced inputs.

Agreed, but it is a truism. I'm wondering why this question even has to be
asked.

>>> I gather the balanced output is "better" - what
>>> differences would be noticed using the balanced outs
>>> compared to the 1/4" outputs?

> In the absense of a problem, you would likely notice no
> difference at all. If it ain't broke, don't attempt to
> "fix" it.

Agreed again.

>>> Are there sound cards with balanced in's that this
>>> could go into?

> Sound cards and lots of other equipment, too.

I'm still wondering why this question even has to be asked.

> "DeeAa" wrote ...
>> Balanced cables keep the noiselevel down.
>> http://en.wikipedia.org/wiki/Balanced_audio

> The technical competence of Wikipedia aside, balanced
> interconnections by themselves do not "keep the noiselevel
> down". They are good for rejecting external interference
> especially for low-levels like microphone, and/or long
> distances. But for short, line-level interconnections in
> an otherwise problem-free environment, there is no
> inherent advantage. Note that this exactly the situation
> that "HiC" is asking about.

I find that the Wikipedia answer is incomplete. Long lines and noisy
environments aren't the only important justification for balanced lines. IME
the more common justification for balanced I/O is system complexity.

Furthermore, length within normal architectural distances (as opposed to
municipal or regional distances) is often not much of an issue at all. I've
routinely run audio over 100's of feet of unblanced line, or watched a
balanced line that I put in be terminated with unbalanced equipment (same
difference) with no ill effects.

In contrast, the place where I find balanced I/O to be a problem-solver are
those situations where I have a big cluster of interconnected audio gear,
like a live sound console with 30+ active sources, recording (tape, hard
drive, CD, video), and other audio subsystems (overflow and other remote
audience multimedia), both source and sink, hung off of it.

> I have used equipment that had MORE noise using the
> balanced inputs than using the unbalanced. Universal
> pronouncements are not valid here.

All things are possible, but I find that to be a little strange. I can
conceive of a balanced system that is not advantageous, but I can't conceive
of a properly-operating balanced system that was disadvantageous. Real world
example?

>> It will be a huge difference if you wire a whole project
>> studio with all balanced versus all unbalanced cabling.

> I seriously dispute this. Balanced cabling certainly has
> its place. But it not a magic cure-all. Nor is it needed
> everywhere.

Agreed. Case in point is my usage of both Delta 1010 (true balanced inputs)
and 1010LT (mostly RCA inputs) for recording. The 1010 inputs just aren't
appreciably quieter than the ones on the 1010LT.

>> Or even live; unbalanced is fine for short cables and
>> instruments etc. however that is one of the functions
>> a D/I box is used for; to change instrument lines into
>> balanced lines before they're run off stage for longer
>> distances.

The hidden issue here is the high impedance of your typical guitar pickup.

> Certainly live venues are a more difficult environment
> and balanced lines make it easier to cope with whatever
> situations you encounter.

There's usually a big difference between a venue and a project studio.

[Richard Crowley]

"Arny Krueger" wrote ...
> "Richard Crowley" wrote
>> I have used equipment that had MORE noise using the
>> balanced inputs than using the unbalanced. Universal
>> pronouncements are not valid here.
>
> All things are possible, but I find that to be a little strange. I
> can conceive of a balanced system that is not advantageous, but I
> can't conceive of a properly-operating balanced system that was
> disadvantageous. Real world example?

I ran FOH for several years for a gospel vocal group who
had a bunch of Biamp stuff (mixer, EQ, power amps, etc.)
The balanced connections between the EQ and the power
amps were audibly MORE noisy (thermal hiss) than the
unbalanced. Since they were in the same portable rack,
there was no advantage to using the balanced ins and outs,
and a significant disadvantage.

[Arny Krueger]

"Richard Crowley" > wrote in message

> "Arny Krueger" wrote ...
>> "Richard Crowley" wrote
>>> I have used equipment that had MORE noise using the
>>> balanced inputs than using the unbalanced. Universal
>>> pronouncements are not valid here.
>>
>> All things are possible, but I find that to be a little
>> strange. I can conceive of a balanced system that is
>> not advantageous, but I can't conceive of a
>> properly-operating balanced system that was
>> disadvantageous. Real world example?

> I ran FOH for several years for a gospel vocal group who
> had a bunch of Biamp stuff (mixer, EQ, power amps, etc.)

If memory serves Biamp was a line of econo semi-pro gear

> The balanced connections between the EQ and the power
> amps were audibly MORE noisy (thermal hiss) than the
> unbalanced.

Somebody ****ed in the soup - that's not what even just average
implementations of such a connection can provide.

> Since they were in the same portable rack,
> there was no advantage to using the balanced ins and outs,
> and a significant disadvantage.

I would say that the conditon of "properly-operating" was breached. OK, it
was in a good state of maintenance, but it was not operating nominally to
begin with. Broken as designed! ;-)

[Scott Dorsey]

In article . com>,
HiC > wrote:
>I've got a Studio Projects VTB-1 mic pre. I've never used the balanced
>outs on it. Have always gone out from the 1/4" jacks to a sound card.
>What are some examples of gear the balanced outs would go into? I
>gather the balanced output is "better" - what differences would be
>noticed using the balanced outs compared to the 1/4" outputs?
>
>Are there sound cards with balanced in's that this could go into?

There is a good description of the advantages and disadvantages of
balanced vs. unbalanced connections in the FAQ. It is worth reading.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[HiC]

On Feb 6, 9:03 am, "Arny Krueger" > wrote:
> "Richard Crowley" > wrote in message
>
>
>
> >> "HiC" wrote ...
> >>> I've got a Studio Projects VTB-1 mic pre. I've never
> >>> used the balanced outs on it. Have always gone out
> >>> from the 1/4" jacks to a sound card.
> >>> What are some examples of gear the balanced outs
> >>> would go into?
> > Typically a mixer or other gear with balanced inputs.
>
> Agreed, but it is a truism. I'm wondering why this question even has to be
> asked.

If you're referring to my original question, from my vantage point it
"needs" to be asked due to a lack of understanding on my part. I'd
like to gain greater understanding of electronics issues and it's
definitely on my "to do" list, but for the moment, I'm trying to get a
feel for whether I'm going to be better off using a soundcard (or
interface of any sort for that matter) that has balanced inputs, or is
it likely to make a negligible, imperceptible or even no difference
whatever in my particular circumstance.


> >>> I gather the balanced output is "better" - what
> >>> differences would be noticed using the balanced outs
> >>> compared to the 1/4" outputs?
> > In the absense of a problem, you would likely notice no
> > difference at all. If it ain't broke, don't attempt to
> > "fix" it.
>
> Agreed again.

In my case, I'm trying to determine whether it's "broke" or not - i.e.
whether using balanced connections will make any difference. When I
hook up the mics/amp/soundcard/computer, yes I get sound, but
obviously looking to see if a simple measure like using a sound card
with balanced inputs will make it demonstrably better. If the answer
is "no", that's fine.

[Scott Dorsey]

DeeAa > wrote:
>"Richard Crowley" > wrote in message
...
>>> It will be a huge difference if you wire a whole project studio with all
>>> balanced versus all unbalanced cabling.
>>
>> I seriously dispute this. Balanced cabling certainly has
>> its place. But it not a magic cure-all. Nor is it needed
>> everywhere.
>>
>That's of course true. While at it, why not just forget about decent
>groundings and power sources, they are also quite indifferent in home
>studios :-9
>
>Seriously, I'm not saying it will _cure_ anything, I'm just saying that if
>you build a project studio especially around computer equipment, it'd be
>silly not to wire stuff balanced. Much better for all kinds of interference
>issues etc. There's no reason not to use it, anyway.

There is, in that it requires more electronics in the signal path in order
to provide that balancing.

There are a number of mastering facilities that are wired all-unbalanced.
To do this requires absolutely immaculate grounding systems and very careful
layout, but it allows you to pull a lot of transformers and op-amps out
of the signal path. If your goal is to eliminate as much as possible and
keep the signal path clean and straight, unbalanced lines can be your
friend.

It's not as big a deal as it was back in the days before electronic balancing,
when everything was transformer-coupled. But it's still useful.

>Hell, I know this guy who is so allergic to noise and such that he even
>converts his guitars and basses into having balanced outputs right from the
>start up - now that's overdoing it perhaps...

The Les Paul recording pickups are the classic example of that. Works very
well. Hardly anybody likes them today, though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"HiC" > wrote in message
ups.com

> In my case, I'm trying to determine whether it's "broke"
> or not - i.e. whether using balanced connections will
> make any difference.

OK, so how do you know something is set up wrong?

The answer is that you know that something is set up wrong when things like
noise or distortion intrude on your work product under normal conditions.

Do you have problems with hiss, noise or clipping in your recordings? If
so - go on the warpath. Ask questions, change things.

> When I hook up the
> mics/amp/soundcard/computer, yes I get sound, but
> obviously looking to see if a simple measure like using a
> sound card with balanced inputs will make it demonstrably
> better.

Under normal conditions, in a simple environment like recording with just a
few pieces of equipment set up close together, balanced I/O often doesn't
do that much for you. One of your biggest advantages is running at +4
levels, rather than a consumer-like -10.

No, for a real-world counter-example. When I made the test 96/24 recordings
for my www.pcabx.web site I was sure I was going to make some recordings
with as much dynamic range as reasonably or even slightly unreasonably
possible. So, I picked the most isolated room of my house, set up an
isolated space in the middle of that room (surrounded with mattresses and
the like), put all of my recording equipment in the next room and only
recorded when the 'hood was quiet. In the process I ended up with my
external phantom power supply on a different AC circuit than my PC with its
high quality PCI audio interface. There was a significant ground potential
difference, one so great that it exceeded the dynamic range of the audio
interface. It hummed like a cheap fan whether the connection was balanced or
unbalanced!

> If the answer is "no", that's fine.

A definate maybe. ;-)

[Mike Rivers]

On Feb 6, 10:03 am, "HiC" > wrote:

> I'd like to gain greater understanding of electronics issues and it's
> definitely on my "to do" list, but for the moment, I'm trying to get a
> feel for whether I'm going to be better off using a soundcard (or
> interface of any sort for that matter) that has balanced inputs, or is
> it likely to make a negligible, imperceptible or even no difference
> whatever in my particular circumstance.

It depends on your particular circumstance, but that involves more
than you can reasonably describe or measure. But you can hear. When
you have gains set up for "normal" recordings, say a vocal or acoustic
guitar, with your favorite mic, do you hear electrical hum or other
noise in the recording when you're NOT playing? Balanced connections
MAY help if you do, but there's no guarantee of that. But they won't
help if the noise you hear is passing cars or your neighbor's chain
saw.

> In my case, I'm trying to determine whether it's "broke" or not

So listen for excessive unwanted electrical noise. If you don't have
any , it's not broke.

[HiC]

On Feb 6, 11:02 am, "Arny Krueger" > wrote:
> "HiC" > wrote in message
>
> ups.com
>
> > In my case, I'm trying to determine whether it's "broke"
> > or not - i.e. whether using balanced connections will
> > make any difference.
>
> OK, so how do you know something is set up wrong?

I'm reasonably certain it's not set up "wrong" per se, the question is
what I can do to improve things. The biggest issue I have with this
setup is noise - specifically hiss. More critical since I'm trying to
sample an acoustic guitar to make a midi patch - i.e. for a single
tracked player the noise level I have right now probably would be
acceptable, but I envision it being problematic when several
independently recorded notes are playing and the noise is compounded.

However, I think I'm coming to the conclusion that the bigger problem
may be my mics.

[Richard Crowley]

"HiC" wrote...
> "Arny Krueger" wrote:
>> "HiC" wrote in message
>> > In my case, I'm trying to determine whether it's "broke"
>> > or not - i.e. whether using balanced connections will
>> > make any difference.
>>
>> OK, so how do you know something is set up wrong?
>
> I'm reasonably certain it's not set up "wrong" per se, the question is
> what I can do to improve things. The biggest issue I have with this
> setup is noise - specifically hiss.

If your problem were hum, then balanced lines would be a
prime area to look for improvement.

However, IME, it is very unlikely that balanced lines would do
anything for a hiss (signal-to-noise ratio) problem. Are you
sure you have your gain structure set properly at all steps?

> More critical since I'm trying to
> sample an acoustic guitar to make a midi patch - i.e. for a single
> tracked player the noise level I have right now probably would be
> acceptable, but I envision it being problematic when several
> independently recorded notes are playing and the noise is compounded.
>
> However, I think I'm coming to the conclusion that the bigger problem
> may be my mics.

Did you mention the make/model of all the hardware in question?

[Paul Stamler]

"HiC" > wrote in message
ups.com...
> In my case, I'm trying to determine whether it's "broke" or not - i.e.
> whether using balanced connections will make any difference. When I
> hook up the mics/amp/soundcard/computer, yes I get sound, but
> obviously looking to see if a simple measure like using a sound card
> with balanced inputs will make it demonstrably better. If the answer
> is "no", that's fine.

In your case, I'd say you're likely to get better results with a balanced
soundcard like one of the M-Audio products. Whether the improvement comes
because it's balanced, or because it's better to begin with, I'll leave to
the theologians.

Peace,
Paul

[HiC]

On Feb 6, 1:33 pm, "Richard Crowley" > wrote:

> > However, I think I'm coming to the conclusion that the bigger problem
> > may be my mics.
>
> Did you mention the make/model of all the hardware in question?

Here's the whole chain - pair of Marshall MXL 990's > Studio Projects
VTB-1's > Audigy Platinum EX.

[HiC]

On Feb 6, 8:38 am, "Mike Rivers" > wrote:

> > > What type of noise environment ?
> > Homemade sound booth - approx 7x9x10, sheetrock over 2x4 frame, R13
> > insulation throughout . . . .
>
> The question really referred to electrical noise. Computers and
> monitors, cordless phones, cellular phones or wireless computer
> networking, dehumidifier or room air conditioner, fluorescent lights,
> SCR light dimmers, shop machinery, refrigerators, etc.

I assume the kind of noise you're referring to would be manifested as
various hums, buzzes, etc.? Don't seem to have issues with that.

[Paul Stamler]

"HiC" > wrote in message
oups.com...
> On Feb 6, 11:02 am, "Arny Krueger" > wrote:
> > "HiC" > wrote in message
> >
> > ups.com
> >
> > > In my case, I'm trying to determine whether it's "broke"
> > > or not - i.e. whether using balanced connections will
> > > make any difference.
> >
> > OK, so how do you know something is set up wrong?
>
> I'm reasonably certain it's not set up "wrong" per se, the question is
> what I can do to improve things. The biggest issue I have with this
> setup is noise - specifically hiss. More critical since I'm trying to
> sample an acoustic guitar to make a midi patch - i.e. for a single
> tracked player the noise level I have right now probably would be
> acceptable, but I envision it being problematic when several
> independently recorded notes are playing and the noise is compounded.
>
> However, I think I'm coming to the conclusion that the bigger problem
> may be my mics.

Okay, to that we can give a definitive answer: unless your soundcard is so
horrible as to border on defective, going to a balanced connection will
*not* improve hiss performance. The improvement in noise performance from
balanced connections is in the area of hum and buzz.

The problem may be the mics, or the preamp's own noise.

Peace,
Paul

[Mike Rivers]

On Feb 6, 2:44 pm, "HiC" > wrote:

> I assume the kind of noise you're referring to would be manifested as
> various hums, buzzes, etc.? Don't seem to have issues with that.

In that case, stop worrying about your system and start recording. If
you have problems with your recordings, we'll have something to talk
about, but it will probably have to do with acoustics, mic
positioning, or setting gains properly in your system.

You need experience, not technical advice about a non-problem.

[Richard Crowley]

"Mike Rivers" wrote ...
> "HiC" wrote:
>
>> I assume the kind of noise you're referring to would be manifested as
>> various hums, buzzes, etc.? Don't seem to have issues with that.
>
> In that case, stop worrying about your system and start recording. If
> you have problems with your recordings, we'll have something to talk
> about, but it will probably have to do with acoustics, mic
> positioning, or setting gains properly in your system.
>
> You need experience, not technical advice about a non-problem.

He identified his problem as poor S/N when trying to record
acoustic guitar samples. He is worried about the effect of
multiple noisy samples building up in MIDI. Sounds like he
has a valid concern.

But since he started a different thread about this topic, the
history is now unlinked.

[RD Jones]

On Feb 6, 1:38 pm, "HiC" > wrote:
> On Feb 6, 1:33 pm, "Richard Crowley" > wrote:
>
> > > However, I think I'm coming to the conclusion that the bigger problem
> > > may be my mics.
>
> > Did you mention the make/model of all the hardware in question?
>
> Here's the whole chain - pair of Marshall MXL 990's > Studio Projects
> VTB-1's > Audigy Platinum EX.

Please note that for a balanced connection to exist between devices
BOTH the output and the subsequent input must be balanced.

rd

[Arny Krueger]

"RD Jones" > wrote in message
ups.com
> On Feb 6, 1:38 pm, "HiC" > wrote:
>> On Feb 6, 1:33 pm, "Richard Crowley"
>> > wrote:
>>
>>>> However, I think I'm coming to the conclusion that the
>>>> bigger problem may be my mics.
>>
>>> Did you mention the make/model of all the hardware in
>>> question?
>>
>> Here's the whole chain - pair of Marshall MXL 990's >
>> Studio Projects VTB-1's > Audigy Platinum EX.
>
> Please note that for a balanced connection to exist
> between devices BOTH the output and the subsequent input
> must be balanced.

Technically true, but much of the advantage with balanced I/O is on the
input side. An unbalanced output driving a balanced input gives the majority
of the advantage of balanced I/O.

[Arny Krueger]

"HiC" > wrote in message
oups.com
> On Feb 6, 1:33 pm, "Richard Crowley" >
> wrote:
>
>>> However, I think I'm coming to the conclusion that the
>>> bigger problem may be my mics.
>>
>> Did you mention the make/model of all the hardware in
>> question?
>
> Here's the whole chain - pair of Marshall MXL 990's >
> Studio Projects VTB-1's > Audigy Platinum EX.

The VTB-1 preamp would have to be a real turkey to be noisier than MXL 990s.

[Mike Rivers]

On Feb 7, 7:54 am, "Arny Krueger" > wrote:
> "RD Jones" > wrote in message

> > Please note that for a balanced connection to exist
> > between devices BOTH the output and the subsequent input
> > must be balanced.

> Technically true, but much of the advantage with balanced I/O is on the
> input side. An unbalanced output driving a balanced input gives the majority
> of the advantage of balanced I/O.

Not true. Technically, there's no such thing as a balanced input.
There are differential inputs.

A balanced output has the same impedance between what's connected to
each side of the input and a common point (usually signal ground).
This is possible with a single ended output (signal on just one wire)
if the "cold" wire follows the same physical path as the signal wire
and presents the same impedance to the input as the "hot" wire.

There is no benefit to connecting the "low" side of an input to the
signal ground point directly, as would be the case with a true
unbalanced output. But put a resistor between the source end of the
"low" wire and source ground and then you'll get common mode
rejection at the input. This can be done inside a TRS plug that's
plugged into a TS output jack if you know what value resistor to
install, but that's not a one-size-fits-all thing. And (as usual) it
requires the knowledge of how to solder and how to identify terminals
in a phone plug.

[Arny Krueger]

"Mike Rivers" > wrote in message
oups.com
> On Feb 7, 7:54 am, "Arny Krueger" > wrote:
>> "RD Jones" > wrote in message
>
>>> Please note that for a balanced connection to exist
>>> between devices BOTH the output and the subsequent input
>>> must be balanced.
>
>> Technically true, but much of the advantage with
>> balanced I/O is on the input side. An unbalanced output
>> driving a balanced input gives the majority of the
>> advantage of balanced I/O.

> Not true. Technically, there's no such thing as a
> balanced input. There are differential inputs.

I'm under the impression that us older chickens all know that a true
balanced input is based on a differential amplifier or a transformer-coupled
input that acts like one. But, it may be worth repeating for the new blood.

> A balanced output has the same impedance between what's
> connected to each side of the input and a common point
> (usually signal ground). This is possible with a single
> ended output (signal on just one wire) if the "cold" wire
> follows the same physical path as the signal wire and
> presents the same impedance to the input as the "hot"
> wire.

Agreed.

> There is no benefit to connecting the "low" side of an
> input to the signal ground point directly, as would be
> the case with a true unbalanced output.

I don't know if this counts as a truism or not, or if it is what you're
trying to say Mike, but a key issue is where you connect that differential
input's negative side to signal ground. A secondary issue is that if the
source impedance is high enough to be significant (and it is often so low
that its significance is low), that both inputs to that differential amp be
sourced with the same impedance.

> But put a resistor between the source end of the "low" wire and
> source ground and then you'll get common mode rejection
> at the input.

Much of the time the resistor is just frosting on the cake for line level
interfaces, which is the topic of this thread.

A simple example would be a source, each side of which has an output
impedance of 100 ohms (set by build-out resistors) driving a differential
input, each side of which has an input impedance of 10,000 ohms.

In order to have the best possible common-mode rejection, the desired signal
applied to the differential input piar needs to be exactly equal and
opposite polarty, with the noise being equal and the same polarity. If we
leave out one of the 100 ohm resistors, then the maximum noise rejection is
about -40 dB. There's also a possibility of a 0.1 dB gain shift, but that is
far less signficant for audio production.

However, in the real world we have a number of other similarly-sized sources
of mismatch.

For example, a lot of studio gear uses 2 op amp inverters cascaded to create
a differential input. The gain of these op amp stages is set with high
quality 1% resistors. However, probable mismatch of these resistors can
limit the maximum noise rejection to 40 dB or worse.

For example, a lot of low cost consoles now use differential amplifiers
whose gain is set by just one resistor, yielding the possibility of > 80 dB
common mode rejection without the use of external precision resistors.
However, the same amplifier stage is used for line level input, by passing
the line level signal through a voltage divider made up of more of our nice
1% resistors. Again, probable mismatch of these resistors can limit the
maximum noise rejection to 40 dB or worse.

IME the difference for a line level input between zero common mode rejection
and 30-40 dB common mode rejection can be huge, but after that you really
need a lot of noise to hear a difference when the common mode rejection goes
like 60 or 80 dB. OTOH, if a manufacturer can go from 40 dB common mode
rejection to 60 dB or more common mode rejection by adding a $0.05 resistor,
it should be done.

For mic inputs (not the topic of this thread), it is very helpful to up the
CMRR ante by 40 dB or more. The more widespread use of op amps that have
true differential inputs with gain setting by just one resistor connected
internally, facilitates this.

[Mike Rivers]

On Feb 7, 9:54 am, "Arny Krueger" > wrote:

> > There is no benefit to connecting the "low" side of an
> > input to the signal ground point directly, as would be
> > the case with a true unbalanced output.

> I don't know if this counts as a truism or not, or if it is what you're
> trying to say Mike, but a key issue is where you connect that differential
> input's negative side to signal ground.

It shouldn't be, because ground is ground is ground.

> A secondary issue is that if the
> source impedance is high enough to be significant (and it is often so low
> that its significance is low), that both inputs to that differential amp be
> sourced with the same impedance.

A typical single ended op-amp output has a source impedance very close
to zero ohms. A "buildout" resistor typically in the 50 to 150 ohm
range between the output terminal of the op-amp and the output jack is
usually built in to prevent short-circuit instability of the
amplifier. The value of this resistor is usually considered to be the
source impedance, and matching it with another one of the same value
usually works well enough to look like a balanced source when going
into a differential amplifier or a transformer.

> Much of the time the resistor is just frosting on the cake for line level
> interfaces, which is the topic of this thread.

My point is that it's important, not just frosting, at least for
typical op-amp differential inputs where (unless it's an input stage
like the THAT InGenius series) there's a finite input impedance,
generally around 10K to 20K ohms between each leg and ground. With a
transformer (unless it has a grounded center tap) or the THAT chip,
the impedance between each leg and ground is extremely high, so the
difference between a source impedance of 200 ohms and zero is
insignificant when calculating common mode rejection. But for a "real
world" 10K input impedance, you really need to provide a resistor to
give equal currents in each leg.

> A simple example would be a source, each side of which has an output
> impedance of 100 ohms (set by build-out resistors) driving a differential
> input, each side of which has an input impedance of 10,000 ohms.
>
> In order to have the best possible common-mode rejection, the desired signal
> applied to the differential input piar needs to be exactly equal and
> opposite polarty, with the noise being equal and the same polarity.

There's no need for having an "opposite polarity" signal in order to
get common mode rejection. We've gone around about this and someone
jumped in and said it's not current it's voltage (or the other way
around), but the idea is that you have a loop through which noise
current (as well as signal current if there's a signal) can flow. If
there's the same noise in both loops, the input impedance is identical
and the source impedance is identical, both inputs (The inverting and
non-inverting inputs) will see the same voltage drop across the source
impedance. When they subtract in the differential amplifier, you get
zero. But as far as the signal is concerned, the difference is the
signal minus zero (no signal on the line with only a dummy resistor at
the source end), and that's the signal.

You can argue that if you have an inverted signal on the low input,
you'll have twice the difference to work with, and that can give you a
higher signal-to-noise ratio, but that isn't because noise is being
rejected, it's because you have more signal and no more noise.

> IME the difference for a line level input between zero common mode rejection
> and 30-40 dB common mode rejection can be huge, but after that you really
> need a lot of noise to hear a difference when the common mode rejection goes
> like 60 or 80 dB. OTOH, if a manufacturer can go from 40 dB common mode
> rejection to 60 dB or more common mode rejection by adding a $0.05 resistor,
> it should be done.

And this is exactly why they do it.

[Arny Krueger]

"Mike Rivers" > wrote in message
ups.com
> On Feb 7, 9:54 am, "Arny Krueger" > wrote:
>
>>> There is no benefit to connecting the "low" side of an
>>> input to the signal ground point directly, as would be
>>> the case with a true unbalanced output.
>
>> I don't know if this counts as a truism or not, or if it
>> is what you're trying to say Mike, but a key issue is
>> where you connect that differential input's negative
>> side to signal ground.

> It shouldn't be, because ground is ground is ground.

IME ground often isn't ground.

Case 1: equipment whose chassis is connected to power line safety ground.
Chassis ground and signal ground might not be at the same potential even
inside the same piece of equipment. Hence ground lift switches. Chassis
ground at the power amp may not be at identically the same potential as
chassis ground at the mixer output. Running equipment from different phases
of the power line can worsen this situation. I've measured small voltage
differences between safety ground pins on power outlets in different parts
of the same building, even when they are on the same phase of the power
line.

Case 2: equipment whose chassis is not connected to power line safety
ground. Every chassis is basically floating until it is bonded to another
chassis. If no piece of equipment in the system has its chassis grounded,
then it all floats together.

Even when chassis are hooked together, the interconnecting link has finite
resistance and finite current flows. There fore there is a voltage drop.
Let's hope it is very small compared to signal voltages, particularly if we
don't have any differential inputs to help.

If we could ground on being precisely ground, we'd only hook up the shield
at one end of every cable, even if that cable had just a single signal line.

>> A secondary issue is that if the
>> source impedance is high enough to be significant (and
>> it is often so low that its significance is low), that
>> both inputs to that differential amp be sourced with the
>> same impedance.

> A typical single ended op-amp output has a source
> impedance very close to zero ohms.

Agreed.

> A "buildout" resistor
> typically in the 50 to 150 ohm range between the output
> terminal of the op-amp and the output jack is usually
> built in to prevent short-circuit instability of the
> amplifier.

Agreed. This resistor may have other benefits, as well.

> The value of this resistor is usually
> considered to be the source impedance, and matching it
> with another one of the same value usually works well
> enough to look like a balanced source when going into a
> differential amplifier or a transformer.

Agreed.

>> Much of the time the resistor is just frosting on the
>> cake for line level interfaces, which is the topic of
>> this thread.

> My point is that it's important, not just frosting, at
> least for typical op-amp differential inputs where
> (unless it's an input stage like the THAT InGenius
> series) there's a finite input impedance, generally
> around 10K to 20K ohms between each leg and ground. With
> a transformer (unless it has a grounded center tap) or
> the THAT chip, the impedance between each leg and ground
> is extremely high, so the difference between a source
> impedance of 200 ohms and zero is insignificant when
> calculating common mode rejection. But for a "real world"
> 10K input impedance, you really need to provide a
> resistor to give equal currents in each leg.

>> A simple example would be a source, each side of which
>> has an output impedance of 100 ohms (set by build-out
>> resistors) driving a differential input, each side of
>> which has an input impedance of 10,000 ohms.
>
>> In order to have the best possible common-mode
>> rejection, the desired signal applied to the
>> differential input piar needs to be exactly equal and
>> opposite polarty, with the noise being equal and the
>> same polarity.

> There's no need for having an "opposite polarity" signal
> in order to get common mode rejection.

Agreed - that's why I included the qualifier "best possible". Common mode
rejection in dB is referenced to the maximum signal voltage, and having an
opposite polarity signal present doubles the maximum signal voltage. A true
differential output can add up from 3 to 6 dB to any signal-to-noise ratio.
The 6 dB should be obvious - twice the signal voltage. The 3 dB minimum
improvement is less obvious - There is probably some uncorrelated noise.

> We've gone around
> about this and someone jumped in and said it's not
> current it's voltage (or the other way around), but the
> idea is that you have a loop through which noise current
> (as well as signal current if there's a signal) can flow.

Agreed.

> If there's the same noise in both loops, the input
> impedance is identical and the source impedance is
> identical, both inputs (The inverting and non-inverting
> inputs) will see the same voltage drop across the source
> impedance. When they subtract in the differential
> amplifier, you get zero. But as far as the signal is
> concerned, the difference is the signal minus zero (no
> signal on the line with only a dummy resistor at the
> source end), and that's the signal.

Agreed.

> You can argue that if you have an inverted signal on the
> low input, you'll have twice the difference to work with,
> and that can give you a higher signal-to-noise ratio, but
> that isn't because noise is being rejected, it's because
> you have more signal and no more noise.

Agreed.

>> IME the difference for a line level input between zero
>> common mode rejection and 30-40 dB common mode rejection
>> can be huge, but after that you really need a lot of
>> noise to hear a difference when the common mode
>> rejection goes like 60 or 80 dB. OTOH, if a
>> manufacturer can go from 40 dB common mode rejection to
>> 60 dB or more common mode rejection by adding a $0.05
>> resistor, it should be done.

> And this is exactly why they do it.

Agreed.

[jtougas]

On 6 Feb 2007 10:15:42 -0500, (Scott Dorsey) trained
100 monkeys to jump on the keyboard and write:

>The Les Paul recording pickups are the classic example of that. Works very
>well. Hardly anybody likes them today, though.
>--scott

I actually had to rewire one of those damned things (varitone switch
died)... great sounding pickups in it, but *very* unforgiving to the
player.

--
jtougas

"listen- there's a hell of a good universe next door
let's go" - e.e. cummings