Topic: unballanced > ballanced line > unballanced preamp

[kuuan]

To make ballanced cables for otherwise unballanced mics to run long cables can I go

• unballanced mic > http://www.fivefish.net/diy/balanced/default.htm resp. http://www.fivefish.net/diy/balanced2/default.htm > unballanced preamp?
• do I need some circuit to 'downconvert' to unballanced to go to the unballanced preamp?
• in the case of the SP-CMC8, is it simply a matter of wiring, no circuit needed at all? - as it seems looking at the AT853 unmod thread, though the pics there are not available any more so I don't understand yet.
• and if so, can I also simply use regular stereo mini plugs, 1 for each mono line, instead of mini XLR or XLR? Or are there disadvantages besides being less robust and interlocking?
  
• and if so, is this - that only wiring, no circuit is necessary - true for the SB-CMC mics only for being modded ballanced mics, but not for other unballanced mics for which a circuit as shown is required?
  
  

oops, should have better fit at the 'cables' section, sorry

[pigiron]

do I need some circuit to 'downconvert' to unballanced to go to the unballanced preamp?

yep...

Notice that the unbalanced plus signal (+) is going to the negative input on one opamp and the positive on the other... this is because a balanced cable carries two signals (hot and cold) 180 degrees out of phase... the advantage is, any noise injected into the cable (placing too near an electric motor for instance) will be canceled out by the preamp input circuit (which only outputs the differences between the two signals and the noise will supposedly be equal and in-phase on both wires).

An unbalanced line is simply a signal compared to ground (needing only two wires per mic)... and this is what an unbalanced preamp is expecting.

BUT... unless you're going fairly long distances or in an (electrically) noisy environment, I'd sure try to make my life easier without all this gorp... i.e. I'd try an experiment using an unbalanced extension cable before I embarked down this path... those circuits add capacitance, impedance, etc to your very low level signal path... and the opamp themselves induce a small amount of noise.

in the case of the SP-CMC8, is it simply a matter of wiring, no circuit needed at all? - as it seems looking at the AT853 unmod thread, though the pics there are not available any more so I don't understand yet.

hmmm... confusion... if you're asking if the SP-CMC8's can go directly into an unbalanced preamp, then I think the answer is yes... most of the Sound Professional mics have a 1/8 inch TRS (Tip, Ring, Sleeve) connector attached to two microphones... hence unbalanced... one of the 3 TRS connections (can't remember the arrangement) will be left signal, one will be the right signal, and one is ground (the same ground is used on both mics).

and if so, can I also simply use regular stereo mini plugs, 1 for each mono line, instead of mini XLR or XLR? Or are there disadvantages besides being less robust and interlocking?

one of the other advantages the XLR connector has over TRS is shielding... and it's also easier to maintain the exact same wire length for the 3 conductors (which is somewhat important for balanced), but I think a TRS connector could be used without much adverse affects (after all, it's used on some balanced pro gear).

and if so, is this - that only wiring, no circuit is necessary - true for the SB-CMC mics only for being modded ballanced mics, but not for other unballanced mics for which a circuit as shown is required?

huh?... I'm totally confused... or stoned 

[Church-Audio]

The mics your talking about are unbalanced mics they happen to be three wire mics meaning that the mics require a separate bias supply. These mics should be used with some type of preamp if your going into a unbalanced line input however if your going into a unbalanced mic input then no preamp is needed. That being said its always a good idea if your going to use a mic input for recording concerts that some form of pad or attenuation be used in front of the preamp to avoid overloading.

The explanation of balanced by Pigiron was very good. The type of balanced circuit he was talking about is called differentially balanced. There is also transformer balanced. There are arguments as to witch sounds better. But he has answered your question very well.


Chris Church

[kuuan]

Thank you very much Pigiron for your extensive answer and Chris for your elaboration.

huh?... I'm totally confused... or stoned 

I don't know if you are. That certainly would add to the communication problem caused by my poor english and because I am, both...

do I need some circuit to 'downconvert' to unballanced to go to the unballanced preamp?

yep...

Notice that the unbalanced plus signal (+) is going to the negative input on one opamp and the positive on the other... this is because a balanced cable carries two signals (hot and cold) 180 degrees out of phase... the advantage is, any noise injected into the cable (placing too near an electric motor for instance) will be canceled out by the preamp input circuit (which only outputs the differences between the two signals and the noise will supposedly be equal and in-phase on both wires).

clever system, thank's for explaining, slowly I understand just how important ballanced really is.

An unbalanced line is simply a signal compared to ground (needing only two wires per mic)... and this is what an unbalanced preamp is expecting.

BUT... unless you're going fairly long distances or in an (electrically) noisy environment, I'd sure try to make my life easier without all this gorp... i.e. I'd try an experiment using an unbalanced extension cable before I embarked down this path... those circuits add capacitance, impedance, etc to your very low level signal path... and the opamp themselves induce a small amount of noise.

understood, thank's, my wish to convert to ballanced just for a cable run is done with.

in the case of the SP-CMC8, is it simply a matter of wiring, no circuit needed at all? - as it seems looking at the AT853 unmod thread, though the pics there are not available any more so I don't understand yet.

hmmm... confusion... if you're asking if the SP-CMC8's can go directly into an unbalanced preamp, then I think the answer is yes... most of the Sound Professional mics have a 1/8 inch TRS (Tip, Ring, Sleeve) connector attached to two microphones... hence unbalanced... one of the 3 TRS connections (can't remember the arrangement) will be left signal, one will be the right signal, and one is ground (the same ground is used on both mics).

'one 1/8 inch TRS connector attached to two microphones..hence unballanced'....again sounds if the are unballanced only because of the wiring into a TRS plug.

Chris however says:

The mics your talking about are unbalanced mics they happen to be three wire mics meaning that the mics require a separate bias supply

3 wired but unballanced...well, I do not understand that.
And that is my confusion: Are they ballanced and can be made into fully ballanced simply by connecting each mic to a three pin connector? Or are they unballanced but can be more easily converted to ballanced than 2 wired mics? What is the significance of the three wires and do they help if I want longer cable runs?

Why I ask all these questions:
I want to separate the mics to be able to e.g. run split omnis and generally longer cable runs, and I was wondering how best to do that.

So better I simply ask:
Separating the CMCs to be able to run them separately with longer cable runs, which is the best solution?
To unmod them? Would they need full phantom power then?
Or - the famous 3 wired battery box?
or...no worries, just put extension cables...
note: I mostly won't record very loud music but simply want to experiment with different mic configurations.

[Church-Audio]

Thank you very much Pigiron for your extensive answer and Chris for your elaboration.

huh?... I'm totally confused... or stoned 

I don't know if you are. That certainly would add to the communication problem caused by my poor english and because I am, both...

do I need some circuit to 'downconvert' to unballanced to go to the unballanced preamp?

yep...

Notice that the unbalanced plus signal (+) is going to the negative input on one opamp and the positive on the other... this is because a balanced cable carries two signals (hot and cold) 180 degrees out of phase... the advantage is, any noise injected into the cable (placing too near an electric motor for instance) will be canceled out by the preamp input circuit (which only outputs the differences between the two signals and the noise will supposedly be equal and in-phase on both wires).

clever system, thank's for explaining, slowly I understand just how important ballanced really is.

An unbalanced line is simply a signal compared to ground (needing only two wires per mic)... and this is what an unbalanced preamp is expecting.

BUT... unless you're going fairly long distances or in an (electrically) noisy environment, I'd sure try to make my life easier without all this gorp... i.e. I'd try an experiment using an unbalanced extension cable before I embarked down this path... those circuits add capacitance, impedance, etc to your very low level signal path... and the opamp themselves induce a small amount of noise.

understood, thank's, my wish to convert to ballanced just for a cable run is done with.

in the case of the SP-CMC8, is it simply a matter of wiring, no circuit needed at all? - as it seems looking at the AT853 unmod thread, though the pics there are not available any more so I don't understand yet.

hmmm... confusion... if you're asking if the SP-CMC8's can go directly into an unbalanced preamp, then I think the answer is yes... most of the Sound Professional mics have a 1/8 inch TRS (Tip, Ring, Sleeve) connector attached to two microphones... hence unbalanced... one of the 3 TRS connections (can't remember the arrangement) will be left signal, one will be the right signal, and one is ground (the same ground is used on both mics).

'one 1/8 inch TRS connector attached to two microphones..hence unballanced'....again sounds if the are unballanced only because of the wiring into a TRS plug.

Chris however says:

The mics your talking about are unbalanced mics they happen to be three wire mics meaning that the mics require a separate bias supply

3 wired but unballanced...well, I do not understand that.
And that is my confusion: Are they ballanced and can be made into fully ballanced simply by connecting each mic to a three pin connector? Or are they unballanced but can be more easily converted to ballanced than 2 wired mics? What is the significance of the three wires and do they help if I want longer cable runs?

Why I ask all these questions:
I want to separate the mics to be able to e.g. run split omnis and generally longer cable runs, and I was wondering how best to do that.

So better I simply ask:
Separating the CMCs to be able to run them separately with longer cable runs, which is the best solution?
To unmod them? Would they need full phantom power then?
Or - the famous 3 wired battery box?
or...no worries, just put extension cables...
note: I mostly won't record very loud music but simply want to experiment with different mic configurations.

Balanced mics have a Positive pin negative pin *these are signal not to be confused with ground* the AT mics your talking about are wired this way they have a Bias pin for the fet supply voltage a signal out pin for the output of the capsule and a ground. They are not balanced a true balanced mic has a three pins one is signal positive one is signal negative one is ground. Then there is the whole impedance issue unbalanced is typically 1k to 10k impedance balanced is typically 150ohm to 600 ohm * there are exceptions to this rule* but they are few and far between.

So how does AT get around this? how do they allow for long cable runs its simple. They use a fet buffer amp on the other end to boost the signal this increases the signal to noise ratio. The other thing they do is produce a capsule with a EDIT hooter "HOTER"output so, that the signal to noise ratio of inducted noise is minimized. This solution works there are also things they do with the output impedance of the mic that makes it capable of running longer distances with less problems as well. But make no mistake about it, just because a mic capsule is three wire does not make it balanced. You always have to have a + output and a - 180 degree output and ground to make it balanced.

[kuuan]

thank's again Chris.

I understand the CMCs are not ballanced, the wiring part, impedance and the rest is - still? moslty beyond me.
Time I looked into the significance of impedance, and

They use a fet buffer amp on the other end to boost the signal this increases the signal to noise ratio. The other thing they do is produce a capsule with a hooter output so, that the signal to noise ratio of inducted noise is minimized.

a fet buffer? This is inside the mic?
but...what's a hooter output?

This solution works there are also things they do with the output impedance of the mic that makes it capable of running longer distances with less problems as well.

goood

What I'd like to find out but still don't know:

I want to separate the CMCs to be able to run them separately resp. with longer cable runs.
How to do that best?
Should I just terminate each with a separate stereo mini plug to optionally run 'normal' unballanced extension cables?
Or is there any other better solution?

• unmod them?
• could the 3 wired battery box come into play?
• any other? 
• anything I must observe so I do not obsolete the advantages of the AT design you mentioned?