Connecting unbalanced outs to balanced IN?

B

boldandfunny

New member
Stupid questions from a noob here - but I can't find an answer on this forum

I am probably buying a Tascam US-600.
Unit has 4 balanced mic inputs + 1 unbalanced guitar HighZ (as a combi with mic1) +
3 balanced line inputs (as combi with mic 2-4).
Description of Mic/Line 2,3,4 combies says:
XLR: (1:GND; 2 Hot; 3 Cold)
TRS (1/4): Tip: HOT, Ring: COLD, Sleeve:GND.

Question 1:
Say I have an unbalanced mike - can I connect it easily? Any problems (like shorting phantom power and killing it by mistake?).
I guess noise will be quit bad if mike cable is of any length.... :-(


Question 2:
I have a small Behringer mixer with unbalanced line out: can I connect those to say 3 and 4 (balanced) line inputs?
I am not worried losing 3 or 6 db of dynamic range really - do I really need a DI box for that?

I am not sure what is standard layout for unbalanced TRS jug : I guess TIP will be hot(signal) and RING/Sleeve will be all long sleeve connected to ground?
So I will get unbalanced "signal" connected to HOT and Ground connected to COLD and Ground - right?

A)Is this going to work?
B)Am I going to get really bad distortion etc?
C)I am not worried about noise probably as I am talking LINE levels here?

Basically is DI a MUST to connect unbalance OUT to balanced input?
Sorry for stupid question probably asked a million times!
Ta very much,
Sergei.
 
bouldersoundguy said:
t
But I have to ask, what mic do you have that's unbalanced?
Click to expand...
Ha-ha - one from Wallmart costing £5. I am not pretending I am a professional :-)

Great article about hum etc. Need more time to figure it out but basically it says unbalanced into balanced might work with a bit of jigery-pockery.

What about danger to phantom power?
I guess a combi XLR/TRS will not have phantom on TRS, but they also sell XLR/TRS adapters ( I have a couple of those). Hopefully they do not short +48V to the ground :-) but I saw manual saying that one can ruin 48V by connecting unbalanced to balanced?
How does this happen? Is this possible?
Thanks!
 
Won't work for me - I need stereo from effects pedal/keyboard so the 2 mono unbalanced outs will have to go into a "balanced line"/mike combi.
I will be probably doing most of my instrument recordings "wet" apart from mikes. No latency issues this way either as my computer is only Pentium 4.

Hopefully 48v is not on TRS "line" input in at all. I guess I can check by sticking a stereo cable (I hope layout of TRS Tip in a stereo cable is the same as a balanced TRS cable?) and checking with phantom on. One would hope that only an XLR connector gets +48v.

Question: Are balanced 1/4 TRS used for condenser mikes at all or is it a no-no?
I mean is there an unwritten rule that a condensed mike must have XLR or do they come with a balanced 1/4 inch as well?
Or in other words: do you ever get a 1/4 balanced TRS input for condenser mikes with phantom power?
Just curious.
 
How to Wire an XLR to a 1/4" Jack

Here ya go.

Phantom power won't be presented at the jack socket of any interface for this reason.
I don't think you mentioned it, but never wire a male XLR as unbalanced; That's where you would run into to phantom issues.


boldandfunny said:
I mean is there an unwritten rule that a condensed mike must have XLR or do they come with a balanced 1/4 inch as well?
Or in other words: do you ever get a 1/4 balanced TRS input for condenser mikes with phantom power?
Just curious.
Click to expand...

There's no rule, but generally speaking professional microphones will be balanced.
Condenser mics will almost always have XLR connection because the require phantom power.
There are exceptions, like battery powered mics or mics that take their power from cassette recorders/cameras etc.

DI boxes are for connecting instruments to microphone level inputs. You shouldn't need a DI box anywhere else in your setup.
 
Thanks Steenamaroo.
Still confused a bit though: :confused:

From Wiki page "phantom power":
<<Phantom powering can cause equipment malfunction or even damage if used with cables or adapters that connect one side of the input to ground, or if certain equipment other than microphones is connected to it.>>
This kind of goes against what your link suggesting (connecting 3 to 1 of XLR connector i.e. Cold signal with ground)?
Or is WIKI page wrong?
As phantom power applied between ground (1) and both cold and hot (2 and 3) then shorting 3 and 1 is shorting the output of the phantom power supply to ground.
I guess most phantom power supplies are happy with it (as current supplied is generally very small there may be a bit internal resistor I guess). This is what Steenamaroo's cable link suggests (I don't really doubt that it works - in most cases).

If WIKI page is right too (that I can actually damage "some" phantom power supplies - it does not say "all" ) this implies that some phantom power supplies to don like to be shorted to the ground (which is reference for phantom power, of course).

Did I get it right there? Or is WIKI page effectively wrong and EVERY phantom power supply is designed to tolerate shorting of it output (as Steenamaroo suggests)? Is it one of these unwritten rules?
Thanks again.
Sergei.
 
boldandfunny said:
This kind of goes against what your link suggesting
Click to expand...

No it doesn't. My link is XLR female to jack male.
Phantom power isn't presented to a jack.


"but never wire a male XLR as unbalanced; That's where you would run into to phantom issues."
Male being the end that goes into an interface.
 
bouldersoundguy said:
Or just stick it in a line input and see if there's enough gain.
Click to expand...
Oh, I thought this would never work - mike is -50/-60 Dbu (1-3mV) and line is -10bBu (300mv).

I'd simply want to know (not guess) if shorting 1 and 3 on balanced input is going to burn our +48 v or not. I lke to know things :-). From what WIKI sample schematics of +48 v source it must have a 3.6 kOhm resistor in series to each of cold and hot. This is probably a standard (i.e. every manufacture have to do this).
I guess this resistor(s) probably protects +48V from dying if shorted. Resistor must be fairly big though (0.6 wt on it when out is shorted). SO if manufacturer is going cheap and uses a smaller wattage resistors they may burn if supply is powerful enough. Just guessing of course but at least I have an idea of how phantom\power works now...:-)

Thanks Steenamaroo and BoulderSoundGuy!
 
There is considerable confusion and concern as to the potential damage that phantom power can cause, both to external equipment and the device supplying that power. Most of the concern is illfounded.

All 48volt phantom supplies feed thru' a 6k8 resistor on pins 2 and 3 of the XLR. Thus the absolute maximum current that could flow if both pins were shorted to pin 1 is 14mA and the dissipation in the resistors a shade under 0.7watts or less than 0.35W per resistor. I suppose a very wee surface mount R could be damaged but any manfctr that made a spook juice output that was not short circuit proof should be shot!

So, scratch one concern, you cannot damage a mic input by shorting pins willy-nilly..BUT! You will cause loud bangs and pops thru the system with possible damage to monitors, cans, ears and nerves!

Can Ppwr then damage external equipment? Yes, most electronics can stand the internal supply voltages on its input terminals but 48volts is way above the norm' so you could pop chips or transistors. It is also possible that the potential 14mA could damage a mic coil or a very small transformer but unlikley.

Ribbon mics are often mentioned and here the damage is mechanical. The current slams the ribbon about and misaligns or even tears it, note however that a CORRECTLY wired ribbon is in no danger but ***t'appen! So if I had a nice 4038 I would keep it WELL away!

Lastly TRS sockets. It is the case that equipment has been made with +48V on a line TRS so always best to check....Everyone in this recording game has a digital multimeter, DON'T they?

Dave.
 
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