Connecting a TS microphone output into a regular XLR snake

[Iamthesky]

I need to connect what is essentially a two-wire microphone to a snake. It's an internal percussion instrument microphone adapter with a 1/4" TS output. Detailed questions got me the following:

 

It is basically just a dynamic microphone capsule adapted to sit dead center in the drum. 600 Ohm 70-12000hz -81+/-3 dB sensitivity.

 

and it's a TS connector because:

 

Electrically there is no gain to a TRS or XLR on a dynamic mic or magnetic pickup for that matter. Without the power requirement, and the accompanying signal noise of a powered mic then there is no need for a ground.

 

Regardless of the validity of that (although I am curious about it), I have to hook this up to a regular XLR snake. I was hoping for a TRS connector so I could just use a directly wired cable with confidence, but anything that involves dropping a wire always makes me want to consult with the experts first. At least as it's a plain dynamic mic I shouldn't have to worry about impedance or signal levels in the snake connection, right? Is there even such a thing as a non-transformer TS to XLR adapter?

 

Now to complicate matters, what if the output from this adapter had to run through guitar effects boxes before hitting the snake? That would require impedance matching to work correctly, I believe, and presumably on both the instrument and snake end of that effects chain?

 

My goals here are simple: get it right in our rehearsal studio and for recording there, and (more important in my mind) not give the sound engineer fits the first time this guy tries to hook this up in a live situation. This is a six-piece band with a lot of gear, and I want to present the sound engineer with a simple connection that he can hook into directly (we even have our own direct boxes where needed).

[trevcda]

I'd run it through a direct box if for no other reasons than to isolate it from the sound equipment and isolate it from any possible phantom power. While there may not be any "~~accompanying signal noise of a powered mic", balanced lines are more about keeping induced noise out of that line over long runs to FOH. My gut tells me that you may have to lean on the gains at FOH (and monitors, if separate) to get usable signal out of it, which may end up with a higher S/N ration than you may like. In that case an instrument preamp at the stage with a direct out on it may be more in order.

[soulx]

Regardless of the validity of that (although I am curious about it).

 

It's complete nonsense. The reason for the additional pin is to provide a balanced signal for noise rejection purposes. This is true whether the mic is powered or not.

[agedhorse]

The reason for the ground pin is to provide shielding of the dynamic element, and to provide a return path for condenser elements.

 

The signal level is WAY too low to pass through a direct box (which usually loses ~20dB from the transformation.

 

Do you know exactly how the existing element is wired. Without this info, there's no way to give meaningfiul advice. TS means nothing without knowing how it's terminated to the element.

[onelife]

The signal level is WAY too low to pass through a direct box (which usually loses ~20dB from the transformation.

 

That was my first thought too but from the OP...

"Now to complicate matters, what if the output from this adapter had to run through guitar effects boxes before hitting the snake? That would require impedance matching to work correctly, I believe, and presumably on both the instrument and snake end of that effects chain?"

If the signal from the mic can get some boost from the guitar effects box(es) then it could be enough to work with the DI.

[agedhorse]

Running through effects pedals, the transformer would be the correct route BUT the trnsformation is in the step up mode (impedance and voltage transform in the same direction).

 

So, the mic would need to go through a step-UP transformer which they make in 1/4"-1/4" for this purpose. It's a mic level to line level with 1/4" mic level in. Not common but it exists.

[wesg]

OP - Do you have one of those little mic pre boxes you can try? dbx Mini-Pre, Behringer MIC-100, Rolls Mp-13, Art Tube MP, that kind of thing?

 

Also, my take from the FP is that tip and sleeve and wired up to the capsule directly....if that's the case, can't he just send it down the snake as though it were a regular microphone, by building an adapter which is female TS to male XLR, connecting tip and sleeve to pins 2 and 3? Building by modifying a COTS TRS->XLR adaptor might be easy.

 

Wes

[agedhorse]

If the capsule is wired to tip and sleeve, no this won't work because the sleeve is always tied to pin 1 which is not part of the differential amp's input. The capsule would need to be connected to pins 2 and 3, the shield (pin 1) would act normally except that there willnot be a shield from the 1/4" connection onward to the capsule which would make it sensitive to hum but a much larger degree to RFI.

 

It could be modified such that pin 2 and pin 1 are connected together and tied to the shield but sometimes noise can become a problem depending on how clean or dirty the ground is, as not griound is tied directly to the inverting input and ground current can induce noise into the audio.

[Iamthesky]

Thanks. I figured this would be a can of worms, and I see I wasn't wrong about that. Anytime someone takes a shortcut for bad reasons, there's going to be problems, and since whatever mic the guy used was presumably set up to connect balanced (what mics aren't?), to hack that into an unbalanced output... well... it makes me cringe. Considering all the effort we go to in providing our own balanced signals through direct boxes and so on, to chop out the shield and force me to spend money to put it back is bordering on criminal.

 

I seems clear that to run through pedals properly, doing it right, we'd go instrument -> pre-amp -> pedals -> DI -> snake. That seems practical too as the pre-amp and DI can just be tacked on to the pedal board. As the vocalist in my last band discovered, depending on the pedals, some of them don't work well with a mic-level input signal.

 

Ideally I'd pull this box apart and hook up a properly wired XLR out instead, but I don't think I have the equipment to hand for that, nor do I really have the inclination to put that much effort into fixing someone else's hack job.

 

I can ask how the TS is wired. It appears to "work" if it's treated as wired like a regular instrument out, and probably that's all the guy figured it would be used for, just to 1/4" it to an amp.

[agedhorse]

Depending on what it is, there may be no way to connect a shield to the capsule. In that case you would wire using pins 2 and 3 as sleeve is not used properly in this case.

 

Standards are standards for a good reason!

[DBR013]

Hello Folks, Been away for a while, I'm back for a little bit. To answer the OP's question with a question. Aren't there transformers to do this job? 1/4" - XLR? Wouldn't they work as well or would there be an issue with those? Just a thought.

'

[DBR013]

Hello Folks, Been away for a while, I'm back for a little bit. To answer the OP's question with a question. Aren't there transformers to do this job? 1/4" - XLR? Wouldn't they work as well or would there be an issue with those? Just a thought.

'

[agedhorse]

Yes, there are transformers but you need to know more details to be sure the ratios are adequate for the application.