ES-57 and plug-in power?

[dgpretzel]

I wonder if it is OK to plug an ES-57, or any dynamic mic for that matter, into a jack with plug power (via non-transformer adapter). Specifically, I'm wondering if the ES-57, and dynamic mics in general, have a blocking capacitor that would protect the coil from the DC current that plug-in power would produce.

I'm tending to think that the ES-57 is protected because I measured the resistance with a multimeter, and got a momentary spike of current, and then an open circuit.

Thank you.

DG

 

[robin watson]

I wonder if it is OK to plug an ES-57, or any dynamic mic for that matter, into a jack with plug power (via non-transformer adapter). Specifically, I'm wondering if the ES-57, and dynamic mics in general, have a blocking capacitor that would protect the coil from the DC current that plug-in power would produce.

I'm tending to think that the ES-57 is protected because I measured the resistance with a multimeter, and got a momentary spike of current, and then an open circuit.

Thank you.

DG

No blocking capacitor in any dynamic I know - it's not the mic that needs protecting, it's whatever's supplying the phantom power that might get damaged. When you say 'a jack with plug power' are you refering to a mini-jack with 'plug-in power,' such as you'll find on an MD Walkman or something?

 

[PhilGood]

Are you talking about phantom power? You need to be more specific.

Phantom power will not hurt a mic like the ES-57 or SM-57 because it has an isolation transformer built in.

 

[dgpretzel]

Thank you for your comments.

No, I am not intending to mean phantom power. Phantom presents across pins 2 and 3. It is, therefore, common mode, and wouldn't affect the coil.

I am referring to the low (typically several volts) DC voltage present in some consumer electronic devices with 1/8" mini jacks for mic input. I am uncertain whether the plug power (isn't is also referred to as bias voltage) is applied across tip and sleeve, or ring and sleeve. If tip, would it not create a continuous DC current through the coil (unless there is a capacitor in the mic)? And, if ring, would the applied voltage not be shorted out when pluging in a TS plug, which some (non transformer-based) balanced-to-unbalanced adapters might use? (I suggest a possible short because, with TS configuration, the sleeve would extend across both the sleeve and ring portions of a TRS plug.)

THank you, again.

Regards,

DG

Edit...
P.S. If there is no capacitor in the ES-57, is there another explanation for the momentary current, then open circuit, which I think (could be "pilot error", I will double check) I observed when measuring resistance across pins 2 & 3 of the ES-57 XLR connector.

2nd Edit...
Ahhh-- isolation transformer would explain why ES-57 would not be damaged or affect the sound, but I don't think isolation transformer would explain the observed open circuit across pins 2 & 3 of the ES-57.

 

[mshilarious]

Thank you for your comments.

No, I am not intending to mean phantom power. Phantom presents across pins 2 and 3. It is, therefore, common mode, and wouldn't affect the coil.

I am referring to the low (typically several volts) DC voltage present in some consumer electronic devices with 1/8" mini jacks for mic input. I am uncertain whether the plug power (isn't is also referred to as bias voltage) is applied across tip and sleeve, or ring and sleeve. If tip, would it not create a continuous DC current through the coil (unless there is a capacitor in the mic)? And, if ring, would the applied voltage not be shorted out when pluging in a TS plug, which some (non transformer-based) balanced-to-unbalanced adapters might use? (I suggest a possible short because, with TS configuration, the sleeve would extend across both the sleeve and ring portions of a TRS plug.)

THank you, again.

Regards,

DG

Edit...
P.S. If there is no capacitor in the ES-57, is there another explanation for the momentary current, then open circuit, which I think (could be "pilot error", I will double check) I observed when measuring resistance across pins 2 & 3 of the ES-57 XLR connector.

2nd Edit...
Ahhh-- isolation transformer would explain why ES-57 would not be damaged or affect the sound, but I don't think isolation transformer would explain the observed open circuit across pins 2 & 3 of the ES-57.

OK, a few things:

Plug-in power is generally, but not always, a stereo connector. That means the voltage is applied to tip and ring, but tip and ring would usually be routed to different microphones. If you connect a single balanced microphone to a stereo plug-in power jack, you may get undesirable results.

So let's say you have a splitter cable that connects pin 2 to tip and pin 3 and 1 to sleeve (for left channel). Yes, that will put a small DC current across the mic's transformer. It is not a short, since the plug-in power will be supplied across typically 4K to 10K ohms, yielding a current of somewhere between say 300 and 700uA. The transformer should not be bothered by that at all.

As for measuring your ES57, pins 2 and 3 should measure the DC resistance of the transformer secondary (or if for some reason it lacks a transformer, the voice coil). Either pin to pin 1 should be open. It would be highly unusual for a dynamic mic to use blocking capacitors, since they don't need them, but if present, that could explain your result. Or it could be pilot error . . .