ruffrecords
Well-known member
Then there must be something wrong with your setup. I a properly wired transformer less mic has no route for phantom current to flow in the mic.
Cheers
Ian
How to protect a transformer-less mic?
- Thread starter Hank Dussen
- Start date
Help Support GroupDIY Audio Forum:
Cheers
Ian
pucho812
Well-known member
I did a few different transformerless 57’s including a couple that have the beta 52 transformerless circuit installed. Never had an issue of phantom on those. I won’t even get into phantom and ribbon mics and what is not recommended but won’t pull your ribbon out of alignment. If phantom is actually applied.
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Bjorn Andersson
Active member
I think the only way to break a dynamic capsule without a transformer is if the cable is unbalanced (pin 1 to pin 2 or pin 3) or accidenly damaged.
With a unbalance cable the coil in the capsule gets the whole +48Volt and gets destroyed...
With a unbalance cable the coil in the capsule gets the whole +48Volt and gets destroyed...
Glenn Wardle
Member
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As an FYI, I have a Native Instruments Complete Audio 6 (MK1) USB audio interface. The 48 volt phantom power pullups are just 1.2k each, so this is getting on for 80mA when shorted to ground. I can't comment if any others follow this questionable practice but I would strongly suggest checking the mic interface if you have concerns.
RuudNL
Well-known member
Standard phantom power resistors are 6.8 K for 48 V. phantom power.
In this case (one resistor shorted to ground) current can only be 7 mA.
In this case (one resistor shorted to ground) current can only be 7 mA.
puddingstud
Member
Why would I? Forums said it was 100% harmless.
puddingstud
Member
Well, let's stick to this unbeatable argument (which isn't, because if cables are often wired incorrectly, then it makes the practice factually unsafe)
I just did a thorough continuity test on the cable: it shows it's wired properly.
You'll tell me maybe it's the soundcard, or anything? Then the conclusion is the same: DO NOT put phantom power on transformerless SM57, as something in the chain could easily make it crash.
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Transformerless, you say? How is it (re)wired internally, then?
"Thorough" as in measuring between pin 1 male & pin 1 female, pin 2 male & pin 2 female, and pin 3 male & pin 3 female?
Or pin 1 male and pin 1-2-3 female, and same for the other two male pins?
puddingstud
Member
I'll check that (that would keep my point: AVOID or CAREFULLY CHECK YOUR WIRING, and don't assume it's safe)
Second.
This is simply a wrong implementation of phantom power, or you're quoting it wrongly.
8mA is not enough to upset a naked '57 capsule
I suspect you' re trolling
/Jakob E.
puddingstud
Member
Pin 1 is originaly wired to shield, and I kept that.
Pin 2 to +
Pin 3 to -
That's ok isn't it?
What else could be wrong? what kind of shortage or mistake could hurt the mic with 48V?
So the green wire coming from inside the capsule to the solder-tag, goes to pin 2, and the yellow to pin 3 (or reversed - that's less relevant)? If that's the case, that should sound about right, indeed.
So the voice coil (that's now between XLR 2-3) measures... open-circuit now?
And/or no chance of any wires having broken off between the bottom of the capsule and the XLR? It takes quite "a few" turns to disassemble / reassemble the body in a 57/58...
puddingstud
Member
I guess so: I changed to colors to +=red, -(marked "FL")=purple
Hmm no, I've got a continuity for some reason... maybe inside the capsule?
OMG i remember something: the mic does not cut all the sound. It render well noises, especially tapping/rubbing on the mic! Just the opposite as a symmetrical cable should do.
Don't know if it's helping...
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GermanTech
Member
GermanTech
Member
Correct ! That doesn'nt destroy a mic coil .
puddingstud
Member
MagnetoSound
Well-known member
Sounds like maybe the coil is stuck. It may have been pulled into the gap when the power was applied and got stuck. In that case it would still pick up handling noises but not function properly as an acoustic microphone.
It would be worth removing the grille to have a look.
If this is the case, it would still imply a misconnection at some stage, as there would have been enough current flowing through the coil to pull it into the magnet.
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Glenn Wardle
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I am well aware that 1.2k is wrong. I only found out because I took the thing apart when I found my voltage measurements for powering my DIY microphone were far higher than they should have been. I've no idea why they would fit the wrong resistors and the MK1 KA6 hasn't been made for years, but I mentioned it as other mic inputs might be similar.
Perhaps it's not 48V after all, but e.g. 12V phantom power?
Phantom Specs says 11-52V - only you need to change resistors accordingly
But still you can't break a naked sm57 capsule with any sort of phantom power variation - the capsule is around 10 Ohms and fairly heavy wire:
https://gearspace.com/board/low-end-theory/728752-sm57-transformerless-impedance.html
Phantom Specs says 11-52V - only you need to change resistors accordingly
But still you can't break a naked sm57 capsule with any sort of phantom power variation - the capsule is around 10 Ohms and fairly heavy wire:
https://gearspace.com/board/low-end-theory/728752-sm57-transformerless-impedance.html
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