Phantom power (48V)

[raggie]

Hi

I have a Presonus Studio 68c.

If I go press the 48V button on the interface (phantom power) and go record using two XLR cables - and also a single TS cable (jack) as a third option, will that jack connection also be affected by the phantom power and maybe go ruin the device that's connected to that line? Or will it be absolutely safe to do so?

I have a Radial Engineering Pro D2 for the two XLR connections, and I was told earlier on, they'd be safe. But I only have one of those.

The third option is of something I go record through a jack cable, only. Will that be dangerous to do so, still? Or will the TS cable (jack) "bypass" the phantom power as it's not XLR?

Best regards,
Ricki

[Arpangel]

The manual,

"48 Volt Phantom Power. Studio-series interfaces provide 48V phantom power for the microphone inputs. Pressing the 48V button switches phantom power on and off for all microphone inputs; the button will illuminate in blue when phantom power is available on the microphone preamplifiers. .WARNING: Phantom power is only required for condenser microphones and can severely damage some dynamic mics, especially ribbon mics. Therefore,switch phantom power off when it is not required. Consult the user documentation that came with your microphone before engaging phantom power.

XLR connector wiring for phantom power:Pin 1 = GND Pin 2 = +48V Pin 3 = +48V.

Note, phantom power is on the pins of the XLR socket.

[Wonks]

There is no phantom power present on the TRS connections for the combi sockets for this unit.

But it's worth asking the question if you are unsure as there have been the occasional units which have added phantom power to TRS connections.

[ef37a]

I think that warning about phantom power and dynamic mics is unnecessarily panic inducing and a bit of A saving from the legal dept?

Hugh has told us many times that 48V is perfectly harmless to dynamic mics and even ribbons except in the case of a faulty cable. For sure! If I had a £5000 vintage ribbon I would not let phantom power anywhere near it but that is just common sense for an extreme situation, 'it do 'appen.

As Wonks says, it is always wise to check that 48V is not present on a jack. Never should be but it does happen. One more reason for newbs to buy a digital multi-meter!

Dave.

[James Perrett]

I think that warning about phantom power and dynamic mics is unnecessarily panic inducing and a bit of A saving from the legal dept?

Presonus are American - and the mics that don't like phantom power also tend to be old American models which aren't so prevalent elsewhere in the world.

However, the average studio is highly unlikely to have any mics that aren't compatible with phantom power unless they have some badly designed custom made mics or badly designed cables. I'll admit to having both of these - but they were made by me in the days before I owned anything that included phantom power.

[Hugh Robjohns]

If I go press the 48V button on the interface (phantom power) and go record using two XLR cables - and also a single TS cable (jack) as a third option, will that jack connection also be affected by the phantom power and maybe go ruin the device that's connected to that line? Or will it be absolutely safe to do so?

We need a bit more information to give a definitive answer because it's what is connected on the end of the XLR cable that matters! I guessing you're not talking about connecting microphones her...

In most — but not all — devices, phantom power is only ever present on the XLR sockets. TS and TRS jack sockets don't normally carry phantom power even if it is switched on. So anything plugged into a jack socket (even a combi-XLR jack socket) is usually safe. But, if in doubt, check!

Phantom is normally required for capacitor mics, but is safely ignored by (balanced) moving coil mics. And most ribbon mics wired correctly for balanced operation are fine with phantom too... but it obviously makes sense to switch phantom off if you don't need it.

However, Phantom can pose a risk to electronically balanced line level sources — Interface outputs, keyboards, DJ consoles etc — potentially destroying the output circuitry!

Ideally, then, these line-level sources should all be connected to TRS inputs rather than XLR inputs... but sometimes you don't get that option.

If you must connect via XLR and if you can't disable phantom power it's a good idea to connect via a DI box or line isolator box. Both will block phantom power from reaching the source

I have a Radial Engineering Pro D2 for the two XLR connections, and I was told earlier on, they'd be safe.

Yes, you were told right! The ProD2 is a passive DI box, and the transformer inside it will block phantom power from the source. It also reduces the signal level from (nominally) line level to mic level, so you'll probably need to dial in some extra gain in the mic preamp.

The third option is of something I go record through a jack cable, only. Will that be dangerous to do so, still? Or will the TS cable (jack) "bypass" the phantom power as it's not XLR?

No problem with the jack input as phantom should not be present (and definitely isn't in that Presonus).