Will this Tascam fry my instruments with phantom power?!

C

cmharwood89

New member
Hi all,

A bit of background: I'm juuuust starting to put together some equipment that I can use to record demos, etc. from home. I'm usually running one mic for vocals, with one instrument (sometimes mic'd, sometimes plugged in), so I'm trying out some basic 2-in, 2-out USB interfaces.
I very recently picked up a Tascam us-122MKII recording interface, which seems solid (Product: US-122MKII | TASCAM). It's discontinued now, so I got a good deal.

However, I just noticed THIS deal on musiciansfriend (TASCAM US-2x2 MXL 990/991 Package** | Musician's Friend) for $199, which seems like a fantastic deal! I'm considering returning the one I have and buying the package, especially because the interfaces look essentially identical.

That's my issue... they LOOK nearly identical, but my question is about the subtle difference in the input jacks. I'm afraid I might lose some functionality if I make the swap.

The US-122 (the one that I own now) has a separate XLR mic input and balanced/unbalanced TRS input on each channel. The US-2x2 has a hybrid XLR/TRS jack on each channel.

If I understand correctly, my current interface (US-122) provide phantom power ONLY to the XLR jacks. So scenario #1: I can switch on phantom power and plug in a condenser mic on say, the left channel. Great. If I plug an unbalanced dynamic mic, line input, or instrument into the TRS jack on the right channel, there's no problem. The TRS jack sees none of the 48VDC phantom power. I can plug my guitar in with the high-impedence switch on, power a condenser mic, and everything will be great.

Now, scenario 2, involving the US-2x2 (the one I'm considering trading for): I can switch on phantom power and plug in my condenser mic on the left channel, just like before. Awesome. BUT NOW, what about the right channel? The user manual states "the phantom power switch changes the settings for both US-2X2 input channels simultaneously..." So if I plug anything EXCEPT a condenser mic into the right channel, I risk frying it.

By combining the XLR and TRS jacks, has Tascam made it impossible to connect a condenser mic and instrument simultaneously? It looks like the pins get shared between TRS and XLR jacks with the hybrid connectors... If I plug in a guitar, will it see phantom power, or is it possible that the line/instrument switch disables phantom power on the channel in question when set to the "instrument" level?

I have a hunch that this is exactly why Tascam offers 2-input interfaces with separate mic and line/instrument jacks (US-322) for a little more money, but I just don't know for sure. If somebody has some experience with what inputs can/can't safely be used together with these or similar interfaces, I'd be super thankful.

Happy holidays!
Casey
 
Dynamic mics don't worry at all about phantom - in fact, many people have mixers that have global phantom - one switch applies it to every socket. The only thing it's not recommended for is ribbon mics, although occasionally I've plugged up a ribbon without turning it off.

Phantom power is pretty well user proof, and the current low enough to not do any harm. I've never had a mic damaged by mis-applied phantom, and although there are many tales on the internet, they rarely are attributable and always friend of a friends next door neighbour's dogs vet's brother stuff.

I've got a one button phantom mixer in one of my studios and it's always on, and it just means any mic works. I don't worry at all.
 
Thanks for the reply. The interfaces I'm looking at indeed have a global phantom switch. Wouldn't an unbalanced input still potentially cause an unbalanced short if phantom power were sent down the TRS jack? In the first of the interfaces I mentioned, the XLR and TRS jacks are physically separated and the manual states that phantom power is supplied to the MIC inputs (XLR jacks). Because of that, I'm pretty confident that the TRS jacks are isolated from the phantom power.

In the second interface, I'm worried that the XLR/TRS combo jacks remove that isolation. This isn't helped by the fact that the manual makes the more-vague statement that phantom power is applied to "ALL INPUT CHANNELS," instead of just the MIC inputs. I'm afraid that if I plug in an unbalanced 1/4 cable while phantom power is on, I'll inadvertently send phantom power down the instrument cable or short out the PP entirely and risk burning up my interface.

Am I crazy?
 
cmharwood89 said:
In the second interface, I'm worried that the XLR/TRS combo jacks remove that isolation.
Click to expand...

The XLR/TRS combo jacks do not remove that isolation.

Phantom power is supplied only to the XLR part.

Phantom power through XLR presents no danger to dynamic mikes
 
Some devices just don't like phantom being shoved up them! Oddly, my experiences seem to show that audio quality is rarely an issue, apart from a few Allen and Heath mixers that seem to develop an odd warble as their own capacitors charge up and discharge in a loop, while Soundcraft light up LED meters but rarely produce audio artefacts. If you are dealing with balanced circuits, you can always disconnect the XLR pin 1 connection, as the audio will be unaffected, but you break the DC path that uses the ground. Always worth a go?
 
Well that seems pretty cut and dry. It sounds like I should be A-OK turning on phantom power for one input and plugging a 1/4" line to a guitar or keyboard into the other. Thanks for the feedback! I think I'll pick up that Tascam package.

Do dynamic mics just leave the ground pin hanging on the mic-end?

It's interesting that the XLR/TRS combo jacks are so popular if the jacks remain isolated from one another electrically. Is it simply a space-saving tactic?
 
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