Ultra-Lite AVB Can I use a 1/4" mic adapter?

[ronausti]

I'm installing my new Ultra-Lite AVB and have just realized that it's possibly the only interface in the category that doesn't have a combo mic jack. My headset mic is an electret (powered by a "battery box") with a standard TS 1/4" (or 1/8") plug. In other words, it behaves like an ordinary cheap dynamic mic with a standard two-conductor (tip/ground) mono phone plug.

Q: Can I use a 1/4"-to-DIN adapter to connect it to the mic input?

In interfaces that have a combo mic jack, I've had no problem with volume level or sound quality.

Even if I could use a Line In for now, I don't want to tie up a line port for that.

Second question: Why do I always discover things like this three minutes after Tech Support closes?

[ronausti]

UPDATE: Please see mikehalloran's reply, below, regarding the possible inadvisability of my solution. As it happens, the UltraLite AVB manual confirms that pin 2 is hot, but it does not indicate how to configure the other two. In my case, I can report that the simple connection adapter I've described works well enough for Skype usage (my VoiceStar headset mic is first run through an Andrea APS-100 battery box), but I don't know what effect it might be having on the signal or the unit. A MOTU tech rep would not sanction it, regardless of whether Pins 1 and 3 are jumped. The rep said that any direct connection is inadvisable, and if connecting through the instrument jacks is not satisfactory, that I should use a DI (direct input) box to the mic input. IOW, if you need to connect a 1/4" plug to a mic input, MOTU expects you to use an XLR box intended for this purpose. Exactly what sort of DI box, I don't yet know.


I'll answer my own question ...

Use a cable or adapter that has a mono, 2-conductor (not balanced) jack (female), connected to all three pins of the XLR plug (male). Pins 1 (neg) and 3 (ground) are Sleeve, Pin 2 (pos) is connected to Tip.

Put another way...
[I've deleted this because it turns out that, in addition to shorting two pins, which Mr. Halloran says not to do, I shorted pins 1 and 2. Why this even worked for me, I have no idea.]

Be sure to turn the mic volume WAY down before unmuting in the mixer or router, then ease it up slowly till you're you've got everything correct.

[mikehalloran]

Use a cable or adapter that has a mono, 2-conductor (not balanced) jack (female),

No need.

The Switchcraft 1/4 TRS-F to XLR-M works just fine but most places sell them un-wired. Markertek sells them already wired.

in this case the ring and sleeve should be shorted

No.

For best results, leave the sleeve connected to pin 1 of the XLR only if using a 1/4" TS instead of a TRS. Do not connect it at the 1/4". You can cause a ground loop and/or induce other noises.

Do not assume that the return and the shield are shorted in a piece of gear that has an XLR. In properly designed gear, it is not – unless you do so at the 1/4" connector. The shield connected to pin 1 will do its job better if not shorted to the return.

In fact, if using a TRS adapter and it is noisy, disconnect the shield at the 1/4" first. That's why there is a ground lift switch on most DI boxes.

Oh, you really don't want to switch on phantom power when using such an adapter, especially if you have created a direct short to ground.

Although most/all US equipment nowadays is pin 2 hot, this is something that should never be assumed with older equipment or any gear from Europe. Always consult the manufacturer's lit first or test with a volt meter if not available.

[ronausti]

I don't know how I managed to get the pins mixed up originally. Maybe I was looking at an oddball diagram online. Anyway, I've cobbled up a new one, pins 1 and 2 only, with pin 2 hot (Tip), and 3 unconnected. Works fine, well enough for a cheap noise-cancelling electret mic on Skype anyway. No hum, good volume, sounds very good in MDR-7506 headphones (better, in fact, after Skype EQs me). I have no idea why they say I need a Direct box for that.

Now if I can only figure out a convenient routing for the recording software I use with Skype. Got recording down pat. Playback without a feedback loop or rerouting each time is still something of a mystery.