Motu M4 inputs 3/4 input impedance

[Rich08]

Can someone tell me what input impedance inputs 3/4 on Motu M4 have? This inputs have best parameters and I want to use this card on the acoustic measurements.
Thanks

[stubbsonic]

I looked at the published specs and was surprised to see that it wasn't mentioned. It's a pretty important piece of data.

[bayswater]

sales@motu.com is a likely place to answer that.

[mikehalloran]

I looked at the published specs and was surprised to see that it wasn't mentioned.

on any piece of MOTU gear that I can find

It's a pretty important piece of data

I can't agree there. When unpublished, this spec is assumed to be 47kΩ.

Here are published Line Input through TRS specs for current interfaces using the Cirrus Logic chipsets:

Fosusrite Scarlett gen 3 60kΩ – 66kΩ
Mackie FxProgen3 ≥10kΩ
Presonus 12kΩ – 16kΩ

Line Out through TRS is normally listed at 80Ω to 120Ω with 100Ω single ended being standard (including the M4/6). There will not be any significant differences with any Input in the 10kΩ – 66kΩ range.

[stubbsonic]

If I understand correctly, guitar-centric gear has input impedance shown as it will have some affect on the tone. Since the M4 has a High-Z input, that's why I expected to see something listed.

But your info about expected values is super helpful.

[mikehalloran]

If I understand correctly, guitar-centric gear has input impedance shown as it will have some affect on the tone. Since the M4 has a High-Z input, that's why I expected to see something listed.

That is part of the CombiJack and it certainly is listed. 1MΩ single end; 2MΩ double-ended (balanced). The problem is that MOTU is calling it a Line In—which it's not—instead of an Instrument In which it is. The actual Line level Ins are the TRS in the rear. The M2 does not have these.

[stubbsonic]

Whoops! Missed that!

[mikehalloran]

Whoops! Missed that!

Easily missed. THe OP asked about 3/4. The best answer is somewhere between 10k and 66k Ohm — where exactly doesn’t matter at all.

[mikehalloran]

Can someone tell me what input impedance inputs 3/4 on Motu M4 have? This inputs have best parameters and I want to use this card on the acoustic measurements.
Thanks

I just looked at your OP again. Although your question was answered, I'm not sure that was the information you needed.

Line Ins 3/4 are for external preamps, mixers, active DIs (a few passive DIs work) and some pro keyboards that have actual Line Level Outs in the 100kΩ range. Whether the ideal 47kΩ Line In spec is achieved doesn't mean a thing. "Close" is more than close enough.

Early MOTU lit said that's where one plugs in keyboards. A few of us tried that when the M4 shipped and found out that didn't work very well for most keyboards including my brand new Yamaha P121 (its headphone out gave me a much hotter level). There are old threads about line level transformers, DIs, using the CombiJacks, support calls to MOTU etc. trying to reconcile that. Although the CombiJacks work really well for most keyboards and electronic drums, what if you also want to use microphones at the same time? Anyway, I used the passive Morley MLLS-2 (was Ebtech LLS-2) in front of Line Ins 3/4 on my M4.
https://www.sweetwater.com/store/detail ... el-shifter

Later, I switched to the active Radial J+4 so that I could also plug in a cassette deck or my iPad or keyboard or vintage drum machine or (old gear here) as needed.
https://www.sweetwater.com/store/detail ... vel-driver


When researching this last week, I was quite surprised to find that very few interface manufacturers publish this spec anymore. Hey, we old gearheads can't be expected to remember everything, right? Huh? What was that question again?