Shure Mic not working with Olympus recorder

[Michael Clark]

I recently bought a Shure SM11 lapel (XLR) to record to my Olympus VN-6200PC, via an XLR-1/8" adapter. However, when I hold the mic right up to my mouth and record, it sounds like the mic is under a pillow, or underwater. It sounds awful, completely unusable. Am I trying to fit an XLR peg in a 1/8" hole? I just cannot figure out what isn't working. The Olympus doesn't have any gain control, and only has a "Mic" input.

[Greg Miller]

Most likely that adapter is XLR-to-3.5mm (not 1/8", which is an outdated US size from the 1970s).

Your problem may take a bit of experimentation to figure out, because the so-called "manual" (which I just downloaded) is less than useless. It says the recorder has a 3.5mm mic jack, but doesn't state one very important detail:
• does the mic input provide "plug-in power" for an external mic?

Without knowing that, I can only proceed by guesswork, some experimentation, trial and error.

(By the way, the published frequency response of this gadget goes down only to 200 Hz. If anything, that may make voices sound rather "thin" [just the opposite of the "under a pillow" quality you are hearing]. The bitrate appears to be 32 kbits/second [8,000,000 kilobits of memory / 71 hours]. That is marginal for voice, and will be useless for music. IMHO you'd be much better off with a recorder in the same price range from Tascam or Sony... they record in stereo, can record uncompressed WAV files, have recording level meters and gain controls, have better specs and also much better manuals!)

However, if you want to proceed with your present recorder and problem (in other words, if there is absolutely no way to return that recorder and get a better one), the first question is: Which pins on the XLR end of the adapter are connected to which pins on the 3.5mm end?

[Michael Clark]

Thank you for the very valuable information. I too was unable to find out if the Olympus would receive non-powered devices. And sorry, yes, I did mean 3.5mm. My mistake. The Shure mic side is a 3-pin male, and the adapter is a 3-pin female.

[Greg Miller]

Originally Posted by Michael Clark

Thank you for the very valuable information. I too was unable to find out if the Olympus would receive non-powered devices.

It's not a question of whether it will "receive" a non-powered mic. It's a question of whether the Olympus mic jack has a DC voltage on it which could damage your dynamic mic!

We will need to resort to a voltmeter to find out that information. That will be important.

Originally Posted by Michael Clark

The Shure mic side is a 3-pin male, and the adapter is a 3-pin female.

Well sure (no pun intended) but... on the adapter, which pin of the XLR is connected to which part of the 3.5mm plug? We really need a specific answer to that question. Or, for that matter, does the adapter contain a transformer, or a blocking capacitor?

[Tom Dickerson]

Hi Michael

I use a lav mic that utilizes a small watch battery into my Olympus DS40. The DS40 is discontinued now but the specs on my mic input jack shows impedance 680 ohms on my DS40 and 2K on your 6200pc.

For these kind of recorders I see a lot of people using the cheap atr 3550 or Miniature Microphone Specialists Stereo - Mono - Cardioid - Omnidrectional Giant Squid Audio Lab

[Steve House]

It is highly unlikely that the dynamic lav has sufficient output to properly drive the recorder's mic input. According to the specs, the lav outputs -64dBV/PA (0.60mv). While Oly doesn't publish a sensitivity spec for the recorder's external mic input, it would be very unusual for it to be intended for anything other than a typical consumer electret mic with a much higher output. Compare the lav's -64dBV/PA output with a Rode Videomic's output of -38dBV/PA (15mv), for example. The Videomic is designed to work into a typical consumer device's external mic input so it's reasonable to surmise that the Oly recorder's input expects something in that same ballpark. The lav is 30 times weaker than the Videomic. Couple that with the uncertainty of the wiring of the XLR->3.5 adapter and it's surprising that you're recording anything at all.

[Greg Miller]

Even if the mic he's using is 26dB lower (20 times weaker) than the recorder expects, it should not sound like it's "under a pillow" as he describes. That's why I suspect something is wrong with the interface.

Either

The pinouts are wrong, and he's running the mic into nearly a dead short,

or

"Plug in power" from the recorder is getting back to the mic and, at the very least, saturating the magetics... more likely seating the diaphragm against the magnet structure.

--

So, as the first step, I think we really need to know what sort of XLR->3.5mm adapter he's using: pinouts, with or without coupling transformer, with or without blocking capacitor, etc.

(And of course I'm entirely serious about getting a different recorder if that's an option. That particular Olympus looks barely adequate for dictation, let alone any sort of "audio" or broadcast use.)

[Shaun Roemich]

I wonder if the recorder is expecting an unbalanced signal or stereo signal and the mic is presenting a balanced signal on 3 connectors... if so, the +ve and -ve (phase reversed) nature of the balanced line will nullify record levels.

Is the 3.5mm male end TS or TRS? (one black band or two?) If you insert it to the FIRST detent, do you get signal?

[Greg Miller]

From the specs, it appears the recorder is expecting a mono (unbalanced) signal.

We have been awaiting a reply from the original poster, telling us the internal connections of his XLR to 3.5mm adapter. Once we know that, we will know what's wrong. The original poster has not checked in for five days, so has perhaps lost interest in solving the problem.

[Shaun Roemich]

Originally Posted by Greg Miller

From the specs, it appears the recorder is expecting a mono (unbalanced) signal.

Thanks for looking into that Greg. In that case, if the adaptor has a TRS end on the 3.5mm male end, THAT is certainly possibly causing the problem due to summing the +ve and -ve balanced lines UNLESS the adaptor has a decoupler in it.

[Greg Miller]

Maybe yes, maybe no. It really depends on the connection of the adapter.

For example assume XLR p.1 -> sleeve... that would almost surely be a given.
Now assume p.2 -> tip, and p.3 -> ring.

If ring is grounded in the recorder, the audio signal would get through fine; however, "plug-in power" from the recorder would go back into the dynamic mic and bottom out the voice coil assembly. (Then the VC could barely move, except for high-energy low-frequency sounds, and the resulting track might well be described as "muddy" which seems to tally with what the OP said.)

OTOH if ring is open in the recorder, the audio circuit would essentially be open, so no significant audio signal would get into the recorder's preamp. (Only very high-frequency signals would be capacitively coupled, resulting in a very weak "thin" track; not what the OP described.)

A different set of connections in the adapter would result in different problems. Many adapter configurations would fail; very few configurations would work correctly.

In any case, if and when the OP tells us about his adapter, then we can tell him what's going wrong.

[Shaun Roemich]

Yes but if the 3.5mm input on the recorder is expecting TS (unbalanced) the Tip (+ve or IN PHASE audio) and Sleeve (-ve or 180 degree OUT OF PHASE audio) would be SUMMED, therefore creating phase cancellation of the signal at the recorder.

[Greg Miller]

No, not at all.

If the recorder has an unbalanced input, it is expecting signal voltage at the tip, relative to "zero" at the sleeve. There is only a single input; it isn't a balanced input with an "inverting" and "non-inverting" input terminal, so it is not summing anything. The input is looking at the difference in voltage between the tip and sleeve.

The dynamic capsule, by definition, has two signal leads. (Hopefully the metal case of the capsule is connected to shield, but there's no signal voltage coming from the case, so we can ignore that connection.)

Most oscilloscopes have unbalanced inputs, the same as this particular recorder. The probe has a shield/ground/common lead, and a "hot" or signal lead on the tip of the probe. Connect the dynamic capsule to the oscilloscope input: one capsule lead to the scope ground (common) and the other capsule lead to the scope "hot" input pin. You will observe some AC output depending on the acoustic input to the capsule. The 'scope is looking at the voltage difference between common (in this case also ground) and the "hot" pin.

Now connect the capsule to the recorder in the same manner: one lead from the capsule to sleeve or "zero" or "common." The other lead to "hot" or tip. Just like the oscilloscope, the recorder will look at the difference between the two leads, and will amplify that signal voltage.

[Shaun Roemich]

Greg is right - my bad... If the INVERSE had been true (the adaptor having a TS and the recorder expecting TRS) you could have had phase cancellation... More coffee before trying to visualize audio connections... Thanks Greg... I don't NORMALLY make errors like that.

[Greg Miller]

Hi Shaun, NP.

I, too, find caffeine sometimes has a lot of "medicinal benefit." Especially when someone wants my brain in gear before 10:00 AM. ;)

The idea of using a given connector for multiple functions causes a lot of confusion, eh? More than once, I've found someone running a balanced mic into a stereo TRS input, thereby recording the two channels out of phase (+ve on one channel, -ve on the other). They don't notice a problem until playing back a mono mix, at which point the result is pretty nearly dead silence, except for any minor signal or channel imbalance.

Of course that situation puzzles me, too: how could you not immediately hear that the two channels are out of phase?! But if you've never intentionally created phase reversed channels, and listened to it, I guess you could hear "that sound" and not associate it with a particular problem.

Carry on!