Topic: LS-10 external mic hum

[rjp]

I recently bought an Olympus LS-10, and while it can do an excellent job at recording, I've found one showstopper. I also have a set of Sound Professionals SP-TFB-2 mics, and also one of their SP-SPSM-16 single-point mics.

I recently tried making a recording with the SP-TFB-2s, with the recorder in a shirt pocket. When I got home and fired up Audacity, I found, much to my horror, a continuous square-wave hum (spectrum analysis says 356 Hz) throughout the recording.

My initial testing couldn't duplicate the problem - at first, I thought there was some EMI/RFI source at the venue. However, I eventually found a way to duplicate the problem, and it's the LS-10 itself.

I decided to monitor the output with a handy set of earbuds, and clip the mics to my shirt, putting the recorder in my shirt pocket. As soon as I was no longer directly touching the recorder, the hum started. Further futzing revealed that the noise was coming from the LCD. If I move the mic capsules directly next to the display, or if I bunch the cable near it, the noise becomes quite prominent. I was also able to duplicate the phenomenon with the single-point mic.

If I'm actually touching the recorder, the noise stops.

I'm not sure if this is an RF phenomenon, or inductive pickup of an audio frequency source. It appears that the only way to insure that the noise doesn't crop up (aside from using the internal mics) is to maintain contact between the recorder and my body. Since I normally wear the binaural mics in-ear, it isn't feasible to monitor them while recording.

Does anyone have any suggestions, besides connecting a grounding strap or trading in for a PCM-D50?

[flintstone]

This isn't an issue with the LS-10 I have.  I use it with
the internal mics, and also with Rode NT-1A mics with
a 48V battery box.

If it's convenient,  take your mics to a dealer and check
out another LS-10.   Otherwise, send the LS-10 back to
Olympus for evaluation.

If the problem is always at the same frequency, you
might remove it with an audio editor.  You're right, that
would be a pain!

Flintstone

[Church-Audio]

This isn't an issue with the LS-10 I have.  I use it with
the internal mics, and also with Rode NT-1A mics with
a 48V battery box.

If it's convenient,  take your mics to a dealer and check
out another LS-10.   Otherwise, send the LS-10 back to
Olympus for evaluation.

If the problem is always at the same frequency, you
might remove it with an audio editor.  You're right, that
would be a pain!

Flintstone

I agree 100% this is not a usual problem for the LS10 It sounds like you got a bad one.

I would also check to make sure your using quality batteries in the LS10 Duracell or something of quality not cheap batteries.


Chris

[gearscout]

If the hum stops when you touch the recorder...check your cables first.  You may have a grounding problem.

Try replacing one of the cables.

[guysonic]

Sounds like a mic grounding problem with either one of the capsules or a broken cable connection.  If it's on just one channel, suspect the mic capsule on that side.

[Church-Audio]

I recently bought an Olympus LS-10, and while it can do an excellent job at recording, I've found one showstopper. I also have a set of Sound Professionals SP-TFB-2 mics, and also one of their SP-SPSM-16 single-point mics.

I recently tried making a recording with the SP-TFB-2s, with the recorder in a shirt pocket. When I got home and fired up Audacity, I found, much to my horror, a continuous square-wave hum (spectrum analysis says 356 Hz) throughout the recording.

My initial testing couldn't duplicate the problem - at first, I thought there was some EMI/RFI source at the venue. However, I eventually found a way to duplicate the problem, and it's the LS-10 itself.

I decided to monitor the output with a handy set of earbuds, and clip the mics to my shirt, putting the recorder in my shirt pocket. As soon as I was no longer directly touching the recorder, the hum started. Further futzing revealed that the noise was coming from the LCD. If I move the mic capsules directly next to the display, or if I bunch the cable near it, the noise becomes quite prominent. I was also able to duplicate the phenomenon with the single-point mic.

If I'm actually touching the recorder, the noise stops.

I'm not sure if this is an RF phenomenon, or inductive pickup of an audio frequency source. It appears that the only way to insure that the noise doesn't crop up (aside from using the internal mics) is to maintain contact between the recorder and my body. Since I normally wear the binaural mics in-ear, it isn't feasible to monitor them while recording.

Does anyone have any suggestions, besides connecting a grounding strap or trading in for a PCM-D50?

I am sorry I misunderstood you if your mics are plugged in and the noise goes away when you touch it there is for sure like G.S said a ground issue with your mics.

[rjp]

More fooling around:

Using the SP-TFB-2s again: Touching the recorder only helps if the mic capsules are away from the LCD. If they're right next to the LCD (yeah, that's not normal operating procedure), the hum is quite clear.

Putting the recorder into a belt holster: if I'm careful about the cord path AND the LCD is not facing my body, no hum at all. Very faint hum if the LCD is facing my body or the cable crosses the LCD.

In a shirt pocket: If the LCD faces my body, hum is a real problem. If it's facing away from my body, the usual cable path considerations apply.

Cheap Radio Shack dynamic mic: Hum is barely audible with the non-removable windscreen touching the LCD.

Sima MZM-1 camcorder mic: Behaves more like the SP electrets (clear hum with capsule next to LCD). The mic has an extremely short cable, so I can't try cable routings with it.

Inductive telephone pickup: 356 Hz hum barely audible with the coil next to the LCD; the pickup is far better at picking up mains hum instead (greatly affected by orientation), and it also picks up computer-type noise when it's next to the LCD.

Only the pickup coil gets the mains hum and computer noises.

I haven't had the opportunity to try brand-name batteries (FYI, I don't believe they'd make a difference), nor have I been able to try my mics on another LS-10.

The fact that little hum occurs with the telephone pickup and the dynamic mic, and that the orientation of the LCD in relation to my body makes a big difference, leads me to believe this is an RF issue rather than low-frequency induction.

[Church-Audio]

More fooling around:

Using the SP-TFB-2s again: Touching the recorder only helps if the mic capsules are away from the LCD. If they're right next to the LCD (yeah, that's not normal operating procedure), the hum is quite clear.

Putting the recorder into a belt holster: if I'm careful about the cord path AND the LCD is not facing my body, no hum at all. Very faint hum if the LCD is facing my body or the cable crosses the LCD.

In a shirt pocket: If the LCD faces my body, hum is a real problem. If it's facing away from my body, the usual cable path considerations apply.

Cheap Radio Shack dynamic mic: Hum is barely audible with the non-removable windscreen touching the LCD.

Sima MZM-1 camcorder mic: Behaves more like the SP electrets (clear hum with capsule next to LCD). The mic has an extremely short cable, so I can't try cable routings with it.

Inductive telephone pickup: 356 Hz hum barely audible with the coil next to the LCD; the pickup is far better at picking up mains hum instead (greatly affected by orientation), and it also picks up computer-type noise when it's next to the LCD.

Only the pickup coil gets the mains hum and computer noises.

I haven't had the opportunity to try brand-name batteries (FYI, I don't believe they'd make a difference), nor have I been able to try my mics on another LS-10.

The fact that little hum occurs with the telephone pickup and the dynamic mic, and that the orientation of the LCD in relation to my body makes a big difference, leads me to believe this is an RF issue rather than low-frequency induction.

There is an grounding / shielding issue with your mics. Most mics will pickup some kind of noise when placed close to the sources you mention. But I had a similar problem with an in ear design I came up with. Its very hard to shield a capsule when you are placing it close to your body.