Audio Hiss and Pop - Sennheiser Wireless Set

[Dave Mercer]

Hey all.

I have a Sennheiser EW100 G2 wireless transmitter and receiver.

Over the past few months it has picked up an annoying habit of picking up lots of static which builds over a minute or two until culminating in a loud pop. Then the audio receives returns to normal.

This could happen at the start, middle or end of an interview ... or could not happen at all.

I've changed some of the cabling to no avail. All connections are tight. I'm using the 3.5mm mini-plug connection.

The rubber protective sleeve on the transmitter's antenna started to come off (no idea why) and so I've taped it with electrical tape.

Also, I use rechargeable batteries, but have them fully charged before using.

Any thoughts?

Thanks.
Dave

[Rick Reineke]

Assuming the mic/input cable is not compromised, it 'sounds' like interference. Have you used the auto-scan and checked for 'unused' channels in your area and/or changed to a different frequency channel? Is the transmitter/receiver/antennas placed and oriented for optimal performance? ie: line of sight, antennas not touching wearers skin or blocked by solid objects.

[Dave Mercer]

Thanks Rick. Your answer prompted me to do a bit more research online. I'll try switching frequencies, and changing a few other settings at the same time.

I often ask my interviewees (who are not used to wireless mics, or most video technology in fact) to put the transmitter in a pocket (after removing cell phones, etc) but have read that the mic cable can often interfere with audio quality if it touches the antenna, which must be happening. Also read that reciever and transmitter antennas should be on the same plane (ie vertical or horizontal) which I haven't been doing, as receiver is mounted to hot shoe on top of my cam.

Someone else also said that 1.2V NiMH rechargeables might not have enough power for the mics to work properly.

Lots to change!! Hopefully it leads to more reliable audio ...

Thanks again.
Dave

[Paul R Johnson]

I've had this happen twice, with different reasons. First was simple to cure. Swap the rechargeable batteries for conventional ones and see if it happens? Gradual hiss build up is common when the terminal voltage drops, the receivers will auto switch off when the battery goes flat, and then repower up. Your cells could be dodgy - when the current demand from the receiver ceases, they can go back in terminal voltage. Normal rechargeables don't do this, but worn out ones can behave oddly. The second time it happened was when the client had insisted they wanted to save the world and had provided their own rechargeables - but oddly, it was not the batteries at all, and was a faulty receiver. Sounded exactly the same. My advice would be to change to a couple of decent alkaline type batteries and see if this makes the fault go away. If it doesn't, then it's a real fault.

I never use rechargeables ever - and run a strict new set for each use policy. This is very wasteful, but I always have a good supply of half used batteries which I give away to friends and relatives for toys, remotes and the other gadgets they have. Last year I think I used over 2000 AA cells. Rechargeables would have saved me lots of money - I have 14 systems - but even with modern good quality rechargeables, the warning of a battery about to go is just not good enough. By the time you realise it's about to die - it has gone. You also have to have a very rigid recharge policy, it's too easy to grab a battery that did NOT go in the charger!

[Don Bloom]

Paul, while I don't have 14 sets of audio gear I do use 12 new AA batteries for every job. Man the cost piles up and so do the half or less than half used batteries BUT like you I once thought about using re-chargables and had a near panic attack just thinking about it.
I'm now known by my grandkids as "grandpa battery." Pretty sad ;-{

[Paul R Johnson]

I've done a couple of handheld radio mic shows recently - and my new sound man is same age as me (i.e. not a newcomer) During the show - which had cabled mics on lecterns, I heard in the headset link from backstage, somebody talking about they could use a radio mic in the next section. Knowing my audio guy had NOT prepared any radios, and they were sitting next to me (I was lighting the show) I passed one to him at the sound mixer - and mouthed, they'll want this. He sent the A2 backstage with the mic, and when the compere asked for a radio mic, it wear handed to him, like magic. Fifteen minutes later it died!

After the show, I commented on the battery life - he said "Oh, I didn't bother with a new one, I only put it in for the last show two days ago, and it only had a few minutes on it!". What he forgot was that the few minutes was at the end - but it had been turned on, for 3 hours before. I told him my house rule - new batteries, every outing - because a pre-used battery is an unknown factor. The receivers were telling him that there was over 2 hours in them, but ten minutes later 2 hours was more like 2 minutes! Second rule - never trust a battery life meter.

I don't re-use tapes either, and am now even starting to use SD-HC cards in the same way - copy to hard drive, number, and stick on shelf - open new one!

[Rick Reineke]

Most rechargeable AAs are 1.2 volts and self-discharge rapidly as well. Opposed to the alkaline @ 1.5V and a much smoother discharge curve. That said, I have been using the Rayovac Hybrid AAs for quite awhile without any 'noticeable' performance difference. (including 'RF hell' Manhattan) They easily last 10+ hours, but one can't go by the battery meter or low battery warning light.. The 'Hybrid' type battery can also be charged ahead of time, due to a much lower self-discharge. Said to retain at least 80% of full recharge after a year.

PS- If the transmitter's antenna touches the wearer's skin, that can cause servere performance issues as well.

[Dave Mercer]

Interesting. Sennheiser USA (who incidentally have been very helpful!) say that my rechargeables should not be a problem, as long as they're fully charged and in good shape.

Will now try fresh batteries and see if the problem persists.

Regardless, I've learned a lot more about how my wireless mics function over the past day. Thanks all!

[Steve House]

I favour Eneloop rechargeables because of their significantly lower self-discharge rate on the shelf and their voltage remains relatively constant until fairly close to the fully discharged point.

[John Willett]

Originally Posted by Dave Mercer

Hey all.

I have a Sennheiser EW100 G2 wireless transmitter and receiver.

Over the past few months it has picked up an annoying habit of picking up lots of static which builds over a minute or two until culminating in a loud pop. Then the audio receives returns to normal.

This could happen at the start, middle or end of an interview ... or could not happen at all.

I've changed some of the cabling to no avail. All connections are tight. I'm using the 3.5mm mini-plug connection.

The rubber protective sleeve on the transmitter's antenna started to come off (no idea why) and so I've taped it with electrical tape.

Also, I use rechargeable batteries, but have them fully charged before using.

Any thoughts?

Thanks.
Dave

The problem is that they are not the correct rechargeables.

Sennheiser make a special rechargeable pack for the G3 - this has an extra contact and talks to the transmitter/receiver.

Normal rechargeables have a different voltage than alkaline cells - what is happening is that the unit is operating on rechargeables that it thinks are alkaline cells and may be drawing current from the cells that is inappropriate for them.

[Tom Morrow]

I've never had any problems using mostly eneloops, and occasionally nimh rechargables with my g3 set. The only thing slightly anamolous is that the battery indicator goes down from 3 bars to 2 bars soon after starting a new pair of batteries. But I can typically get in a day of shooting with 1-2 sets of eneloops. I change the batteries as soon as I can when they get down to 1 of 3 bars on the battery indicator.

[Dean Sensui]

I only use these batteries in my Audio Technica wireless mics. I consistently get a safe working time of 5 hours in the transmitters. These are low self-discharge but I'll charge them before going out into the field.

Maha AA 2400mAh 4 Pack Rechargeable Batteries NiMH Low discharge

I generally power the receivers with an external battery with a multitrack recorder setup. But the NiMH batteries are also used with the receiver if it's mounted on my camera.

This is the charger I'm using.

MAHA MH-C801D AA - AAA Battery Charger<br>DELUXE 8 Cell Professional Battery Charger w/ Full LCD Display

It has a soft-charge setting that is easier on the batteries. Batteries are charged individually which is how batteries are supposed to be charged.

[Chip Gallo]

I have been using the Maha's (not the low discharge) in a Sennheiser G3 wireless no problems up to a 4-hour shoot. I recharge before each event.

[Zoran Vincic]

I use Eneloop (regular white ones) and I usually get more than 6 hours on my G3's.
Slightly longer run time in the RX than in TX.