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Lectro Problem

Donald Kauffman

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Hi there


Really hoping someone might be able to shed light on an issue I'm having.

I have 2 SMbs and an SRb, 606 band. I am getting this strange noise on them, almost like the type of modulating whispyLectro Problem.wav noise you get after a hissy recording is denoised. I've tried most obvious things I can think of but nothing seemed to make a difference, and the issue is virtually the same on both RX. So I sent them to Ambient to be serviced. They couldn't find anything wrong. I've just tested them out after getting them back and I'm sure I can still hear the same issue.


I have uploaded a quick clip as an example. Can be worse but always seems to be there. Can anyone shed some light on what might be causing this? 


Thanks a lot

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Hi Donald,


Often, audio issues can be traced back to a number of different factors. None of these are "we think you're doing something wrong" but nevertheless we have to ask these troubleshooting questions:


First, sometimes interference that is low-ish in level and allows for relatively normal performance can cause a certain amount of noise in the audio. How are you choosing your frequencies? Are these frequencies coordinated with other RF sources via an app like Freq Finder?

Are there any wideband digital RF sources in the vicinity, like wireless cameras or other digital equipment?


Next is audio gain structure - how are you setting your gain? If you are not "tickling the limiters" on your audio peaks, then you may get an improvement simply by increasing transmitter audio gain and reducing receiver output levels or mixer input levels. 


What mics are you using and how are the mics wired? Some wirings have lower sensitivity, thus more noise gets into the transmitter input from the beginning due to the required higher gain setting, then "envelopes" to follow speech, as a function of the noise reduction. 


Are you running SmartNR noise reduction? If so, how is it set?


Do you have "hop" transmitters, or any digital transmitters adjacent to these receivers in your bag?


How are the receivers powered? We have seen issues with ground loops causing audio issues before. 

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Hi Karl


No absolutely, all good questions.


So I am choosing frequencies just with the scan function on the SRb. Rescanning and changing Freqs has so far made no difference to this.


It has happened in all sorts of different places and scenarios so I don't think it could be connected to interference from outside (could be wrong). In the example I posted I switched to Sennheiser G3s (also on 606) and it sounded clean as a whistle in comparison.


Now gain setting is something that I thought might be the problem and have experimented with it quite a bit. I generally set the tx as it recommends in the manual (-20 & -10 flashing green, -20 occasionally flashing red) and then the Rx to give a healthy signal into the 633. Bumping the gain on the tx does seem to help it a little but it is odd if to get a cleaner signal you have to push the tx to a point where a shout or something unexpected could end up clipping.


I'm using DPA 4060s and 4071. Not sure how they're wired but the 4060s need a lot less gain than the 4071 (usually set around 23 on tx. 4071 needs to be higher, about 33). But never had an issue with noise with any of them previous to this.


I'm pretty new to Lectro and the Smart NR so I had thought it might have something to do with it. So I tried every setting including off and it didn't solve it.


Getting annoying that the G3s I've moved away from are currently sounding nicer and cleaner than the Lectros.


Could powering be causing it at all?









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Donald, thanks for covering all those questions with the details - looks like you've tried all the right things, but that you also have your setup well dialed-in. 


What compat mode are you using? If you are in Europe and your transmitters are the E01 type, then they conform to the ETSI mask and have +-50 kHz max deviation. If your receiver is set to "400 mode" or "NA Hyb" then this could be the problem. The receiver should also be set to "EU Hyb". 


Powering may be the issue - if you have a way to test each receiver separately with battery power (I once rigged up a ratty DC cable with a 9V battery) then you can eliminate this variable as well. 


Failing all these things, we should probably look at those units at the HQ. Since we haven't sold SRb receivers in some years now, I'm assuming you purchased these used? 

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Yes purchased used over a year ago. Didn't notice this issue when I first used them, not sure when it started.


Yes I'm in Europe. I have the Compat set to HBR. Other options on the receiver are m.3/300/110/m.6/IFB/HRB TB.


Not sure what you mean when you say test each receiver separately as it's just the one dual receiver? Its currently powered by a single L mount battery in a Hawkwoods adapter.


Thanks for taking the time to respond.



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With those compat modes in the list, that is an EU receiver - should be marked SRb/E01 on the case. 


So the issue wasn't happening before but at some point started up - it would seem that the receiver and the transmitters should be examined by our HQ - it is certainly not behaving correctly. 


When you have time, please give our shop a call at 001-505-892-4501 or send an email with serial numbers and detailed problem description (and recordings, if you have them) to service.repair@lectrosonics.com

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  • 1 month later...

Just wanted to come back and say that I sent these to Lectrosonics  and they are now fixed. And not only did they sort the issue but they did it under warranty due to the fact that I'd already paid Ambient who didn't fix the problem.


Lectro were so quick to come back whenever I emailed them and the whole process was really quick and easy. Brilliant customer service. And thanks again to Karl for the help here too.



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On 6/19/2021 at 10:39 AM, Robert Buncher said:

What was the repair?

On the SRB receiver, we found and corrected a fault in the 1st conversion oscillator for channel 1. On both transmitters and the receiver we installed many circuit updates (hardware) that had come out since the products were originally manufactured. On all units we updated the firmware and of course, did a full alignment on all devices sent in for repair. We added laser engraving to the SRB housing to indicate that it had been "upgraded to SRB". 

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