Lectro SR issues

[PTA]

Hello everyone, I've been having some audio issues using my SR receiver and SMQVs as transmitters for a camera hop.

To describe the noise I have been hearing on occasion, it seems to be a very high type of hiss that almost tends to "breathe" with dialogue.  It only happens every now and then, for example it only happened on one or two takes out of one morning of shooting.  It doesn't seem to happen when the audio is noticeably loud or soft but seems to follow the voice that is being captured.  Here are thesettings I was using at the time:

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2 SMQVa Transmitters. The meters on the transmitters illuminate both LEDs green with highest peaks on the mixer causing the -20 LED to turn red, so I believe I'm using the right range in the transmitters.

Audio level set at 13 on both.

Output of Sound Devices 552 mixer at -10 (With the 2 options being Line, -10, and Mic level).

+5 Level on the SR Receiver going in set to line level on a Panasonic HVX.

I was always close to the camera, never straying more that 10-15 feet and always staying at least 4-5 feet away.  It was all outdoors, cleanline of sight from me to the camera.

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It's a very subtle noise, but I notice it.  I'm aware that there is an obvious noise floor associated with the HVX that is present. I hope to find out what this is since I wish to use this system as a camera hop on several projects I will be working on but don't feel confident using it as a reliable hop if I don't know why it is happening and when it will happen. 

I thought maybe someone here might have some ideas and I'm also talking with Lectro about it too.  Let me know if I have left out some key information, which is very possible.

[Zack]

Figures some odd news of the very unit I just ordered today pops up lol.  Anyways...  so you're hearing this sound from the headphone monitor of the HVX?  If so, do you hear this same sound before the hop send... ie: the mixer?    If not, go back to the HVX maybe look up some of the audio settings... is there an auto gain control on?  Do you have your frequencies spaced out far enough between the channels (as noted in the manual)?  Is the same noise present when using an onboard mic on the HVX?  Are you able to A/B the SR unit with another receiver to see if there are any changes?  Finally, is this noise making it to tape... when you playback on your camera or in the editor, do you hear the same noise?

Not sure how much of the elimination process you have gone through so far, but if you're positive you have it isolated down to the SR unit itself, maybe contact lectro and speak with their tech support.

[Derek H]

My best guess:  The high-pass filter on the transmitter is disabled and you're sending it too much low frequency sound.. kicking in the transmitter's limiters before the level of the voice would warrant it..

This would create a hard to describe noise that is keyed with the voice as the limiters are pumping when they speak. 

Play with your high-pass filters (low-cut), both on the mixer and on the transmitters and see if that has any effect.  Rolling off 70-80Hz will have a negligible effect on the person's voice but may save you from pre-mature limiting.

Be sure to check this out on the talent transmitters as well.. it may be coming directly from the first Tx in the chain.

Good luck!

[Derek H]

Also,

Make sure all your lavs and cables are wired for servo-bias input and not the older Lectro wiring scheme.  The wrong wiring could also introduce this kind of noise.

I hate when working on a show with rented gear and the house gives you a mish-mash of both types..

[PTA]

Zack:

So I'm hearing this noise on the actual recorded material, not hearing it on the mixer end before it is hopped to the camera.  The frequency spread for both channels is 1 @ 522.5 and 2 @ 534.9, so I think I'm OK there.  I didn't notice any odd frequency bleed between channels when powering up.  I've only noticed this noise when using the hop and it only happens every now and then.

Derek H:

Thanks for the information about the high pass filters.  I checked and it showed that one of my transmitters was at 35 Hz and the other was set to 100 Hz, so one was a little low.  I will talk with Lectro as well to see if they agree, and thanks again for the info.  I have changed both transmitters to 70 Hz roll-off, do you think this will solve the 'hiss' pumping?  I'll play with it to see if this is the case as well.

I will also check to see that the cables are wired for servo-bias and not the older scheme.

Best,

Palmer

[PTA]

So I'm still a little stuck with this issue.  If I remember correctly, I'm pretty darn sure that I had the filter on the mixer set at least above 80 Hz, so I don't think there should have been any low frequency issues.

Also, let's say that the cables I'm using are not wired servo-bias, and are the older Lectro Scheme.  Would this cause the hiss I'm hearing to be intermittent?  I'm only noticing it on certain takes, and by no means is it happening a lot.

Hmmm...

[hemmerlinj]

P-Did,

Try running full line level into the TX's.  I had a similar problem a few years back and the only fix was running line level.  I had even tried the properly made cables for the newer TX's and it didn't help.  For some reason it seems that Sound devices and Lectro TX's you need to use line level out with the mixer.

Double check to make sure that your TX RF boards and not damaged.  See if you notice any strange noise or quick increase and decrease in sound level when you touch the antennas of the transmitters.  If so you may have to send the TX's in for repair.

And the HVX is notorious for having a very noisy headphone amp, but the recorded signal should be clear. 

And you should be using the Lectro freq. chart that give you with a new unit.  With the SR you have to choose freqs. that are in the lower grouping for 1 TX and in the higher grouping for the 2nd TX.

The hiss with the talking sounds to me like it's a freq. thing.  You maybe getting interference from something that you don't expect.  With the changes going on with the freq's people are finding more and more places are getting harder and harder to get good signal.  A friend of mine had troubles with his lectros in the middle of no where in Vermont.  He had several different blocks of lectros and had problems with everyone.  You really need to pay attention to your freq choices now a days and may have to make changes everywhere you go.

Good Luck,

J Hemmerlin

[PTA]

Running line level out of my 552 seems to be way too hat for the transmitters, even adjusting the transmitter audio levels extremely low.  I have been having to use the -10 pad setting, in between line and mic level.

It doesn't seem that the RF boards are damaged, they are new transmitters and don't seem to be doing any of the things you mentioned.

I hate the noise from the headphone amp on the HVX, but have learned to live with it.  Anyway, the noise is on the recorded signal as well when played back on my computer system.

I'm starting to lean towards a frequency interference thing as well, as it is happening intermittently.  The hard thing is that I am using it as a camera hop, so I'm not able to monitor it and change it when it does happen.  It is so subtle that the camera op doesn't notice it.

[hemmerlinj]

Running line level out of my 552 seems to be way too hat for the transmitters, even adjusting the transmitter audio levels extremely low.  I have been having to use the -10 pad setting, in between line and mic level.

It doesn't seem that the RF boards are damaged, they are new transmitters and don't seem to be doing any of the things you mentioned.

I hate the noise from the headphone amp on the HVX, but have learned to live with it.  Anyway, the noise is on the recorded signal as well when played back on my computer system.

I'm starting to lean towards a frequency interference thing as well, as it is happening intermittently.  The hard thing is that I am using it as a camera hop, so I'm not able to monitor it and change it when it does happen.  It is so subtle that the camera op doesn't notice it.

Should have asked this before, but what freq blocks are you using?  Including any other wireless for body mics and such?  As I mentioned before you really need to use the freq chart that lectro provides when you're using multiple wireless.  You can create a lot of headaches by not doing so.

If you have adjacent freq. blocks then you're making it harder to use the SR setup, as the way that you need to setup the SR for stereo use doesn't really work well with using adjacent freq blocks.

J. Hemmerlin

[Chris R]

To describe the noise I have been hearing on occasion, it seems to be a very high type of hiss that almost tends to "breathe" with dialogue.  It only happens every now and then,

I had the same issue with my original SRa5p when I bought it last year.

It got sent back and they did some firmware upgrades that solved the problem.

I have a question of my own..

Does anyone who owns the SRa receiver have an issue during the scan mode

where every single freq shows up as 3-4 bars of RF hitting it?

My original unit had that issue..sent it back and it was fixed.

I just bought a 2nd..same problem.

They sent me a replacement..

SAME problem.

Its back at the factory right now but they are puzzled and cant recreate

whats happening to me.

I sent them a photo showing every freq in the scan with a solid block.

The fact that this has happened to 3 units

im curious if others have run into it.

You'd think the possibility was my external power except after the original unit

came back its fine using the same exact power scheme.

[Zack]

Well I'm getting my new SRa today and have 2 days to prep it and get used to it for a show....I sure hope I didn't get one from the same batch as you guys.  Now you got me worried.

[PTA]

Hey Chris,

What version of the firmware did you have before you sent it in?  I believe I'm at 1.1 now, and they are at 1.4, I'm hoping if I send it in it will fix the problem.

In regard to your other question, I have noticed something similar on my scans every now and then.  It only happens once in a while where all the frequencies have some solid block throughout the entire systems.  On the same scan on a different day, it can be completely clear for a majority of the scan.

[Zack]

Well I just received my SRa a few hours ago... attached the sled, did a scan and gave them a go.... amazing!  Very happy so far with the test I did.  Version I got was 1.9.  How long ago did you receive your 1.4 update?  .... PS: Block [22]

[PTA]

Well I just received my SRa a few hours ago... attached the sled, did a scan and gave them a go.... amazing!  Very happy so far with the test I did.  Version I got was 1.9.  How long ago did you receive your 1.4 update?  .... PS: Block [22]

Wow! I didn't realize that they were up to 1.9 already. I wonder what differences are between 1.4 and 1.9 and if it is only hardware related.

Reading through the firmware upgrades from 1.1 to 1.4, I feel that some of these might address the issues I have been having.  They are noted below.

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SRA 

v1.4  2009/09/29  Improved diversity and noise squelch systems for substantially quieter operation under moderate to weak RF conditions.

v1.3  2009/06/26  FIXES

    * Fixed problem wherein user group V could not always hold 16 channels.

    * Applied bug fixes and sonic refinements to mode 3.

    * Balanced CPU load to speed factory diagnostics.

    * Inverted audio polarity.

    * Turned off unneeded signals to reduce RF radiation from DSP.

v1.2  2009/03/30  Fixed minor display glitch, added automatic birdie warning, improved response to sharp acoustic transients.

v1.1  2009/01/20  Added immunity to the slow-ramping power supplies in some cameras.

v1.0  2008/10/24  First production release.

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I'm also using these cables from Remote Audio from mixer to my SMQV transmitters but I'm having a hard time finding out how they are wired, I never got a definitive answer from them.

CALECXL3/5LXLR3-F - TA5F Lectro Line level, BDS compatible. For use w/ balanced 3-pin XLR outputs, 18".

http://www.remoteaudio.com/cables_adapters/lectro/

Sound devices recommends that they be wired this way:

http://www.sounddevices.com/notes/general/lectro-connections/

But me not knowing much about cables yet, I can't verify it for myself.

I still don't know that a cabling issue would cause a problem that is intermittent, to me that would be something that I would be hearing all the time.

I did also talk to Lectro about the frequency charts, and although they do say the chart is good in a perfect world, the best best is to go by your scans and work from there.

[studiomprd]

" I still don't know that a cabling issue would cause a problem that is intermittent,  "

problems in cabling are frequently intermittent!

[PTA]

" I still don't know that a cabling issue would cause a problem that is intermittent,  "

problems in cables are frequently intermittent!

I didn't realize that, you learn something everyday

Do you think a cabling issue such as what Lectrosonics is describing, I believe from their older wiring to their newer servo-bias wiring, could cause the "following hiss" on dialogue that is described in this thread?

I don't know enough about wiring to know this.

[studiomprd]

I have edited the quote you refer to...

while the cables themselves can sometimes become intermittent, or even fail hard, usually the intermittent cabling problems are in the connections, or very close to connections, or other strain points, or heavy wear points...

[beartrax]

i don't have an sr unit as of yet, however in my experience, if the line level signal from the mixer is too hot for the "line level" cables from remote audio they are most likely wired for an older lectro config

- note um & sm are not the same, however at one point certain vendors claimed they were. i learned this when trasitioning from um to sm with my dpa lavs which required new ta5 adapters. the problem was similar, the level from the mic was very hot even when the transmitter was all the way down

since i think you mentioned smqv, i thought i'd throw this out there, in my experience when set to 250mw there can sometimes be some spray due to the strong signal, so that could cause some rfi. if there is not allot of rf to have to "fight" through & the hop to camera is only 10'-15' then a lower setting should suffice

also i'd check the talent mics to be sure there are interference from those

then of course there's the dp that may be talking & texting on his phone next to the camera while looking though the viewfinder.......

[studiomprd]

"note um & sm are not the same, however at one point certain vendors claimed they were. "

well, not exactly...

it isn't UM compared to SM, however there was Lectro's original wiring scheme, and the current Lectro "servo bias" wiring scheme...

there was also a change in the basic SM input gain shortly after the SM's were introduced.

[beartrax]

"note um & sm are not the same, however at one point certain vendors claimed they were. "

well, not exactly...

it isn't UM compared to SM, however there was Lectro's original wiring scheme, and the current Lectro "servo bias" wiring scheme...

there was also a change in the basic SM input gain shortly after the SM's were introduced.

i thought all sm were servo bias & um were not?

i loosely learned of it a while back when transitioning & had to replace or reconfigure all my dpa>lectro adapters, so i may be forgetting something...?

anyway the odd gain structure in question in this thread made me remember my troubles with my dpa mics & has me guessing that there may be some odditty with the wiring

[studiomprd]

Lectrosonics has upgraded (?) all of their current TX's to the servo-bias input; on models that did not have this before, they have added an "a" suffix to designate servo bias version.

[PTA]

Well now I seem to have a new issue with the system.  I ended up ordering the MC41 cables from Lectosonics that are the servo bias wiring scheme. Even though the cables say they are for mic level, I was told that they would take both line and mic level and the SMQVa would take both level signals. When I tried feeding line level to the SMQV's the level was WAY to hot, and only mic level was appropriate. So apparently the MC 41's are only mic level cables.

Here is the odd thing, regardless of the cables I use, whether they are the new MC 41's or the old Lectro ones I was using, the receiver doesn't pump out a hot enough signal.  All the settings are the same as before on the SMQVa's and the SR, nothing at all changed, but the SR doesn't generate a line level signal like it did before.

Did I fry something in the transmitters?  Everything sounds good to my ears, the visual audio levels are fine too... I'm stumped.

[Marc Wielage]

When I tried feeding line level to the SMQV's the level was WAY too hot, and only mic level was appropriate. So apparently the MC 41's are only mic level cables.

I ran into the exact same problem with a camera hop set-up a few months ago, and it drove me nuts. I was eventually able to tweak the gain-staging to the point where neither noise nor distortion were problems, but there was some trial and error involved. Going mike level ultimately worked for me.

I haven't had any issue getting a decent level out on my SR, at least judging by the last Red project I used. If anything, I worried more about keeping the level a little low to avoid any headroom issues on the Red.

I'm about to try the D4 on a Red project in 2 weeks, and am going to try to go in digital (if the DP can figure out the input menus).

--Marc W.