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Bob Cole
mic/line level questions: pre-amp & Sennh G3 settings
on Aug 6, 2010 at 9:11:54 pm

Short version first:

1. Is there such a thing as a high-quality in-line XLR to XLR pre-amp which can transform a mic level output to line output?

2. I looked for a line-out setting on my Sennheiser G3 ew100 G2 and G3 wirelesses. Sennheiser sells a CL2 cable which is positioned as a line-level input adapter. But I don't see any explicit setting for mic vs. line inputs on the transmitter, nor mic vs. line outputs on the receiver. On the transmitter, there are "AF Out" level settings from -30 to +12. Is that how I set to mic vs. line level?

Background to question 1: On my Sony HVR-Z1U (HDV camera), the Line 1 input is noisy when set to mic level in. (It's fine at line in; the Line 2 input is fine with mic or line in.) It's not terribly noticeable, but the fact that it differs from truly "clean" bothers me. I talked to a repairman who said it could be a tired capacitor... or anything - impossible to predict the repair charge in advance.

I'm considering whether to have this repaired. I still have a clean mic level on Line 2. Since this is a camera that is nearing the end of its loyal service, I'm considering whether to simply reset my Line 1 input to Line Level - as long as I can find a mic-line level adapter. Opinions welcome.

Bob C


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Ty Ford
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 3:17:42 am

[Bob Cole] "2. I looked for a line-out setting on my Sennheiser G3 ew100 G2 and G3 wirelesses. Sennheiser sells a CL2 cable which is positioned as a line-level input adapter. But I don't see any explicit setting for mic vs. line inputs on the transmitter, nor mic vs. line outputs on the receiver. On the transmitter, there are "AF Out" level settings from -30 to +12. Is that how I set to mic vs. line level? "

Yes, but you'd still need a preamp for hardwired mics.

regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Bob Cole
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 4:55:59 am

[Ty Ford] "Yes, but you'd still need a preamp for hardwired mics."

Thanks Ty. Good point.

I'm still puzzled about inputting a line level to the Sennheiser transmitter. (I assume the CL2 is just an adapter cable from XLR to Sennheiser's 1/8" plug, with no alteration in the signal.)

If I want to use the CL2's female XLR to take a line output from a mix board into my ew100 G2 or G3 transmitter, how do I keep the transmitter from getting overloaded by the line signal? Even with the lav, I have to adjust the transmitter's sensitivity to the lowest point (-30). (Perhaps because I have not adjusted the receiver's AF Out to -6, as recommended in the manual that I'm studying a bit more closely, thanks to this problem....)

On the phone you recommended I look at Sound Device's MP-1 pre-amp, which looks very interesting. For one thing, it offers 48v and 12v phantom powering. I assume this will not help with my Schoeps, which needs 12v "T" powering. That would be very nice.

D


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Ty Ford
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 12:44:42 pm

[Bob Cole] "If I want to use the CL2's female XLR to take a line output from a mix board into my ew100 G2 or G3 transmitter, how do I keep the transmitter from getting overloaded by the line signal? Even with the lav, I have to adjust the transmitter's sensitivity to the lowest point (-30). (Perhaps because I have not adjusted the receiver's AF Out to -6, as recommended in the manual that I'm studying a bit more closely, thanks to this problem....)"

IIRC, the CL2 relies on the fact that the input jack on the transmitter is actually a TRS (tip ring sleeve). The mic level is ring -sleeve and the line level is tip sleeve, or vice versa. So same input hole, different input capability. Very clever those german engineers.

per the T-power...a short thrip to the Sound Devices web site reveals the following.

"Flexible microphone powering provides phantom power at 48 volts or 12 volts and 12-volt T-power. It is powered from two-AA batteries or external 5-18 VDC."

Perhaps you should peruse the site yourself.

Here, let me help you: http://www.sounddevices.com/products/mm1master.htm

Regards,

Ty Ford

PS: I thought you had a Sound Devices 302 or something.

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Bob Cole
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 2:03:55 pm

Thanks Ty - great find; this has been a valuable learning experience. I still wish my camera's internal mic level worked better, but if I become a convert to Line In, maybe that won't be such a bad thing. Is your basic principle: Don't use Mic Level In on cameras? Does it really make a difference? Do you think it's advisable to boost the mic level to line as early in the chain -- as close to the mic -- as possible?

The first device you told me about, the MP-1, must not have T power as it only mentions phantom. But the MP-1 is a bit smaller, and would, in combo with a barrel 48V Phantom-to-12V T adapter, do the trick with the Schoeps that needs T. (I assume that is okay?) With the monitoring capability, the MM-1 looks great as a boom op control. I still wish there were an inline pre-amp, but that obviously is asking too much.

For some documentary shoots, minimal gear works best, so I tested using the Sennheiser ew100 G3 receiver as a pre-amp, essentially, and it seems to work. If I set the transmitter's sensitivity to 0dB (as opposed to -30dB, my usual setting) and the receiver's AF Out to +12, and the camera to Line In, I get a good level (though not quite as hot as I'm used to with settings of -30/0/Mic In, on transmitter/receiver/camera, respectively). I'd like to borrow your ears sometime to make sure I'm not fooling myself.

I'm beginning to see why audio guys have all those tools.... Every time I look at a product review by an audio recordist, it seems that I see the words, "great tool that belongs in every recordist's kit."

Bob C


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Ty Ford
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 2:31:29 pm

Bob,

"Best Practices" is to go line level to the camera when possible because line level is hotter than mic and will be less susceptible to interference. Also because the mic pres in cameras are usually not that great. Having said that, I have personal experience that some camera mic preamps seem perfectly acceptable, others not.

Audio people would like camera audio inputs to be designed so that the line level input completely bypasses the camera mic preamp. Due to cheapness, many just stick a pad in front of the mic pre when the "line level" switch is engaged. So the signal still goes through the camera's mic preamp. Usually not ideal, but there you have it.

Audio is like plumbing. Once you find you need a basin wrench, nothing else will do.

Sure, stop by and we can do an experiment. I have some time this week. (as most of us do these days)

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Bob Cole
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 2:42:21 pm

[Ty Ford] "Due to cheapness, many just stick a pad in front of the mic pre when the "line level" switch is engaged. So the signal still goes through the camera's mic preamp. Usually not ideal, but there you have it."

Wow. That sounds insane. Is that fact ever mentioned in camera spec's? I don't recall ever having seen that. Double-system, though a pain, sounds like a very good idea, especially as a back-up. I've always avoided it as a primary method, as being too time-consuming in post. I wonder whether software like PluralEyes can be used to automate the process now.

Thanks very much!

Bob


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Ty Ford
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 2:58:47 pm

Bob,

I don't think I've ever seen it mentioned, but some of the folks who have the full manuals with circuit diagrams have made the point. Insane, perhaps. CHEAP, yes. Speaking of CHEAP, Sony digibeta cameras can't output stereo from the headphone output; only dual (mixed) mono. They do have a 5-pin XLR on the back for audio out, but then you need another gimmick to get that to your mixer's camera return input.

PluralEyes is exceptionally cool. I have it and provided the cameras are getting the same audio, as in from the same feed, you're golden. I have even bent the rules by using mixer to one camera and camera mic to another camera and got sub-frame accuracy.

Pluraleyes also seems to fix that sub-frame problem you can get with two cameras when the audio doesn't quite match on the FCP time line because of where it falls on the frame.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Ty Ford
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 7, 2010 at 4:57:40 pm

here's another fer-instance for PluralEyes.

If you could feed a zoom recorder from the mixer for a whole scene. You could use its audio as a master track and shoot 2-3 or more cameras, each either getting the same feed or using their camera mics (provided the camera mics could get a decent recording in the space. The cameras could stop and start at will and their clips could be automatically aligned to the Zoom recorder audio track on the timeline.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Jordan Wolf
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Aug 8, 2010 at 6:56:02 am

Ty, you're right about the connector. Here's a screenshot from the manual.



Wolf
<><


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Jason Brooks
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Mar 13, 2011 at 3:39:47 am

This is actually a lot easier than it is. You can take a line level signal by simply engaging the PAD in the menu and taking the level to -30 db. Why? The difference between mic or line level (+4) is 50 dB. If you were to buy a inline XLR line to mic adapter that is what does is take the signal down -50 dB. The PAD setting in the transmitter is -20 dB, engaging that & taking the AF to -30 dB does the necessary padding for line to mic. If you are dealing with consumer line level (-10dB), meaning anything with a RCA or mini jack connection, you simply do the math between the 2 line levels which is 16 dB, then subtract from 50 dB. You need a reduction of 34 dB. Engaging the PAD (-20 dB) and -14 on the AF gives you a consumer line level input into the transmitter. Another solution is to have an adapter made for either mic or line level. If you open the connector for the Sennheiser, simply resoldering the + connection to the other pin will give you line level in.


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Bob Cole
Re: mic/line level questions: pre-amp & Sennh G3 settings
on Mar 14, 2011 at 2:26:52 am

[Jason Brooks] " If you open the connector for the Sennheiser, simply resoldering the + connection to the other pin will give you line level in."

Thanks for the response. Is this true of the G2 and G3 receivers, specifically?

My goal is to get all my mics to be line in. I had hoped to use the G2 and G3 receiver's AF Out adjustment to achieve this, but +12dB is not enough.

Thanks again.

Bob C


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