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Mic or Line?


JDirckze

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  • 2 weeks later...

So my mixer finally arrived (Alphamix) and I've been playing with my 411's before I head off on this trip to Venezuela...

Sending tone from the mixer (440Hz/0dBVU) into the Tx using a line level cable to interface, the -20 & -10 LED's on the Tx both light up green. This strikes me as curious, as I would've thought this doesn't leave me much headroom. This is with zero gain applied on the Tx.

It was my understanding that only the -20 LED should light up green.

At this stage I am more inclined to stick with Mic level, even though this means going through the camera mic pres, unless anyone out there can confirm that the -10 LED on the Tx being lit up is not an issue???

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I don't have the UM400's, but it looks like a little too hot of a signal to me.  I would think that the trim pot on the TX would have at least a bit of gain added..  Does the Alphamix output +4db? or 0db?  Do you have a pad you could insert inline to see if that helps?  How does it sound with dialog?, maybe that is where the Tx should be set??

-Jason

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Thanks again for the replies boys!

I think at this stage for the next gig I will stick to Mic level from mixer through to camera. i'll pick up some of those cables of pads at some stage.

Now I just have to sort out this other issue I am having with the Alphamix. There seems to be an issue when using an internal NP-1. The mixer won't power on when I first insert the battery, I have to partially remove the battery until I hear a 'click' and then re-insert before the mixer will power up. Have sent an email to PSC but no reply so far...

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It's brand new Scott...

I fired off an email to PSC but no response as yet, and have also let the retailed know about the issue. Unfortunately, I'm off in a few days for a 3 week shoot so don't have enough time to have another shipped out before I leave. We have to order them in from The US.

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Jason,

Maybe I'm misunderstanding something here.

When you say "0" gain on your UM400, how is the input level control set?  Do you mean the knob is at 12:00?  If so, you can turn it down to get the proper level.  If the UM400 gain structure is similar to the UM200 there is a buffer amplifier stage prior to the gain control but it will handle pretty high levels prior to overloading -- about 1.5v IIRC.  From what Larry Fisher told me, even at the 9:00 (pointing left) position, with the transmitter modulating correctly, you shouldn't be too concerned that the signal's so hot that it's overloading the input stage.  Again, that was with the UM200C.

Do some testing and see how it sounds.

If it is overloading, it's not too difficult to rewire the connector for a different gain structure.  You could even throw a little resistor in series with the hot input lead inside the TA connector to tame it a bit (you need a tiny resistor and careful hands).  I forget what values I used but I made two different sets of line level cables, one for the line out on a 302 (0dB) and another for the tape out (about -15dB).  IIRC, there are three different gain structures you can wire the input connectors for and then I used a padding resistor into the one for 0dB because I thought it was a tad too hot.  Maybe 3.9K ohm but I could be wrong about that value.  It's been more than two years back since I wired them.

To adjust the levels into the transmitter, I'd recommend being more concerned about when you hit the limiter than what your 0dB level tone does.  In other words, set up the mixer the way you're going to use it and then talk into a mic and set the mixer levels to where you would normally adjust them and see how your levels are going into the UM400.  Adjust them so that you only hit the transmitter's limiter on rare occasions, or, even better, to a level just below where the transmitter would engage the limiters on your highest peaks.

JB

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John: With the Tx (UM400) the gain is all the way down, so no gain applied at all ie: 7:00 - And this is with the 'special' Line level XLRF to TA5F cable.

Sending tone from the mixer to the Tx at 440Hz/0dB VU both the -10 and -20 LED's on the Tx light up green. Scott suggests this is normal.

I'm not bad with the soldering iron, but my electronics theory lacks somewhat. Thanks for the tips though. If I'm feeling adventurous I'll pull apart the cables and have a play.

I'll do some testing with voice as per your instructions, but I'm more worried about loud screams etc, as this next gig will be dealing with spiritual healers and ceremonies in the the amazon, and I imagine I will be dealing with a lot of dynamics, from quiet possessed gurgling to blood curdling screams.

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Thanks Glenn...

I bought some line level cables yesterday for the Lectros.

Jason,

you might want to try Mic level cables. a majority of mixers use mice level for camera hops. when I send out kits, I send out mic level cables (MC40 ? can't remember right now) actually I have no problem sending both cables and I usually do to make sure the mixer is covered. and when the gear is returned, and I asked what cable they used, it is the mic level cable.

also,

going on a shoot out of the country, you really wan to bring some back up cables.

bring both the mic & line level cables (2 ea.) along with your other back ups, don't forget Tc cables, bnc & xlr turn-arounds, connectors and adapters stuff you won't find in VEN. don't think they have a radio shack near by.

Gd luck

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Jason,

When I say adjust for the highest peaks, that's exactly what I mean -- the screams, etc.  Simulate what you think you might encounter and adjust so those screams, etc. either don't engage the transmitter's limiter, or just rarely catches it on the wildest peaks.  In my experience, you're typically better to have your mixer catch errant peaks than to hit the transmitter's limiter with them.

Be careful what you scream, though.  The wrong incantation could give you webbed feet.

From your description, it doesn't sound to me like you got cables wired for line level.  Try using the same cable with either a tape out or the mic out and see what the results are.  Run the transmitter between 9:00pm and 12:00 - ideally, between 10:00 and 12:00.

JB

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Guest afewmoreyears

Jason,

John Blank is correct....

  The Lectro trans.  is supposed to flash the -20 and -10 green lights during transmission of signal.... lectro even recommends tickling the red light just a little..... Just a tickle..... Thats what they have always told me.....

  Bottom line,  do what John says.....  put your dial on the transmitter at between 9:00 and 12 noon....  9:00 would be for very loud delivery.... and 12 noon is the basic starting point for MOST audio at spoken levels...  If your recording very soft voices or small kids, a bump to 1:00 might be worth it.....

  As far as a SM or SMQ.....  start at around 27 and test as john says until BOTH green lights flash and tickle the red at the dialog level you THINK will be spoken. Stand there like a fool talking into it till your comfortable.... remember to provide the same distance to mic and basic placement when testing.... Always consider this before each use..... but leaving the non SM unit at Noon will provide a good starting point.

Also the 400 series receiver level should be set at between 22 and 25 as well....  Non 400 series,  Noon again works great... 

  If your mic burns up due to improperly set levels at the transmitter.....  not much you can do down the line at the mixer....  This is your best protection to ensure your mix will be a quality one...

  Screaming never sounds too good on a lav, but with a few exceptions like the Sanken COS11s at 127 or the countryman at 130 db maximum spl  you stand a chance....  Some lavs even have more.... check around...

  With screaming, If you cant boom it, placing the Lav mic lower than normal on talent also helps a great deal, even a few inches. If you are booming the screams,  have your boom op mix a bit with the pole.....  by raising and placing the mic end slightly off axis during the scream, it can really help the overall quality of the loud scream or yell...

  We are almost always wireless boom, unless screaming is to be recorded, then we will go old school with a wire...  Again, we dont want to trigger the transmitter limiters....

One more thing,  If you are recording One mic or 1 boom,  into two channels.... Reduce the input volume on the right track and use it as a backup track in case your primary (left) burns up with a REALLY loud  unexpected delivery...  I almost always do this, when warranted, in certain situations... why not,  you never know....  The argument is, wasted file space and increased transfer time for your files....  But sometimes it is worth it, especially for potential screamers....  I typically don't care for limiters too much....

Oh yeah....  Think about this gear pkg. of yours 10 times before you leave.... Bring every cable you even THINK you will need...  this goes for all your gear....  There is a fine line between too much stuff and your ass in a sling....  I always think through every possible scenario, and bring what I need...  Dont forget batteries!!!!  They suck overseas....  horrible....

Hope this helps.....

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I disagree (partially) with one thing: when sending duplicate signals to camera, the practice of lowering one channel for protection.  Although there is a place for this, I don't do it in general practice for several reasons.

A local sound mixer I know does this, but let's examine what his results are.  He's coming out of a Shure FP33 mixer with a maximum headroom of about 15dB and going into a digital camera with max headroom of 20dB and turning the right channel on the camera down by about 6dB.  The mixer's output will distort long before the lower camera level on channel two will protect him.  The only thing he gains is more noise on the second channel.

One of the biggest problems with this practice is that we, as sound mixers, are making a dangerous assumption:  that everyone else in the chain cares as much about sound as we do.  I hate to have to be the one bearing this news, but that just isn't the case.

With analog cameras, when sound and picture are captured, ideally, someone lines up the sound levels via tone.  Unfortunately, that doesn't always happen; they often just use, "standard levels."  With digital transfer, it's worse, since what you get is what you got -- there is no level tweaking during capture.

A typical scenario in post is that once the sound and picture are captured and the editor goes to work, aware that he/she is probably already behind the ridiculous schedule that management has given him/her, time is of the essence and all they care about sound is that it's there.  If there are two channels of sound, the nonlinear editing system will automatically pan one left and one right.  The editor finishes the job and it airs -- with the right channel at a lower level than the left channel.  All too often, there's little time to tweak audio the way us soundies would.  In the fast and furious video world, sound is frequently used just the way it comes in.

Another reason I seldom do the "split-level" thing, is that I consider it my job to get the levels right.  If I know what I'm doing, and I do it well, there's no reason for "split-levels" to CMA.

I would much rather have a good limiter on the mixer protect me than to anticipate that post will unexpectedly begin to care more about sound.

I also consider wireless to camera a compromise and mis-adjusting levels makes this compromise worse IMHO.

Just one person's opinion; I'm interested in what others think of this practice.

JB

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Guest afewmoreyears

John,

  When I do do this,  I make sure that the Sound notes state VERY clearly...in red ink that that is the case....

  Of course the idea is to mix the material correctly the first time,  but when un expected VERY loud signal comes down the pike, the second channel will in fact be helpful....  I am not saying to raise the left track,  but to simply reduce signal to the right.....

  Not a cure all, BUT CAN BE HELPFUL AT TIMES.....  If properly stated on notes....

As mixers, it's all you can do... If down the line people hurry through their jobs, not paying attention to ANY notes or information in special circumstances....  Not my problem...

  I have in fact done this for years where warrented without EVER having one problem doing it.....  So what works best for one , may not be preferred for others.... 

Just how I do things....  I also like to consider myself doing a fine job,  but on a scene where talent speaks softly and unexpectedly delivers very loud dialog,  there is only so much you can do as a mixer to keep all the levels sounding nice...  Most of the time we all peg it....  but I do not mind CMA as you say.... I am not so proud...

  I also do not care for keeper audio sent wireless to camera...... Agree... :)

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Just to be clear, I'm not saying my way is better for everyone or that I have any franchise on the best way to do things.  We're all "fighting the good fight."  What I'm offering is my approach and my rationale for that approach.  It's about different approaches to achieve the same goal of good audio while maintaining a modicum of sanity.  Granted, sanity's overrated, but a bit of it once in a while comes in handy.

My thinking is, it's very much about gain management.  If my mixer has 20dB headroom and the camera has 20dB of headroom, I don't see any point in giving the camera more headroom.  There's little to be gained and the aforementioned downsides to be lost.  Sending a signal to a Betacam SP, there's less camera headroom.  However, in both cases, I prefer to let my lightning quick reflexes (okay, when I'm not napping), and even more realistically, the mixer's nice limiters, keep me out of trouble for those unexpected screams.

Unless, of course, the screams are coming from the sound crew.

JB

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you might want to try Mic level cables. a majority of mixers use mice level for camera hops. when I send out kits, I send out mic level cables (MC40 ? can't remember right now) actually I have no problem sending both cables and I usually do to make sure the mixer is covered. and when the gear is returned, and I asked what cable they used, it is the mic level cable.

The reason I wanted to stick with line level was to bypass the mic preamps on the camera...

going on a shoot out of the country, you really wan to bring some back up cables.

bring both the mic & line level cables (2 ea.) along with your other back ups, don't forget Tc cables, bnc & xlr turn-arounds, connectors and adapters stuff you won't find in VEN. don't think they have a radio shack near by.

Yep! I have backups/spares of all cables/connectors etc... just no backups of hardware. Production denied the request for a backup mixer and shotgun mic.

Cheers!

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When I say adjust for the highest peaks, that's exactly what I mean -- the screams, etc.  Simulate what you think you might encounter and adjust so those screams, etc. either don't engage the transmitter's limiter, or just rarely catches it on the wildest peaks.  In my experience, you're typically better to have your mixer catch errant peaks than to hit the transmitter's limiter with them.

Be careful what you scream, though.  The wrong incantation could give you webbed feet.

I have a feeling most of this gig is going to be boom work...

From your description, it doesn't sound to me like you got cables wired for line level.  Try using the same cable with either a tape out or the mic out and see what the results are.  Run the transmitter between 9:00pm and 12:00 - ideally, between 10:00 and 12:00

The mic and line cables are definitely different. I'll measure the difference today...

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Re: The Alphamix battery compartment issue - This is what I received from PSC this morning. I'm copying it here in case someone else has this issue.

"We have had a few occasions where the "IDX" batterys have not made proper contact with the battery contacts on the Alphamix.  Rather than have you send the unit in for adjustment I will inform you how to fix it on your end:

There are 3-battery contacts at the far end of the battery cavity on the alphamix.  They are on the bottom side of the unit.  The contact closest to the back side of the unit needs to be moved slightly toward the rear or back side of the unit for proper alignment with the IDX batterys.

You can use a long screwdriver or other tool that will reach down into the battery cavity to butt up against the left side of the contact and push it to the right slightly.  If you push too hard, you may deform the contact so be careful.  It will take some good pressure to move it though.  It need only be moved a few millimeters or so. 

Once this is done, check the IDX batteries as well as any other brand you may have to make sure they all are functioning properly"

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The reason I wanted to stick with line level was to bypass the mic preamps on the camera...

If we're still discussing the signal level going into the transmitter, you're talking apples and oranges.  You should be using the correct cable going into the transmitter to properly modulate the transmitter.  Using a mic or line level into the transmitter doesn't determine what level the receiver will be operating at.  You send the correct level to the transmitter to properly modulate it (which means the signal will push the transmitter to just below where it would cause the signal to overmodulate.  Since it's an FCC no-no to overmodulate a transmitter, the transmitter's brick wall limiter kicks in and prevents this from happening.  However, that limiter doesn't sound nearly as good as one on the mixer, so it's desirable to rarely hit the transmitter's limiter -- if at all.

With a properly modulated transmitter, the Lecto receiver will unmodulate the signal and amplify the signal to a normal line level.  You then choose what level the receiver's output is by using its output level controls.  On a Lectro receiver, this output control is simply a passive resistor network that pads the signal down to the level you choose.  If you're going line level into the camera, I suggest using the highest output from the tranmitter since you're not pushing the transmitter circuits any harder, you're simply not attenuating the signal as much.

I hope this helps clarify it a bit.

JB

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Thanks John... this is all helping tremendously!

At this stage I am certain that I have the correct Line level XLRF-TA5F cables, and I've done some extensive testing with my Macbook and Mbox mini, made some recordings etc... all sounding great. The 411/400 + COS-11s sounding great through the Alphamix. We have a day in Caracas to get all our gear together so I'll have a chance to put the rig through it's paces with the camera.

Now just waiting on a Rycote softie and K-Tek K81CCR to be shipped in...

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Just when we thought this thread was dead....

I'm building cables for a UM400a, and ran into a similar situation as Jason with line level (too hot signal with Tx gain turned all the way down).  Details are further down (in case I'm overlooking something obvious, do tell me...), but my question is this:

Why does Lectro's "normal hookup" wiring for line level input to the transmitter seem to be too hot coming from a 0 dBu line level output?

From the UM400a manual:

===========

Line Level Signals

The normal hookup for line level signals is:  Signal Hot

to pin 5, Signal Gnd to pin 1 and pin 4 jumped to pin

1.  This allows signal levels up to 3V RMS to be applied

without limiting.

If more headroom is needed, insert a 20 k resistor in

series with pin 5.  Put this resistor inside the TA5F con-

nector to minimize noise pickup.

===========

Seems to me the 20k resistor is a requirement for using 0 or +4 outputs.

Why is it in the manual as almost an afterthought?

Is it so rare to send a professional audio line level to a transmitter that the UM400 has been engineered to be happier with a -10 line level?

Looks like I'll be testing resistor values to find the best attenuation.

The specs for my tests:

-"Normal Hookup" line level cable - TA3 to TA5 - wired correctly (pin 2-->5 ; pin 1-->1 ; 4 jumpered to 1)

-CS-104 - 0 dBu line level out via unbalanced TA3.

-UM400a gain level = turned all the way down

-Tone (at -8 dB on the CS-104 ; 8 dB below average dialog levels) lights up BOTH green LEDs.

-Dialog lights up the -20 Red very quickly.  As a matter of fact, the red LED on -20 kicks in only a couple dB up from the -8 dB on the CS-104.  More importantly, I hear the limiter kick in at average dialog levels (around 0 dB on CS-104).

Following this thread, I tried plugging that TA3 into the tape out.  That plays nice.  I can bring up the UM400a gain to around 9:00, and the Tx limiter only engages when the CS-104 is pinned out.  Also tried setting the unbalanced TA3 out to mic level.  Again, happiness.... UM400a comes up to around 1:00, same headroom scenario as the tape out before limiting.

I'll be re-labeling that cable as a mic out cable, not a line out cable....

Brian

PS - jason, how did you determine that you have the correct line cables?

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Don't know if this helps or not but the line level cables for a UM400 don't work properly with a um400a or a SM with the new wiring scheme and vise versa. and then you have line level from some gear is -10 or 0 or +4 which adds to the confusion. Then you have Sound Devices wiring diagrams for their version of line level.

I saw the notes about the servo compatibility with the older/newer lectro's.  Moot point for me, I don't have any other lectro's.

I always considered 0 or +4 (even +6) to be typical line level for pro audio gear, not the so-called "consumer" level of -10.  But it really seems like the UM400a is not natively capable of handling a 0 or +4 signal.  Resistance is futile....I mean...required.

Sound Devices' version?  On the mixers, or the recorders?

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PS - jason, how did you determine that you have the correct line cables?

I bought both mic and line cables and basically just swapped between the cables noting the differences between them when sending tone from the Alphamix.

Using the line cables, when sending tone from my Alphamix to the Tx, with the Tx level knob turned all the way down or fully attenuated, both LED's are green, which struck me as strange at first, BUT I can bring the level knob to 9:00 and both LED's still remain green, which is normal according to the manual. After doing some tests with Protools, I'm happy with the results...

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