calibrating the SVU-1
 

I just got an SVU-1, one of Beachtek's portable VU meters. I'm a little confused by the directions that came with it as to how to calibrate it so I can monitor audio levels correctly. I'm using a Canon XL1s. Part of my confusion, I guess, is because the directions mention "not letting the audio peak past 0 db, but -12 on the XL1s is considered 0, or the ideal peak level at least. . .and it's all very confusing to this guy. Any of you guys know how to do this? Explicit detailed instructions would be excellent.

Nothing will be lost in your audio signal until the levels get to zero. It's digital so when they do get there, they're gone. Total distortion.

If you are trying to dub to an analog format, like beta, then you need to keep in mind that analog formats have some overhead. So if you set reference at -12(or -20) and keep you levels around there you can have short plosives that go over and analog equipment will handle them fine.

If you are staying digital all the way to delivery, then still think of -12 as a safe place to stay to give you a little room to work. You never know when someone will lean toward their microphone.

I guess I could record tone from an NLE to a tape, and then play the tape back through the camera's VCR function, to give me a reference?

Alright, still need some clarifcation, as I seem to be retarded.

I recorded, from my NLE, to tape, 1Hz for some reason) tone, at -12 db. I calibrated it so that on playback through the camera, -12 on the camera's VU meter was also -12 on the SVU-1. I also recorded tone at 0db, with the same result. One thing that worries me, though, is that I can't get the SVU-1 to go into the red (the +3 and +6 indicators), even when I can hear the sound distorting in the headphones. If 0 db is the maximum the XL1s can handle, then when I hear distortion, shouldn't I be able, on the SVU-1 to see the +3 and possibly +6 light up? It never peaks past the yellow (0 db), no matter what.

Call Harry at Beachtek, he made it so he knows best how to explain it. He's a very helpful type.

Yeah, I've been in email contact with him. . .but I always figure two (or more) heads are better than one.

Well if you want this external indicator to react like an analog vu, then you should set your reference tone at -12 from your camera to be 0 on the SVU. Now if you keep your signal around 0 on the unit with a few peaks into the red, your audio on the camera should still have be a strong enough signal to avoid the noise floor and have a little bit of headroom to avoid clipping.

I'll wager that you'll often/usually see distortion at -12. Panasonic calibrates analog to -14, Sony to -18, JVC to -18, Tascam to -18, and the ATSC spec is -20. http://www.atsc.org. You can read 2 white papers there for free. Then you have to pay to read the rest.
I don't know where the -12 thing comes from, but it's pretty common on the web.

DSE,

Distortion on what? He's recording to an xl1, it shouldn't distort until he pegs zero.

Interesting that manufacturers have established totally different relationships between their analog and digital gear. Won't it be nice when everything is digital except you monitors.

Martin

If he's sending tones from an analog device to create a -12 signal to a digital device, chances are he'll be hitting zero with audio going into the XL1. If not, chances are still good in a direct transfer that the XL will be too hot to a beta deck. For the meter to "react like an analog VU" and be accurate, -12 isn't enough attenuation.

After re-reading his/your post, I recognize there is a different meaning than I'd read the first time though...so I'll leave it at that. I've got digital INPUT speaks, and even they suck. Yes, it would be great though if all things were digital, or at least a metering display standard could be observed. It's confusing as heck to most everyone, including me, because it's difficult to always remember what meter you're using.
I use a Dorroughmeter for most things, it helps a LOT

I'm just saying. . .if I see "-12" or something (any level) on the Camera's VU meter, don't I want to see the same thing on the SVU-1? I bought it so I could monitor audio (besides headphones of course) by another method then squinting at the camera's tiny built in VU meter. I'm just trying to make sure I'm calibrating it to get that result--sorry if I complicated things.

I'm just saying. . .if I see "-12" or something (any level) on the Camera's VU meter, don't I want to see the same thing on the SVU-1? I bought it so I could monitor audio (besides headphones of course) by another method then squinting at the camera's tiny built in VU meter. I'm just trying to make sure I'm calibrating it to get that result--sorry if I complicated things.

That zero things still bugs me though. . .

Since I don't know the VU1, I'm gonna assume it's calibrated to analog, not digital. If it is, you'll see a different reading on it than you will on the XL. Trust the XL, and calibrate the SVU1 accordingly.

I'm sorry; how do you mean?

Harry from beachtek emailed me this: Does it sound about right? I didn't see how it makes sense before, but I think I do now, too low is too low, and too high is still to high, the numbers are just different:

It appears that the XL1s cannot put out more signal after 0 VU. I believe the Canon owner’s manual suggests setting the audio levels to the -12 dB mark. In that case, You may want to calibrate the SVU-1 so that 0 VU on the SVU-1 corresponds to -12 dB on the camera. This way, you will plenty of breathing room before you reach the distortion level.

<<<-- Originally posted by Josh Bass : I didn't see how it makes sense before, but I think I do now, too low is too low, and too high is still to high, the numbers are just different:-->>>

yeah, this is true. It's a very simple explanation though. In analog, you've got a little flexibility. In Digital, you have none. Analog=forgiving
Digital=one mean bastard if you cross it's threshold.

Ok then, so where do I want to stay between, (for dialogue) with these new numerical values (on the SVU-1): they range from -21 to +6

Here's something weird--I can't turn the little screws that adjust the calibration past a certain point. It won't quite reach zero, that is, I can't adjust the SVU-1 so it reads 0 when the XL1s is at -12, the screws stop turning once the SVU-1's meter reaches 6. I'd rather not force anything

Well that fits with what Douglas Spotted Eagle, has been saying. Put zero on the VU = -20 on the digital recorder. It's probably a good habit anyway, since that's now the standard.

Sorry, gents, that doesn't seem to work either. . .I can only turn the pots far enough to where, when the XL1s is displaying -20, the SVU will display -12, and then I get the hard stop from the pots.

Harry said:

"It appears that the XL1s does not have sufficient level from the RCA output jacks to drive the SVU-1 to read 0 VU. Did you try the same test during recording? You will have to see if you can change the AUDIO 1 RCA jacks to function as output during recording as they are normally used as input.

I'm not clear on how that would work; I've always used them for output only. Could that be part of the problem? The only input this SVU has is RCA.

I have very little experience with the xl1, but I was under the impression, that when you are in camera mode, the audio rca jacks were inputs, and that that was the best way to get signal into the camera.

Were I you, I'd get a 2 mono to stereo mini cable, about 8" in length, and use the outs from the SVU to the mic in of the XL1. That's how we've always done this, truthfully I've never used the RCA inputs on the XL because they are also for the 12 bit/32K 4 channel operation of the cam. I've only used that lower quality feature to demonstrate the crappy sound that comes out of any cam at that sample rate.
You'll be fine with the mic in. Are you sure the RCA's aren't line in? I think they might be.

Uh. . .how do I know if the RCAs are line in? As for that stereo mini cable, can I get a longer one? One of the reasons I wanted the SVU was to be able to have someone who's not right near the cam monitoring the audio. . .like maybe just hold the unit in their hands and stare at it.

Do mini cables resemble RCA? In the shape and size, I mean?

Mini cables are like what plugs into your Walkman headphone plug. Look on the right side of your XL1, near the handle, where the mic cable plugs in. There are 2 connectors; one is sub-mini, that provides power to the mic. There is a mini-stereo, that provides sound from the mic to the camera.
RCA connectors look sorta like doughnuts. Metal outside, with a hole in the middle. RCA connectors on the XL1 are found under the trapdoor near the handle. I think this is what you are currently plugging into, no?
You can get a cable as long as you like, but if it's more than about 10 feet, you'll start to incur noise in the line due to loss of voltage from the SVU to the camera. So the person monitoring isn't hearing what the camera is hearing. If you want a long cable, have it be the headphone cable and keep the cable run as short as possible between the SVU1 and the camera.

Alright, thanks. I'll try it.

One thing that concerns me (haven't gotten the cable yet), if I plug into the mini plug, will the camera know what to do? I've never used anything but the RCA cables for audio out. . .don't have any experience with it. Any special settings or anything?

Will this work for both playback and recording? I've done all the tests so far during playback with a tape with tone recorded on it.

The miniplug is an INPUT only. Has nothing to do with output. Monitor from the camera by using the headphone out on the cam, so you you know what's going to tape. Output either via the RCA or Firewire outputs.

That's what I thought. . .what I meant was, how will the mini plug, if input only, connect to the SVU-1 in such a way as to send the audio signal to it? That's why I've been using RCA--I thought it was the only way to send a signal to the SVU.

Alright, so I sit here with many little cables and adapters around me, and have only gotten the unit to work by doing it the way I did the first time--the camera's RCA audio outs (on the back) to the SVU's audio in. I tried the mini-plug to RCA adapter, plugging the miniplug into where the shotgun mic (the one that came with the camera) usually plugs in. . .nothin'. What am I doing wrong? Can the submini plug at the back of the camera (between the RCA in/outs) be used to do anything?



*Put in later*

Alright, I've figured out one small piece of the puzzle--by attaching a male mini plug to male miniplug cable to the mic input on the handle (where the onboard shotgun goes), I can now power my beacktek XLR adapter by plugging the other end into it's auxilliary port (allowing me to get readings on the SVU from my ME66). This allows me to use the RCA connectors on the back to attach the SVU. Was this the idea all along, or am I still on the wrong track?

Alright. . .after exhaustive discussions with Harry, and Jay Rose, here's the deal: Neither through the Audio 1 RCA in/outs on the back of the XL1s, nor through the mini plug for the headphone jack (I don't see how the other miniplug can be used. . .please explain if it can), can you generate enough signal to allow the SVU-1 to be set to 0 when the camera is set to -12, the ideal for this camcorder. Harry at Beachtek says set 0 to 0, bad idea, according Jay Rose, for the aforementioned reasons.

So I'm confused; no one else out there who has an XL1s has ever bought an SVU-1? If so, how did they make it work for them?

Josh, apparently no one HERE has purchased an SUV1 for an XL1, I've asked Beachtek many times for a review unit for the mags I write for. They don't even respond to my mails nor my requests in person at trade shows. So....can't help you.
What I can tell you is that if the unit won't go to -12, let alone -20 to be calibrated in tandem with the camera, then it's a waste of money and I'd be truckin' back to the store with it.
If Harry at Beachtek can't tell you whether the displays are calibrated to FS or VU, and tells you to set it to zero, I sincerely hope that you are only misunderstanding him rather than him not knowing the difference. That would scare the heck outta me. and would surprise me too. (him not knowing)
[edit] I've just downloaded the brochure and looked at the specs. It has a -21dB low end adjustment value according to the book, so it should be able to match what you have on the cam.
Print a 1K tone at -12 from your NLE to a tape. Put the tape in your cam. Play it. Use the jewelers screwdriver to adjust to match the output levels also being shown on your XL1. This should be all you need to do. If the brochure is wrong, then I'd be surprised as it appears to be fairly standard.[edit]

All I'm saying, and the last I'll say (I think, you never know), is this: If I set 0 on the Camera's VUs to 0 on the XL1s' VUs, then the problem is

1) when and if the camera's VUs peaks, and the audio distorts, I will simply think, looking at the SVU (yes I'll also have headphones, but that's not the issue here), that I've simply gotten to the bare limit of what's acceptable, not that it's actually distorting, since the readout on the SVU won't push past 0 and into the +3 and +6 range.

2) Since the lowest number on the SVU is -21, if I record anything lower than that (say, background noise, whatever), it'll look like I'm not recording anything at all, since the SVU won't read any lower.

These two things would seem to suggest that unit is not meant to be calibrated to my camera's 0, but there doesn't seem to be any other way to make it work.