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#1
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Pro Tools outs clipping A&H Line ins?
We just swapped our Mackie 24 8 bus for a new Allen & Heath MixWizard3
board. Trouble is the main outs (1/4" balanced) from our Digi 002R are clipping the line ins on the board even with the trims all the way down... When PFL'd the A&H meters show between +9 and +16. It's only a problem with hot material (full mix with an L2 on the master fader), but it is definitely audible on louder passages. Very annoying! This was never a problem with the Mackie (granted we were using tape returns there.) This board sounds better, has better EQ, and fits our needs size wise so i'm really hoping this is solveable. Any help is greatly appreciated. Thanks, Dan Fox ZUMIX, Inc |
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#2
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In article .com,
Daniel Fox wrote: We just swapped our Mackie 24 8 bus for a new Allen & Heath MixWizard3 board. Trouble is the main outs (1/4" balanced) from our Digi 002R are clipping the line ins on the board even with the trims all the way down... When PFL'd the A&H meters show between +9 and +16. It's only a problem with hot material (full mix with an L2 on the master fader), but it is definitely audible on louder passages. Very annoying! This was never a problem with the Mackie (granted we were using tape returns there.) This board sounds better, has better EQ, and fits our needs size wise so i'm really hoping this is solveable. Any help is greatly appreciated. Thanks, Dan Fox ZUMIX, Inc Check out your manual and see if the 002 will allow you adjust its hardware output level. This option exists on other Digi gear like the 192k and 888 interfaces. Just need a little screwdriver. Don't know if the 002 does ... Even with the adjustment, you may have to live with lowering the output lower levels to your board. Proper gain staging, especially if you are using the board's eq, is very important. David Correia Celebration Sound Warren, Rhode Island www.CelebrationSound.com |
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#3
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#4
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Daniel Fox wrote:
We just swapped our Mackie 24 8 bus for a new Allen & Heath MixWizard3 board. Trouble is the main outs (1/4" balanced) from our Digi 002R are clipping the line ins on the board even with the trims all the way down... When PFL'd the A&H meters show between +9 and +16. It's only a problem with hot material (full mix with an L2 on the master fader), but it is definitely audible on louder passages. Very annoying! So, stick a pad in there. Always make sure to have a bag of adjustable pads around. They are one of the most useful things in the junk drawer. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#5
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Where do I get these? And will they have any effect on the signal
other than attenuating it? I'm almost positive the 002R does not have an output level control (hardware or software) but i'll double check. Dan Fox |
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#6
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Daniel Fox wrote:
Where do I get these? And will they have any effect on the signal other than attenuating it? They may alter the impedance as well, which is not a big deal. I recommend the switchable Shure attenuators, which give you 15 dB to 25 dB attenuation depending on how you set the switch. Any Shure dealer will carry them, although Markertek is probably cheaper than your local music store. Get a dozen. I'm almost positive the 002R does not have an output level control (hardware or software) but i'll double check. Look for a "reference level" setting either in software or on some DIP switches. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#7
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The converters' calibration is not adjustable on the 002 line of
products. For reference, -14 dBfs = +4 dBu. This particular spec isn't atypical these days, and as long as you observe nominal levels when tracking (same calibration at the A to D), really ought not to give you problems with modern mixers. |
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#8
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Chris Cavell wrote: This particular spec isn't atypical these days, and as long as you observe nominal levels when tracking (same calibration at the A to D), really ought not to give you problems with modern mixers. Well... it is and i'm not doing anything atypical. Even if I play commercial songs through ITunes (using digidesign core audio manager) I have the same problem. The only Shure pad that I've found is the A15AS with XLR ins and outs for $35!! Thats near $300 bucks just for pads for all 8 Pro Tools outputs! Plus the cabling from the patchbay (TRS) and from the pad to the line in (TRS). This has got me steamed! These are pretty standard pieces of gear (002R and MixWizard3) and I just can't believe that neither Allen & Heath nor Digidesign has made any provisions for such a typical setup. I am willing to build some simple pads if someone was so kind as to have a schematic and parts list. Otherwise we may have to return the A & H and put the Mackie back in place (I just shed a single tear). Dan Fox ZUMIX, Inc www.zumix.org |
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#9
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Daniel Fox wrote:
The only Shure pad that I've found is the A15AS with XLR ins and outs for $35!! Thats near $300 bucks just for pads for all 8 Pro Tools outputs! Plus the cabling from the patchbay (TRS) and from the pad to the line in (TRS). This has got me steamed! That seems about a reasonable price. If you want, you can make your own, but the barrel connectors will cost almost that much. These days, with the bargain basement equipment available today, it is not surprising to see cabling, connectors, and miscellaneous interface things like transformer boxes and pads costing as much as the equipment. These are pretty standard pieces of gear (002R and MixWizard3) and I just can't believe that neither Allen & Heath nor Digidesign has made any provisions for such a typical setup. I am willing to build some simple pads if someone was so kind as to have a schematic and parts list. You can build cables with pads. Try 6 dB to start with. Schematic is in the Audio Cyclopedia under "T-pads." Otherwise we may have to return the A & H and put the Mackie back in place (I just shed a single tear). You'll just be down this road again somewhere else with some other gear. Get a big bag of pads and a big bag of isolation transformers and you'll be fine. You will always need them for something. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#10
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Okay...this may seem a bit obvious, but have you tried the -20dB
Pad/Line switches located at the gain trims on the A&H? They should be engaged when the inputs are line level instead of mic level. (If you aren't using these, they'd probably give you better results than an in-line pad...iirc, they bypass a fixed 20dB gain stage. If you are using them properly, and the problem persists...I'd say get a different mixer.) But, the inputs of the MW3 line spec out a max in of +30dBu...you're probably just hovering around +13dBu judging by what the you've said the meters are displaying...kind of odd...the mixer should be able to handle it. |
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#11
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Right. A&H actually told me +27. A typical modern recording
especially pop/rock/hiphop/etc (whether my mix or commercial) hovers around +12 on the A%H meter with the red light at the top of the ladder flickering every once in a while. This does not indicate +27... But I swear I hear some distortion in the high mids that goes away when I pull down the master fader in pro tools 6 db or so. I'm think i'm going to learn a lesson in building an 8 in 8 out trs to trs pad box. grumble grumble... Dan |
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#12
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If you make a box, it's pretty easy. For every pair of xlr connectors
you'll need three resistors...that's pretty much it. Point to point will work fine for this kind of thing. |
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#13
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"Daniel Fox" wrote in message
ups.com Chris Cavell wrote: This particular spec isn't atypical these days, and as long as you observe nominal levels when tracking (same calibration at the A to D), really ought not to give you problems with modern mixers. Well... it is and i'm not doing anything atypical. Even if I play commercial songs through ITunes (using digidesign core audio manager) I have the same problem. The only Shure pad that I've found is the A15AS with XLR ins and outs for $35!! The Proco fixed pads are about $20. http://www.swee****er.com/store/manufacturer/Pro_Co/pn8 see MAX10, MAX20, etc. You can make your own for as little as $10. First buy the classic Switchcraft S3FM male-female XLR shell http://www.sandlpro.com/ItemView.cfm?INV_ID=3989 or some Hosa polarity inverters http://www.swee****er.com/store/detail/GXX195/ Then dissassemble and rewire as attenuators per this web page: http://www.uneeda-audio.com/pads/ |
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#14
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Thanks so much for the links and info Arny. Very much appreciated.
Now if only something existed like those hosa barrel inverters but TRS - Jack to Plug with enough space inside for the resistors. Dan |
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#16
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Daniel Fox wrote:
Right. A&H actually told me +27. A typical modern recording especially pop/rock/hiphop/etc (whether my mix or commercial) hovers around +12 on the A%H meter with the red light at the top of the ladder flickering every once in a while. This does not indicate +27... But I swear I hear some distortion in the high mids that goes away when I pull down the master fader in pro tools 6 db or so. I'm think i'm going to learn a lesson in building an 8 in 8 out trs to trs pad box. grumble grumble... The line ins on some older SSL consoles crap out when you hit them hard with digital signals too. I was used to engineers trying to track as hot as they could, but it always sounded much much better when Tom Lazarus would come in and record on the 16bit 3348's with pretty conservative levels ( 0VU = 20DBfs .) Now, with 24 bit recording you really really don't need hot levels like 0VU = -14DBfs, and I don't understand why Digi does that. If you track as if your -6DB level was 0, it should sound fine and you won't crap out the line ins on your console. There may be third party meter plug ins you can use with a selectable 0VU level reading. As for a meter reading +12 or + 16 level crapping the +27 headroom A&H line ins, sure! +16VU with a 12 db peak (easy enough to have) will hit +28, no? It's the transient peaks that will nail the line ins and make them crackle, sometimes transient peaks that some cheap meters or those little A&H leds lamps cannot even read well enough to warn you about. So bottom line, I'd try to create a workflow with adjustable plug in metering so you don't track as hot as you have been. Then you'd need no pads. With the stuff you already have tracked, you might want to compare the sound of mutiple tracks with pads engaged compared to multiple tracks with their individual output faders just pulled down 6-7DB across the board. Does the added math really sound worse than the added pads? Or maybe just pad the tracks that actually give you trouble - or maybe just mix the project currently in process "in the box". Will Miho NY Music and TV Audio Guy "The large print giveth and the small print taketh away..." Tom Waits |
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#17
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WillStG wrote: As for a meter reading +12 or + 16 level crapping the +27 headroom A&H line ins, sure! +16VU with a 12 db peak (easy enough to have) will hit +28, no? Not possible with a 002. You shouldn't be able to get anything much greater than +14VU tops out of it...peaks and all. The machine's calibration has only got enough headroom to reproduce +18dBu at full scale. I totally agree with absolutely everything else you said though. The "track hot to digital" customary practice from the first generation ADAT days are killing alot of guys that don't know any better with their 24bit machines today. Cheers, Chris |
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#18
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Chris Cavell wrote:
WillStG wrote: As for a meter reading +12 or + 16 level crapping the +27 headroom A&H line ins, sure! +16VU with a 12 db peak (easy enough to have) will hit +28, no? Not possible with a 002. You shouldn't be able to get anything much greater than +14VU tops out of it...peaks and all. The machine's calibration has only got enough headroom to reproduce +18dBu at full scale. I totally agree with absolutely everything else you said though. The "track hot to digital" customary practice from the first generation ADAT days are killing alot of guys that don't know any better with their 24bit machines today. Doh! - of course 0VU=14DBfs can't produce peaks above ODBfs. But Daniel *was* mentioning levels of +16 prefade occasionally lighting up the peak led. So the levels are likely a bit hotter than that, no? Besides there not being Unity gain in this setup, something else is probably going in here. Let's see what the A&H MizWizard specs say. Hmmmm.... "[TRS] line inputs, with internal option for +4dBu, routed via level controls and underpanel switches to Mix1 and Mix2." Daniel, are you sure your Mizwizard is internally setup for the line inputs to be at +4? Will Miho NY Music and TV Audio Guy "The large print giveth and the small print taketh away..." Tom Waits |
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#19
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#20
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Good points Will but let me offer some clarification of my original
statements. I do understand the difference in setting levels in a 24 bit digital environment vs tape for example and work accordingly. If I send a mix out (as stems) on all 8 digi outputs and PFL on the A&H I am getting readings in the vicinity of 0db. No problem there. These 8 channels summed in the board are not exeeding the headroom of the board. Problem is when I do "mix in the box" I need to present the A&H with a stereo mix out from Pro Tools, often with a L2 limiter on the whole mix putting levels in the box right near full scale digital (-.2 db). This is how I monitor my mix. This hot stereo out is lighting up the A&H meters. So all your suggestions are exellent and make sense when mixing on the board, but monitoring my "in the box" mix is where the problem lies. Dan |
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#21
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Will,
Are you reading the MixWizard3 (newest model) specs. I believe that the balanced line ins from the factory are +4. Dan |
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#22
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Another interesting (but maybe unrelated) development:
I ran a test today sending a 1khz test tone (-6 db) out of all 8 digi outputs to the board. When PFL'd the meters showed +3 db. When the channel and master fader were put at unity gain the meters read 0. This was consistent on all 8 channels and also when the same test was run at 40 Hz, 10Khz, and 20Khz. For what reason would the PFL meters read 3 db higher than the same signal at unity gain? Dan |
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#23
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To generate more headroom at the mix buss on the board...i think that's
what they claim in the manual anyway...it's nothing new; mackie's been doing the same thing for years. However, that 1k tone should be set at -14dBfs to give you a 0VU reading on your board. |
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#24
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just to make sure, have you bothered to check with a multimeter to make
sure things are operating where they are supposed to at +4dBu. If anything, it might point out a problem with the A&H meters perhaps... |
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#25
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"WillStG" wrote:
[...] you might want to compare the sound of mutiple tracks with pads engaged compared to multiple tracks with their individual output faders just pulled down 6-7DB across the board. I recently had to cut together a bunch of stuff that had been imported from "all the way up" sources (peaks at 0dBFS). I just pulled down the faders in Pro Tools when transferring it out to other devices in the plant. Even when you can't control the level on the way in, controlling it on the way out is easy. -- "It CAN'T be too loud... some of the red lights aren't even on yet!" - Lorin David Schultz in the control room making even bad news sound good (Remove spamblock to reply) |
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#26
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#27
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#28
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#29
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Daniel Fox wrote:
Problem is when I do "mix in the box" I need to present the A&H with a stereo mix out from Pro Tools, often with a L2 limiter on the whole mix putting levels in the box right near full scale digital (-.2 db). This is how I monitor my mix. This hot stereo out is lighting up the A&H meters. So all your suggestions are exellent and make sense when mixing on the board, but monitoring my "in the box" mix is where the problem lies. This kind of problem also would sometimes happen on big consoles when you try to bring a DAT tape return into a 2 track return, and because 0VU on the DAT deck might be set at say -14DBfs for the particular mix session, it would be way too hot. Anyway, you can try using the headphone out for your monitoring (which has an adjustable gain pot, yes?) - or just use the -10 rca jacks out of the 002 and patch them into a tape return on the Mix Wizard. Will Miho NY Music and TV Audio Guy "The large print giveth and the small print taketh away..." Tom Waits |
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#30
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Is it possible to be overdriving the virtual bus within Pro Tools even
if no clip lights are lit anywhere? |
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#31
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Daniel, yes...in a way...
The master fader is different than other tracks in that the plugins are post fader, but the meter is post plugins. You could be clipping the buss (disable all plugins on the master fader and lower the fader until it doesn't light up the clip light). Or you could be clipping a plugin...and that often won't show up anywhere but in the plugin itself depending upong your chain. |
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#32
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Chris Cavell wrote: Daniel, yes...in a way... The master fader is different than other tracks in that the plugins are post fader, but the meter is post plugins. You could be clipping the buss (disable all plugins on the master fader and lower the fader until it doesn't light up the clip light). Or you could be clipping a plugin...and that often won't show up anywhere but in the plugin itself depending upong your chain. No you got me thinking. Worst case scenario (and I certainly try not to let this happen): with no plug ins on the master fader (set at unity) the sum of all tracks is clipping the master fader. I then insert a waves L2 limiter on the master fader. The L2 it self will not clip because it incorporates a "ceiling" (which I usually set at -.2). The resulting master fader meter does not show clipping, but levels near the top. My understanding was that the L2 took the overly hot sum of all channels and limited it so as to keep it under the "ceiling". Are you saying that in this case I could be inducing digital distortion even though none of the meters indicate this? Dan |
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#33
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Daniel Fox wrote:
No you got me thinking. Worst case scenario (and I certainly try not to let this happen): with no plug ins on the master fader (set at unity) the sum of all tracks is clipping the master fader. I then insert a waves L2 limiter on the master fader. The L2 it self will not clip because it incorporates a "ceiling" (which I usually set at -.2). The resulting master fader meter does not show clipping, but levels near the top. My understanding was that the L2 took the overly hot sum of all channels and limited it so as to keep it under the "ceiling". Are you saying that in this case I could be inducing digital distortion even though none of the meters indicate this? The whole POINT of limiters is that they clip. They clip softly and less offensively than immediate overload, but they are basically clipping devices. If you put a ceiling at -.2, the overload indicator will not come on because the overload indicator lights when a certain number of consecutive FS samples are seen, and with the ceiling brought down to anywhere below FS, there will be no FS samples at all on the limiter output. But the limiter is still hacking the top off the waveform like some sort of wood planer, gouging the crap out of everything that sticks out. That's what the limiter does. If you're regularly seeing more than 3 dB or so of limiting, you are going to hear some audible effects. The overload light won't come on, but it will still sound like crap. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#34
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Daniel Fox wrote: Chris Cavell wrote: Daniel, yes...in a way... The master fader is different than other tracks in that the plugins are post fader, but the meter is post plugins. You could be clipping the buss (disable all plugins on the master fader and lower the fader until it doesn't light up the clip light). Or you could be clipping a plugin...and that often won't show up anywhere but in the plugin itself depending upong your chain. No you got me thinking. Worst case scenario (and I certainly try not to let this happen): with no plug ins on the master fader (set at unity) the sum of all tracks is clipping the master fader. I then insert a waves L2 limiter on the master fader. The L2 it self will not clip because it incorporates a "ceiling" (which I usually set at -.2). The resulting master fader meter does not show clipping, but levels near the top. My understanding was that the L2 took the overly hot sum of all channels and limited it so as to keep it under the "ceiling". Are you saying that in this case I could be inducing digital distortion even though none of the meters indicate this? Dan You ARE clipping the output of the summing buss, then following it with a limiter that hides this fact from view. The master fader in pro tools functions as a bit selector for the summing buss, and as you have it positioned currently, it's not selecting all of the bits to send on to the plugin chain that follows, it's chopping off meaninful musical data before sending it on. |
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#35
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Jeez, That's the problem! All this time i've been using carpentry
tools to work on music. What was I thinking? But seriously, your point is noted however, when I use a L2 it is usually only doing 1-3 db of GR. Dan |
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#36
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Hmmm. That makes a lot of sense. I'm going to do some more testing
and listening to make sure that I am attributing the audible distortion to the right part of the signal chain. The input is pretty hot at the board but I suppose it's possible the crunchiness came from within the software. Hopefully I won't have to don the duncecap. Dan |
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#37
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Daniel Fox wrote:
Jeez, That's the problem! All this time i've been using carpentry tools to work on music. What was I thinking? But seriously, your point is noted however, when I use a L2 it is usually only doing 1-3 db of GR. Then you might be able to get away with even more of it. Just keep listening and crank the levels into the L2 up until you hear it starting to sound funny. Then drop them back down. You shouldn't be hearing dramatic tonal changes in the L2, other than maybe a little softening on the top end. If you are hearing it, you are hitting it too hard. If you have to hit it that hard to get your levels right, you probably aren't compressing properly before you hit the L2. If, on the other hand, the top end is still screwed up even with the L2 bypassed and levels down, you're probably compressing too much beforehand. Or at least too fast. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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