Getting Around The Latency Bugaboo

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Getting Around The Latency Bugaboo

Postby Howler » Mon Mar 01, 2004 8:03 pm

If any of you are using a MAS recording system and have to deal with latency on overdubs or recording, here's a simple way around it. The latency occurs because of the buffer size required for the MAS to run cleanly. Add buffer size to ease drain on the CPU and the latency increases. Catch-22.

To deal with this problem, I use preamps which have dual outputs, sending one to MAS and one to the board, or use a special cable which goes from my insert point (or direct out wih a normal hi-z cable) on the board channel to the MAS system. Thus the board becomes a really nice headphone mixer. If my tracking room sounds good, and I use the correct mic on the instruments, I don't need any EQ going to MAS. I emphasize this point, because good mic selection and a balanced room will save you many, many hours and $$$.

During overdubs, I play the MAS output through the board and repeat the recording process, so the musicians are overdubbing to the live playback and hearing themselves in realtime. This really simplifies the whole recording process and gives my CPU extra guts for playing back many tracks and still recording new tracks effortlessly.

Any of you ever tried this?

sf
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Postby jayte » Tue Mar 02, 2004 5:55 am

That's one thing (of numerous, actually) I really appreciate about this Creamware stuff.

Most of my outboard gear is connected to one of their converters (an A16), and fed via lightpipe to a Pulsar card's inputs (a Yamaha TG55, which is unbalanced, feeds the analog input). The Pulsar's lightpipe outputs head back to the A16's D/A, which then feeds a Furman HDS-6 headphone amp, and NHTPro A-20 and B-20 amps (the Pulsar's analog output--which is unbalanced--connects to one of the inputs on my stereo).

Anyway...

The thing is about as... "straight-wire with a tap" as I could ever imagine (the "tap" being the recording software). I don't know if that was one of Creamware's design goals, or not, but... there is absolutely no discernable latency between source and monitor. Well... none that I've noticed, anyway (and I've recorded only a couple of singers, but... they never complained of anything sounding "weird", etc).

But the neatest thing about this - what you hear from the monitors or headphones is exactly what's on its way to disk.

Anyway...

Jeff
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Postby Howler » Tue Mar 02, 2004 7:01 am

Yeah. That's a good routing system. I wondered when somebody was gonna notice the obvious and put it into a system I've been doing this for 4 years, ever since I went to the MOTU system. My G4 is only 400 MHZ, so I had to be careful with the latency. Finally I said "screw this" and tapped the incoming into a split. It makes life sooo much easier and I get to devote large buffer size to the DAR system, which lets it work effortlessly.

Back in the mid-80s, along with two other fellows (one of whom later co-invented virtual reality), I designed the first digital recording system under a development grant from Ampex. We used two VAX storage units, one to record on, and one for what we called "spillover". When the firdt VAX got half-full it started dumping to the second in the background while the first VAX continued recording. We had a working system (8-tk, which could be stacked/chained to make 16, 24, etc) using MIDI control, 6 months before NED came out with the Synclavier. Ampex, in one of the dumbest moves I have ever witnessed, decided "The musicians want to watch the reels go 'round and 'round" and would "never embrace a digital recording system", to quote an Ampex VP.

Point is, we used exactly the same type of routing system to monitor incoming/outgoing signal so we didn't have to load the CPU down. The CPU recorded, and it played back. Period. This is the time period when a Commodire C-64 was a honker. LOL We HAD to figure out ways take all the load possible off the CPU.

Of course, NED sold tons of Synclaviers (at twice the price our system would have sold at) and revolutionized the industry. Ampex made tape for a while and has now faded. I lost a chance to retire to St. Thomas and watch belly buttons dance by.

I hated to see Ampex go down, because my dad designed the hysterisis drive for the first Ampex machines, which had revolutionized the industry back in the early 60s. I was partial to them, but they made a bad decision based on nothing more than supposition. As with most engineers, I don't care what i record on... tape, hard drive, tin can.. whatever.... as long as it gives me back exactly what I record. And, as we have all seen, musicians don't care either. They just want clean, cheap recording time.

Best
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Re: Getting Around The Latency Bugaboo

Postby Paul Woodlock » Tue Mar 02, 2004 3:18 pm

Howler wrote:....Any of you ever tried this?

sf


Yes, I've been doing it for years :)


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Postby backountry » Tue Mar 02, 2004 11:01 pm

hey howler:
i am presently looking to reroute my headset monitoring for muscian overdub. i am running protools le 001 and latency is not a real problem monitoring out of protools breakout box. the problem is protools is a harsh, thin sound in the headset monitoring and i am looking to monitor out of my mackie board to see if it sweetens it up any. i had figured that i needed to tap in at the breakout box to monitor all parts, including the live take. the group i am recording now has one musician who has a real keene ear for music and this includes delays. so if you don't mind i would like to recap my routing to relate to what you have said here. i have plans to test this in the next couple days but would love to hear what you guys think..

mic to preamp to protools a/d converter to capture...
mic to preamp to board (preamp or insert?) to headset amp
captured tracks to d/a converter to mackie (preamp or insert?) to headset amp

writing it out this way shows me that the live signal and captured signal both go through three units to get to the headset. maybe i shouldn't be concerned. so you guys are seeing no delay concerns for the musician? does it matter if you monitor the board off the main outs or aux sends? sorry of my ignorance but your help is appreciated.

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Postby Howler » Wed Mar 03, 2004 12:42 pm

>mic to preamp to protools a/d converter to capture...

That's the original live session? Correct. And you're sending them a headphone mix from the board, which is monitoring the preamps? That's the cleanest signal path.


>mic to preamp to board (preamp or insert?) to headset amp

This signal runs to the Mackie? That's correct. Lessee... trying to remember Mackie config... I believe if you patch to insert you bypass the Mackie preamp but still can use the EQ... that would be correct.

>captured tracks to d/a converter to mackie (preamp or insert?) to headset amp

This is CPU to Mackie also? Correct. Again, insert... but this is only for headphone monitoring, so it doesn't really matter. The Mackie preamps are clean enough to patch into "line in" on the channels. You can also run the stereo mix from CPU to an "aux in" and mix it in with the live tracks

You're just using the Mackie for a super nice headphone mixer. You can even run directly out of the Mackie headphone sends... it has a nice HP amp, and you should be able to level the CPU output to mix it in with the live signals.

The trick is monitoring the preamps throughout the process. Every preamp splits the "line out". One line to the PT AD/DA, one line to the board. Everything stays realtime. Once it's all set up, it'll work seamlessly from then on.

And if you want to use the Mackie channels as an input/preamp for mic lines, just send from the "direct out' to PT and you're happening. Monitor the mics-to-headphones via an aux if you want a discrete mix.

As Paul says... it works great. You'll like the ease of setting up headphone mixes and the musicians will LOVE it.

sf
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Postby backountry » Wed Mar 03, 2004 8:00 pm

hey stephen:
thanks for the heads up on headset monitoring. i will be in the studio in the next day or two rerouting that and a couple other things in my patchbays. you saved me some valuable time just in time.
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Postby Howler » Thu Mar 04, 2004 12:38 am

cool. glad to help

sf
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Postby Howler » Thu Mar 04, 2004 1:05 am

cool. glad to help

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