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Cubase, laptop, and interface for live vocal fx processing

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Cubase, laptop, and interface for live vocal fx processing

Postby dbirchmier » Sun Apr 10, 2011 9:24 pm

Hey there,

I'm thrilled to find this forum! I think it would be the perfect place to post my question...with such a great combination of LIVE and STUDIO experts.

Here's what I'm attempting to do:

Run Cubase 5 on a laptop
Cubase connects with a RME Fireface 800 interface
Two standard Shure SM58 microphones connect to the interface XLR inputs.
Vocals come in on a separate tracks, have delay, reverb, compression, EQ, and autotune applied. (Separate presets for different songs)
Using routing, each PROCESSED vocal track is outputted to balanced LINE outputs on the RME.
These are converted via a standard adapter like...
http://accessories.musiciansfriend.c...ter?sku=335209
Then it runs into the LIVE mixer board XLR input.

Gain is set like this:
Normal gain is configured on the RME interface (computer with processing) -- turn it up until it peaks, then back down for safety.

Since the gain is HOT coming out of the RME, into the live mixer, the live mixer has almost NO GAIN set for the individual microphone inputs.


I suspect you will say:
Why aren't you using a LINE input on the LIVE mixer?
Well, here's my fear:
We are a smaller group and still play at a lot of poor venues with idiotic sound guys. Asking them to do something out of the ordinary, like run two vocal tracks as line inputs, could either confuse them, p*** them off, or they'll just refuse to do it.

I thought what I'd do is have the option for both:
XLR standard mic input option -OR-
for the smart ones, a 1/4" balanced line input.


My questions are two fold:
1) Am I setting the GAIN right? (Gaining it almost entirely on the RME interface, hardly any on the LIVE board)
2) Is it a terrible idea to run it XLR into a standard input?
3) What effects should I be applying? I.e. Is it OKAY to EQ if I do it gently, or will it screw things up in a live environment since every sound application is different? Are the other FX i'm running OKAY?
4) Am I connecting things right? I.e. should I be using a Direct Box instead, or something different than how I'm doing it?

I'm using this in a practice environment right now...and everything does work. Feedback seems a little worse with this setup though.

I SINCERELY appreciate your expertise. I'm just a little lost on what the "right way" is for something like this.

P.S. I've been reading more, and from what I understand, you really don't want to be gaining twice -- using a preamp (recording interface) then sending it out to a LIVE interface XLR input and using gain AGAIN. I guess my only question is "As long as the gain is all the way down / off" on the XLR input, is this OKAY -- or is this not a good idea?

P.P.S. I've actually posted this question on another forum, but no one has responded. I'm not sure if what I'm asking is really dumb and no one wants to help me out, or perhaps I'm not providing good information. If I'm ignorant, please accept my apologies and lead me down the right path. I'll be more than grateful for your guidance!
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby dmills » Sun Apr 10, 2011 10:15 pm

Almost certainly what you should be doing is coming out of the interface into a DI box which will both convert the line level out of the interface back to something like mic level and isolate it to remove any potential for hums.

Give these signals to the FOH guy, who can then treat them as if they were mic signals.

Compression makes feedback worse, and if the foldback is run from FOH you may want to supply an unprocessed signal for that use, as expecting a singist to pitch when the monitors are being fed from an autotuned signal is a bit much.

As far as gain is concerned, make sure you leave plenty of headroom, modern interfaces are fairly quiet so you dont need to run anywhere near peak clipping, and the DIs will take things back down to mic level so the sound guy can do whatever he is used to.

I would note that on many cheaper desks the XLR input cannot be turned down far enough to make it useful as a line input, so you really need those DIs.

Regards, Dan.
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby dbirchmier » Mon Apr 11, 2011 4:12 am

Hey Dan,

You have my deepest gratitude for replying and helping me out!

Sorry for the ignorance, but I have a few more questions!

First, I was actually using a DI box previously. Then it came to me (in a dream?!) that it wasn't necessary to use a DI box because a DI box converts an unbalanced signal to balanced, and in my situation, my original signal (coming out of the RME interface) is balanced.

That aside, I understand that regardless of it being balanced or not, in this case I would use it to REDUCE the gain before sending it to the live board.

My only confusion is that when I did have the DI box hooked up, it didn't seem to reduce the gain any?
I'm using this DI box:
http://www.amazon.com/Behringer-DI400P-High-Performance-Passive-Injection/dp/B000KUA8G6

It's just a cheap-o, so maybe that's the problem. Do I need something else?

This line:
"Give these signals to the FOH guy, who can then treat them as if they were mic signals. "
Made a ton of sense. This is exactly what I'm trying to do! (Thank you for understanding and putting it in clear terms!)

"Compression makes feedback worse, and if the foldback is run from FOH you may want to supply an unprocessed signal for that use, as expecting a singist to pitch when the monitors are being fed from an autotuned signal is a bit much. "
Long term, we'll setup a separate output without autotune to feed monitors...for now we're just going to stick with a simple setup -- but great point!

As for the COMPRESSION part, are you suggesting that:
1) I disable compression completely.
2) I disable compression for the MONITOR feed only.
3) I use very little / light compression.


"As far as gain is concerned, make sure you leave plenty of headroom, modern interfaces are fairly quiet so you dont need to run anywhere near peak clipping, and the DIs will take things back down to mic level so the sound guy can do whatever he is used to.

I would note that on many cheaper desks the XLR input cannot be turned down far enough to make it useful as a line input, so you really need those DIs. "

I totally get what you're saying. Can you point me in the direction of a DI box that would bring my HOT line output back down to a standard mic level so the sound guy can treat it as such.



One last (probably stupid!) question:
If I'm gaining on the interface, bringing the levels down on the DI box, and then gaining AGAIN on the live board....
Does this present any feedback issues / or things picking up more because it's being GAINED TWICE?
I just don't totally understand how it works when things get run into two different pre-amps, or have gain applied to the same signal twice.

Your expertise is greatly appreciated. Thanks!!!
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby DPoll » Mon Apr 11, 2011 8:27 am

I dont think that DI boxes do change the input volume (other than through inherent losses maybe?) as the conversion isn't line level to microphone level, but comnversion from high impeadance signal (inst) to low impeadance (mic). if the interface has balanced outputs, I'd make up some balanced Jack - XLR leads then take them straight down the multicore like that.

+1 for the point about having signals too hot.
+1 for processed singals going to Monitors too.

Can i ask why exactly you want to take your signals through your interface prior to going to FOH? Generally speaking, taking all your audio though a PC prior to FOH is a bad idea. if the PC dies/ crashes, you may end up with a complete lack of audio until you re-boot.
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby Mike Stranks » Mon Apr 11, 2011 9:47 am

DPoll wrote:I dont think that DI boxes do change the input volume (other than through inherent losses maybe?) as the conversion isn't line level to microphone level, but comnversion from high impeadance signal (inst) to low impeadance (mic). if the interface has balanced outputs, I'd make up some balanced Jack - XLR leads then take them straight down the multicore like that.

I think you'll get in a muddle if you think of a signal having an impedance. It's the input that has the impedance. It is more helpful to think of levels and impedances separately.

So a line-level signal is ideally about 1 volt (give or take because it's AC) whereas a mic-level signal is measured in millivolts - usually between 3 and 15 depending on the type of mic (Purists: back-off; I'm trying to keep it simple! :D)

A line-level signal expects to see an impedance of idealy 100kohms+ whereas a mic signal would normally go into around 2kohms.

NB: depending on the type of pick-up on a guitar it might be happier 'seeing' a higher impedance of around 500kohms. Decent DI boxes handle this fine.

The purpose of the DI box is to take the line-level signal and drop it to mic-level and balance it too. That means you can run the signal up long lines and straight into the mic input of a mixer. Many FoH desks are wired for everything to go into the mic inputs and, aside from other considerations, if you ask for a line-level input at the mixer you will either cause hassle or simply refused.

NB: Some of this is deliberately simplified to explain principles. Hopefully the techno-purists will understand why I've said what I've said.
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby DPoll » Mon Apr 11, 2011 11:27 am

Mike,

My description may be a little off (im aware that its the output device which has the high impeadance rather than the cable itself), but my sentiment was not.
You don't need to DI a balanced signal, because its balanced! You can convert from jack to xlr and take it straight down the multicore.

Responding to the original question maybe more helpful to all than than picking at slight descriptive errors, particularly considering the sentiment of the message. ;)
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby James Perrett » Mon Apr 11, 2011 11:40 am

DPoll - I'm afraid I'm with Mike here. A typical PA system will only have mic level XLR inputs available on stage. If you try to feed line level to these inputs they will clip. If you turn the volume down in your software you will end up with a noisy signal as the DAC in your audio interface is designed to work at line levels. So, at the very least, you will need an attenuator. There is also the danger that the venue may be wired in such a way that you end up with a ground loop. In that case you will need a way of lifting the signal ground. All of these features are built into a DI box so it makes sense to use one.

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Re: Cubase, laptop, and interface for live vocal fx processing

Postby seablade » Mon Apr 11, 2011 2:16 pm

DPoll wrote:Mike,

My description may be a little off (im aware that its the output device which has the high impeadance rather than the cable itself), but my sentiment was not.
You don't need to DI a balanced signal, because its balanced! You can convert from jack to xlr and take it straight down the multicore.

Responding to the original question maybe more helpful to all than than picking at slight descriptive errors, particularly considering the sentiment of the message. ;)

Actually, the other respondants are correct and aren't nitpicking sentiments but rather trying to explain why a DI box can be useful even with balanced signals.

A passive DI box will inherently lower signal levels to something more in range that a mic preamp can deal with. Often times on cheap consoles, the XLR inputs are only connected to the preamp, and can't handle line level, thus padding the line level signal becomes necessary, something that happens naturally in passive DIs.

That being said, there is another stronger reason to use a DI when plugging into a sound system, and that is for the simple fact of ground isolation, which most, even cheap, DIs have a ground lift switch. This helps prevent ground loops from coming through your system in the sound, which especially in the case of computers don't necessarily sound like a hum but rather a high frequency buzz that varies typically depending on various factors of the computer. It isn't the only cause of such a buzz, but it is one of the primary causes, and the most typical when using external interfaces.

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Re: Cubase, laptop, and interface for live vocal fx processing

Postby mpostor » Mon Apr 11, 2011 2:41 pm

Also, a DI box will prevent 48v phantom power being fed into the XLR to jack adapter and then into your nice expensive soundcard when the engineer hits the global phantom power button to get power to a C1000 or similar...
Passive DI boxes see the voltage and ignore it. Actives use it instead of battery power. Both ensure that none of that voltage gets sent to your equiopment.
And as an added bonus, there's no more hunting for a 9v in your cable case, or trying to cadge one from the venue...

It's a small investment, but a DI box has many practical uses.

Don't leave home without one (or two, if you need two channels looked after. Or one stereo one, if you don't fancy carrying two mono ones around.........).

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Re: Cubase, laptop, and interface for live vocal fx processing

Postby Mike Stranks » Mon Apr 11, 2011 3:05 pm

DPoll wrote:Mike,

My description may be a little off (im aware that its the output device which has the high impeadance rather than the cable itself), but my sentiment was not.
You don't need to DI a balanced signal, because its balanced! You can convert from jack to xlr and take it straight down the multicore.

Responding to the original question maybe more helpful to all than than picking at slight descriptive errors, particularly considering the sentiment of the message. ;)


Apologies if my post caused irritation - certainly not my intention to come across as a smarta**e; that's not my style.

My concern was as stated that you used the term 'impedance' in connection with the signal.

'nuff said; let's move on.

Mike
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby DPoll » Mon Apr 11, 2011 4:30 pm

All very valid points, I'll eat my humble pie... I was thinking about too narrow mindedly.

Thanks for the education chaps.
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby dbirchmier » Tue Apr 12, 2011 10:40 pm

First let me say...

This forum is absolutely freaking awesome! I'll certainly be back with all of my questions.

You guys have started a great discussion.

I'll re-cap with what I think I've learned:

1) I need to lower the output level of my signal. I can do that with a DI box that has a pad switch on it. The ones I have right now DO NOT have one. Which one would YOU suggest?
Alternatively, instead of a DI box, my RME Fireface 800 has the ability to LOWER output levels by -10db. Would it be a smart idea to just use the INTERFACE to lower the OUTPUT LEVELS? (My understanding is that signals coming in TOO hot will cause problems!)

2) No matter what I choose above... I SHOULD still run a DI box. Maybe not turn the pad switch on, but at the very least, run it. It's good because it will kill phantom power (which I'm not sure why that would be on if I have it off on my interface) and it's also good because it will have a ground lift switch on it which will reduce HUM.


3)It's a terrible idea to run a computer / interface to the FOH guy.
-- Yeah, you're probably right. The factors that it could fail are much higher than hardware...BUT, we're a smaller group that wants to sound like a big group. We don't have a ton of extra cash to throw at it, and this will let us sound like we do on CD, live :) Well...at least that's the idea in theory! So far in a practice envrio, it's been totally awesome. Just having delay, reverb, and compression has been night and day, not to mention the EQ and light autotune.




That's what I've gotten out of this so far -- correct me if I'm wrong on anything.


I'm still confused about this:
IF I use a pad on a DI box, or reduce gain on the output of the interface by say -10db, and then run it to the board, won't I be running gain TWICE? Because the live board will have to have gain turned up, plus my interface. Isn't this bad? Will cause more feedback?
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Re: Cubase, laptop, and interface for live vocal fx processing

Postby Mike Stranks » Wed Apr 13, 2011 12:08 pm

dbirchmier wrote:1) I need to lower the output level of my signal. I can do that with a DI box that has a pad switch on it. The ones I have right now DO NOT have one. Which one would YOU suggest?
Alternatively, instead of a DI box, my RME Fireface 800 has the ability to LOWER output levels by -10db. Would it be a smart idea to just use the INTERFACE to lower the OUTPUT LEVELS? (My understanding is that signals coming in TOO hot will cause problems!)
Why do you think your signal is too hot? If it's at standard line-level then any DI box should be OK with it. Drop the level by 10db if you think that'll help.

2) No matter what I choose above... I SHOULD still run a DI box. Maybe not turn the pad switch on, but at the very least, run it. It's good because it will kill phantom power (which I'm not sure why that would be on if I have it off on my interface) and it's also good because it will have a ground lift switch on it which will reduce HUM.
Yes to DI. Because you're going into the MIC inputs on the FoH desk, phantom will be coming up the line from there. The DI box will either use it if active or prevent it going further if passive. Ground lift doesn't always deal with hum, but it will often do so.


I'm still confused about this:
IF I use a pad on a DI box, or reduce gain on the output of the interface by say -10db, and then run it to the board, won't I be running gain TWICE? Because the live board will have to have gain turned up, plus my interface. Isn't this bad? Will cause more feedback?
Technically it's not ideal to be lowering signal levels then raising them again, but in reality with decent gear and especially live the benefits of using DIs far outweigh the disadvantages. Don't get too hung-up on gain... each piece of gear needs to work at it's optimum gain structure for best results; that's why most gear has volume/gain controls. Feedback results from many factors. In fact setting the correct gain down the chain should help prevent it. As has already been said, compression and reverb affect gain. FWIW I always get twitchy when musos put their own compression onto a signal - it reduces the headroom before feedback and gives me much less to play with to get an optimum FoH sound.

HTH. Mike
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