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Author Topic: Soundcraft Impact Gain Control Artifacts?  (Read 1170 times)

Dave Coulter

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Soundcraft Impact Gain Control Artifacts?
« on: April 22, 2017, 07:38:10 pm »

Hi everyone - I just demo'd an Impact and immediately noticed that there were quiet artifacts in the signal when turning the gain encoder. Present enough to be a no-go for me.  It was on multiple inputs, routed to multiple outputs, so it was system-wide.

With all the positive things I'm reading on this forum about the Si series, surely this is an anomaly?  The salesman didn't know whether that was normal or not, so I'm asking your experiences.  My work is live corporate and broadcast, and I have to make small adjustments in gain on live mics enough that my clients would be be going crazy hearing that.

Thanks in advance.
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Samuel Rees

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #1 on: April 22, 2017, 09:56:56 pm »

LS9s and M7s definitely do something like that. I've head some other consoles make a little something if you spin gain real fast. I have not used the impact myself so I don't know how severe it is, but it's not totally unheard of for there to be a small sound.
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Dave Coulter

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #2 on: April 24, 2017, 01:19:31 am »

Thanks Samuel. I know there are a lot of mixers on this forum who use the Si series. It would help me out a lot if any of you could weigh in on this.  Do you find the gain control to ever induce noise into the signal? Thanks.
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Samuel Rees

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #3 on: April 24, 2017, 09:18:18 am »

Thanks Samuel. I know there are a lot of mixers on this forum who use the Si series. It would help me out a lot if any of you could weigh in on this.  Do you find the gain control to ever induce noise into the signal? Thanks.

I have an an Si Compact and I mix on Expressions here and there. I don't explicitly remember whether or not there are any artifacts. I can test the Compact when it gets back from a rental today if I have time. Even Digico MADIrack pres make a little something when you spin them real fast IIRC... unless the sound on the impact is unusually severe I probably wouldn't worry about it myself.
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Robert Lofgren

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #4 on: April 24, 2017, 09:56:18 am »

This artifact is usually known as 'zipper noise' and is more or less present in all digitally controlled preamps.
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Jim Rutherford

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #5 on: April 24, 2017, 09:36:03 pm »

I've never noticed any 'zipper noise'.  SI Expression 3.


Sent from my iPad using Tapatalk
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Dave Coulter

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #6 on: April 24, 2017, 11:51:54 pm »

I have an an Si Compact and I mix on Expressions here and there. I don't explicitly remember whether or not there are any artifacts. I can test the Compact when it gets back from a rental today if I have time. Even Digico MADIrack pres make a little something when you spin them real fast IIRC... unless the sound on the impact is unusually severe I probably wouldn't worry about it myself.

My main experience with digital consoles is the QL1, M32, and the 01V series, which I don't think exactly apply to this.  I'm just talking about subtle adjustments... if I were doing radical fast movements I wouldn't expect it to be usable live anyway.  I don't believe I've ever heard "zipper noise" on the Midas or Yamahas.

If you get a chance to listen to the Compact I'd appreciate it, as I suspect most if not all of the Si's might have similar gain encoder behavior.  Thanks.
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TJ (Tom) Cornish

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #7 on: April 26, 2017, 09:36:26 am »

I don't believe I've ever heard "zipper noise" on the Midas or Yamahas.
The 01v series has analog preamp gain, so that wouldn't do it.  LS9/M7 definitely do - internal relays select different gain ranges for the preamp.  I haven't found it to be a problem in real-world situations as gain changes during the show are rare.
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Tim McCulloch

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #8 on: April 26, 2017, 10:06:33 am »

Hi everyone - I just demo'd an Impact and immediately noticed that there were quiet artifacts in the signal when turning the gain encoder. Present enough to be a no-go for me.  It was on multiple inputs, routed to multiple outputs, so it was system-wide.

With all the positive things I'm reading on this forum about the Si series, surely this is an anomaly?  The salesman didn't know whether that was normal or not, so I'm asking your experiences.  My work is live corporate and broadcast, and I have to make small adjustments in gain on live mics enough that my clients would be be going crazy hearing that.

Thanks in advance.

It's called zipper noise and it's based on the incremental "size" in dB of the gain steps.  The bigger the step the more obvious the noise especially if you move the encoder quickly.  There is no way around this and it's common to EVERY digitally controlled preamp regardless of brand.

What makes a difference is the size of the step and the speed at which you adjust the encoder.

What is worse - a signal that is too low or clipping - or a small noise?  If your clients are that picky you need to get a different (and likely much more expensive) mixer, possibly analog if you can't abide by this characteristic.
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John Roberts {JR}

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #9 on: April 26, 2017, 10:42:37 am »

Yes zipper noise from digital step size during gain control changes is generally only noticed when music is present. There is a design strategy to mitigate this, namely coordinate the gain changes with signal zero crossings, that way the gain change gets multiplied times zero for lower audibility. This clearly increases circuit complexity so isn't always used for every gain trim. Some premium digital mic preamp gain controls build the glue circuity to support ZC coordination inside the chip set to manage this transparently.

I have no idea what technology Soundcraft is actually using under the hood inside the Impact (mixer?).

A few years ago I spent some bench time working on a processor using digital pots for gain control. I expected zipper noise so designed in zero crossing capability, but never needed to turn it on because in general use the gain step artifacts were not noticeable (in my application, mostly speech).

Continuous musical tones at low level will probably be most noticeable during gain step changes, while the step size can also make a difference. Fewer larger steps will obviously be more audible than more, smaller steps (which costs more money too, I used a lot of small steps in my project). 

Do you experience these artifacts from faders, designed to be manipulated while listening to signal, or only on the gain trims? Maybe they don't intend for customers to mix on those trims? Covering a large gain range with only a handful of gain steps could be more audible. 

JR
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Dave Coulter

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #10 on: April 26, 2017, 02:14:27 pm »

My jobs are mostly speech, plus music and playout videos which can be preset.  Quite often I'm taking stems from a house A1 to remix for broadcast/streaming, so depending on the other mixer I'll get very different levels coming down the same lines, and readjusting gain (for consistent dynamics response as much as any other reason) has just become habit. No, I've never heard it on faders.

I've had a chance to demo several other consoles lately, and yes they all seem to have some degree of zipper noise, but they present differently. The Impact actually generates noise, where with some you just hear the steps, which is no big deal.  I'm just surprised because I've never found myself having to work around it with the QL1 or the M32, and now it's really jumping out at me. I suppose in the end it's just a matter of technique and choosing when to make the adjustments.
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Steve Ferreira

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #11 on: April 26, 2017, 02:44:35 pm »

Are you and the A1 setting gain structures before hand? Working corporate events in the past I have never ridden the gains just faders. Is the A1 sending you an aux, matrix?
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Dave Coulter

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #12 on: April 26, 2017, 03:38:27 pm »

Are you and the A1 setting gain structures before hand? Working corporate events in the past I have never ridden the gains just faders. Is the A1 sending you an aux, matrix?

It's always different - different venues and operators.  My main client likes a very tight dynamic range, and I'm putting compression on every stage to even things out... I find myself riding gain more than usual because I'm trying to slot it into the first stage of dynamics just right. Their consoles seem to just have audible "steps" rather than noise, and that really hasn't bothered me.  As I look for a new personal console I'm just running into some that are actually noisy.  I'm surprised what I'm hearing in the Impact doesn't distract more people.
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John Roberts {JR}

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #13 on: April 26, 2017, 04:51:29 pm »

It's always different - different venues and operators.  My main client likes a very tight dynamic range, and I'm putting compression on every stage to even things out... I find myself riding gain more than usual because I'm trying to slot it into the first stage of dynamics just right. Their consoles seem to just have audible "steps" rather than noise, and that really hasn't bothered me.  As I look for a new personal console I'm just running into some that are actually noisy.  I'm surprised what I'm hearing in the Impact doesn't distract more people.
Since the customer is always right I won't advise you to not mix on the trims, but it could be a design trade-off based on the expectation that trims would be set up ahead of time and then rarely re-adjusted during the performance.

I believe mic preamps exist that do not exhibit gain trim artifacts, but there could be any number of valid reasons why one wasn't used for that application.

There would probably have to be a lot of trimming going on before the audience would notice, but artifacts showing up in the talent's monitor mix could be a problem, as the gain trim would be pre- everything. 

Good luck...

JR
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TJ (Tom) Cornish

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #14 on: April 26, 2017, 10:58:29 pm »

For what it's worth, I haven't noticed this on my Allen&Heath GLD systems, but I don't typically mix with gain knobs, so I won't bet my life on it.
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Dave Coulter

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #15 on: April 27, 2017, 10:45:24 am »

Thanks very much for all the feedback. For the record I'm really not "mixing on the trims", but I do find myself readjusting them for each phase of a show... new talent on the same mic, slight readjustment of the trims sometimes. Quiet single speaker means sometimes that might be audible.

Outside of the M32R, the other best sounding trim in the $2000-$2500 range was actually the QU16 so far. Very quiet zipping. 
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brian maddox

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #16 on: April 27, 2017, 12:16:50 pm »

Thanks very much for all the feedback. For the record I'm really not "mixing on the trims", but I do find myself readjusting them for each phase of a show... new talent on the same mic, slight readjustment of the trims sometimes. Quiet single speaker means sometimes that might be audible.

Outside of the M32R, the other best sounding trim in the $2000-$2500 range was actually the QU16 so far. Very quiet zipping.

Gotta hop in and verify that my friend Dave [who i've worked with a number of times] does, indeed, know what he is doing and isn't using his trims to mix on.   :)

***Sidenote:  "Hi Dave!.  Welcome to the Forum!***

And yes, out in corpy broadcast world the input gain structure can often change dramatically, especially since you rarely, if ever, get to sound check with the Actual Talent before the show.  In PA world those trim changes can be made fairly easily and are usually totally inaudible.  But when you're dealing with a Broadcast Signal that is MegaCompressedtm it gets a little trickier.  If the Soundcraft is inducing audible noise during those changes, even if only at a low level, that is a pretty big problem.

Good thread, Dave.  And good info on the QU-series.  I've not had a chance to touch one yet.  Maybe i need to get out more...  :)
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John Roberts {JR}

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #17 on: April 27, 2017, 12:53:03 pm »

Thanks very much for all the feedback. For the record I'm really not "mixing on the trims", but I do find myself readjusting them for each phase of a show... new talent on the same mic, slight readjustment of the trims sometimes. Quiet single speaker means sometimes that might be audible.

Outside of the M32R, the other best sounding trim in the $2000-$2500 range was actually the QU16 so far. Very quiet zipping.
Yes, these can be made to change mic pre amp gain quietly, so that is apparently a design feature you will need to confirm when choosing between models if your application demands that. I would not presume that all brand XYZ do it one way or the other.   

There are surely enough users of different models around here to provide some hands on feedback for specific models.

JR

PS: This is me being gentle.  8)
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Christopher Irwin

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Re: Soundcraft Impact Gain Control Artifacts?
« Reply #18 on: May 01, 2017, 03:48:37 pm »


There are surely enough users of different models around here to provide some hands on feedback for specific models.


I just mixed on an SiImpact this weekend and didn't notice anything, even with a few gain changes mid show. That said, it wasn't the cleanest system and wasn't corporate work, which I do about half the time.  I also regularly mix on SiPerformer and SiCompact consoles and have never noticed noise from changing the gain.  That said, the M7 change in gain staging drives me bonkers, but maybe that's because I am looking for it...
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