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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Sean Chen on May 06, 2019, 12:45:44 PM
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For some reason I am having difficulty with the mic preamp on the X32 and XAir mixers when I set the mic preamp to above +32 dB or more, the distortion and floor noise seems much more pronounced compared to +26 dB or lower. I am more experienced with Allen & Heath digital mixers where I have no problem using preamp gain up to +40 dB for a live mic signal. May I ask the Behringer X32 or X Air owners if you have come across similar issue?
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Have not. I regularly set to +35
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Does this happen regardless of the mixer's power source (ie different venues, different power conditioner/UPS/power distro rack)? Does it happen on all channels on the mixer? Is the signal going through a digital stagebox or direct analog to the mixer? Phantom power on/off? Ground lift? What steps were taken to make you think that it's the preamp?
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Does this happen regardless of the mixer's power source (ie different venues, different power conditioner/UPS/power distro rack)? Does it happen on all channels on the mixer? Is the signal going through a digital stagebox or direct analog to the mixer? Phantom power on/off? Ground lift? What steps were taken to make you think that it's the preamp?
I noticed the sound is more harsh with preamp set to +32 dB (PFL meter averaging +6 dB), so I turned it down to +26 dB (PFL metering averaging 0 dB) and pushed the speaker volume up, which made the harshness go away. Maybe there is clipping going on that is not registering on the meter. This leads me to think if there is sufficient usable headroom on the preamps.
My experience on Midas M32 does not have this impression.
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Are you clipping somewhere else in the mixer?
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If you are satisfied that you aren't clipping elsewhere (eg, you still hear it via PFL) then try this:
Solder a 200-ish ohm resistor between pins 2+3 in an XLR male plug.
Put that into the mic input on the mixer. Still got noise? Think preamp/mixer. Noise is gone? Think mic/cable/stuff thataway.
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My experience with the X32 et all is that they do not like running the HA hot or " cooked " as we call it. For most vocal mics I will end up around +17 or +20 and usually never higher than +24 for spoken word. On some instruments like keyboards, I will have to push the gain up over 30, but the incoming signal is low enough that there is no other way. I do not notice so much a distortion or change in sound ( and I have experiments that show there isn't any ), but I find that the operational characteristics change enough that you have to work outside of best standards and practices. I would guess that I have had to run an X32 up to +45 in maby half a dozen situations over the nearly 10 years I have been using them.
Some tests I have done with the X32 specifically about HA settings and its effect on mixer performance has shown that the HA is 100% linear and introduces no distortions until the red light is clipping. What goes in, comes out. What does change is the operational needs in order to deal with such hot HA settings. The aux sends are logarithmic just like a real pot and if you run the desk like you normally should with cooked HA settings, you will have excess noise and it is more prone to feedback due to the logarithmic nature of the pots fader. The self-noise of the HA is evident once you start getting past about +35 and after about +40 to +45 I find the self-noise to be very bad.
The X32 and X-Air line as far as I can tell really prefer to be run in the more textbook manner. I.E. setting the HA level so that the signal sets right around -18dbu on the meter. This usually means the HA setting will be right around +20 ish. I err to the cold side and try to have the peak of the signal just touching the -18dbu and find the X32 to be very clean, quiet and well performing when done as such.
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Both my XR-18 and my X32 I run around 25 for most vocalist and around 22 for a person with a set of pipes. Same for most everything else when micing a full band around 25 ish. Loud snare comes down to 21-22, hot active bass I have had as low as 16, ratty old P-bass as much as 30, but rarely.
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My experience with the X32 et all is that they do not like running the HA hot or " cooked " as we call it. For most vocal mics I will end up around +17 or +20 and usually never higher than +24 for spoken word. On some instruments like keyboards, I will have to push the gain up over 30, but the incoming signal is low enough that there is no other way. I do not notice so much a distortion or change in sound ( and I have experiments that show there isn't any ), but I find that the operational characteristics change enough that you have to work outside of best standards and practices. I would guess that I have had to run an X32 up to +45 in maby half a dozen situations over the nearly 10 years I have been using them.
Some tests I have done with the X32 specifically about HA settings and its effect on mixer performance has shown that the HA is 100% linear and introduces no distortions until the red light is clipping. What goes in, comes out. What does change is the operational needs in order to deal with such hot HA settings. The aux sends are logarithmic just like a real pot and if you run the desk like you normally should with cooked HA settings, you will have excess noise and it is more prone to feedback due to the logarithmic nature of the pots fader. The self-noise of the HA is evident once you start getting past about +35 and after about +40 to +45 I find the self-noise to be very bad.
The X32 and X-Air line as far as I can tell really prefer to be run in the more textbook manner. I.E. setting the HA level so that the signal sets right around -18dbu on the meter. This usually means the HA setting will be right around +20 ish. I err to the cold side and try to have the peak of the signal just touching the -18dbu and find the X32 to be very clean, quiet and well performing when done as such.
Thanks Luke for your insight.
To clarify my setup, it involve 2 totally different settings:
One is with the X-32 Rack for a live rock band gig at a bar. Mic is Beta SM86 for a male lead vocalist. At preamp gain of +26 I cannot bring him above the everything else in the mix, so I proceeded to up the pre gain to +32. I didn't notice the LED clip, but ouch it sounded harsh with the PRX pushing full volume. Maybe it's the combination of the mic, pre, and the speaker at that volume.
The other is with X-Air 12 for a Karaoke set up. Mic is wireless MiPro ACT-8 digital. With gain set to +32, there is artifacts that sounds like clipping, although it didn't appear so on the EQ page RTA. But after I reduce the gain to +26, the clipping went away with the average PFL level around + dB on the EQ page RTA. I was like, "Really"? I have to run this thing at 0 dB? Well, I had to turn up the speaker's input gain to get the volume back up, which increased the floor noise.
I've read there should be no discernible difference with modern day preamps. Or is there? If the Behringer X series mixers need to be run outside (colder) than typical gain structure practice, I would have difficult time spec'ing it in a system I put together.
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Thanks Luke for your insight.
To clarify my setup, it involve 2 totally different settings:
One is with the X-32 Rack for a live rock band gig at a bar. Mic is Beta SM86 for a male lead vocalist. At preamp gain of +26 I cannot bring him above the everything else in the mix, so I proceeded to up the pre gain to +32. I didn't notice the LED clip, but ouch it sounded harsh with the PRX pushing full volume. Maybe it's the combination of the mic, pre, and the speaker at that volume.
The other is with X-Air 12 for a Karaoke set up. Mic is wireless MiPro ACT-8 digital. With gain set to +32, there is artifacts that sounds like clipping, although it didn't appear so on the EQ page RTA. But after I reduce the gain to +26, the clipping went away with the average PFL level around + dB on the EQ page RTA. I was like, "Really"? I have to run this thing at 0 dB? Well, I had to turn up the speaker's input gain to get the volume back up, which increased the floor noise.
I've read there should be no discernible difference with modern day preamps. Or is there? If the Behringer X series mixers need to be run outside (colder) than typical gain structure practice, I would have difficult time spec'ing it in a system I put together.
What output are you using on the mixer? And what is your routing to the output? Is there anything else in the signal chain? Have you looked at all of the pages under the meters button and looked to see if you can see anything clipping or looking weird? Can you upload your scene here or have you tried asking the same question on the Behringer forum? Have you tried moving the mic to a different input to see if it behaves the same way? I don't use the Behringer versions of these mixes much myself but I have never had the kind of problem on one that you are describing. Bu it sounds like you have a gain stage issue somewhere.
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Both my XR-18 and my X32 I run around 25 for most vocalist and around 22 for a person with a set of pipes. Same for most everything else when micing a full band around 25 ish. Loud snare comes down to 21-22, hot active bass I have had as low as 16, ratty old P-bass as much as 30, but rarely.
My experience with our XR-18 is similar. 26-28 for most vocalists and I've used Sennheiser 835, 935, SM58 mics with it. Instruments vary wildly depending on the level of pre-amplification.
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First off I'm not aware of an sm86 beta.
I have and using sm86 my favorite male vocal mic.
You have checked at the phantom power is on if it is indeed an sm86, right?
Never had a problem with distortion.
I think if you don't know quite enough to go deep into your mixer you might do better to just reset to factory defaults and start from there.
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Check your DCAs , see if that channel is assigned to a sub group, see if an effect is inserted on that channel or group that is altering volume. Also check the dynamics, gate and eq settings on the channel to be sure you're not losing gain anywhere in the channel strip.
SOP on the X32 set gains so you are just tickling the first yellow light, -18.
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On most digital mixers I try to hit -18 to -12 on the channel meter. IMHO that is the way most digital boards should be operated. With X32/M32 and dynamic vocal mic (SM58/e935 etc.) my mic channel gain is usually 22 to 25 dB. With really quiet singers 25 to 30 dB. With XR18/MR18 the desks preamps and the whole thing is completely different, you need to add about 5 dB or more gain to achieve the same result. Gain is only gain, who cares what the number says on the screen. Don't overthink it.
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On most digital mixers I try to hit -18 to -12 on the channel meter. IMHO that is the way most digital boards should be operated.
Not unreasonable. The maximum output of the X32 is spec'd to be +21dBu. On pro level analog consoles of yore 0Vu was usually +4dBu. That means -17 on the X32 meters is about the same as 0Vu on a PM4000 or Midas XL4. On those analog consoles you usually only had a few dB of meter left above "0" so unless you just pegged the meters against the stop you weren't going much above +8dBu, which would be about -12dBfs on an X32.
Mac
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SOP on the X32 set gains so you are just tickling the first yellow light, -18.
Thanks I will use this guideline for X32.
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First off I'm not aware of an sm86 beta.
I have and using sm86 my favorite male vocal mic.
You have checked at the phantom power is on if it is indeed an sm86, right?
Never had a problem with distortion.
I think if you don't know quite enough to go deep into your mixer you might do better to just reset to factory defaults and start from there.
Sorry, it is not Beta. It does not have a blue ring. It should be a SM86. Phantom power is on.
It is not my mixer.
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Sorry, it is not Beta. It does not have a blue ring. It should be a SM86. Phantom power is on.
It is not my mixer.
I love the SM86 mic over any of the other lower cost options (SM58, B58, E8xx, OMx, etc). If it sounds harsh it's likely either something else in the signal chain or a damaged mic.
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I would check out what Lyle said above. Whilst knowing the io of the Behringer isn’t the best I’ve generally not had the same experience you’ve been experiencing. I would, as a big generalisation, suggest if you are using gains much over 32-35db, perhaps the problem is elsewhere. Usually using a 58 on a vocal you are looking at head amp gains in the 27-32 dB range at most. I would most definitely change a lead and check the mic first and the multicore if you are using one.