Mbox3 Pro: +4 Line Input Unity Gain
I don't own one, but use them frequently at a regular freelance gig.
When using this interface in combination with an external preamp sending out +4 line level via 1/4" TRS, what is unity gain on the knob in the front of the MBox3? I'm assuming it's all the way down (counter clockwise). A couple of times, I've gone to this studio to find the knob at 12 o'clock from a previous session. Before I mention this and look like an idiot, can someone from Avid confirm that the channel's gain knob should be all the way down when it's receiving a normal, +4 line level signal from an external preamp? The manual seems rather quiet on this matter. Thanks... |
Re: Mbox3 Pro: +4 Line Input Unity Gain
You really should be gain staging this with your ears.
But to understand stuff... you have everything you need to answer all these questions in front of you. Signal Gen in Pro Tools. Sine wave output. Confirm the analog level output with an multimeter. Then probe the line (and outboard mic) inputs with that signal. You can mark gain marks on the knob if you want to. (and are other folks engaging the -10dB pad? And why?) |
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Hello. Thanks for responding, although I can do without the "mansplaining". There's a -20 pad that can be engaged by pulling the gain knob out. I've never seen this messed with, but the line input switch in the back of the unit is sometimes set to -10 unbalanced line level. Why is this being done? I have no idea. I just make sure I'm at +4 before I get signal going. This isn't the kind of gig where I have time to calibrate everything before a session with a voltmeter. I just need to know what unity gain is as far as setting the knob in front. I assume that if it's all the way down counter-clockwise, no gain is being added and this is pretty much unity gain (as close to bypassed as you can get). I've used the outboard preamp they have there hundreds of times so the MBox is the only thing I'm not used to. As far as what I see in Pro Tools the levels look "normal" when the knob is set this way. Also I'm having no issues with noise or headroom. If you read into this a little more, it's might be fairly obvious that I would prefer the information come from Avid than from me as far as my employer goes. Make sense? |
Re: Mbox3 Pro: +4 Line Input Unity Gain
Unlikely anybody from Avid is going to read this or reply. This is a user forum.
Unlikely most active users here have an Mbox. And unlikely other users here know the exact answer or care to make the measurements you can make in several minutes yourself. I could be but I would not assume any gain knob on any device is OdB at any extreme. If it is important measure it. |
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I once had the "chief engineer" (whatever that means) at some dump in DTLA argue with me about how the BAE 1073 output trim knob should always be at 12 o'clock (unity gain, right? LOL). I always set it fully clockwise (as your supposed to...it's a trim knob). In this case I could point him to the manual which stated: "OUTPUT KNOB The output knob (grey) should be fully clockwise to achieve the highest headroom am [sic] cleanest signal path." If it were the 500 series Neve 1073LB, the output knob can add a little gain, so he would be more correct in that case. Thanks again, but unfortunately the issue is more politics than me just being curious about the mysteries of gain staging and all that. |
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If you would prefer an Avid employee to ask you that question you can purchase a support ticket and contact Avid support. |
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Ok, when I go back in there, I'll make sure that when set to +4 and when using a "1/4 TRS plug, the gain knob is bypassed. I hope that's the case and that I'm just way off. Thanks again. -R |
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I can't be hanging out after my sessions there to run tests on their interfaces. It's not that kind of situation. I have no problem RTFM, but it's not helpful. |
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