Low input levels - Help!

[iboersma]

Hello,

Let me preface this by saying that I am an audio hardware newbie, so pardon any serious oversights on my part...

I just bought a Firebox to use with my Shure SM7B mic and Windows XP
(SP2) system for doing voiceover work. I followed all the instructions about how to install the driver (v.1.20) that came with the system, and everything seemed to install fine.

However, now when I fire up either Adobe Audition or Cubase LE, the
recording input levels seem artificially low. I have my SM7B mic
connected to the Mic XLR port on the front of the Firebox and my
headphones connected to the headphone jack. Those are the only 2
items I have plugged in to the box since my VO work doesn't require any more gear than that. I have the gain for the Mic XLR
jack at it's highest level on the box and also have the "Mic 1" volume
at it's highest level in the software Mixer application that came with
the Firebox. I also have the "Out 1/2" volume in the Firebox software Mixer at its maximum level and have also toggled on the extra 12dbs of boost for Mic 1
and Mic 2 in the "Hardware Settings" screen. Even with all this,
speaking in a fairly loud voice (louder than the average voice I use in a commercial read, for instance) only produces a peak of -12db in both
Audition and Cubase. I would expect that jacking all the volume
settings up on both the physical Firebox AND the software mixer would
have me redlining the input, but I'm not even close. I can also not
get the "Clip" light on the Firebox to ever light up, indicating that I'm not getting enough "juice" to the box to clip. The Firebox comes with 2 Presonus pre-amps with the XLR mics, so I'm at a complete loss at this point. Shouldn't a "normal" system have me at least able to get to 0dBs (zero) on the meter if I jack all the gains up? With this arrangement, I can't even hope to get near zero in a normal speaking voice...

The Shure SM7B is a dynamic mic, and it needs no phantom power, so
that can't be the issue. It's also a broadcasting industry standard,
so it's not like it's some cheapo, fly-by-night mic...

I've switched the firewire cable from one jack to the other, both on
my computer as well as on the Firebox itself, and it makes no
difference.

Any ideas? I am running a Dell 8400 P4 with 3.00 ghz processor and
1GB of RAM. I have Windows XP with SP 2 and I have my Firebox plugged into one of two open IEEE 1394 ports on my box.

Help!

Ian

 

[scrubs]

I don't know the gain specs of the firebox, but I would guess that the preamp on it is not providing adequate gain for the SM7B. Those mics require quite a bit of gain (dynamics, in general, require more gain than condensors). If you are getting some signal (even low levels), you might get some benefit from adding a little compression/limiting to boost the signal (you'll probably be doing this anyway for voiceover work). Adding a small external preamp before the firebox would be another option. Something like the Rane MS1B would give you a boost.

Edit: The gain on the firebox preamp is 45 dB. However, it looks like the firebox has line outs on the back. You could try connecting the line out from channel 1 to the input of channel 2, chaining the two preamps together. I have never tried this, but I've read you can do it with preamps to boost the signal. I make no promises that your gear won't blow up, though.

 

[mshilarious]

The SM7 is a nice mic, but it's less sensitive than many other dynamics. Looking at the specs for the Firebox, I see it only offers 45 dB of gain. I think that's your issue right there--the SM7 is happier with 55 or 60dB.

If you are 12dB short, I wouldn't worry too much, just increase the gain in Cubase. Yes, you will lose some dynamic range, but you probably won't miss it.

 

[iboersma]

I don't know the gain specs of the firebox, but I would guess that the preamp on it is not providing adequate gain for the SM7B. Those mics require quite a bit of gain (dynamics, in general, require more gain than condensors). If you are getting some signal (even low levels), you might get some benefit from adding a little compression/limiting to boost the signal (you'll probably be doing this anyway for voiceover work). Adding a small external preamp before the firebox would be another option. Something like the Rane MS1B would give you a boost.

Edit: The gain on the firebox preamp is 45 dB. However, it looks like the firebox has line outs on the back. You could try connecting the line out from channel 1 to the input of channel 2, chaining the two preamps together. I have never tried this, but I've read you can do it with preamps to boost the signal. I make no promises that your gear won't blow up, though.

Hey Scrubs,

Thanks for your input on this. I'm afraid it's becoming apparent that I chose the wrong mic for the Firebox (or perhaps the wrong setup for the mic!) as I've got this puppy topped out and don't get close to 0dB...

If I need to look for another microphone, would I compare the "output" spec for each mic I have in mind? The SM7B has an output of "Output Level (at 1,000 Hz)
Open Circuit Voltage* – 59.0 dB (1.12 mV) . . . . . . . . . .
*0 dB = 1 volt per Pascal" as per their tech specs. By contrast, the RODE NTK (another mic I was considering) has a maximum output figure of "Maximum Output: > +29dBu (@ 1kHz, 5% THD into 1k( load) ". I'm not sure if these two figures are directly equivalent, but it looks like the SM7B only provides -39dB at 1khz while the Rode provides +29dB at 1kHz. Maybe I'm not comparing apples to applies, but I want to look for another mic that I know will have much more initial signal strength BEFORE it hits my Firebox to ensure I can at least hit 0dB in my audio editing package and then back down the levels appropriately.

Let me know if I'm on track or not.

Thanks,

Ian

 

[iboersma]

The SM7 is a nice mic, but it's less sensitive than many other dynamics. Looking at the specs for the Firebox, I see it only offers 45 dB of gain. I think that's your issue right there--the SM7 is happier with 55 or 60dB.

If you are 12dB short, I wouldn't worry too much, just increase the gain in Cubase. Yes, you will lose some dynamic range, but you probably won't miss it.

Mshilarious,

Thanks for the help. I'm learning quite a bit about mics with the help of experienced folks like you on this site.

I've already maxed out the gain in both Cubase and Adobe Audition, and still can't get the levels up to where I need them to provide the best range (speaking in a normal 'read' voice, the meter reads between -25dB and -12dB). I'd like to at least be able to land around -3dB for my average VO read, which isn't possible with this mic.

Peace,

Ian

 

[GABritton]

I wouldn't get rid of the mic, it's not your problem. Your pre-amp doesn't push a hot enough signal for the SM7. Something as simple as an ART pre or some other single channel pre will give you better boost to your firebox...

 

[iboersma]

I wouldn't get rid of the mic, it's not your problem. Your pre-amp doesn't push a hot enough signal for the SM7. Something as simple as an ART pre or some other single channel pre will give you better boost to your firebox...

After looking at the price difference between buying an ART pre-amp ($50.00) and moving to a more expensive condenser mic like the RODE NTK ($100.00 more expensive than my SM7B) I think you've convinced me...

I'll grab one later today and update this thread to let you all know how it worked out.

Thanks to all for your timely and knowledgeable help. I'd be a sitting duck without you guys...

- Ian

 

[mshilarious]

The SM7B has an output of "Output Level (at 1,000 Hz)
Open Circuit Voltage* – 59.0 dB (1.12 mV) . . . . . . . . . .
*0 dB = 1 volt per Pascal" as per their tech specs. By contrast, the RODE NTK (another mic I was considering) has a maximum output figure of "Maximum Output: > +29dBu (@ 1kHz, 5% THD into 1k( load) ". I'm not sure if these two figures are directly equivalent, but it looks like the SM7B only provides -39dB at 1khz while the Rode provides +29dB at 1kHz.

No those are different stats--the Shure output is being measured at 94dBSPL, whereas the max output of the Rode is being measured at 158dBSPL!!!

The equivalent stat on the NTK is -38dBV, so yes it would solve your problem as it is 21 dB louder.

However:

I've already maxed out the gain in both Cubase and Adobe Audition, and still can't get the levels up to where I need them to provide the best range (speaking in a normal 'read' voice, the meter reads between -25dB and -12dB). I'd like to at least be able to land around -3dB for my average VO read, which isn't possible with this mic.

No there must be a function somewhere called "gain change" or something like that. DAWs can increase gain any amount. What they can't do is increase dynamic range--you'll be limited by your setup to about 96dB of dynamic range, less if the cranked Firebox is noisy--but at least you can get you level hotter. Really 96dB is plenty for VO, especially if this is destined for radio.

 

[iboersma]

No those are different stats--the Shure output is being measured at 94dBSPL, whereas the max output of the Rode is being measured at 158dBSPL!!!

The equivalent stat on the NTK is -38dBV, so yes it would solve your problem as it is 21 dB louder.

However:



No there must be a function somewhere called "gain change" or something like that. DAWs can increase gain any amount. What they can't do is increase dynamic range--you'll be limited by your setup to about 96dB of dynamic range, less if the cranked Firebox is noisy--but at least you can get you level hotter. Really 96dB is plenty for VO, especially if this is destined for radio.

Cool - I'll take a look at Audition and Cubase to see if I can spot the "Gain Change" setting you're talking about and see if that makes any difference. I may still invest in the ART pre-amp that was mentioned earlier just as insurance if I strike out on the Gain Change option. It seems like $50.00 well-spent.

Peace,

Ian

 

[scrubs]

Hey Scrubs,

Thanks for your input on this. I'm afraid it's becoming apparent that I chose the wrong mic for the Firebox (or perhaps the wrong setup for the mic!) as I've got this puppy topped out and don't get close to 0dB...

If I need to look for another microphone, would I compare the "output" spec for each mic I have in mind? The SM7B has an output of "Output Level (at 1,000 Hz)
Open Circuit Voltage* – 59.0 dB (1.12 mV) . . . . . . . . . .
*0 dB = 1 volt per Pascal" as per their tech specs. By contrast, the RODE NTK (another mic I was considering) has a maximum output figure of "Maximum Output: > +29dBu (@ 1kHz, 5% THD into 1k( load) ". I'm not sure if these two figures are directly equivalent, but it looks like the SM7B only provides -39dB at 1khz while the Rode provides +29dB at 1kHz. Maybe I'm not comparing apples to applies, but I want to look for another mic that I know will have much more initial signal strength BEFORE it hits my Firebox to ensure I can at least hit 0dB in my audio editing package and then back down the levels appropriately.

Let me know if I'm on track or not.

Thanks,

Ian

No, I don't think you need to get another mic. The 7b is one of the best mics for your needs. You probably just need a stronger preamp than the one in the firebox. Also, how close are you to the mic and how loud is your voice? Get close!

You don't need to be at 0db for digital recording. -6db is probably plenty.

 

[iboersma]

No, I don't think you need to get another mic. The 7b is one of the best mics for your needs. You probably just need a stronger preamp than the one in the firebox. Also, how close are you to the mic and how loud is your voice? Get close!

You don't need to be at 0db for digital recording. -6db is probably plenty.

I'd like to stay with this one, as it's a big hassle to box it up and return it (not to mention the hit on my wallet for a condenser...) I'm speaking very up close and personal with the mic and have had to actually raise my voice to levels that I never get to during VO sessions, so it's not the vocal input that's the issue...

If I could get to -6dB using a "normal" level of voice (as opposed to shouting), I'd be pretty satisfied, but as it is now, I'm sitting around -18...

You think the ART pre-amps are a good choice for voiceover work, then? I don't know much about tube pre-amps, but have heard that they can color your voice a bit; something I don't really want to do. Any other options out there? I'd be willing to spend up to $200.00 just to get this whole thing wrapped up...

Thanks again,

Ian

 

[scrubs]

I'd like to stay with this one, as it's a big hassle to box it up and return it (not to mention the hit on my wallet for a condenser...) I'm speaking very up close and personal with the mic and have had to actually raise my voice to levels that I never get to during VO sessions, so it's not the vocal input that's the issue...

If I could get to -6dB using a "normal" level of voice (as opposed to shouting), I'd be pretty satisfied, but as it is now, I'm sitting around -18...

You think the ART pre-amps are a good choice for voiceover work, then? I don't know much about tube pre-amps, but have heard that they can color your voice a bit; something I don't really want to do. Any other options out there? I'd be willing to spend up to $200.00 just to get this whole thing wrapped up...

Thanks again,

Ian

I've read very mixed things about the ART. I would guess it will color your sound more than you might want. For clean gain, I would suggest the Rane MS-1B. They are about $150 new. If you need 2 channels, then the M-Audio DMP3 is a good choice in your budget.

Out of curiosity, I am going to try the connecting the output from one channel to the input of another channel with one of my pres tonight. That may be all you need to do and it would save you any additional investment.

 

[iboersma]

I've read very mixed things about the ART. I would guess it will color your sound more than you might want. For clean gain, I would suggest the Rane MS-1B. They are about $150 new. If you need 2 channels, then the M-Audio DMP3 is a good choice in your budget.

Out of curiosity, I am going to try the connecting the output from one channel to the input of another channel with one of my pres tonight. That may be all you need to do and it would save you any additional investment.

I'll check out the Rane and DMP3's. I've also heard the PreSonus BlueTube DP is worth a look.

You're a brave man, considering you mentioned the possibility of that cross-connect frying the pre... I appreciate you taking the time to look into this.

- Ian

 

[mshilarious]

Yeah, you don't want the ART for your application. It has up to 70dB of gain, but the last 20dB have a lot of 'character', which means you'd only be a little better off than with the Firebox.

 

[scrubs]

Out of curiosity, I am going to try the connecting the output from one channel to the input of another channel with one of my pres tonight.

Alright, I am giving this a go with a Shure SM57 and an Alto Alpha MicPre (it is a shitty preamp anyway, so I don't care if I toast it). Mic is connected to pre channel 1 via XLR, then 1/4" TRS from output 1 to input of channel 2. 1/4" TRS from output 2 to Tascam US-122 interface. Actually, it seems to work o.k. It's been running for about 10-15 min at max gain without any smoke! There is plenty of gain. Too much, really. It is clipping somewhere when I turn it up all the way. Surprisingly quiet. The "toob" blend sounds better than I remember. I give it a B+.

 

[mshilarious]

Alright, I am giving this a go with a Shure SM57 and an Alto Alpha MicPre (it is a shitty preamp anyway, so I don't care if I toast it). Mic is connected to pre channel 1 via XLR, then 1/4" TRS from output 1 to input of channel 2. 1/4" TRS from output 2 to Tascam US-122 interface. Actually, it seems to work o.k. It's been running for about 10-15 min at max gain without any smoke! There is plenty of gain. Too much, really. It is clipping somewhere when I turn it up all the way. Surprisingly quiet. The "toob" blend sounds better than I remember. I give it a B+.

You aren't going to destroy anything chaining preamps. You might clip them, which will sound bad but won't hurt. If the first stage isn't hot enough, then it's less than 1V, which basically makes it like a weak line level input into the second stage. No big deal. Consider that a hot mic with a loud source is going be 8V or more.

The question is whether the noise that accumulates in the two preamp stages negates the benefit of additional gain. Try the chained preamps against increasing the gain digitally and see which is noisier.

Make sure if you chain to use the line input rather than the mic input for the second preamp.

 

[scrubs]

You aren't going to destroy anything chaining preamps. You might clip them, which will sound bad but won't hurt. If the first stage isn't hot enough, then it's less than 1V, which basically makes it like a weak line level input into the second stage. No big deal. Consider that a hot mic with a loud source is going be 8V or more.

Good to know. I just thought I'd test it out on cheap equipment first, just in case.

 

[iboersma]

Broke down and bought a pre-amp

Hey all,

Thanks for all your help on this post. I got a voiceover read that I needed to do tomorrow (Monday) so I bit the bullet and bought a PreSonus BlueTube DP which will arrive just hours before I need to provide the audition reads. It has the advantage of having both a solid-state as well as tube-driven pre-amps, so I can select which one I want to use depending upon the application. I was a bit worried about the color the tube amp might lend to my voice, so I wanted a solid-state option as well.

I'll let you know how it turns out.

Thanks again,

Ian

 

[iboersma]

Pre-amp to Firebox using Mic1 or Input1?

OK -

Now that I've got my pre-amp I have another great newbie question:

Should I be hooking up the output of my pre-amp to my Mic 1 input (XLR) or the Input 1 (1/4" jack) on my PreSonus Firebox interface? Since I got so little boost from my Firebox's on-board pre-amps last time, I was planning on just plugging my pre-amp into the Mic 1 XLR port, but I don't know if that's the best way to do it or not.

Suggestions?

- Ian