Is needing over 50dB of mic gain and most of the channel's volume normal???

[fishboy]

I'm running a Shure Beta 57a into a Mackie Tapco Blend6 mixer and then into a Delta44, which leads to Sonar 5. EVERYTHING is connected with balanced cables and I've tested all of them with a multimeter on its continuity setting.

The Blend6 manual say that to set gain levels you shoudl zero the console, make your noise, and adjust the gain until the little green light starts flashing. Then you can increase volume with the ordinary volume controllers.

The thing is, in order to get the little green light going, I need to max out the mixer's gain, or set it maybe 1mm below that.

And even then, setting channel and mains gain to unity (12 o'clock) produces a weak signal, one that reaches maybe -24dB if I sing at the top of my lungs. And it barely even registers on the Blend6 master level LEDs - occassionally the bottom one goes off, but that's it. To get a decent signal (peaking around -6dB) I need to set the channel volume to 3 o'clock or more, with the master at unity.

So my questions are:

1. Is needing this amount of gain to get a decent signal level normal in general? Is it normal for this mic?

2. To boost levels to an acceptable point, is it better to use the channel or the main volume control? I'm thinking about keeping noise to a minimum, though I must say that I'm thrilled with the set-up's current effective -78dB noise floor with the mic open (that's when it's peaking at about -12dB, with channel gain at max and channel volume almost at max).

3. Am I on a wild goose chase, searching for the unnecessary or unachievable?

4. I understand that with every 6dB decrease in sound, your not using 1 bit of your recording potential. With the Delta44's 24bit recording, should I even worry about this?

I'd really like to get to the bottom of this, assuming there is a bottom to get to. On the bright side, I am stunned by the quiet pre-amps and amps on the Blend6 -- they're virtually noiseless at ultra-high settings. Getting these levels on my former mixer --a Behringer MX602a (extremely common, but with a different model number in different parts of the world)-- produced so much noise that I thought I was in a power plant.

Thanks in advanced

[Farview]

I don't know about the beta 57, but the sm57 (if I remember correctly) specs say that it needs 55db of gain.

For most converters, line level = around -18dbfs (it depends on how it's calibrated, there is no standard) but your peaks should still be above that.

[AdamJay]

it really depends on how loud your source is

[fishboy]

Originally Posted by AdamJay

it really depends on how loud your source is

To give you an idea, when I sing VERY LOUD with my mouth about 1/2" from the grille, I get maybe -12dB output tops, with mixer gain at full (+50dB according to the specs) and channel volume at 9 o'clock.

[ProPower]

As I read this either your mic is frapped, cables bad (though you did test them) or the mixer is not healthy.

1) Mic bad? Have you tried a different mic ?
2) Cable bad? Switch mic cable
3) Mixer sick: Use a signal source of known amplitude (from DAW 1kHz for instance) and feed into mixer. Set channel for specific gain (+3 and +50 are convenient choices) and feed output of mixer into input channel of DAW. See if it adds up.
3a) If 3 looks to hard could try -setting the gain to +3 (min) on Ch 1 and 2 and injecting the output of a cd palyer into channels 1 and 2 (panned hard L and R). They should light up almost all of the ouptut LEDs with the rest of the mixer at unity.

-Lee

[fishboy]

Originally Posted by Farview

I don't know about the beta 57, but the sm57 (if I remember correctly) specs say that it needs 55db of gain.

You'll have to forgive my ignorance, but what's this particular spec called? I was just looking up the Beta 57a's specs ( http://www.shure.com/ProAudio/Produc...eta57A_content ) and I couldn't find anything that I could clearly identify as required gain?

Does this have anything to do with it?


Output Level (at 1,000 Hz)
Open Circuit Voltage -51 dBV/Pa* (2.8 mV)
*1 Pa = 94 dB SPL


Cheers!

[fishboy]

Some more info, based on more testing:

I tried the exact same setup as before, but used a Shure 16a battery-powered condensor (not exactly top-of-the-line, and discontinued to boot, but anyway...).

I got more signal out of the 16a than out of the Beta57a, but not astoundingly more -- maybe 6dB more on average. This seems to me to be a reasonable difference between two different mics, and especially two different mic types (condensor vs. dynamic), so at this point I'd hazard to conclude that the mics are ok.

As far as the mixer goes (Mackie Tapco Blend6), it is indeed cranked up (gain to maybe +48dB, channel volume and master volume to unity), and I was indeed singing very loud (how's that for precise measurement). Now, no matter what I did (even setting gain, channel volume and master volume), I couldn't get the Blend6's meters to go above -4dB, even when I was practically shouting into the mic.

However, I ran the signal through a Samson S-Com Plus compressor, completely zeroed, and its input meter read around +18dB when I did this. And Sonar would peak (clip) during the same experiment, but I couldn't tell by how much.

Seems everyone calibrates their products differently. Argh. And by the way, both my Delta44 and the S-Com Plus are set to the +4dB level. The Blend6 has no such setting.

Finally, with the same mics and my old (cough, sputter) Behringer MX602A mixer I also had to crank the gain and volume WAY up to get a decent level. However, with that POS the pre-amp and amp noise was wretched, completely unusable.

So... is it normal to need so much pre-amping and amping to get a good, strong signal from these mics?

Thanks to the extremely clean amping of the Blend6, I could live with this -- it won't prevent me from recording with virtually no line noise. But I really want to rule out the possibility of having bum equipment.

I'm going to post the specs of both the Beta57a and the 16a. I'd greatly appreciate it if anyone could find the relevant figure and tell me if these mics need as much gain as I'm giving them.

Thanks in advance.

========== Beta57a ==========
http://www.shure.com/ProAudio/Produc...eta57A_content

Dynamic (moving coil)
Frequency Response: 50 to 16,000 Hz
Polar Pattern: Supercardioid
Output Level (at 1,000 Hz): Open Circuit Voltage -51 dBV/Pa* (2.8 mV)
*1 Pa = 94 dB SPL
Impedance: Rated impedance is 150 ohms (290 ohms actual) for connection to microphone inputs rated low Z
Phasing: Positive pressure on diaphragm produces positive voltage on pin 2 with respect to pin 3


========== Shure 16a ==========

Type: Condenser (electret bias)
Frequency Response: 50 to 15,000 Hz (see [3])
Pickup (Polar) Pattern: Cardioid (unidirectional) (see [4])
Impedance (Z): Low (600 W balanced)
Output Level (at 1 kHz): Open Circuit Voltage: –68.0 dB (0.40 mV) *
*0 dB = 1 V/mbar
Maximum SPL (at 1 kHz): 120 dB
Polarity: Positive pressure on diaphragm produces positive voltage on pin 2
with respect to pin 3.

[u b k]

Originally Posted by fishboy

To give you an idea, when I sing VERY LOUD with my mouth about 1/2" from the grille, I get maybe -12dB output tops.

-12dbV on the board, or -12dbfs in your converters? either way, something is wrong with your setup.

when you have the mic plugged into the pre, gain up, and the board's master fader at unity, *all other gear physically disconnected*, what're the board's meters reading?


gregoire
del
ubk

[fishboy]

Originally Posted by u b i k

-12dbV on the board, or -12dbfs in your converters? either way, something is wrong with your setup.

when you have the mic plugged into the pre, gain up, and the board's master fader at unity, *all other gear physically disconnected*, what're the board's meters reading?

Well, for once in my life I'm quite pleased to feel stupid.

I did what you suggested and got nothing whatsoever on the board. Then it it me. Or rather, I hit me -- right smack in the forehead.

The Control Room button was switched to CD/TAPE, instead of Main Mix. This is how I get Sonar's metronome plus what I've already tracked to the headphones while I'm playing and tracking.

According to the Blend6 manual, this switch also has the effect of switching the meter input it measures from what's going into the board's 6 channels (e.g. what I'm recording) to what's coming back from the control room (e.g. the material recorded up to this point).

So...

After switching the button to Main Mix, setting the gain all the way up (+50dB) and setting channel and main vols to unity, I was getting 0dB to +4dB when I sang loud. Turining the channel gain to max sent me up to +12dB or so. No matter how hard I tried, I couldn't max out at +18dB, but that's not something I'll ever want or need to do.

As far as not being able to get the meters over -4dB before I tried this, as if I had a brickwall limiter somewhere in the circuit, I imagine this was either Sonar or my Delta44 refusing to put out more than digital 0dB.

So after your kind suggestion, I think I have things solved here.

The only thing I'm still wondering is -- is 50dB of gain reasonable for the Beta57a? Or did I get a clunker?

Thanks a million!

[u b k]

50db of gain is not unreasonable for a dynamic mic. my console pre's are vintage, only doing 45db max, and i've got an old 421 for which that's often not enough even with the fader adding 6.

glad you got it sorted out.


gregoire
del
ubk
.

[goldphinga]

yeah you need to crank on the gain on a 57 and usually add some brightness.....