Having to set gain too high on Mix-Pre sound mixer?

[Stuart Graham]

Chris and Ty:

I rang the suppliers and have arranged to send it back to them. They said they will check if it is working and speak with Sound Devices for me.

I think it must be defective judging from my tests and by your experiences Chris. Thanks for letting me know it works fine with your At815b mic.

Jay:

I tried using the mic setting on the camcorder, as opposed to line in, and it gave terrible results, very noisy audio and it was very difficult to adjust the levels on the mixer without giving huge variations on the camera. I don't think it's an option.

[Jay Massengill]

As I stated in my post, you'd have to use an attenuator between the mixer and the camera in order to set the camera input to mic-level successfully.

The reason I mentioned all that about the mixer's external DC input connector type, is to judge which balanced output type your particular mixer has and therefore what attenuator type you could use successfully. It could also give us another clue as to why your setup is giving relatively low input into the camera.
What external power jack does your Mix-Pre have?

[Stuart Graham]

Hi Jay

It's the 4 pin power jack type, so it's the new model. Unfortunately I don't have another line level input source to test the camera with. The low in camera response with the XH A1 is normal though, I've seen that mentioned in other threads. My main concern is the low levels I'm getting on the mixer really.

Good idea about getting an attenuator and using the mic in on the camcorder to boost the signal. Are attenuator's expensive?

[Jay Massengill]

Attenuators aren't very expensive, although they aren't exactly cheap either. Definitely good to have on hand though and a necessary expense I feel to handle different situations that may come up.
Switchable models are handy but you can also get single level units.
That's good news about your model of mixer as far as attenuators are concerned. You can use regular, readily available ones instead of custom ones.
I often have to open up the control on my Mix-Pre a lot with quiet sources, but I don't have an AT815b to check. I do have an AT897, which has slightly less sensitivity, and it sometimes requires turning the Mix-Pre control to 3 o'clock to get a good level. I've never noticed it as a problem that I couldn't get enough gain though.

[Stuart Graham]

Jay:

Thanks for the info Jay. What levels do you get on your Mix-Pre at maximum gain with speech spoken at moderate volume about 8-10" from your AT897? I only get about +4dBu with my 815.

Chris:

Do you happen to remember what sort of peak meter levels you got on your Mix-Pre for speech with the 815 attached?

--

I called Sound Devices today and they said they thought the mixer was fine and that speech peaking at +4dBu units is okay. Unfortunately they haven't tried an At815b with the mixer before so couldn't comment on its compatibility. I'm not sure whether +4dBu is enough as I will have the mic further than 8" away from talent during filming, probably at least double that giving -2dBu. Is -2dBu too low? Anyone have any handle on what types of levels I should expect or aim for on Mix-Pre LED meter readout when capturing speech?

The people at the company that supplied my mic also think +4dBu is fine. I'm going to listen to my test audio again and see if I can determine if the sound quality seems acceptable.

[Brooks Harrington]

You wouldn't by chance have your limiter turned on..... and have it adjusted way down to about +6... which is the lowest it will go?

[Stuart Graham]

Hi Brooks

No, the guy at Sound Devices asked me that. Unfortunately the limiter is definitely off.

Good idea though.

[Stuart Graham]

Jay:

Thanks for the info Jay. What levels do you get on your Mix-Pre at maximum gain with speech spoken at moderate volume about 8" from your AT897?

I only get about +4dBu with my 815.

Chris:

Do you happen to remember what sort of peak meter levels you got on your Mix-Pre for speech with the 815 attached?

Anyone have an idea what levels I should expect or aim for on a Mix-Pre LED meter readout when capturing speech?


Audio Tests

I have compiled an audio file containing tests with the At815b mic plugged into the Mix-Pre and/or the XH A1.

Bit rate: 768kbps
Sample size: 16 bit
Channels: mono
Audio sample rate: 48kHz
Distance from microphone tip to subject: 7.5"
When the Mix-Pre mixer was used gain setting was at maximum
Roughly the same in camera peak meter levels were used in all tests (peaking at around -12dB on the XH A1 meter)
Slight differences in peak levels were corrected in Media Composer (peaking at -14dB)

If you listen to the file you will hear the tests in the following order:

1. no audio
2. At815b through Mix-Pre into XH A1, 6 x "Test, 1, 2..."
3. At815b direct into XH A1, 6 x "Test, 1, 2..."
4. no audio
5. At815b through Mix-Pre into XH A1, "Mary had a little lamb..."
6. At815b direct into XH A1, "Mary had a little lamb..."
7. no audio

Anyone have a comment on the quality of the audio in the various tests?

Here is the audio file:

[Stuart Graham]

I've done even more tests! The tests are the same as the last set but this time the distance from microphone tip to subject was a more realistic 20 inches. When the Mix-Pre mixer was used the gain setting was at maximum as before.

Roughly the same in camera peak meter levels were used in all the tests (peaking a little higher than -20dB on the XH A1 meter and giving a corresponding 0dB on the Mix-Pre meter).

Slight differences in peak levels were again corrected in Media Composer (peaking at -14dB)

If you listen to the file you will hear the tests in the following order:

1. no audio
2. At815b through Mix-Pre into XH A1, 6 x "Test, 1, 2..."
3. At815b direct into XH A1, 6 x "Test, 1, 2..."
4. no audio
5. At815b through Mix-Pre into XH A1, "Mary had a little lamb..."
6. At815b direct into XH A1, "Mary had a little lamb..."
7. no audio
8. At815b through Mix-Pre into XH A1, "The rain in Spain..."
9. At815b direct into XH A1, "The rain in Spain..."
10. no audio

[Stuart Graham]

I've done some final tests using high gain on the XH A1 to see if it gives better quality audio than using either the Mix-Pre or more conservative XH A1 gain settings. Again the distance from microphone tip to subject was 20 inches.

When the Mix-Pre mixer was used its gain setting was at maximum as before.
When the mic was connected directly to the XH A1 with 'normal' gain this corresponded to 6 notches on the gain wheel as opposed to its maximum setting of 9 notches that was used in tests 3, 7 and 11. The max gain setting gave audio peaking at about -6dB on the XH A1 readout.

If you listen to the file you will hear the tests in the following order:

1. no audio
2. At815b through Mix-Pre into XH A1 at 'normal' gain, 2 x "Test, 1, 2..."
3. At815b direct into XH A1 at maximum gain (but no clipping), 2 x "Test, 1, 2..."
4. At815b direct into XH A1, 1 x "Test, 1, 2..."
5. no audio
6. At815b through Mix-Pre into XH A1 at 'normal' gain, "Mary had a little lamb..."
7. At815b direct into XH A1 at maximum gain (but no clipping), "Mary had a little lamb..."
8. At815b direct into XH A1, "Mary had a little lamb..."
9. no audio
10. At815b through Mix-Pre into XH A1 at 'normal' gain, "The rain in Spain..."
11. At815b direct into XH A1 at maximum gain (but no clipping), "The rain in Spain..."
12. At815b direct into XH A1, "The rain in Spain..."
13. no audio