Low Volume Buzzing and Jack Question

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Rimbama
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Joined: 2011-05-18
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I have been using Ardour for several weeks now and I am loving it. I read the floss manual and feel like I have a decent handle on Ardour now. Unfortunately I am completely lost when it comes to Jack. Is there any place someone can refer me that has documentation that will explain Jack to me? This brings me to my other question...

I was recording something that is soft today, and when playing it back there was a buzzing noise (Yes I checked the room and instrument), but only when I was playing. If there was silence in the piece there was no buzzing noise. I could only hear it if I cranked up the volume, but it is pretty apparent with head phones. It was also present after I exported. This is the raw recording, I have not added any plugins to it I suspect maybe my Jack setting are wrong, which is why I asked the previous question. Or is this normal?

I would appreciate any help. I have a link for both a wav and mp3 of what I recorded, and I will provide as much information about the laptop I am using to record and its Jack settings. (QjackCtl)

http://www.mediafire.com/file/evlcqoo7qtoibz7/Whatiswrong%3F.mp3
http://www.mediafire.com/file/mfdrmyvczd3imf8/Whatiswrong%3F.wav

Laptop: Aspire 5538, AMD Athlon 64 X2 1.2 GHz, 4 GB Memory
Audio Interface: M-Audio MobilePre
Ardour 2.8 with Ubuntu Studio

Jack Settings: First of all, made sure I selected my MobilePre

Realtime is checked
Driver: alsa
Priority: Default
Sample Rate: 48k
Periods/Buffers: 2
Port Maximum: 256
Timeout (msec) 500
Start Delay (secs): 2
Dither: None
Audio: Duplex
Input Channels: Default
Output Channels: Default
Input Latency: Default
Output Latency: Default
Latency: 42.7 (I have read 5 msec is not a bit deal, I take it 42.7 is?)

I am sorry if I listed any non essential information. Thank you for any help you can provide!

R

Rimbama
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I should add that I tried lowering the Sample Rate to 44100 and increasing the Periods/Buffers to 3 and 4 and that did not help. (Saw that suggested in a different thread, not sure why I thought it would help my problem....)

nowhiskey
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Joined: 2006-09-30
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hallo,
for your first question, maybe reading this will help you:

http://jackaudio.org/faq

cheers,
doc

DonF
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Is your interface running at 24 bits, or 16? It sounds to me like quantization noise (which is more of an issue at 16 bits than at 24).

Rimbama
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Thank you nowhiskey

http://www.m-audio.com/products/en_us/MobilePre.html

Is there a way to verify that I am running at 24 bits? The link above says it is a 24 bit device.

Thanks!

anahata
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If what you are recording is consistently quiet though the whole take, maybe you need to crank up the mic preamp gain. Your recorded data should be peaking at about -12dBFS (or -20dBFS for 24 bit); if it's much lower than that, you are losing resolution and will benefit from more analog signal going into the converter.

Even so, quantization noise should not appear as a buzzing noise.
A properly dithered conversion will have only a smooth background white noise.

If there's a way of monitoring the sound though just the A-D and D-A conversion without any processing, recording and playback in between, try that - if you still get the buzz the fault is with the audio interface. It could even be in the analog circuitry - a fuzzy distortion that is at a low level and appears only with signal could be crossover distortion.

Another thought: with USB you may need Jack set to 3 periods / buffer. That's the easiest thing to try first.

Rimbama
User offline. Last seen 2 years 43 weeks ago. Offline
Joined: 2011-05-18
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Thanks for all the suggestions. I did solve the problem, and it was due to my inexperience with recording. All I had to do was reposition the microphones and yes, turn up the gain.....I looked up quantization, and that set me on the right path to fixing it. Thank you all again. It is great to have a place to come and ask questions!!

R