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How to get maximum performance from portable digital recorder?

I recently acquired a hand-held stereo linear PCM recorder for the purpose of recording different pipe organs. The recorder allows bit depths of 16 or 24 and sample rates of 44100, 48000 or 96000.

Having watched the primer videos at xiph.org I know that there is no obvious advantage in distributing files with greater bit depth or sample rate than 16/44100 for playback. I am also aware that on a portable device the effective bit depth of the recording will not come close to 24 bit. Storage space on the device is not an issue for me with the availability of cheap, high-capacity SD cards.

My question is which combination of sample rate and bit depth settings are likely get the most out of what I assume is relatively common ADC hardware? For reference, the recorder is a TASCAM DR-05, which is a $100 device.

Re: How to get maximum performance from portable digital recorder?

Reply #1
Record in the best quality the device can do, provided you have enough space. Make sure the input level gain is correct so you maximize the signal level without clipping. You can always downsample and reduce bit depth later.

Re: How to get maximum performance from portable digital recorder?

Reply #2
48000 is more than enough. Use 24 bits just to give head room when recording, in case you don't get gain right - but once recorded, normalize it to 16 bits.

Re: How to get maximum performance from portable digital recorder?

Reply #3
Record in the best quality the device can do

The OP is specifically asking about what combination is best. Are you assuming a higher sample rate is always better?

Re: How to get maximum performance from portable digital recorder?

Reply #4
Quote
I am also aware that on a portable device the effective bit depth of the recording will not come close to 24 bit...

My question is which combination of sample rate and bit depth settings are likely get the most out of what I assume is relatively common ADC hardware?
I think you've pretty-much answered your own question.

From what I understand, even the best ADCs don't achieve 24-bit accuracy.

The "pro standard" is 24/96, and there's no harm in using that.   But, if you're making CDs (16/44.1) there's no reason for going higher than 44.1kHz.   

You do loose resolution if you record leave headroom...  If you record at 16-bits and your peaks only reach -6dB, you're only using 15-bits.  But in reality, you are unlikely to hear any quality loss even if you go to -12dB (or lower).   Don't try to "compromise"...    Clipping is MUCH worse than a little loss of digital resolution!     

I'll agree with half of what KozmoNaut  said.  It's very important to avoid clipping  (Make sure your levels NEVER hit 0dB.)      It's NOT so important to maximize the signal, especially at 24-bits.  Pros often record at around -18dB (at 24-bits).    Live sound levels are rather unpredictable and I'd start to worry if you get above  -6dB.

Mic location is also very important, especially if there is an audience.      Even if there isn't an audience, you'll probably want more direct sound (and less room-sound/reverb) than you hear in the usual seating position...    The amount of reverb that sounds wonderful in a music hall or church, usually sounds "stupid" coming out of a pair of speakers in your living room.

Get a mic stand and whatever stand-adapter you might need, even if you have to improvise something.  You may not be able to find a shock-mount for that recorder, but try to isolate it from any vibrations, and once you're recording the show, don't touch it!

Also if there's an audience, you might want to set-up a 2nd recorder to capture the applause (assuming you're not recording church services).  That could be a laptop, a video recorder, or a phone, etc., and then you can mix-in the appropriate amount of applause in post-production.

And if at all possible, experiment (especially with different mic locations) by recording rehearsals and/or multiple performances.    And once you've "got it right" it's a good idea to record multiple performances (if possible) because stuff does  go wrong!


Re: How to get maximum performance from portable digital recorder?

Reply #5
Can you use the internal mic to record 10-20 seconds of silence (e.g. put the recorder in a drawer) in 24-bit 96k WAV and attach the file here?

Re: How to get maximum performance from portable digital recorder?

Reply #6
Thanks everyone for the replies.

Can you use the internal mic to record 10-20 seconds of silence (e.g. put the recorder in a drawer) in 24-bit 96k WAV and attach the file here?
What input level should I use for this test to be useful? Should I max the input level?

Re: How to get maximum performance from portable digital recorder?

Reply #7
Yes, that's important. I don't know what kind of unit the recorder uses (such as dB, % etc), how about three files:
[1] maximum
[2] one step above minimum
[3] default (if any)?

Also, if the device has some sort of auto gain function, disable it for this test.

Re: How to get maximum performance from portable digital recorder?

Reply #8
What kind of microphone are you using? As far as I can see, the DR-05 claims to be able to handle input at 125 dB with its built-in mic, and if it is reasonably smart, it will align the 24-bit with sufficient headroom to capture anything the microphone can handle. (If then you clip in the digital domain, the signal was ruined already when it got that far.) But if you use an external microphone, then it is another story.

if you're making CDs (16/44.1) there's no reason for going higher than 44.1kHz.

That assumes that even portable recorders have good enough highpass filtering and do not start way below 22.05? Otherwise there is a theoretical - though I would suppose insignificant - improvement from downsampling later.
(Is that a battery-intensive operation? If so, could it be that a portable device has chosen a compromise solution?)
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Re: How to get maximum performance from portable digital recorder?

Reply #9
I recently acquired a hand-held stereo linear PCM recorder for the purpose of recording different pipe organs. The recorder allows bit depths of 16 or 24 and sample rates of 44100, 48000 or 96000.

Having watched the primer videos at xiph.org I know that there is no obvious advantage in distributing files with greater bit depth or sample rate than 16/44100 for playback. I am also aware that on a portable device the effective bit depth of the recording will not come close to 24 bit. Storage space on the device is not an issue for me with the availability of cheap, high-capacity SD cards.

My question is which combination of sample rate and bit depth settings are likely get the most out of what I assume is relatively common ADC hardware? For reference, the recorder is a TASCAM DR-05, which is a $100 device.

I've been using portable digital recorders with some pretense of quality for about 10 years. Or, should I say that about 10 years ago I bought a first generation M-Audio Microtrack, and have used it for any numbe of live recording assignments, since then.

It turns out that the Microtrack does 24/96 which I have used on occasion for technical reasons. The Microtrack has about  98 dB dynamic range in 24/96. It comes close to the theoretical 93 or so dB limit of 16 bits.  So we're talking 5 dB of headroom difference, which is not a lot in practical use. In general, I record at 16/44 and never have felt like the recorder was holding back the quality of my work.  

The phantom power feature has gotten a lot of use. The issue of battery life needs to be considered. If I'm recording for more than a few minutes, I hook up an outboard battery pack just to be sure.

The most important technical parts of any live recording that you can control are the microphones you choose and how you position them. I have found that relatively inexpensive small diaphragm microphones get the job done very nicely.

The quality of the musicianship and the acoustics of the room you are recording in are issues that strongly affect listener pleasure, and that you generally can't do a thing about them.

Re: How to get maximum performance from portable digital recorder?

Reply #10
I have attached three files. Unfortunately the drawer didn't cut out all the road noise so there is a car sound towards the end of the file with max input level.

Re: How to get maximum performance from portable digital recorder?

Reply #11
I scanned your files and the screenshot shows the relative (which means look at their differences, not the dB value) noise level of your files.

Red: max
Yellow: middle
Blue: one_above_min
Green: Theoretical lowest noise level of 16-bit 96k recording (attached).

Assuming your drawer is quieter than the place you record the pipe organs, these are the best noise levels you can get. one_above_min is still slightly noisier than 16/96's limit, so I don't think it is useful to record in 24-bit. A lot of audio editing software, including the free Audacity, process at 32-bit floating point precision regardless of your files' original bit-depth, so there is no need to worry about if your files are 24-bit or not.

The test cannot show high sample rate performance though. Feel free to record some pipe organs at 96k and attach the audio files here, and tell us what level you use during recording.

Re: How to get maximum performance from portable digital recorder?

Reply #12
Record in the best quality the device can do

The OP is specifically asking about what combination is best. Are you assuming a higher sample rate is always better?

No, but you can always throw away, it's much harder to add back, plus storage is cheap. And OP didn't mention whether he needed to edit anything.

Will recording at 44.1 or 48 be bad? No, absolutely not.

Re: How to get maximum performance from portable digital recorder?

Reply #13
I scanned your files and the screenshot shows the relative (which means look at their differences, not the dB value) noise level of your files.

Red: max
Yellow: middle
Blue: one_above_min
Green: Theoretical lowest noise level of 16-bit 96k recording (attached).

Assuming your drawer is quieter than the place you record the pipe organs, these are the best noise levels you can get. one_above_min is still slightly noisier than 16/96's limit, so I don't think it is useful to record in 24-bit. A lot of audio editing software, including the free Audacity, process at 32-bit floating point precision regardless of your files' original bit-depth, so there is no need to worry about if your files are 24-bit or not.

The test cannot show high sample rate performance though. Feel free to record some pipe organs at 96k and attach the audio files here, and tell us what level you use during recording.
That's really helpful. Thank you very much. I have no doubt that the noise from the organ blower alone will be louder than the drawer where I made those recordings, so I suppose 16 bits should be enough.

As far as the sample rate is concerned, would I get better quality recording at 96000 and then downsampling to 44100/48000 with SoX for playback or should I record at a lower rate to begin with (bearing in mind that I am using a relatively cheap recorder)?

Re: How to get maximum performance from portable digital recorder?

Reply #14
As far as the sample rate is concerned, would I get better quality recording at 96000 and then downsampling to 44100/48000 with SoX for playback or should I record at a lower rate to begin with (bearing in mind that I am using a relatively cheap recorder)?

Just record at 44.1 or 48, and don't worry about it :-)

Re: How to get maximum performance from portable digital recorder?

Reply #15
If for some reasons a cheap recorder sounds worse than an expensive one after some double blind listening tests, the reasons are usually mic quality and flexibility (some recorders allow position and angle adjustment of their built-in mics).

Nowadays converter technologies are very mature, even budget (not faulty) ADCs won't ruin 44k recordings in audible ways when compared with SoX downsampling. 96k may still be usable if you need to record ultrasonic sound, or you need do edit the recorded files, e.g. change playback speed and pitch.

 

Re: How to get maximum performance from portable digital recorder?

Reply #16

As far as the sample rate is concerned, would I get better quality recording at 96000 and then downsampling to 44100/48000 with SoX for playback or should I record at a lower rate to begin with (bearing in mind that I am using a relatively cheap recorder)?

Everything is easier and nothing useful gets lost if you record at 44 KHz.

IME recording from internal mics is the opposite of high quality audio recording.  Worrying about sample rates, bit formats, and converter quality while ignoring mic selection and placement is a clear case of utterly misplaced priorities.

It is like ignoring the role of headphones and speakers in reproduction.

 
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