CD quality field recording rig

Describes how to assemble a field recording system that is: battery powered, capable of six hours continuous record without recharge (and much more from the wall), CD quality (44.1 kHz 16 bit stereo), less than U$1000, and capable of being concealed in a handbag, backpack or jacket.

Step 1 Get your stuff: Nomad

In our world of excellent quality, tiny digital cameras and videocams, one would think there would be similar development in audio recording also, but that just isn't the case. While there are a few solid-state recording devices, they are expensive or large or both, and rely on compact flash, with its limited capacity.

With a little shopping around, however, one can put together a unit that meets requirements. This is possible for one reason, and one reason only: the Creative Nomad Jukebox 3. This product, long discontinued, is the result of audio engineers known mostly for their sound cards, interfaces and other geek toys being turned loose on the consumer mp3 player market. The resulting device is the antithesis of the iPod: heavy, built to resemble a portable CD player, and covered with ports: a headphone port, two line outs, and a line in that accepts optical and 1/8", FireWire, USB, 5vDC and IR port (turn this off). It is that optical port that enables the one function which makes this the Must Have Item: the njb3 records optical 16 bit signals as .WAV in 48 and 44.1 kHz stereo. Hallelujah.

The njb3 has other key advantages: it comes with one lithium ion battery pack, but can be converted over to two, giving an actual six hours of record time. Equally cool, it has a standard 2 1/2" laptop style hard drive and can be easily upgraded. The stock 20 gb is good for 30 hours or so of .WAV, and it's all capacity from there.

The optical port is the main thing, though. Many mp3 players, including the njb3, can record line-in sound or even provide a preamp. The resulting recordings suck: the A/D converter is the cheapest one they can find, and rightly so, since the hard drive noise is going to ruin your recording anyway, as will the electrical noise. This is not the way; although this rig will allow you to run in a 'stripped down' mode that looks a whole lot like listening to a CD player, the quality must be improved by an outboard AD converter in order to meet our spec.

The njb3 is no longer produced, but many new-in-box units exist and creative still sells batteries off and on...someone will eventually pick up an aftermarket for these batteries if Creative drops the ball, because as the eBay price for a used one will show you, these puppies are coveted. As for other mp3 players that can do the trick, Neuros is waffling on a digital in for the Neuros 3. Express your preference that they do this, because then we will have no longer to deal with the quirks of a long out-of-production proprietary codebase. There are no other contenders, to my knowledge. Your Nomad should cost around U$300.

Comments

[gokufast]

same image in all the steps

[paulpropst]

The Gemini IKey USB audio recorder does the same for about $130 street price. The one I use is so simple it can only record. If you want to play back the files (mp3 or wav 16/44.1) you have to remove the thumb drive and play it on another device. I comes wit a stereo mike, RCA inputs for line sources and a headset jack for monitoring. I think a newer version than mine (about a year old) may have more features. I use the aux outs on a small mixer. This lets me use condenser mikes, etc.

[kuuan]

Hi atman,nice set up. I am also just trying to set up a rig for recording while travelling: it must be very portable, long recording time, long power etc..even though I learned that the A/D of an HiMD should be superior I opted for an iriver H120 for it's onboard storage and drag+drop functionality. I also just bought SoundProfessionals SP-CMC4s and an SP Battery Box ( used, not yet arrived ) Can you please tell me, just how much does the AD-20 improove on the quality of your recordings? I also want to record 'ambience' and therefore need a system of very low 'self-noise' and I am wondering if I will need the AD-20 for that or if I can avoid the additional bulk and weight. and: from where did you get that cable adapter to connect your mics or battery box ( mini stereo ) to the 2 mono XLR of the AD-20? Or did you make it yourself? If so, could you tell me how to wire it?

[atman]

If the iRiver has a digital input, the AD-20 will improve performance, as explained in the instructable and comments. If it does not, this device is not likely to be helpful to you. The cable adapter is from Sound Professionals.

[omgnotanotheraccount]

For around the same money I'm using an Edirol R-1 ($440 street price) with a Sony stereo mic, plus a couple of large CF cards. The R-1 is a very sweet little unit. Among other things it has a lock feature so you can set it to record, turn on the lock, and throw it in your pack, and even if any buttons on the unit get pressed while it's in your pack, it just continues doing what it was set to do. It can also do digital out (optical or USB) so if you wanted to you could hook it up to an external storage device like the Nomad, but I haven't tried this. Next on my to-do list is to make an external D-Cell power supply, since the R-1's battery life is only around 2 hours. Nice thing about the R-1 is if steath is required, it's just one wire to a mic, that's it. Simple. And if stealth is not required, the unit has quite good built-in mics on board, and since it's solid state (no spinning hard disk noise) it is dead quiet. Plus it has 24-bit recording if you need it. And long duration as well (assuming an external power source). I can get 24 hours with MP3/192, which is pretty decent quality. I like CF cards because instead of having all my eggs in one basket (a large hard disk that could get stolen, lost, confiscated, etc.) the data can be put away safely after it is recorded. But SD cards would be even better. Actually to talk about dream audio recording setups, my dream setup would have some sort of reliable short-range wireless data capability so the recording could be done by one person while the storage was done by another person. Thanks for the article! Great to learn more about some of these devices.

[Myself]

Ooooh, the short-range wireless is genius. Bluetooth A2DP should make this trivial. You could even put the left and right mics on different accomplices and get really crazy with the stereo separation! I wonder if any cellphones have audio hardware that's a bit more capable than is required for a phone call. That'd be the ultimate in stealth, since the mic and bluetooth radio are already there. Quality is doubtful though. I can picture some sneaky mods to improve preamp / ADC quality without being externally detectable...

[mungo]

How do the Nomad Jukebox 1 and 2 stack up against version 3? They both seem to offer toslink digital in. Do they offer equal recording quality, or do they have some other problems?

[removed1]

Simpler and cheaper solution (on one hand): Buy a HiMD recorder, plug a portable mic straight into it. With a unit like the RH10, you can use the internal battery + an alkaline AA to keep recording for over 5 hours at 16-bit 44.1kHz LPCM (and over 10 hours @256kbps atrac3plus, which is more than sufficient for non-purist recording of any kind). The recorder and a mic (such as the earworn SP-TFB-2 binaurals that I use) will cost less than $450USD. Additional 1GB discs can be found for between $5-10USD. Has optical in and thus can be used with external A/D if so desired. The caveats: having to use SonicStage to upload your recordings (which, if you have more than a pea for a brain, isn't a problem); slow upload/download speeds (a restriction of the magneto-optical media used); no direct XLR inputs or Otherwise, the recorder fits in your pocket, doesn't require any additional external hardware at all for most portable recording situations, is cheaper than any other current solution available, and makes remarkably high-quality recordings for something that fits in your pocket and runs off one battery. And it outperforms the M-Audio recorder. For the budget-conscious, there is literally nothing else currently on the market that can compare.

[Rob D]

I am really impressed with HiMD recorders as well-- even for very demandning applications like recording ambience in quiet locations. For me, quality starts with the preamps and pres in the HiMD recorders have exceptionally low noise perfromance-- low enough to allow one to use noise condenser mics with 12dBA self noise without the mic pre contributing noise. For recording ambience and soft sounds, the preamp's high gain of 75dB can provide bit depth saturation and effective resolution greater than recorders with 24 bit recording because these units often have 53dB gain or less. Its understandable that people would be sceptical that a <$200 recorder could have such quality, so I made "a hear it for yourself" test in which a pair of very low noise Rode NT1-A mics (5.5 dBA self noise) are first run through a Sound Devices 722 recorder and then through a ($70) Rolls PB-224 phantom power supply and into a Sony NH900 HiMD's mic input. The M-Audio Microtrack recorder is also included in the comparison. http://tinyurl.com/894ke (4mb quicktime movie) For long duration recording, HiSP mode supports 7 hours and 50 minutes of ATRAC 3+ quality which, if saturations are kept high, is of surprisng quality. Rob Danelson

[atman]

The biggest caveat, from my perspective, is that a 1 GB disk will simply not enable a six hour recording session, nor will a gumstick battery. The HiMD is another DAT killer; good for it. The optical in marks in its favor, but one needn't be a purist to ask for CD quality and get it; one might be planning to release the recording in CD format, or planning to extensively post-edit the sounds, perhaps as samples, in which case one wants as much bit depth as possible. There is no way you're going to get the kind of quality A/D conversion that a dedicated preamp A/D will give you, not with that minidisk spinning millimeters away. This is probably okay though, for applications under two hours. The truth is, you have a lot of options, in that department. DAT still has some juice in it; anyone want to bring it up? You can make a CD quality recording with DAT, still, to this day...if you don't mind it being under two hours.

[atman]

Purps here has done the research. The deal with the AD-20 is that its noise floor was designed to be at/around 16.5 bits. What that means is that with truncation, perfect signal with analog dither results. So, were I to upgrade to the corresponding phantom supply and a good set of condenser mikes, which would cost as much as my rig or nearly so, I could have nothing but signal, all the way down. That would be dank; as it is my mikes aren't really good enough to take advantage of this, I've probably two bits of noise on there as an estimate from what others have found. I have a recording of the kitchen sink online:

http://xenetix.net/files/mu/water.wav

If you have some nice gear, try that out on it.

Yah I don't look ghetto when I'm using my rig, more 'scruffy Burner' than anything. As for the mAudio unit, I do believe it's been mentioned.

[PurplePeople]

I have to admit that the Deneke pre-amp specs out really well, especially compared to the m-Audio, which seems to be the cleanest of the CF recorders. Notice that Roland does not publish the noise specs for the Edirol... always a sign of bad work... and that iKey, it's a bit iffy at more noise than my power amplifiers.

[gthing]

Yea this project looks way too expensive. How about 96Khz recording at 24 bit for half as much and you don't have to look ghetto when you use it.

http://sewelldirect.com/maudio-microtrack-mobile-2496-digital-field-recorder.asp

[spinach_dip]

more on the i-key. there is a good discussion here: http://www.audiomastersforum.org/amforum/viewtopic.php?t=4417&highlight=ikey

manufacturer claims specs as follows:
Records wav files at 44.1k 16-bit
Dynamic Range 98dB
THD & Noise -91dB
Frequency response 20Hz - 20kHz (amplitude limits not quoted)

quoting SteveG in regards to measurements he made of his i-key: If you do an A-weighted measurement (of the ikey), it comes out at -84.3dB, and the dynamic range is 81.4dB. But it's a messy noise floor, and it rises up more and more the lower you go in frequency - which is why the A-weighted figure is a lot better than the observed noise floor in Audition.

[atman]

I-key looks pretty slick! I doubt the qualiy of the .WAV is up to the spec of the AD-20, since it's native 16 bit rather than the fancy handwaving 20 bit truncated noise floor business, and you'd need to preamp your mikes somehow, but hooking mics to a preamp, to an i-key, to a portable hard drive, strikes me as a doable system for a couple hundred dollars less...I'd want to have an audiophile run some reference noise through both A/Ds for a conversion before deciding this was a better approach, but it'd work for sure. I've had eeensy bitty media cards go missing on me; it sucks. Nomad can be backed up to a computer off Windows, Mac and Linux with downloadable software; when it's in the field, it rides in the same case as all my other audio stuff, which I protect. Avoiding eggs in one basket is a noble ideal, but when backpacking, this is by definition how you operate. I buy the biggest memory card for my camera for the same reason. If confiscation is a concern, the fact that the Nomad looks like a CD player would be a major point in its favor, I would think. I didn't mean to dismiss compact flash units so quickly, but they simply aren't what I am talking about. It's been nearly a full year since I put my rig together, but I recall the Edirol and Marantz units being around U$800 then. At the state of the art, Compact Flash units are DAT killers; they don't go where the Nomad goes or do what the Nomad does. The question you ask is: Do I anticipate recording for more than two hours? If not, you can optimize on a CF system, get good rates and invest in a couple thousand dollars of audiophile equipment to enjoy your high-rate recordings. If you do intend on recording for three or five hours, shenanigans will ensue with a Compact Flash, where the Nomad will truck on. This is a combination of storage capacity and battery life, basically; there are ways of getting around both, which would get complicated enough to warrant an Instructable documenting this improved rig! On a single weekend in Bangkok, I recorded a Muay Thai fight, market sounds, a substantial amount of Thai classical music, and monks chanting sutras at Wat Arun. I lacked the right adapter to charge while I was there; the Nomad made it possible. It's a good little solution provider. I'm still looking forward to seeing it replaced with newer tech; if Neuros follows through I'm going to be stupid happy about it.

[spinach_dip]

How about this for $150: it only RCA inputs and has no built in storage. instead it relies on USB storage device, a memory stick or a portabe HD.
http://www.ikey-audio.com/ikey.htm

[atman]

Nomad has twice the battery life and as much as 30 times the storage, and costs half the M-Audio unit. Your 4 GB is going to be eaten up pretty quickly at 24/96, making this essentially like a DAT in that you have to change media every hour or so. You can get around this by recording at CD quality, thus extending your recording for the duration of the charge (three hours maybe). This rig was meant to be taken to Asia; I wanted to have excess capacity and Loooong times between charges. If optimizing for stealth, a compact flash recorder is a good choice, and the M Audio one is the only one I'd call affordable. If you want to be able to take six hours of audio recording a day for 30 days straight, you're going to need a Nomad. It's aptly named. Also (wax technical for a second here) if the specific goal is CD quality audio, which it is (vide title), you're better off recording at the native sample rate than recording at a higher sample rate and truncating/interpolating to fit. That is, something recorded at 44.1 will sound better than a 44.1 interpolation of a 96 recording, while of course the 96 will sound better than the 44.1, assuming good hardware and ears undamaged by nasty grungy Detroit rave parties. This is why 88.2 exists, granted, and the M-Audio does support it. The M-Audio unit can make a better one-hour recording than the Nomad, and is a smaller solution for a three-hour one; it can't make a six hour recording at all, and it can't make a better CD quality recording, either (as set up with preamp). Six hours, for the record, is a number I've achieved in the field, not a spec number. But it is small, and sleek, and functional, so thanks for mentioning it.

[Dan Patey]

Yup, my 3rd Gen iPod with iPod Linux has been great for me at concert's lately. Granted this route will give you much more space and a slight increase in sound. Great article!

[PurplePeople]

M-Audio compact flash recorder. Maybe only 4GB microdrive storage but about the size of your basic Altoids tin.

[PurplePeople]

M-Audio compact flash recorder. Maybe only 4GB microdrive storage but about the size of your basic Altoids tin.