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    Kirt Blattenberger,


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Post subject: 16bit / 48KHz PCM Audio Recorder? Posted: Sat Jan 27, 2007 2:23 am


Joined: Sun Jan 21, 2007 4:57 am
Posts: 6
I'm trying to build a PCM (wav) audio recorder that would have some basic controls like record (duh), play, pause, next track, previous track and have the ability to start a new file for each recording. I'm looking for the absolute lowest noise floor possible, that's why I'm not hacking an mp3 recorder or some such consumer device.

The main goal here is to have the smallest recorder possible because of limited space inside the housing of a wideband radio receiver.

If anyone can give me some pointers on where to start, schematics, parts, a rough block diagram, it'd be nice.


Post subject: PCM recorderPosted: Tue Jan 30, 2007 1:37 pm


Joined: Wed Feb 22, 2006 3:51 pm
Posts: 104
OK, physical size is important. How do:
1. Cost (per unit)
2. Cost (to develop)
3. Power consumption
4. Volume
5. Total recording time
rank in importance to you?

Do you need stereo/5.1/7.1/other multi-channel recording?

Do you need analog playback, or does the signal get out of the recorder in digital form (for example, SPDIF)?

What about monitoring what's recorded?

Are there any available resources in the receiver that you don't have to implement for your recorder? (I assume power supply, but there might also be program storage space, so that a flash EPROM wouldn't be necessary - a program could be downloaded onto a single-chip microprocessor or DSP).

Good luck!


Post subject: Posted: Tue Jan 30, 2007 4:10 pm


Joined: Sun Jan 21, 2007 4:57 am
Posts: 6
Hi Fred,

Power is supplied by three AA 3000mAh batteries for a total of 3.5v - 4v.
Volume is not really a factor since the output from the receiver will be soldered directly to the recorder's input. In other words, this is going to be a straight line level (about 200mV) audio connection. As far as channels are concerned it doesn't have to go beyond stereo, so 2 channels should be enough.

Analog playback will not be nessecary. In fact, a mini USB connection would be ideal for file transfers to a PC.

The receiver uses a Mitsubishi M38267M8L-256GP CPU and an Asahi Kasei Microsystems (AKM) Serial CMOS EEPROM model AK93C10A along with a Rohm DTA144EE Digital Transistor.

Some other components of note are: TI Differential Opamp & M35017-001FP On Screen Display.


Post subject: RecorderPosted: Tue Jan 30, 2007 9:17 pm


Joined: Wed Feb 22, 2006 3:51 pm
Posts: 104
Oops, my fault in not asking the questions clearly.

When I said "volume" I meant like "cubic inches", not dB!

How long does it need to record for? If it's seconds, some chips have enough memory on-board. Minutes implies external RAM, hours implies Flash - so it's important to know the size of the records.

sounds like power efficiency is critical, too - at 11 Watt-hours battery, you couldn't use a 1W DSP, for example.

Good Luck,


Post subject: Posted: Tue Jan 30, 2007 9:59 pm


Joined: Sun Jan 21, 2007 4:57 am
Posts: 6
I'm aiming for 4 hours of storage, so a flash based storage system is a must, either NAND, SD, or CF. If space becomes an obstacle then I can make the housing a little taller and wider to accommodate all the components. It's a cast magnesium alloy and I have a place that can do that from a 3D CAD file.

Volume wise, I can only think of a rough figure right now, something in the neighborhood of 6 cubic inches; 3L x 2 W x 1H.

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