Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: 16bit / 48KHz PCM Audio Recorder? Posted:
Sat Jan 27, 2007 2:23 am
Joined: Sun Jan
21, 2007 4:57 am
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
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
OK, physical size is important. How do:
1. Cost (per unit)
2. Cost (to develop)
3. Power consumption
rank in importance to you?
Do you need stereo/5.1/7.1/other
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).
Posted: Tue Jan 30, 2007 4:10 pm
Sun Jan 21, 2007 4:57 am
Power is supplied
by three AA 3000mAh batteries for a total of 3.5v - 4v.
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
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
Oops, my fault in not asking the questions
When I said "volume" I meant like "cubic inches", not
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.
Post subject: Posted: Tue
Jan 30, 2007 9:59 pm
Joined: Sun Jan 21,
2007 4:57 am
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.
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.