Trying to make sense of the SD card

[Paul Steel]

I just purchased a DP-24 for use in church. I am frequently going to be recording 6+ tracks simultaneously for long periods of time. So, the 2GB card is too small. I am using a 32GB card (Sony SF-32NX class 10) and I formatted it using the long format (took forever) and it showed that I had 100:47 (hhh:mm, from what I calculate) of recording time. When I arm more than one channel it immediately drops to 6:45 and no matter how many tracks I arm after that, it remains at 6:45. I expect it to drop as I add armed channels, but not to stay at 6:45 with 2 or more armed.
What am I doing wrong? I even reset the device to factory settings in case I had changed a required setting.

 

[cmaffia]

Please tell us what it drops to as you add 1 track at a time. For example:

No armed tracks: 100:47
1 armed track: ?
2 armed tracks

etc

 

[Paul Steel]

Please tell us what it drops to as you add 1 track at a time. For example:

No armed tracks: 100:47
1 armed track: ?
2 armed tracks

etc

None 100:47
1 armed track 100:47
2 armed tracks 6:45
3 armed tracks 6:45
4 armed tracks 6:45
5 armed tracks 6:45
6 armed tracks 6:45
7 armed tracks 6:45

I did have the tracks grouped, but also tried it without groups assigned.

 

[cmaffia]

and what happens when you start recording on these tracks... what time is left..one by one..

 

[Paul Steel]

It counts down correctly minute by minute. I wasn't expecting it to drop immediately to what I would expect from a 32GB card recording 8 track simultaneously, when arming the second track. Just confused . . .

 

[cmaffia]

I think its only an estimate until it starts recording. I believe this is working as designed.

 

[Paul Steel]

Odd, but I'll take your (experienced) word for it until I can come up with a better one. Thanks for your speedy responses to my questions. I will post back to this thread if I find out any other details.
Thanks again

 

[Jeff Brunton]

I also replaced my SD card with a 32GB one and noticed the same thing on my DP-24. I'm no expert but the way I understand it is there is a 6 hour 45 minute limitation for each song created. So even though your 32GB SD card gives you over 100 hours recording time you will only get 6 hours and 45 minutes for any given song loaded. I am speculating from my own experience so if anyone out there knows otherwise please jump in and correct me.

 

[Paul Steel]

After doing some more research I have discovered (I think) that there is a 2GB per file maximum filesize. If you do the math for 44.1Khz x 16bits it works out to be around 6:45 (hhh.mm) see the chart below. Between the three of us, I think we now have a solid reasoning behind this dilemma.

http://www.audiomountain.com/tech/audio-file-size.html

File size per minute is calculated as:
Bitrate: 44.1(kHz)x16(bits) = 705.6Kbits per sec
Bits to Bytes: 705.6Kbits per sec/8(bits) = 88.2KBytes per sec
Seconds to Minutes: 88.2KBytes per sec * 60(sec) / 1024(KB) = 5.168MB per min

2GB = 2,048MB so 2,048MB/5.168MB per min = ~396 min or 6:36 (hhh:mm)

Makes sense now! I think this solves the mystery.

Thanks cmaffia and Jeff Brunton