PDB audio amplifier?

smpl · 2011-12-11 05:54

I have the Professional Development Board and a VMusic2 Module. I am connecting the line L&R outputs of the VMusic2 to the audio input X7 on the PDB. The audio level on the internal speaker is so low that it is barely audible. I also tried an external 8ohm .5w speaker and I get the same results. So thinking there might be a problem with the VMusic2 output, I connected my IPOD the the X7 audio input on the PBD and again the same result. I need to turn the IPOD volume all the way up to even hear anything and still the audio level is super low. Am I missing something here?

Ron Czapala · 2011-12-11 06:03

Have you tried feeding the VMUSIC2 output into your PC's sound card "line input" or tried plugging headphones into the VMUSIC2 front panel jack?

I have had no problem with the VMUSIC2 sound level. The use the VSV command to set the VMUSIC2 volume level where 0=max and 254=min

See my Propeller VMUSIC2 project here: http://forums.parallax.com/showthread.php?135033-IR-Remote-controlled-VMUSIC2-MP3-Player

Falcon · 2011-12-11 06:05

Did you adjust that volume trimmer pot beside the speaker? I hate to ask such a question but I've been bitten many times by the simple things that seem to obvious to even consider.

I did use that PDB amp once to amplify audio from my TV but there was way too much static to be useful.

falcon

smpl · 2011-12-11 06:13

Yes, the pot is fully clock wise. LOL. I have tried the volume commands on the VMusic2 and when set to 255 I hear nothing and when set to 0 I barely hear anything. I have to put my ear 2" from the internal speaker to hear anything. Same results with my IPOD connected to it @ full volume which is way to hot of a signal for a Line Level Audio input.

Ron Czapala · 2011-12-11 06:33

The VMUSIC2 uses a VS1003 chip which according to the specs has a "stereo earphone driver capable of driving a 30 ohm load" - the minimum is 16 ohms.
Here is the spec sheet http://www.vlsi.fi/fileadmin/datasheets/vlsi/vs1003.pdf

Maybe 8 ohms damaged the VMUSIC2...

smpl · 2011-12-11 06:57

I am not driving an 8ohm speaker from the VMusic2 headphone jack. The VMusic2 also has L and R line out pins which I have connected to the X7 input on the PDB and an 8ohm speaker connected to the ext speaker connection of the PDB and the jumper set to ext..

Ron Czapala · 2011-12-11 06:58

Here is a video with my headphones plugged into my VMUSIC2 jukebox. Of course it sounds tinny when the camera is 2 feet away but the volume is certainly loud enough...

Direct link to HD video

[video=youtube_share;m2bv32JZ-ko]

smpl · 2011-12-11 07:10

Ron sorry but I am unable to view the video clip. When I press play it just says "This video is private.". Anyway, have you ever tried to use the Line Out pins on your VMusic2? I wonder if the line output pins are the same as the headphone jack ie.. looking for a 30 ohm load.

Ron Czapala · 2011-12-11 07:13

smpl wrote: »

Ron sorry but I am unable to view the video clip. When I press play it just says "This video is private.". Anyway, have you ever tried to use the Line Out pins on your VMusic2? I wonder if the line output pins are the same as the headphone jack ie.. looking for a 30 ohm load.

Opps - SORRY! Try it again. I changed it from private to unlisted...

I think the output pins and front jack are the same connection.

smpl · 2011-12-11 07:39

Ok video now works. Plenty of headroom. I need to get some headphones and do some further testing.

Ron Czapala · 2011-12-11 07:45

Good luck! I hope you didn't fry the output...
I am very happy with sound quality - it sounds as good as my Sony 300 CD changer on the home stereo.

smpl · 2011-12-12 08:00

Ok. It seem my VMusic2 module is ok. I connected the audio output to a 3W mono audio amplifier I got from RS and it works fine. I seem to be having a problem with adjusting the volume. This is what I found. BTW, I am using a BS2p24.

Using:
SEROUT 0,240, ["VSV 0",CR] 'Does nothing. Very quiet output.
However Using:
SEROUT 0,240, ["VSV ",0,CR] 'Outputs full volume.
Once I had full volume I tried this:
SEROUT 0,Baud, ["VSV 254",CR] 'Changes the volume however its not muted. Its the same as the first attempt. Very quiet output.
Also when I replace the value 254 with anything from 0 to 254 I get the same results. Very quiet output. All at the same very quiet output.

I think I have read just about every post on this subject and I yet to find a solution. Has anyone had success with the "VSV" command with
a BS2p?

Mike Green · 2011-12-12 08:24

From the Vinculum firmware manual ... maximum volume is 0x00. Minimum volume is 0xFE. This translates to the following statement:

SEROUT 0,240,["VSV ",volume,CR]

Use volume = 0 for maximum, volume = 254 for minimum. It makes no difference whether you're using a BS2p or a BS2. Only the Baud constant is different.

smpl · 2011-12-12 08:38

Worked like a charm.

Vol VAR Byte
Vol = 30 '(Any value from 0 to 254 ie.. 0=Full volume thru 254= Mute)

SEROUT 0,240,["VSV ",Vol,CR]

Thanks Mike.

Ron Czapala · 2011-12-12 08:51

Glad you got it working! It's always a good idea to post your code. I think 255 equates to mute - 254 is just the lowest volume - probably a "moot" point

EDIT: Actually, I think the VMUSIC2 defaults to full volume at power-up - if you had not tried to set it, it probably would have worked.

smpl · 2011-12-12 09:11

This all started because my PDB's built-in audio amplifier didnt seem to work well so I thought I had a low output from the VMusic2. When I changed my code to modify the VMusic2 volume level It still wasnt working like expected ie.. Low Volume. I then ran the audio output to a seperate 3W mono audio amplifier I got from RS and whola I was getting audio. Measured nom. 78dba @ 3 feet @ full volume. I think either I have a problem with the PDB's built-in audio amplifier or it simply wasnt designed for the application for which I was using it.

Thanks Ron.

PDB audio amplifier?

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