Good news everyone!
I've got the volume working properly over line out. Only in Win98 and DOS for right now, but it shouldn't be too hard to make a Linux initialization routine to do it.
Basically, the BT835 chip has a number of general purpose I/O (GPIO) lines. For those that don't know, systems designers can pretty much use them as they see fit to control or monitor other parts of the system. Well, GPIO6 is tied to the output system. It must be raised in order for the sound to come out at full volume.
I'm not sure what purpose this serves, but I suspect it was designed this way to prevent irregular output to your receiver during system initialization. Perhaps, it even offers a bit of protection. I only wish they tied it to the GPIO pins on either the 5530 or Cyberpro because both are much easier to program. Programming them on the 835 is a little more complex because it is tied to the Cyberpro via an i2c connection and that is how you program it. Fortunately, these tools are already here for us!
First, you'll need to download either i2c.exe (command line, ideal for autoexec.bat) and/or 5ktvio.exe from
To use the command-line version:
C:\> i2c 88 22 0
C:\> i2c 88 21 40
The first command tells the BT835 to use all GPIO pins for output (really only 6 and 7 are tied to anything).
The second line raises GPIO6 (1 shl 6)
To use the Windows version, execute 5ktvio.exe while running Win98. I'd suspect it'd work just fine under Win95.
In the I2C section of the application, do the following:
1) Set addr to 88
2) Set subaddr to 22
3) Set data to 0
4) Click Send. Result should show OK.
5) Set subaddr to 21
6) Set data to 40
7) Click Send. Result should show OK.
8) Run your favorite audio application.
On a side note, the LED labeled Connected on the front of the box is connected to one of the GPIO pins on the 5530. We should be able to make it display disk or network activity.