There have been some complaints in recent times about the quality of the 
dual audio pot. (At low volume setting the two channels are badly 
unbalanced.)
Also, this pot is difficult to source. (Only two sources, both with long 
lead times.) 
Also, this pot is not cheap ($2.25-$2.50).

		??? IDEA ???
Replace the pot with a 256 position electronic audio volume control. The
components would be : 2 DAC-08 ICs (one for each channel) $0.80 each, 1
74ls273 @ $0.30 and about 8 discrete compoments ($0.01 each). Total component
cost is $2.00 and about $0.16 for the extra board space. 

How it would work. 
Putting the game into self-test after power-on would cause a volume 
adjust screen to come up. The volume would be adjusted using the regular 
control panel controls (maybe while the game goes thru an attract sequence 
with audio enabled). The volume level would be stored in the game EEPROM. 
On power-on the volume level would be set from the EEPROM.

I am considering this as a direct possibility on the new SA (stand alone) 
Audio board currently in development for Catacombs and probably a few other 
games. The only disadvantage that I see is operator familiarity and ease 
of use. I am sure that many of you see other problems.

What do YOU think.
Replies to theis address will be appreciated.
						Pat Mc Carthy.

Thank you for your comments and suggestions on the digital volume control 
suggestion. Those replys can be seen in [mccarthy.psu]dacpot.txt.

The biggest concern voiced was "lack of familiarity and ease of use". The 
other major concern was "what if the 6502 goes crazy and turns up the 
volume to the max".

As stated before I basically agree that ease of use is a major issue. The
best solution I have is to put either a two way return to center toggle
switch or else two buttons inside the coin door, for VOLUME UP and VOLUME
DOWN. I am considering membrane switches for this purpose (plus the extra
functions of 'aux credit' switch and 'enter self test' switch. This
membrane panel would either stick to the audio PCB, or it could be remotely
mounted (stuck to a cleat) near the coin door. With this arrangement, there 
is no need to enter self test to set volume.

I am also looking into the idea of an interlock on the volume latch to 
avoid the problem of the 6505 going crazy. Two writes would be required to 
change the volume level.

Here is a summary of the other changes that are being made to the original 
design, based on the well attended design review held on Jan 15.

. The address bus buffers were removed, (deemed not necessary)
. The data bus buffer was removed, (deemed not necessary)
. The spare 27256 ROM socket was removed. More than 32k bytes of program 
   memory requires the use of a 27512. 
. The IRQ counter chain design was not altered. (The alternatives suggested 
   were either not feasable or were too costly.) 
. IRQ acknowledge was added. (This was inadvertently left out)
. The audio op-amps supply voltages were heavily filtered.
. The CPU can be run from either 1.79 Mhz or 3.58 Mhz. When run from 3.58 
   Mhz, the cpu must be a 65c02 (cmos version). 
. The Bank select and address decode circuitry was simplified to a single 
   PAL ic.



			Pat.