Increase Digital Volume

Project: Increase volume level of the SID's digital output
Target : C64 (new boards with 8580)
Time   : 20 min.
Cost   : <1 US$
Use    : Make digital voice (switching volume on/off rapidly) as
         loud as the other ones so that it will not be drowned out.

Summary

Details

Ingredients

• 1 330kohm resistor (value not necessarily optimal for your machine)

  optionally:

• ~30cm of two-core cable
• 1 single-pole switch

Instructions

1. Select a tune containing a digital voice (e.g. Iron Maiden), listen to it and remember the volume.
2. Pull off all cables and open case.
3. Solder the resistor between pin 26 (EXT IN) and pin 14 (GND) of the IC socket carrying the SID, optionally via the switch. If you have a potentiometer, you should try this first. When the volume of both digital and non-digital sound is okay (is about equal), measure the resistance of the potentiometer and solder in a resistor of that value.
4. Listen to the selected tune again and check the volume. Listen to non-digital music, too, and check if the volume is roughly as loud as the digital volume.
5. If the volume seems to be okay, close the case again, otherwise experiment with the resistor's value (or use a potentiometer).

   Note! The smaller the resistor's value, the more silent is the non-digital music, so you have to check BOTH the volume of digital and non-digital ('normal') music when you experiment with the resistor's value!

Possible failures

• Connected resistor to wrong pins - ARGH!

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