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--- troubleshooting [2026/02/18 20:11] – sol
+++ troubleshooting [2026/07/17 21:00] (current) – [Only left audio channel from 3.5mm jack while A/V jack connected] fritigern
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 If you are wanting to use GEOS or any other program that requires the REU, you may need to double check the address for UltiSID 2.
 Out of the box, UltiSID 2 was at $DF00, which conflicts with the C64U's built-in REU and causes programs to not see the REU. Instead, I move UltiSID 2 to $D420, and it now works flawlessly.
-  * To get there: C64U Menu - Audio Setup - SID Addressing - UltiSID 2 Address.
+  * To get there: C64U Menu -> Audio Setup -> SID Addressing -> UltiSID 2 Address.
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 When an A/V cable with mono audio is connected to a CRT monitor, the 3.5 mm audio output on the Commodore 64 Ultimate only plays the left audio channel. If the A/V cable is unplugged, both left and right channels work normally through the 3.5 mm jack. Some original custom Commodore 64 A/V cables were wired so that AUDIO IN (pin 5) and GROUND (pin 2) are tied together to reduce interference. The Commodore 64 Ultimate, however, repurposes pin 5 as the right audio channel (see User's Guide p.205). When you plug in one of these older-style cables, pin 5 is shorted to ground and silencing the right channel entirely.
   * **Solution:** Use an A/V cable designed specifically for the Commodore 64 Ultimate, or one that does not connect pin 5 to ground. Once the correct cable is used, both audio channels will work normally from the 3.5 mm output.
+===== Dual SID files sound horrible, or only one channel can be heard   =====
+Make sure that you have the following settings in Audio Settings -> SID addressing:
+  * SID 1 : Unmapped
+  * SID 2 : Unmapped
+  * UltiSID 1 Address: $D400
+  * UltiSID 2 Address: $D420
+  * Auto address mirroring: Disabled
+The options that were NOT mentioned do not affect the ability to play dual/stereo sids.
 {{tag>troubleshooting GEOS REU wifi audio}}