I recently got SpikeOut running in my Blast City, and one of the problems I came across was getting the sound correct. I only had pictures of the hardware to go on and trying to copy that was a bit difficult. So I fumbled around with 2 of the smaller mixers but it wasn't to my liking. Finding the schematic was almost impossible, I say almost as I did mange to find them in the finish thanks to Mo at Videotronics. 
Because SpikeOut has front + rear sound effects combined with a DSB2, if you don't use the mixers the game expects then the music will be too loud which in turn drowns out some of the sound effects such as the speaking. You can get away with using 2 of the smaller mixers, but when you use the larger mixer combined with the smaller mixer the sound levels are perfect.
Anyway, rather than sit on the schematics so no one else can benefit from them I've scanned them and uploaded them to this thread.
I hope they are useful to someone out there. The schematic is for New Astro City, but if you have a Blast City with a Model 3 loom then all you need is the bits for the DSB2 + mixers.

Because SpikeOut has front + rear sound effects combined with a DSB2, if you don't use the mixers the game expects then the music will be too loud which in turn drowns out some of the sound effects such as the speaking. You can get away with using 2 of the smaller mixers, but when you use the larger mixer combined with the smaller mixer the sound levels are perfect.
Anyway, rather than sit on the schematics so no one else can benefit from them I've scanned them and uploaded them to this thread.
I hope they are useful to someone out there. The schematic is for New Astro City, but if you have a Blast City with a Model 3 loom then all you need is the bits for the DSB2 + mixers.