Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JustMike on May 27, 2024, 10:27:33 am

Title: Yamaha Soldano Buffered FX loop (can't read schematic)
Post by: JustMike on May 27, 2024, 10:27:33 am

 Can one of the smart guys figure out what the value of this R is coming off cathode 2 (pin 8) of this (R3) is? I know it makes up part of the voltage divider that feeds the loop. I just can't read this old scan. It looks to be either 100k 0r 180k.
 I had one of these amps a while ago and the clean channel sounded really good. I'm trying to build one out of an old Peavey Triumph 120 donor amp (and attempting to use the old PC board- a tedious process!).
 Sorry for the rotated pdf. My free reader won't let me "save rotated".
 Thanks,

Title: Re: Yamaha Soldano Buffered FX loop (can't read schematic)
Post by: tubenit on May 27, 2024, 01:58:50 pm

It's 100k


Yamaha_t50_t100.pdf (el34world.com) (https://el34world.com/charts/Schematics/files/Yamaha/Yamaha_t50_t100.pdf)


With respect, Tubenit

Title: Re: Yamaha Soldano Buffered FX loop (can't read schematic)
Post by: JustMike on June 02, 2024, 10:25:31 am

Thanks Tubenit. That schemo is much clearer than mine.
 So in tracing the clean channel, there are a couple of things I don't quite understand. It looks to me like the path is V1a (gain)>V1b (gain)>HUGE attenuating R (5.6M)> V3a (gain)>V3b (fx buffer, no gain)> V5a (tone stack buffer, no gain?)>P.I. Does this sound right?


 I'm beginning to think that this may not be the best template for a clean channel only design since it looks to me like the 5.6M attenuating R is there because of the signal path that's shared with the OD channel. But I'm intrigued by the late stage tone stack. What impact does this have on the clean channel sound?