Duocast almost working

bloke_zero

New member
I'm having some issues with my Duocast build - there is a terrible jagged hum overwhelming the base sound.

The low cut works, the lo channel works (but with a massive hum) and the hi channel seems to have no effect. I can't see any solder bridges and the parts all seem correct. But voltages not quite right - I'm getting 8.4V and 33V on the switch. Could the 50 year old mallard OC71 be dead? Or my BC549C wrong way around? I assume the red dot above the leg on the OC71 goes next to the square on the PCB?

Sound passes through and the LED's light correctly.

The solder side has some rosin but I've checked carefully with a jewellers loupe for bridges. Apologies for such an ugly build!

IMG_0258 s.jpg IMG_0257_s.jpg
 

bloke_zero

New member
Man alive! I had the input and output wired wrong. Sounds great with the Mullard OC71. I really like the 9V sound but would be upset if that was all it did - the higher voltage adds an amazing amount of body. Really digging it on bass with a lot of low cut.
 
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