Holiday PCB build

[Dandy]

I'm just about to assemble a PP EL84 amp, using a nice PCB design from Germany. I'll attach the schematic.

My first question: the B+ required is only 230V which is diode rectified. 6.3V for all the filaments (4 x 12AX7 and 4 x EL84). As my line voltage is 240V, can I insert this directly (i.e. without a HT transformer), and just use a small transformer for the 6.3V supply?

 

[gadget73]

Not safely. One side of your line cord would become B-, which is usually chassis ground. Get between that and earth and you have 120 vac. The transformer will provide isolation from that situation so you won't shock yourself to death.

 

[Renslipevol]

I'm with Gadget. I would use a transformer as well. That way you can also earth ground your chassis. Also, you can use a 1watt, 220R from your floating ground to chassis ground. I've done this with all of my builds, never had a problem with hum either. Just make sure you don't ground out the RCA's as they go through the chassis.

 

[Dandy]

Thanks gadget and rens for the sound advice. I'll abandon that idea. Somehow, looking at the PCB in isolation made me overlook the obvious need for isolation! Back to the drawing board, as my spare transformers are all 300-0-300.