Hi PJ,
OK if it is for safety reasons (with respect to not running it off the main transformer) , then provided the switch transformer had enough grunt to run the additional circuit (I note it is only 1.5VA) then I would say it would be ok to piggyback off that (again assuming that there is some sort of regulation on the circuit or that it can run over a range of voltages). Probably best to pose the question on the ESP forums  If you can save one transformer it is probably worth it... They can be noisy, not to mention the extra $$$.
I did note the discussions around safetfy ground on your main thread (I assume this is why Stuey has posted the earth loop article) . I can't remember the handle of the person wanting to earth the rca's to the chassis, but I can definitely say from experience that this will almost certainly result in very loud hum!  My first DIY amp which I made in 1984 had this problem. The hum was so loud that I had trouble hearing the music
I ended up implementing the earth loop breaker which Rod Elliot suggests on his site for my Gainclone. The reason was that I was hooking it up to my PC, and it hummed with just standard safety earth connection (most HI-FI components (at least in aus) don't have 3 pin power plugs, so earth loops generally aren't a problem, but a PC does have a three pin plug, and so does an amp. With the earth loop breaker it is dead silent
Tony.
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16th August 2009, 08:30 AM
. But a useful resource. Thanks Stuey.
My first DIY amp which I made in 1984 had this problem. The hum was so loud that I had trouble hearing the music 
