You're referring to the more detailed schematic of course. http://www.nutshellhifi.com/Karna.gifizzy wizzy wrote: ↑Mon Jan 07, 2019 2:01 pm Look at the input grid point. That's referenced to earth and then to both the other stages star points albiet the 2nd stage shares the 0V and supply. I imagine your 2nd and 3rd stages would be referenced to the input grids as he has done with his 3rd stage.
Cheers,
Stephen
Lynn (actually Gary Pimm did the grounding design) follows what I'd picked up as the mantra ... "though shalt have only one chassis connection, and that shall be at the input point". However the similarities start to break down. For a start he shares power supply between input valve (6H30 etc) and driver (45). But yes, the centre taps of the signal transformers are referenced back to that chassis earth connection by the input tx. His RCA input floats across the input TX primaries and so is not grounded, while he doesn't show XLR pin 1 grounded at all. Also my chassis is wooden - any exposed metal is connected to safety earth at the mains input.
My plan is ...
- 26 local star at base of cathode resistor
- XLR input pin 1 to 26 local star
(I plan to make this liftable as I'm never sure whether this makes a ground loop with the previous equipment or not)
- Input TX C/T to 26 local star
- PSU return path from 26 local star to LCLC
- heavy gauge connection to Channel Star Ground, thence to mains earth
- 71A local star at base of cathode resistor
- Interstage 1 C/T to 71A local star
- PSU return path from 71A local star to LCLC
- heavy gauge connection to Channel Star Ground, thence to mains earth
- 45 local star at base of cathode resistor
- Interstage 2 C/T to 45 local star
- PSU return path from 45 local star to LCLC
- heavy gauge connection to Channel Star Ground, thence to mains earth
The only other thing I propose on top of that will be additional tubecaps across B+ (anode centre-tap) to local star as proposed by Mike. 20uF for 26, 30uF for 71A, 47uF for 45. I have those spare and and am building in mounting points for them, I will try them once I have the amp working and stable.