I am looking at starting to consider design aspects of a long-term project now a few things have been completed in the system. My experience currently extends no further than cross-over building, uprating components in existing circuits and building a kit dac & SUT in to a box. Whilst I am reading valve design books I think I would prefer to build a known design of sorts as staryting from scratch as a newbee will probably only end in a lot of trial and error. I would however like it to be a bit modular to allow swapping out of a PSU or Board for a new alternative if required.
I would like this to be of good quality and probably of simple design using very good quality components. I don't massive gain for line or current for long lengths of cable so I am considering a single triode (or pentode wired as triode) used as an active line stage.
I am essentially thinking of at present building a valve pre with phono stage incorporating MC SUTs (I may add a DAC later as well). I plan on building this in to 2 boxes; box 1 containing seperate power supplies and regulation for each section and the second box containing all the signal handling components.
A couple of questions for the experienced if I may
1) Use of copper for chassis - what is the benefits of this? I believe the copper is non ferrous hence non magnetic and reduces eddy currents from transformer floating around the case and presumably either impacting on signal carrying components or other transformers? If I use a 2 box design with PSU seperate is there any benefit? Does copper still provide good RFI? Is it worth considering running any heater AC wires in copper microbore pipe internally or is this a really dumb idea and showing my inexperience?
2) Power supply selection - heater circuits, do these need to be DC for line level? For phono stage it seems many designs use DC so I assume it is required or much better practice for such low level signal? I have started playing with the PSU designer software and probably erring toward a valve regulated supply or 2 (1 for line and 1 for phono).
3) Any suggestions on circuit deisgn or links to known good sounding circuits or kits?
4) Pre-amp output transformers or capacitor coupled?
5) Any suggestions on transformer manufacturer, I am currently looking at Lundahl and Sowter purely as thgat is all I have read about in DIY circles.
6) I am concerned about hum as anyone who has had a go at building something normally has massive hum issues with tube amps, is this mainly due to AC heater wires not being run correctly typiclaly? Any tips?
I am hoping to construct modules on boards but using tag strip hardwire connections so that a module can be removed a la PCB but with hardwired connections for ease of swapping components and sound quality.
All suggestions and discussion welcome and any input is greatly appreciated. I may have something working in 2 years or so!