Baseline R26 setup to which I applied shielding
R26 in my system already had two measures to very effectively sink away RFI/EMI noise on the ground plane:
- Quartz Acoustic grounding box connected to the outer conductor (ground) of the spare s/pdif coaxial input on the R26. I also have QA boxes connected to a couple of other components.
- R26 power cable connected to Puritan PSM156, with its grounding post connected to the Puritan Ground Master with a cable its own dedicated ground rod (OK copper strap) in the garden. Five other primary components were connected to the Puritan too.
I mention this as each of these measures had progressively reduced the effect of electrical noise (whatever the source) on the R26 producing a satisfyingly more natural sound with less glare, greater dynamics and soundstage scale. So my baseline setup is likely more electrical noise-resilient than average.
Shielding approach and limitations
I should say this is still just a rough proof of concept / test case with cardboard and copper foil.
I used cardboard shapes for each section (the square for the R2R ladder, the upside down V over the vertical circuit board and the lid of the digital section) which I shielded with overlapping strips of copper tape to achieve coverage. I connected the sections using more overlapping sections of copper tape. The extent of the overlap varied a lot, not scientific. So a limiting factor here is the lower conductivity of the adhesive and the surface area of overlap, multiplied by the number of joins from end to end. I just went to measure the resistance but my multimeter battery is dead dammit.
I look forward to retrying this with slightly thicker copper sheeting to minimise joins, lower end-to-end resistance, hopefully improving shielding effectiveness.
Shielding coverage
I did follow your design and add a copper shielded flap (or rather folded down piece of what was the lid of the middle section) on the streamer side of the vertical streamer & bluetooth board, but it wasn't tight or close shielding, as the flex of the carboard and tape meant the bottom of the digital side lifted out a bit so was sitting on an angle. A new piece of copper taped cardboard was added on top of this as 'lid' for the digital section, with continuity of grounding/shielding via copper tape. I thought I may as well connect the lid across to the vertical divider/shield between the toroidal power supplies and digital section as Gustard had felt it worthwhile putting in such a shield so why not make it a little more RF-tight. I also used a little copper tape to narrow the hole in that divider through which the silver power cables pass.
Grounding approach
Take 1 - My grounding approach initially was much more casual than
@St12 - I used copper foil tape about 3-4cm deep on the PS side of that divider which is connected by screws to the chassis base. I also used a doubled-up 10cm long strip of 1cm wide copper tape as a conductor I used to connect the copper digital section 'lid' to the ground screw and cables by the IEC socket. I pressed the copper strip firmly over and around the screw and chassis underneath it. Imperfect but the two would have achieved a level of conductivity.
Take 2- I later improved on it by connecting 2 x 14 gauge copper cables splayed into a fan to the top of the middle lid of the copper shield, with another piece of copper tape on top and the weight of the lid with a dumbbell on top helping keep the two compressed. These cables were connected to my Puritan Ground master which connects to my dedicated ground rod/strap in the garden.
I didn't do this, I just worked with what was there, so it would've been imperfect. The difficulty is there are semi-stacked or layered boards, might be worth trying but not something I'd be in a hurry to mess with.
Initial experimentation impressions
I need to caveat these as I had the R26 turned off for a good half an hour or so while measuring, fitting and updating the shielding which took quite a bit of mucking around to get right. So it would've taken a little while to warm up decently after (at least 10 mins I'd guess from cold as a minimum, ideally half an hour), meaning there's no quick AB possible here. A wee bit of a challenge for the auditory memory.
Anyway my initial impression with grounding Take 1 was it was a smoother, more relaxed, more analogue presentation than I would expect from the R26 in a cold/partly warmed state when things would normally be more brittle. Female vocals in particular were sweeter, softer. My reaction was OK, this is promising.
As it warmed up the theme of more relaxed, natural presentation, less etched edges in vocals particularly remained a constant. The resolution and soundstaging was good but understated - not the best I recalled - which I put down to the more analogue presentation. But it prompted me to try alternative grounding...
Grounding Take 2 retained most of the naturalness of vocals, if a touch less weight, but more finesse, detail and dynamics. Impact and speed of bass increased, soundstage widened. So clearly the quality of grounding had been a limiting factor. The character of improvements was typical of higher quality grounding from my experience. I also tried a Take 2B with a DIY ground box of 3kg of copper blocks instead of the which was somewhere between the two.
At one point I removed the fo.Q damping on my LHY switch - the size of the soundstage collapse and loss of vocal weight and softness surprised me - clearly I'd gotten accustomed to its beneficial effect, so what I was enjoying with the internal shielding was very much the whole being greater than the sum of the parts, of which the internal shielding was just one part. A big negative delta (and then positive when I added it back), a little larger than moving to the better grounding TBH. Emphasising once more, as if I needed to be reminded, the quality of the digital source is paramount. I mention this to put the shielding effect in perspective in my system.
It was getting late so I concluded by removing the shielding and grounding cable and having a quick listen. Sure enough vocals got a bit grainier, lighter, less refined and palpable... a bit more glare. Sometimes it's easier to hear the delta of subtraction and this was the case here.
But then it occurred to me to try one last thing to test the impact of the chassis grounding via Groundmaster sans internal copper shielding. I inserted the splayed copper cables of the ground cable between the R26 back plate and lid, closing it tightly with a dumbbell on top. Sure enough, a fair bit of what I'd lost from removing the shielding + ground cable came back - maybe 2/3rds. Which left me scratching my head as to the relative significance of the shielding vs the better grounding.
To be continued with better shielding in due course....
