HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

I quite like the sound of this little unit but unfortunately, electronically speaking, it is a noisy little beast. I wanted to have a look inside to see if I could add some copper shielding tape lining for the (oh so very plastic) casing. And also to have a look to see if I could add a second power supply so the digital and audio are "cleaner."

Nothing surprising about the back panel: I think this is pretty generic depending on the boards used inside.

Removing the four small rubber feet revealed a quartet of small Philips screws, and the thing comes apart quite easily. (Front and back panels just slot into grooves. (Horrible but functional.)

Any advice on adding copper tape to the bottom there - and maybe the sides? And/or some mechanical damping perhaps?

I think the little black wire goes to a really crappy looking Wi-Fi receiver aerial on the base. (No wonder this this sprays digital noise downwards and into my Phono 1 - I currently have it standing on a sheet of tinfoil for just that reason.)





5V power goes in through the micro-USB socket top-right in this image.





The top board is the Khadas Tone-Board (could I add a separate power supply for this bit?) and below if is a small Nord board for Digital in/out and a toggle switch for external/extrnal digital.




PS. I put it back together as it was, and it still works!

If u don’t use the wifi disconnect / disable it and see if that helps

Old guitarist's trick, for lining guitar control cavities... I don't know how much copper insulation tape retails for these days, but this stuff works equally as well and is still probably a lot cheaper. https://www.amazon.co.uk/Slug-Tape-Copper-Repellent-20mm/dp/B00DDVFS7I/ref=pd_lpo_3

Just unplugging the wifi antenna would yield unpredictable results, you'd need to terminate it with a 50 or 75 ohm resistor. That'd be a fun soldering job. I'd lift the antenna and reposition it on the side of the unit and line the top and bottom of the box with foil or preferably carbon foam if you have the space. Ground the lining to one of the RCA out socket grounds. Good luck.

What ever copper tape you use, remember to solder the strips together.

r3xj0hn570n wrote: ↑Sat Aug 14, 2021 9:06 pm Just unplugging the wifi antenna would yield unpredictable results, you'd need to terminate it with a 50 or 75 ohm resistor. That'd be a fun soldering job. I'd lift the antenna and reposition it on the side of the unit and line the top and bottom of the box with foil or preferably carbon foam if you have the space. Ground the lining to one of the RCA out socket grounds. Good luck.

Can you explain why I would need the 75ohm resistor if the antenna is removed: isn't that the same as OS or a big resistor? Also why do I need to earth to the RCA out? I'm thinking of shotgun earthing on certain cables and the effect of simply placing a conductive "skin" around the noise? Thanks in advance.

CycleCoach wrote: ↑Wed Aug 18, 2021 7:40 pm Can you explain why I would need the 75ohm resistor if the antenna is removed: isn't that the same as OS or a big resistor? Also why do I need to earth to the RCA out? I'm thinking of shotgun earthing on certain cables and the effect of simply placing a conductive "skin" around the noise? Thanks in advance.

Morning!

So you've got this radio transmitter, expecting output along a transmission line to a matched impedance antenna. If you just unplug it, there is no longer a constant impedance transmission line, just an open end where the transmission wave will reflect back. This might or might not cause a resonance. Think of the transmission line in terms of a pressure wave in a pipe expecting some sort of pneumatic device on the end. Just chop it off and you have an open pipe, with associated potential resonances (think blowing across the top of an empty bottle).

An ungrounded shield can simply become part of the antenna, or not, depending on all sorts of things. Ground it and you assure it will not become part of the antenna.

r3xj0hn570n wrote: ↑Wed Aug 18, 2021 7:54 pm

CycleCoach wrote: ↑Wed Aug 18, 2021 7:40 pm Can you explain why I would need the 75ohm resistor if the antenna is removed: isn't that the same as OS or a big resistor? Also why do I need to earth to the RCA out? I'm thinking of shotgun earthing on certain cables and the effect of simply placing a conductive "skin" around the noise? Thanks in advance.

Morning!

So you've got this radio transmitter, expecting output along a transmission line to a matched impedance antenna. If you just unplug it, there is no longer a constant impedance transmission line, just an open end where the transmission wave will reflect back. This might or might not cause a resonance. Think of the transmission line in terms of a pressure wave in a pipe expecting some sort of pneumatic device on the end. Just chop it off and you have an open pipe, with associated potential resonances (think blowing across the top of an empty bottle).

An ungrounded shield can simply become part of the antenna, or not, depending on all sorts of things. Ground it and you assure it will not become part of the antenna.

A good explanation. Can I just add that a Faraday cage is not always earthed but in this case there is a transmitter inside the enclosure so, unless it is earthed, all you are doing is keeping the RF in, which is not what is required at all.