Yesterday evening I found that touching the Knob gave a tingling sensation and generated extra, low, humming sounds and decided that some protective gear was in order. Luckily for my listening pleasure (one tends to get impatient), I had some spare laying around.
For those visually oriented:
Looking fine. 
As I do not cultivate a herd of spare knobs, I ordered three this morning, in varying degrees of utilitarian ugliness. No bakelite yet.
Iāve been checking out knobs on the Internet too ā¦ no wait, I mean volume controls. Havenāt had anything leap out at me yet.
Still finding it noisy. I can configure the aerial to minimise wifi noise, maybe even put a USB extender on and take it right away. But I get process noise whenever I hit play in Roon. Low level, but can be heard in quiet passages.
I see that Pi 2 Design have published an update with a Python script that looks very similar to one I saw here first. Dare I say rovinggecko = BAS ? Nice job and a real help to a lot of folks.
@andybob @RBM - hereās one for you: a snip at $485. Mind you, I donāt think itās available any more. I wonder why?
I snapped up the last 10. Selling for $995, but for members of this community Iām willing to let go of a few for only $750. Iām cool like that.
Busted 
As it seemed they were not as quick with a script as theyād initially indicated I mailed them, just in case it would helpā¦
I like the look of them, and obviously theyād sound better. Itās just the lack of an incorporated quantum purifier thatās holding me back.
I think wider looks better for the unit and might be easier to use one handed. Having to use both hands to turn the unadorned shaft is getting old.
On the bright side my noise issues appear wholly related to the proximity and placement of the WiFi aerial. Iāve got a short extender cable coming which should deal with that. Had a lovely listening session last night with no noise at all.
Edit: have ordered one of these.
Is that the one that goes to eleven?
With the impedance selecter set to 32 ohm (middle position), I donāt think I get the volume past about 1 oāclock (where 7 oāclock is off). Thatās plenty loud enough, with a nice bottom end. So Iāve added a note to my order that these knobs only have to go up to 6.
@RBM Did you order & try AUDIOPHONICS I-Sabre V3 DAC?
After some web research it seems really good quality DAC out there, and has good oscillator and lineal power supply input and split to DAC and PI.
Nope ā not yet. Right now Iām using the Hifiberry DAC+ Pro for my headphone set and the Digi+ Pro for the big rig ā and Iām quite pleased for now. Iām sure in due time Iāll develop an itch for Mamboberry or Audiophonics though. 
I use an Aqvox linear PSU with the Digi+ Pro. Sounds great, but Iām not sure Iād able to reliably detect any significant differences with a regular switching PSU in a double-blind ABX. Peace of mind comes at a price, I guessā¦
Does anyone know if there is a linear power supply available that will fit into the 503HTA?
24 volt, 2 ampere is the brick power that it comes with.
Any linear power that does that would work.
Some observations about noise after trying a couple of configurations.
There are three types of low level noise Iām hearing, in increasing order of annoyance:
a very intermittent crackle, uncorrelated with anything;
a little burst of white noise associated with playback processing;
a WiFi associated constant buzz.
All of these low level noises are well masked by the music, except between tracks or very quiet passages, but if we were accepting of noise weād have to hand in our audiofool badges, right ?
Initially I was using the 47 ohm (middle) position on the output resistance slider. The input impedance of my headphones (Nokia) is 47 ohm. I noticed that the manual reccomended starting at 100 ohm (right) and reducing output resistance if there wasnāt enough gain. There is heaps of gain and at 100 ohm the noise is a bit lower, so thatās my new setting.
I have the Pi 2 but initially I bent HAT pins 1&2 away to remove the 5v supply back to the Pi, which had caused some noise issues for the Pi 3. I no longer do this. If there has been any increased noise from reverting it is only a very minor affect on the crackle, which is so intermittent as to not bother me. It is definitely more convenient to have one power supply only. Being in a bedroom I donāt like the light from leaving the Pi on and inserting the Pi micro USB power connector is a game for a younger man.
I was worried about potential corruption of the SD card by powering off the Pi with the amp, but DietPi writes the logs to RAM and only stores to the card every few minutes, so the likelihood of corruption is greatly reduced. I could organise for software powerdown, but havenāt done that yet.
I tried a couple of different separate power supplies for the Pi, oddly the iFi seemed to exacerbate the WiFi noise and created a proximity buzz around the tube and when touching the volume pole (yet unadorned with a knob). I found the device less noisy not using the iFi (ymmv).
The solution to the WiFi noise is likely to involve moving the antenna away from the tube. Changing direction can help. So far I havenāt found an extension lead that allows the dongle to work, I may need a powered hub.
I have grown to like the look of the device.Its a lot of fun.
Perhaps switch to wired? If you don;t want to do cabling through the house, those ethernet over power things might be interesting?
Thereās a phone socket in the bedroom. I might see if I can pull some CAT cabling through the duct.
Mineās dead quiet, but thatās with the Pi+DAC separated from the amp. Maybe if it rains tonight, Iāll try to mount the Pi directly underneath the amp, just to see what happens.
(I guess the DAC+ Pro performs a little better and I do need L/R balance control, so it wonāt be permanent).
Oh, and @andybob ā while weāre at it: how is your knob?
Oh, and @andybob ā while weāre at it: how is your knob?
Firmly in the grip of Australia Post still. Looking forward to it being released this week.
