I have been investigating an alternative 'Line controller' approach using of all things a solid state volume control chip.
With my long time involvement in electronics I was still under the impression that analogue multiplexers or chips that included them were very inferior, with very imperfect 'on' resistances that were far from linear with varying signal levels.
How things have come on now with modern CMOS processing
. The Burr Brown digitally controlled analogue volume chips PGA2310/2311 have staggeringly low published distortion figures of 0.00002%
I have acquired a slightly older ready made volume control unit from Mshow:
Construction is reasonable but one omission is a mute relay, as there is a pronounced click at turn off.
This is the internal shot after certain modifications:
To glean the ultimate performance from these chips needs consideration of the operating conditions with regard to noise and impedances.
Both regulators feeding the supply to the chip have been replaced with low noise regulator modules and a buffer stage has been fitted driving the input pins.
The buffer stage can be seen in the foreground and the mute relay has been fitted directly to the output sockets.
The unit came without a remote control but I have been able to adapt one to work.
Performance you ask? Stunning, really transparent
Leading on from the Mshow experiments I ordered a new unit along the same lines, this time under the Weiliang Audio name.
It is from China of course so availability now may be a bit delayed due to the current situation.
Part 1.
The pcb is very well done with some quality caps fitted, Elna and Silmic. It also has a mute relay included on board.
I have fitted a buffer stage which improved on the as built performance but am still waiting to receive some low noise regulators.
Compared to the Mshow it is only a few percent behind, hopefully with low noise regulators fitted it will have equal performance.
The soundstage and spacial clues come though exceedingly well, this is in use at the moment.
Part 2.
I have received the low noise regulators and have now fitted them.
Wow this is now very open, looks like I have two equally as good solid state volume controllers.
Putting a buffer before the control chip and substituting low noise regulators really does get the best out of these chips.
Today.
Whoahh am I enjoying this combination.
The performance off vinyl is stunning, the sheer transparency of the modified Weiliang line controller is allowing such detail and depth through that it is like hearing different records
Just listening to Annie Lenox 'Diva'. I have not heard all the subtle mastering before, it's fantastic.