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In Reply to: RE: motorized volume control posted by AbeCollins on October 29, 2017 at 18:56:40:
> > Do you know if a CMOS solid state switch - CD4066 IC - might sound better? Do these analog CMOS switch devices exist specifically for audio applications... with and without internal resistor network? < <
As noted before, I have found relays to be absolutely the worst sounding switching solution available. They aren't particularly cheap either.
As for as FET switches go, they have distinct limitations that limit their applications. The maximum rail-to-rail voltage limits them to line level applications for the most port. Their minimum on resistance is not very low, and is generally non-linear with signal. Their parasitic capacitance between terminals and between each terminal and AC ground is variable and non-linear with signal. Finally, they are sensitive to both ESD and overvoltage breakdown.
Properly protecting them is not something I've ever seen explained in a datssheet or app note from any manufacturer, but it can be done. If they are used in specific applications they can sound excellent and a close second place to a solid-silver contact switch. But their limitations really limit their applications.
There are some "digital pots" with 32 and 64 taps that are available withe log tapers that are OK for audio. I think Audio Research uses them quite a bit on their preamps. They are far from state of the art, but miles ahead of relays, IME.
Most of the ones designed specifically as "audio volume controls" are designed to be used in the feedback network of op-amps. That doesn't work for our applications, as op-amps are based on high levels of negative feedback.
Your AX-7 has a unique volume control Ayre developed about 15 years ago. Several years later we shared it with Aesthetix. It largely uses HC4066 8-input MUX chips in a unique configuration. Then Bascom King bought an Aesthetix at accommodation. A few years later he designed a preamp for PS Audio that just happened to have the same unique volume control concept as was used on the Aesthetix.
There's nothing wrong with using unpatented IP, but whenever Ayre does this, we give credit to the inventor, whether it be Bart Locanthi, Gordon Rankin, John Curl, or Richard Baker. It seems to me to be a little silly to pretend you invented something that you merely copied. Maybe that's just me.
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Follow Ups
- RE: motorized volume control - Charles Hansen 10/30/1701:29:49 10/30/17 (0)
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