With relay controlled volume array being employed in next gen products two of which are now the best measuring integrate in the market (topping 90 and benchmark headphone amp), i had an idea that the next step would be ditching the high quality relays and using smd mosfets for the job. Yay or nay?
MOSFET's as you know, have an intrinsic diode which can introduce distortion. For alleviate it ussualy is used two anti-series MOSFET's with their sources joined. There are also commercialy available such a switchs with optoisolation led controlled.
While MOSFETs can nowadays be very low in on-resistance, they do have appreciable capacitance which might cause clicks/pops - digital feed-through - when changing volume.
I looked at this a few months ago and came to the conclusion that relays were going to be cheaper. There are a few mosfets switches with the low capacitance/on resistance that would have suited (anti parallel too), but they're not cheap. There are also digital potentiometers, but none that I saw looked to be HiFi quality.
I'm going to stick with latchable relays, simple & well documented. Though of course with component shortages, finding the right relay drivers and other chippage has turned out to be a complete pain 🙂
I decided to design some boards for this and input selection for control through an Arduino over WiFi + rotary encoder as part of a learning KiCad exercise. It's all stalled due to life. Hoping to order boards early in the new year after some prototyping with the Maxim I2C chips I plan on using.
I'm going to stick with latchable relays, simple & well documented. Though of course with component shortages, finding the right relay drivers and other chippage has turned out to be a complete pain 🙂
I decided to design some boards for this and input selection for control through an Arduino over WiFi + rotary encoder as part of a learning KiCad exercise. It's all stalled due to life. Hoping to order boards early in the new year after some prototyping with the Maxim I2C chips I plan on using.
Those FET switches are always more nonlinear than relays.
Whether it becomes audible depends a lot on the designers' chops, but they are not as linear.
Jan
Whether it becomes audible depends a lot on the designers' chops, but they are not as linear.
Jan