CMOS analog switches, ADG43x series, in tube preamps?

[nuke]

I was visiting the idea of using analog switches instead of relays in tube amp signal switching. The Analog Devices, LC2-MOS process used on many of their analog switches look pretty good from lot of aspects. Low power, low leakage, fast switching, and wide dynamic range.

Another interesting aspect is the analog signal range of Vss -2v, to Vdd +2v, and Vdd to Vss maximum of 44v, the data sheet indicates analog signal range of +/- 15V.

The ADG433 is interesting in that it is four SPST switches, with inverted logic on two of the switches, making it easy to implement a relay type of functionality. the ADG431 and ADG432 are 4x SPST with all the same logic input, either normal or inverted to ON/OFF states.

They're a little expensive, and I've never used them in anything. Any experience?

https://www.analog.com/en/products/adg433.html

[flemingmras]

CD4053 has been used in MIDI preamps, namely the Marshall JMP-1. Contains 3 SPDT CMOS switches.

The updated version is the TMUX4053. Can run on up to a 28V supply, and signals can be within -0.5V of Vss and +0.5V of Vdd, so 29Vpk-pk (about 10Vrms, or +22dBu).

Your device is rated for +/-15V, so 30Vpk-pk. I feel like the TMUX4053 would be simpler to implement due to having three channels of SPDT switches available. They are CMOS as well.

https://www.ti.com/lit/gpn/TMUX4053

[nuke]

Yeah, I'd stayed away from the classic 4053 and its brethren, due to sometimes large voltage signals in tube preamp stages. Hadn't looked at the TMUX4053 figuring it was similar.

The max supply differential on the TI part is 24v (=/- 12v). The AD part is a bit wider at a max Vss-Vdd of 44v, but the data sheet seems to disagree with itself a bit on what that means exactly.

I happened upon a couple of pieces of the AD devices in ceramic mil-spec DIP-16 through-hole packages and looked them up.

[flemingmras]

Yeah, I'd stayed away from the classic 4053 and its brethren, due to sometimes large voltage signals in tube preamp stages. Hadn't looked at the TMUX4053 figuring it was similar.

The max supply differential on the TI part is 24v (=/- 12v). The AD part is a bit wider at a max Vss-Vdd of 44v, but the data sheet seems to disagree with itself a bit on what that means exactly.

I happened upon a couple of pieces of the AD devices in ceramic mil-spec DIP-16 through-hole packages and looked them up.

While it does have a wide rail voltage range, the data sheet highlights state +/-15V analog signal range.

The On resistance is < 24 ohms, which I find laughable that they call that "low". This may be the limiting factor as to why the analog voltage range is quite lower than its rail voltage range.

[R.G.]

Random notes follow.
1. Holy cow those things are expensive! Mouser wants about $10 a piece for ADG43x parts.
2. Panasonic TQ2 relays in PCB packages can be had as DPDT for $2-$3.
3. All CMOS switches will have voltage limits. The price goes up a lot above the jellybean CD405x series.
4. Relays have voltage limits too, but they are typically 125Vac. The Panasonic line of low-signal relays in AGN and TQ2 share this.
5. With some circuits thinking, you can use latching relays and not have to expend power to hold them on and off.
6. PCB style relays are often offered in DIP compatible pinouts, so you can socket them if you're worried about wear. But generally low signal relays are rated for 10k and more operations.
7. There's another choice. Panasonic's TQ@ and AQH.... series of MOSFET solid state relays are even lower cost, $1 to $2, and switch 60V signals.

If you're worried about solid state switches distorting, the quantities to review are the internal resistance flatness values compared to the load resistance. If the load resistance is uite high compared to the resistor flatness value, then you get essentially no distortion. I have used CD405x, relays, and MOSFET SSRs in pedals and amps, with no noticeable distortion at all.

[nuke]

For me, the issue is board space and some simplification of the circuit if I don't have to drive a relay coil.

I was catalog shopping a bit and TI's offerings are interesting. The TMUX821x series are 100v supply, low THD+noise, easy to control from logic, all from either a TSSOP-16 or a WQFN 4x4. The 8213 is kind of handy in that implements 4 SPST with inverted logic on two of the control pins, turning it into easy relay replacement. They're expensive though, $9.63 in qty 1.

The TMUS721x are bit cheaper, with a +/- 44V supply and rail-to-rail signal.

Relays are cheaper, but most of us also ignore a lot of stuff in the data sheets they warn us about, such as MSL and continuous duty of the coil in a non-latching coil causing failures.

[R.G.]

Makes sense.
Let us know what you come up with.