DG412 mixer vs ch446Q

I've breadboarded a DG412 based mixer to compare it to the CH446Q one.

To make things simpler, I've only breadboarded four inputs and two outputs, with two DG412/413 chips - this is half of everything on the CH446Q board (if we include the output mixer for the two FX channels, which I did when measuring current consumption on the CH446Q.

The biggest difference here, except for the size, is that the DG412 has parallel control inputs (i.e. one signal per switch) and the CH446Q uses SPI-ish. Thus, to compare the power consumption I should really add whatever current a 16 channel i2c port expander uses.

Anyway.

Current consumption

+12V: 12.3mA (24.6mA for full circuit)

-12V: 12.3mA (24.6mA for full circuit)

This is very interesting! If one ignores the fact that the negative current consumption of the CH446Q was very high for one device, this is exactly the same as the CH446Q board. The port expander (PCA9539) has a negligible supply current (200uA).    

Bleed through

Average bleed through is +/-13mV for a +/-10V input.

As with the CH446Q, the switch sees the current from a +/-5V signal, and the output is +/-5V. To compare this with the CH446Q we need to multiply with 1.5 to get the +/-7.5V we have at the outputs, giving us a +/-20mV bleed through. This gives us -51dB, which is definitely not better than the CH446Q. Now, the datasheet says that off isolation should be -68dB which is quite a bit better than this so I'm not sure where the leakage is. 

With TWO inputs of the same signal going to a mixing op amp, I see +/-23mV (=+/-35mV) leakage, which is to be expected I guess, as both switches leak. 

I cannot see any leakage to the neighbouring channel so no visible crosstalk, just bleed through.

Conclusion

The performance of the DG412 vs CH446Q is not that different, neither in terms of current consumption or bleed/crosstalk. What I choose to use comes down to two things:

- board space - The DG412 solution takes up much more space if using DIL chips)

- serviceability - The CH446Q is extremely custom and may be hard to get at a reasonable price whereas the DG412 is available from several suppliers and I have a lot in stock. Also, it is possible to replace a single DG412, if the CH446Q breaks I must replace a whole bus board.