Analog switching

[akis]

Hi

For a new guitar amp I am thinking of using a 4066 chip to do remote (pedal) channel selection and also final amp selection.

There will be two pre-amps, a Channel A and a Channel B. A pedal will allow what's plugged in A to go through B (eg A clean, B distortion).

|There will also be two post amps, and a panel switch will allow 3 possible configurations for the post - amps:

1 -- Channel A on Post Amp A and Channel B on Post Amp B --- this will allow two musical instruments to use the same guitar amp but each with their own independent settings as if there were plugged into two guitar amps.

2 -- Channel A on both Post Amp A and Post Amp B --- this will allow a solo guitar on A to use both post amps

3 -- Channel B on both Post Amp A and Post Amp B --- this will allow a solo guitar on B to use both post amps

To do the pedal switching, at least, I am thinking of using a 4066 chip , eg MC14066B. To switch "on" I will drive Vcc to its enable pin. To do "off" I will have the enable pins permanently grounded(Vee) through, say a 10K resistor.

The above works in simulation, but am not sure how well it work in practice. Also I am not sure if the chip will add its own distortion, noise or leaked signal in the off position, to the delicate un-amplified guitar signal.

I have tried the same using discreet jFETs but the 4066 is neater and much less component count.

I would be grateful for ideas and suggestions.

[Mooly]

The 4066 or slightly inferior (higher on resistance) are perfectly adequate.

The points to be aware of for ultimate fidelity...

Arrange if possible so that the switch never sees any "voltage" across it. That can be accomplished using a virtual earth amp (inverting opamp mixer).

Also if only using one switch element be aware that there can be some breakthrough at high frequency due to capacitive effects.

All that is being super critical about it though and in practice they are fine. The breakthrough is no worse than a standard Lorlin type switch.

Personally I find suitable FET's are better as used here (post #2),

My MOSFET amplifier designed for music.

[Elvee]

You may also find the CD4053 useful: the physical switches are basically the same, but they are prearranged in a SPDT configuration and the logic input also incorporates a voltage translation feature.

[akis]

Thanks, I will buy a 4066 and experiment a bit. Power supply is +/-15.5 Volts. The 4066 goes up to 18V (+/- 9V) so I will have to connect it appropriately. Max signal will be +/-1.76V, so there is plenty of headroom for the 4066.

[Mooly]

Originally Posted by Mooly

The 4066 or slightly inferior (higher on resistance) are perfectly adequate.

That should read "or slightly inferior 4016"

To actually have a play with one is the best way to learn.