Conceptual question about switching tonestacks in circuit. Channel switching amp

garybdmd

Member
2016-01-03 5:13 am
Hi all, thanks for looking.

I have a question about hooking up tonestacks in a channel switching amp.
In this amp, there is a clean channel and a distorted high gain channel. I built a preamp which switches from channel 1(low gain/clean) to channel 2(high gain/distorted). When I switch from channel 1 to 2, I switch tonestacks so there are independent eq controls for each channel. The way I made it is shown above in the top part of the diagram, which works fine. Now, I'm trying to simplify the circuit as much as possible, and found that if I eliminate the switch at the input to the tonestacks as shown in the bottom part of the diagram, the voltage presented to the amp section remains essentially the same. But the bottom schematic (where 1 switch is eliminated) the current flowing through each tonestack basically divides in half. So the power going into the top eq is 1/2 as much but the voltage remains the same. I'm interested in eliminating the DPDT switch and replacing it with a SPDT switch as shown.

Will this cause the sound to be degraded? The voltage is not changing but the power and current are split. Do I really need the DPDT switching or is it ok to use the SPDT switch to simplify the circuit?
 

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If you eliminate the first switch, the preamp is now driving a load impedance of 50k (the two 100k in parallel). But since the output impedance of the preamp is only 1k, it should drive this heavier load with only a very slight reduction in its output voltage.
The voltage is the 'signal'.
So, I think it will be fine without the first switch.