Making a switch for Output A, Output B or BOTH?

Thread Starter

JemNotJeff

Joined Feb 26, 2019
3
Hi there,

I am new to circuits and am hoping to make a guitar pedal to switch between two outputs or use them together.

The basic idea is in the attached photo. I am wondering how to make the three switches so that if one is on, the other two are automatically off. I am sure there is a simple solution but as mentioned above I am new to circuits.

Thanks in advance!

DSC_0794_JemNotJeff.JPG
 

crutschow

Joined Mar 14, 2008
29,828
I assume you want them to be momentary switches (?).
For that you could use a radio-pushbutton type of circuit.

Edit: Here's an example that uses one OR-gate and two NOR-gate packages, which can be modified to do what you want:
This could also be simply done with a microprocessor, of course, but that would require a little programming.
upload_2019-2-26_11-20-0.png
 
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MisterBill2

Joined Jan 23, 2018
11,925
Is this switch supposed to be connecting the outputs of the amplifiers to speakers? Or is it supposed to be connecting some source to the inputs of the amplifiers? I missed that part. It could be as simple as one toggle switch with three positions, if you can find any place that sells them. It is a double-pole switch with one side changing with the toggle in one direction from center and the otgher section changing with the other section changing when the toggle lever is moved in the other direction. I think that DigiKey carries them, at least it used to.
 

Thread Starter

JemNotJeff

Joined Feb 26, 2019
3
Is this switch supposed to be connecting the outputs of the amplifiers to speakers? Or is it supposed to be connecting some source to the inputs of the amplifiers? I missed that part. It could be as simple as one toggle switch with three positions, if you can find any place that sells them. It is a double-pole switch with one side changing with the toggle in one direction from center and the otgher section changing with the other section changing when the toggle lever is moved in the other direction. I think that DigiKey carries them, at least it used to.
A 3 way toggle switch would be easier to make but this is going to be a footswitch and I am hoping that I can switch to any of the three settings without having to press more than once hence the three switches
 

MisterBill2

Joined Jan 23, 2018
11,925
I have seen setup
A 3 way toggle switch would be easier to make but this is going to be a footswitch and I am hoping that I can switch to any of the three settings without having to press more than once hence the three switches
s where that foot switch was a pedal that could rock forward and backward, or stop in the center. Not at all like the stomp switch you are describing. My point being that it can be done and has been done. But to do it with a stomp switch will require a small bit of logic, such as a dual flipflop counter set to count only to three. And then two small relays to switch the audio signal and light the LEDs so you know where you are. There are also pushbutton switches for lights that offer one, the other, or both, but then the next position is off, so you would need to hit it twice.
 

crutschow

Joined Mar 14, 2008
29,828
Here's the Radio PB circuit modified to control two relays, which should do what you want.
The circuit requires one CD4017 IC and two CD4001 IC's.
The three pushbuttons, S1, S2, and S3, control two relays, U10 and U11.
Thus S1 (blue trace) turns on the Amp_A output (green trace), S2 (yellow trace) turns on the Amp_B output (purple trace) and S3 (red trace) turns on both.
The buttons can be pushed just once in any sequence to energize the desired output(s).

The supply voltage can be any from 5V-15V, with the corresponding voltage relay selected.
The sim resistors at the bottom are just for the simulation and are not needed for the real circuit.

upload_2019-2-27_11-27-28.png
 

MisterBill2

Joined Jan 23, 2018
11,925
Or the very simplest way is to have two on/off alternate action switches, one feeding to amplifier "A" and the other feeding to amplifier "B", close enough so you can hit them both at once and yet far enough apart so that you can switch just one if you choose.You could even use double pole switches and have LEDs indicating which switch was on. Simple, cheap, easy, and reliable all at the same time.
 

eetech00

Joined Jun 8, 2013
3,163
Hello,

One thing that needs to be considered (and I don’t see this in any posts) is that the switching of the inputs will need to be noiseless. That is, without introducing “clicks” or “pops” when switching. Especially since the circuit is switching guitar amplifier inputs. Some switch circuits do this by using make before break contacts.

eT
 

sghioto

Joined Dec 31, 2017
3,296
One thing that needs to be considered (and I don’t see this in any posts) is that the switching of the inputs will need to be noiseless.
Agreed. I had thought of this but was on wait and see depending on what type circuit the TS might decide on. My thinking was if the audio switching is completely independent of the control circuit as it is using relays then any click from dc switching may be unnoticeable. Any clicks from switching between amps with the relay contacts would depend on the input section the amp in question.
SG
 

MisterBill2

Joined Jan 23, 2018
11,925
Agreed. I had thought of this but was on wait and see depending on what type circuit the TS might decide on. My thinking was if the audio switching is completely independent of the control circuit as it is using relays then any click from dc switching may be unnoticeable. Any clicks from switching between amps with the relay contacts would depend on the input section the amp in question.
SG
How about using some LDRs, Light Depandant Resistors? They switch slow enough to not produce any clicks or pops. And still, the two button approach allows non-sequential switching.
 

MisterBill2

Joined Jan 23, 2018
11,925
Been there and Done That, although it was only 30 boards, but those boards had a hundred times more parts on them. And I had LOTS of soldering practice and got to be quite good at soldering circuit boards.But stuffing ICs into a board is better than stuffing in lots of little parts that must go in just so and then have their leads bent and trimmed. Yes it did take a few hours but the pay was good and it was during my feree time and so it was not bad at all.
 

crutschow

Joined Mar 14, 2008
29,828
Thanks to AK's comments, here's the circuit with all three IC's of the same type.
(And per MB2's comments, I also prefer the extra IC over two diodes and one resistor.)
Since these are all static latches and gates, you don't really need a decoupling cap at each IC.

upload_2019-3-1_12-46-35.png
 
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