Hello everyone,
Just as I was re-re-redrawing schematics for my custom A/B switch with looper and tuner out/mute (my first DYI stompbox project) I was running in to some questions, and as it happens I found this forum today. So if you don't mind I'll ask some beginner-level questions (thanks!);
I am making a pedal to perform the following functions :
A/B Switching between 2 amps
Tuner output that mutes the sound
Looper that provides true bypass for my wah
LED indicators for all functions (I am using 3PDT switches)
My questions :
With the switching between two outputs/amps ; When I select output A is it nessecary/desireable to wire the switch so it then connects output B to ground (and vice versa) ? Will it prevent audible pops/clicks ?
Is the pull-down resistor only used on the input side ?
To me it seems weird to use a common ground for both the LED's power (9v DC from adapter or battery) AND the guitar signal. Should I keep them separate or doesn't it matter ? (or is this a really ignorant question? :? ) and also : how can I best include housing of the box into the grounding (hammond enclosure) ?
btw Are any of you using special software or VISIO stencils to draw diagrams? My standard visio gives me no suitable symbols .. and that resulted in pretty crappy schematics.
Thanks a lot in advance for those take the time to read/answer.
Greetings,
Martijn
He martijn, welkom ;)
Yes, you're going to want to ground the unused output. If there's a high-gain pedal sitting in there it might oscillate or make noise, so ground it just to be safe.
Second, if you're only switching without any buffers a pulldown resistor isn't needed, and will load down the signal. Not much of course, but still.
Thirdly, if you're making an audio circuit you need to connect guitar/amp ground to the circuit ground, but if you're only turning LEDs on and off you don't have to. It won't make any difference but it is common practice to connect the grounds together anyway :)
Ik hoop dat het geholpen heeft ;)
groetjes
Ben
Hi Martjin,
I used a free schematc software named Circuit maker by Protel,there's many components and a spice simulation
Bruno
Hi Martjin,
A little help?
Ther's a DOD bypass switching box that use a resistor for grounding the unused output for switching beetween two amps but i don't remenber the value ,i've got to open it and i'll give you the value .On all my projects (pedalboad or stompboxes i've always connected input ground with output ground and more supply too on a same ground .If you use a real good power supply you wouldn't
get hum if you only use an amp .If you use two amps ,it's better to let the ground plug on the amps and remove the shield at one extremity of only one of the cables used to connect amps to your A/B box ,by this way you're going to have only one ground path (no ground loop :no hum!)
I hope this help you
Bruno
thanks everyone, so far its been very helpfull.
Ben suggested > 2M resistors to me earlier, I am curious to know what DOD used in their box.
Regards,
Martijn
Well the resistor used in the manner gearbuilder mentioned is different from a pulldown resistor. I explained that pulldown resistors allow caps to drain off their charge when the circuit is disconnected, and that values >2M were good for this, depending on the cap size but I use 2M. This however isn't a pulldown resistor and would create more hum rather than less ;) If you put a resistor into your schemmo, Martijn.
Using the schematic you showed me would be fine mate :)
Hi Martjin,
the resistor i was speaking of is a resistor that allow to ground your unused channel in an A/B box with one input and two outputs,system used for switching two amps.The pull-down resistors are used when your signal go in an A/B loop with two effects and an output that goes to your amp.These are used to only take-off clicking noises due to the effects capacitors that are not at the same pot .Wait i'm going to give the values, ah if just open it,Dod has put a 1 Mohn resistor to ground the unused channel,perhaps it does the same than the pull down resistor ,no click! :wink:
Bruno