#1
This is a follow on from my post about switching systems over in GG&A:
https://www.ultimate-guitar.com/forum/showthread.php?p=22446368
I decided the DIY approach was the way to go, and it would be more appropriate to discuss it in this forum.

I put together a quick and dirty circuit idea. It's a double loop switcher. Nothing fancy at all, it's not programmable or anything like that, but it does everything I currently need to do, and I may as well start simple before trying to build anything complicated.

The idea's that it has two modes: clean and distorted. For each mode, there's a pre-preamp loop and a post-preamp loop. The pre-preamp loop is for effects that go in front of the amp, and the post-preamp loop is for effects that go in the amp's effect loop. When in clean mode, the clean loops are engaged and the amp's channel is set to clean; when in distorted mode, the distorted loops are engaged and the amp's channel is set to distorted. Nice and simple. It uses DPDT relays to switch between loops, and a SPST relay to switch the amp's channel.

I'm a bit of an electronics n00b so I've no idea if this is actually correct and would work as intended. Sorry the diagram's a bit messy but it's a simple circuit so should be easy enough to understand. Thought I should get it checked out before I go and get the parts. Any thoughts?



(also, I know that my amp footswitch is actually stereo, I've just drawn a mono jack for the channel switch to keep things simple).

I'd put my Bad Monkey in the distorted pre-preamp loop; EQ and noise gate in the distorted post-preamp loop; nothing in the clean pre-preamp loop for the moment (so just a patch cable); chorus and delay in the clean post-preamp loop.
#2
I'm no expert on relays, but it looks like you've got the switching all right

like I said, I'm not very familiar with relays, but is there any difference between putting them all in prallel, as opposed to series like you've got?
it's not very likely that one'll fail, but considering it as a posibility, parallel would mean only the failed one is the only one not working properly.

but..yeah. that questions mostly for my own education ..if theres any other difference you'd find putting them in parallel instead of series..

one thing I'd suggest to change is possibly adding a second LED, or changing it to a bi-colour LED, so you have a 'clean on' status light, as well as the 'distortion on' status light

its an overall neat idea, but personally, I'd have seperate switches in place of the relays..
thats just what I'd find more useful for me, though.
if this suits your purposes, then its pretty much perfect
#3
Quote by james4
like I said, I'm not very familiar with relays, but is there any difference between putting them all in prallel, as opposed to series like you've got?
it's not very likely that one'll fail, but considering it as a posibility, parallel would mean only the failed one is the only one not working properly.


I guess I may as well put them in parallel then, won't exactly be much harder. As far as I know it won't make much difference other than the failure resilence, but then I'm no expert either. The current would be split between the parallel branches rather than going to each one in series, but I don't think that makes any practical difference in this case.

Quote by james4
one thing I'd suggest to change is possibly adding a second LED, or changing it to a bi-colour LED, so you have a 'clean on' status light, as well as the 'distortion on' status light


Great idea, will probably do that .

Quote by james4
its an overall neat idea, but personally, I'd have seperate switches in place of the relays..
thats just what I'd find more useful for me, though.
if this suits your purposes, then its pretty much perfect


Aye, for me the whole point of it is to be able to switch between two completely different sounds with one button. I'm considering expanding it in the future, possibly with more modes and Octa-switch style programming ability, in which case i'll add more buttons. There's definitely lots of possibilities for upgrades anyway.
#4
if the relay coils are each rated for 9v, you have to hook them in parallel. In the diagram, those coils are only seeing 3v a piece. if they are only 3v coils, then that's just fine.

battery life may not be very long.

i cant make much of that diagram. if you'd have used the text and straight line tools in mspaint (looks like you used mspaint) and taken some time to do a good job, it'd have been much much neater and would be more readable.

you'll want a diode across the coils to prevent inductive kick, which will eventually destroy your switch. when you switch off power to a coil of wire, hundreds of volts are produced and it arcs across the switch as it leaves contact from the 'on' position. this will quickly burn out and destroy switch contacts.

also those relays are gonna pop loud as hell. you'll need a high-value resistor across the input and ground (higher than 1M would do).
#5
Quote by Invader Jim
if the relay coils are each rated for 9v, you have to hook them in parallel. In the diagram, those coils are only seeing 3v a piece. if they are only 3v coils, then that's just fine.

Didn't think of that, I haven't actually got the parts yet but I'll consider that when I do.
battery life may not be very long.

I guessed as much; I'm planning on using it with a power supply. I've got a 1 Spot that supplies 1700mA max. Should be plenty to power the relays and a few pedals right? If not I can give it its own power supply.
i cant make much of that diagram. if you'd have used the text and straight line tools in mspaint (looks like you used mspaint) and taken some time to do a good job, it'd have been much much neater and would be more readable.

Sorry, should've made more of an effort, was just being lazy and getting something done quickly. I'll make a neater diagram with the fixes you've mentioned later on when I'm not at work...
you'll want a diode across the coils to prevent inductive kick, which will eventually destroy your switch. when you switch off power to a coil of wire, hundreds of volts are produced and it arcs across the switch as it leaves contact from the 'on' position. this will quickly burn out and destroy switch contacts.

also those relays are gonna pop loud as hell. you'll need a high-value resistor across the input and ground (higher than 1M would do).

Ah, didn't realise I had to consider all that. As I say I'll put up an improved diagram later. I take it I need a resistor for both the inputs (guitar input and amp effect send input)?

Thanks!
#6
remember that series circuits are voltage dividers and parallel circuits are current dividers. if you know ohm's law and kirrchoff's laws, you're set for almost anything.

all you have to do is rewire the coils. no components needed.

you'd need a resistor for all inputs. the higher the better because it can add noise.

BUT.

a better option would be a simple little FET buffer. i have a schem for one if you need it. only like 5 components iirc.

instead of jumpering the hot and ground (which is what a resistor alone essentially does, which makes the whole system more noisy), a 1M resistor simply references the FET's base to ground if there's a floating (unconnected) input. this will silence the circuit when there's no cable plugged in, and the high value pull-down resistor pulls the pops to ground and out of the signal.
#7
Cool, the FET buffer schem would be useful, cheers.

Does "all inputs" also include the returns for all the loops?