#1
I am about 3/4 of the way through building and soldering together a DIY amp. My only problems are that the input jack I have is stereo instead of mono, and I have no idea which one of the three wires is meant to go where on my amp.

On my input jack there are 3 wires: a black one (thats earth, I assume), a white one (I think this one is left) and a red one.

Am I meant to mix the white wire and the red wire together to change it from stereo to mono? Or am I meant to just ignore the red wire? Am I meant to solder the black wire to the negative of the battery? And which wire gets connected to the "in"?

BTW, here is the amp blueprints:
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#2
On a stereo jack with a mono plug inserted, the right side is shorted to ground.

An easy way to find out which wire is which, is to plug in a cord and check from the other end with a multimeter.

And, the positive of the jack, (the tip), is most likely in, with the ground grounded of course.
#3
The whole point of the stereo jack is to allow you to switch your amp on and off by inserting a jack. You wire the negative from the battery to the ring of the jack, the sleeve goes to the board grounds and the hot goes to your signal input. When you insert a mono jack (which 95% of guitars use), the negative and grounds are shorted together, which allows the circuit to turn on (just remember to unplug it when you're done ).
You can see what I mean on this picture.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#4
Quote by the_random_hero
The whole point of the stereo jack is to allow you to switch your amp on and off by inserting a jack. You wire the negative from the battery to the ring of the jack, the sleeve goes to the board grounds and the hot goes to your signal input. When you insert a mono jack (which 95% of guitars use), the negative and grounds are shorted together, which allows the circuit to turn on (just remember to unplug it when you're done ).
You can see what I mean on this picture.
Thanks again. Now I just got to use the electic meter to tell which wire is which.
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#5
Quote by demonofthenight
Thanks again. Now I just got to use the electic meter to tell which wire is which.


If you get a picture of the jack, it's fairly easy to point out which is which.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#6
Looking at your picture, shouldn't the board grounds be connected to the negative of the battery anyway?
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#7
Quote by demonofthenight
Looking at your picture, shouldn't the board grounds be connected to the negative of the battery anyway?


It's just the picture
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#8
One more question, will this work?
What I'm trying to do is have my switch disconnect both the input jack and the battery at the same time, that way there is no chance that my battery is going to run flat whilst I'm not using my amp. I know a DPST switch would work better, but that would mean taking another 45 minute walk to jaycar and spending another 2$ on a switch .
I just wanna know if this won't blow my jack or short my battery and make sparks in my beautifull wooden cabinent (from experience, sparks on wood, not a very good idea), or even worse, blow my speakers.

EDIT: dont worry, i found a better way
Attachments:
dpdt.JPG
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Last edited by demonofthenight at Sep 27, 2007,
#9
Quote by demonofthenight
One more question, will this work?
What I'm trying to do is have my switch disconnect both the input jack and the battery at the same time, that way there is no chance that my battery is going to run flat whilst I'm not using my amp. I know a DPST switch would work better, but that would mean taking another 45 minute walk to jaycar and spending another 2$ on a switch .
I just wanna know if this won't blow my jack or short my battery and make sparks in my beautifull wooden cabinent (from experience, sparks on wood, not a very good idea), or even worse, blow my speakers.

EDIT: dont worry, i found a better way


It's not particularly a better way - you're going to be connecting the input to +9v, which is a bit pointless. You only need a SPST to disconnect either the positive or negative side of the battery from wherever it's connected to.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#10
demonofthenight,

The wiring you've drawn will have an unpleasant side effect. When the toggle switch is turned off, you immediately connect the input to the + of the circuit. The battery is disconnected, but the capacitor ( 100uF ) is still charged up. So you're sending a pulse back through your pickups as the capacitor discharges through them.

It probably won't kill anything, but I would compare that to slamming your knee into the back of your guitar every time you finish playing. Perhaps no bad will come of it, but why would you do that?
Meadows
Quote by Jackal58
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#11
Quote by SomeoneYouKnew
demonofthenight,

The wiring you've drawn will have an unpleasant side effect. When the toggle switch is turned off, you immediately connect the input to the + of the circuit. The battery is disconnected, but the capacitor ( 100uF ) is still charged up. So you're sending a pulse back through your pickups as the capacitor discharges through them.

It probably won't kill anything, but I would compare that to slamming your knee into the back of your guitar every time you finish playing. Perhaps no bad will come of it, but why would you do that?
I'm not too enthusastic about the amp being on whenever my lead is connected. As it appears, putting my lead in completes the circuit and the amp would still be on. I want a switch to allow my lead to be still plugged in but the amp would turn off, whats more is that I dont want to walk back to jaycar and spend another 2$ on a switch when I already have a DPDT switch.

Thanks both of you, and sorry for my noobiness. Electronics isn't really my forte.
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#12
Quote by demonofthenight
I want a switch to allow my lead to be still plugged in but the amp would turn off, whats more is that I dont want to walk back to jaycar and spend another 2$ on a switch when I already have a DPDT switch.


No problem.
You know, just because a switch has 6 terminals, doesn't mean you need to use all of them.

1 - Leave the red wires connected as they are to the switch.
2 - Disconnect the green wires from the switch, and connect them together.
3 - Get rid of the jumper across the top of the switch. It's just clutter.

Now your toggle will shut off the amp, even if the cable is plugged in.

No more whacking your pickups with a 9 volt pulse.

No extra trip to the store necessary.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.