Onboard amp/effects wiring problem

[ponce]

Hi,

I have installed an LM386 based amp into my guitar build, together with the speaker and I also wanted to add a simple fuzz circuit only to be used through that onboard speaker, leaving the guitar output signal unchanged. I have followed these schematics and added a SPDT switch:

https://sites.google.com/site/thediyprojecthub/home/creator-projects/lm386-audio-amplifier-circuit

The circuit works and I get an OK sound from the speaker, but I've also noticed that the ground wire from the little amp changes the sound of the guitar played through a normal "offboard" amp when connected to the guitar ground on the back of the pot. I think I loose more than 30 % of volume together with some highs.  So I added a DPDT switch to be able to break that ground connection when I don't use an onboard amp and want to have an unaltered signal via guitar output jack. Is this the way to go or is there a right way to do it?

P.S. I have omitted the additional fuzz circuit when I encountered this problem, but I'm still interested how this would be properly done.

[antonis]

Do you use bi-polar power supply for the amp and single for Fuzz..??

[ponce]

I actually never integrated that fuzz circuit because of this problem- it's still an idea. And the amp is powered by a 9 v battery

[antonis]

My bad...
(now catch your problem..)

Maybe the 10k amp pot is loading your guitar's Level pot..

[PRR]

Guitars want loads way over 5,000 Ohms, preferably over 500,000 Ohms.

The input of the naked LM386 is 50,000 Ohms; that circuit puts another 10,000 Ohms on it. This is a very heavy load for guitar.

First thought IS to switch out the connection when not in use. It is usually sufficient to break the "hot" lead and leave the ground connection.

More clever is to find a Switch Jack to fit the guitar. If no cord plugged in, signal passes to the internal amplifier. If plugged, internal amp is disconnected.

You are never going to get full soprano/alto highs with that LM386 circuit until you add a buffer in front. There are a bunch of such designs. True, if you are on a 3-inch speaker you may have no lows either, so muted highs may still be "balanced sound".

[ponce]

Thanks, actually I'm pretty satisfied with the sound of my internal speaker, just don't want that the onboard circuitry interferes with the guitar sound when using big amps. I know that this is offtopic but since I've taken apart my whole guitar now, I have noticed that there are 2 different wirings for 2 p90s, one volume, one tone control and a Gibson style toggle switch. I mean the one where a hot wire from the switch goes to the outer lug of the volume control and then to the middle lug of the tone control, vs the one where the hot wire connects to the outer lugs of both volume and tone pots, which also changes the way a tone capacitor is connected. Why is that so?

[ponce]

I mean this:



https://www.google.hr/imgres?imgurl=http%3A%2F%2Firongear-direct.com%2F2_x_a90__1_vol__1_tone__3-way_toggle_igwatermark.gif&imgrefurl=http%3A%2F%2Fastrapt.com%2Fwiring%2Fepiphone-single-pickup-wiring-diagram.php&docid=wTSeIY3NXDCP6M&tbnid=sBz7UzzndD0ClM%3A&vet=1&w=1263&h=1657&bih=662&biw=1366&ved=0ahUKEwjZjLbC3KHQAhWKjSwKHQ8PAiAQMwg8KBcwFw&iact=mrc&uact=8


and this:

https://www.google.hr/imgres?imgurl=http%3A%2F%2Fi1096.photobucket.com%2Falbums%2Fg333%2Fbullfrogblues%2FGuitar%2520stuff%2Fp90-diagram_zpsc503d616.jpeg&imgrefurl=http%3A%2F%2Fwww.tdpri.com%2Fthreads%2Ftwo-p90s-one-volume-pot-three-way-switch.421551%2F&docid=3bolWUNZd_nNQM&tbnid=ww387nUI-tCxOM%3A&vet=1&w=792&h=612&bih=662&biw=1366&ved=0ahUKEwjZjLbC3KHQAhWKjSwKHQ8PAiAQMwggKAYwBg&iact=mrc&uact=8