freestompboxes.org

Hey, so... I'm rather noobish at pedal building and am trying to make a simple booster based off of the electro harmonix lpb-1. Thing is I want to have 2 inputs, going to 1 output....the goal is to have it switch from boosted to true bypass with a 3pdt each input.. I copy, pasted and scribbled over a schematic to help you guys see what I attempted.



The issue that I'm having is the signal doesn't get boosted well enough unless both channels are on. Before just starting over using a 4558, I'm wondering if any of you guys could come up with a quick fix to get the boosting to work properly when just one input is going through the pedal. I've tried a few things like blending the to outs of the pedal after the pot, with polarized and non polarized caps, messed with diodes and resistors a little but I'm not having any luck.


It seems like this should be an easy question for most of you, any help/knowledge is appreciated.

Oh, and if I'm able to get this working, with the help of the form, by this friday, before midnight... I promise to foolow-up post the working circuit art/component layout, .psd and jpg.

only had a quick look, but it looks like you're wiring the 3pdt in a strange way..
it looks to me like your output of each booster is going to have the signal go through a <100K path to ground..

output of one goes to the output jack, but also goes to the 100Kvol pot of the other booster, which has that path to ground.
if you take the output of each booster instead directly to output, but to the middle row of the 3pdt poles and output that way it should ensure they're isoltaed..

did that make any sense?
if not, can you put up the picture without the trace wires and I'll draw what I think should happen.

it could be nothing to do with what you're experiencing but it's where I'd start anyway.

actually, the more I think about this, the more I think you're stuffed either way.. if both are engaged, you'll still be halving the impedance to ground of the output signal.
no idea how to address that.

I'll try that in about a half hour. but here is this incase.



BRB

here's what I'm getting at.. I'm sure someone else could explain it better (or better yet, correct me cos I'm prolly wrong.. I just know how to solder stuff, don't know much about this stuff).

the orange on the lpbboth.jpg shows the signal going to gnd via the 'other' pot.

So there's still a volume level difference, It gets a lot louder when both pedals are engaged.

rocklander wrote:actually, the more I think about this, the more I think you're stuffed either way.. if both are engaged, you'll still be halving the impedance to ground of the output signal.
no idea how to address that.

how would you go about balancing impedance? maybe like this? With an added resistor when both switchs are on?

I really don't know where my brain is today.. I totally omitted putting the input to the switches
so you'd maybe need a 4pdt.

I'm totally the wrong person to be answering any of this.. I can see a problem (I think), but no idea how to solve it.
you'll have to wait till someone who actually has a technical clue can chime in... I should just stick to making smart arse comments, it's where my talent really lies.

haha well thanks anyways. I at least have some shit to google with the 'impedance' problem you pointed out. we'll wait to see if anyone else posts. thanks

Well. here's an update. i used the 2 to 1 buffer explained here

https://www.freestompboxes.org/viewtopic ... 6360fa23ed

the signal from each channel goes through the booster then the buffer when on. and only goes through the buffer when off. and it seems to be working as expected. some of the values will have to be adjusted to blend the 2 schematics cleanly.... there's just one issue. its still not technically true-bypass. But that has me wondering... is it even possible to have two true bypass signals go to one output? wont that cause all sorts of volume issues if you have lets say a guitar in one input and a line level instrument in the other output essentially being connected through a y cable? if that makes sense. I'll draw a picture of how i blended the 2 schematics once I'm on my home computer.

So here is how i wired it.


Problem is... it's still not true bypass....

Here is the image clean if anyone wants to scribble on it.


Any words of wisdom or wisecracks appreciated...even though its past the deadline.