My first schematic (will it work?)...

[Cymastar]

Well, hello all. I can't say I'm new to this, and I can't say I'm incompetent. I've modified and repaired several of my pedals, and I've even built a few (the first of which being a momentary killswitch ). That being said, I have no idea how much of this stuff works, so bare with me...

I designed this schematic:


Based off of the Thing-A-Ma-Bob and the Rambler. My question is simple: Will it work?

I honestly have no idea, so I'm asking everybody out there to critique this for me. Any gaping flaws? Any horrible misconstructions? Any major no-nos?

Help a first time designer out and post something!

(Of note: the connection between pin (1,4) of IC1 and Ground was an accident. (1,4) should go through C1, then to Ground.)

[Thomeeque]

 This is not schematic, it's a layout

Your links to Rambler and Thing-A-Ma-Bob are broken (you should check what you post and use MODIFY function if something is wrong).

Your Gnd pad is probably switched with VR2/Yellow pad (or something like that - I have no idea what it should do to be honest, but R1 in series with GND seems weird).

Good luck T.

[01370022]

You're gonna have problems if you plan on connecting Pin 4 to gnd solely thru C1, since you need a clean ground connection. I've never seen a circuit with a grounding like that. I'd say get the old breadboard out and build it up and see what happens

[anchovie]

You need a breadboard. It'll be a much better use of time than making layouts for circuits based on guesses and assumptions.

[FUZZZZzzzz]

breadboarding was also my advice in the other topic.. its hard to give an advice with just looking at some layout..

[thedefog]

You need an input and output capacitor in your layout.

[darron]

a schematic rather than a layout would work better.

it looks like your are trying to send the input straight into diodes (back to back). the signal won't pass through the diodes because it's not strong enough yet. you can use diodes like this going from the signal to ground after an amplification stage where the signal is about 100x stronger and will break through the diodes and distort.


don't forget with the image on the right that it will need to be the mirror image when you look at the copper side of the board.

breadboards are very cool!

[01370022]

Now that I've had a look at it when it's not 5 min before bed, here's a few more thoughts

+1 on the diodes. Also you'll need some sort of biasing arrangement, otherwise the signal will be this half wave messy sort of thing. Which may be what you're after. If you put in biasing, you'll also need an input cap as mentioned to avoid the possibility of bad things happening down the line and stop it causing problems the other ways (without putting in a DC blocking cap on the input, your DC bias will move up the line to the previous FX output, which may not be designed to handle that sort of thing). C3 acts as a output cap, blocking any DC from the 386, but since lug 3 on the volume pot is connected to ground through R1, there's probably gonna be DC on that point anyway, so you'll need another cap after VR2 fix that problem. And then you'll also need pull down resistors to avoid pops when switching.

So no, it's not going to work in it's current format for the reasons previously suggested.

I'd either move the diodes behind the 386 and add an output buffer, or add an input buffer with a gain boost of some sort before the diodes, put in a biasing system so you will pass the full signal (unless you want the half wave thing going on, could sound cool  ) which also means putting in DC blocking caps and pull down resistors (>1M) before the input cap and after the output cap and get rid of R1, going straight to ground. I might add some sort of filter for a tone control depending how complex I wanted to make it.

Otherwise from that, you've got yourself the basis for a nice little distortion circuit. Keep going and we'll see what cool things you come up with. It's always a great feeling when you get one of your own designs working, even better when you've tweaked it to your liking and boxed it up.

[DC9V]

it looks like your are trying to send the input straight into diodes (back to back). the signal won't pass through the diodes because it's not strong enough yet. you can use diodes like this going from the signal to ground after an amplification stage where the signal is about 100x stronger and will break through the diodes and distort.

Err... Pardon the silly question, but that's the way we noobs learn Wouldn't this work with Shottky diodes? I remember seeing a thingy sold (quite expensively) as a "guitar onboard passive overdrive" or something and which was really just 2 Shottky diodes back to back (or were they stabistors? Can't remember for sure). Perhaps putting the diode clipping stage before the 386 would have an impact on the sound? That is, provided the 386 isn't driven to clipping too?

[darron]

Err... Pardon the silly question, but that's the way we noobs learn Wouldn't this work with Shottky diodes? I remember seeing a thingy sold (quite expensively) as a "guitar onboard passive overdrive" or something and which was really just 2 Shottky diodes back to back (or were they stabistors? Can't remember for sure). Perhaps putting the diode clipping stage before the 386 would have an impact on the sound? That is, provided the 386 isn't driven to clipping too?

ah yes. that can be done with some shottkys, but in a different configuration. they should connect from the signal to ground/earth, but the signal shouldn't go through them and then continue on through the circuit. it gives a mild overdrive but also causes a bit of loss in volume, so that's why you'd normally amplify it first.

so the signal will go straight through from input to output, but when it touches the diodes going to ground, if the signal is strong enough (about 0.1V with schottky) then the top off the signal will be cut off (connected to ground, therefore muted) which makes the signal squared off at the top, which is exactly what most distortions do.

if you wanted something easy you could build a simple booster, then add the diodes, then add a volume control at the end. you might get quite a bit of satisfaction from doing that. then you could take it from there with adding further filtering etc.


edit: oh! and that's not a silly question!

[anchovie]

If you go back to the first post, there's a link to Tim E's Rambler which the OP says part of his circuit is based on. The original Rambler schem shows Shottkys in that arrangement.

[darron]

If you go back to the first post, there's a link to Tim E's Rambler which the OP says part of his circuit is based on. The original Rambler schem shows Shottkys in that arrangement.

ahh that's true. i am finding it very hard to imagine the signal breaking through that except for moments on a hard strum? i suppose as mentioned it will give the rectified effect. interested to see how it sounds because like i said it's hard to imagine it.....


okay, so if you want to make the rambler exactly as the schematic shows then forget what people said about an input cap and byassing.... input caps are a nice courtesy to prevent problems but it is nt here. the 386 chip should give itself sufficient byassing.

here are some observations:

1) don't forget to tie the last terminal of VR1 to ground

2) maybe draw a donut for the top-right pin ( of the IC.

3) why is everything going to ground going through a 3.3k resistor? for the pots that's okay but for the IC and the electro cap it's not so good.

4) the cap coming out of pin 7 should go to ground, not reconnect back to pin 8.

other than that i think it's cool? i'd like to breadboard it but my breadboard is full right now.

[DC9V]

ah yes. that can be done with some shottkys, but in a different configuration. they should connect from the signal to ground/earth, but the signal shouldn't go through them and then continue on through the circuit. it gives a mild overdrive but also causes a bit of loss in volume, so that's why you'd normally amplify it first.

so the signal will go straight through from input to output, but when it touches the diodes going to ground, if the signal is strong enough (about 0.1V with schottky) then the top off the signal will be cut off (connected to ground, therefore muted) which makes the signal squared off at the top, which is exactly what most distortions do.

if you wanted something easy you could build a simple booster, then add the diodes, then add a volume control at the end. you might get quite a bit of satisfaction from doing that. then you could take it from there with adding further filtering etc.


edit: oh! and that's not a silly question!

Thanks for clearing that out. I'm not planning to build this particular circuit but I try to reduce my ignorance of electronics theory every chance I get 

[darron]

Thanks for clearing that out. I'm not planning to build this particular circuit but I try to reduce my ignorance of electronics theory every chance I get 

i find the best thing to do is sit around this forum and read as much as you can of what goes through that interests you. your interest will follow links to other things and you'll develop a greater curiosity and need to satisfy it! there's a wealth of information here from guys/girls with years behind them, and it's great to (subjectively of course) take in as much as they can give you.