first distortion design, please proof for me !!

[TimWaldvogel]

and because i suck at making layouts so far lol, i often keep my perfboard layouts spaced out and confusing, using lots of jumper wires lol

so from i understand, i just use the same bias from the beginning of the circuit? and how does the values of the bias resistors affect tone?

[JKowalski]

how can i change values to make this a more functional pedal. maybe lower the gain of the distortion stage. and from what i understand the boost is only a 10db boost circuit

The circuit is functional, but I would suggest changes that would basically end up turning it back into the original distortion pedal  

The first "boost" stage is basically exactly the same as the second "distortion" stage. Each op amp provides gain to the signal. The only distortion effect occurs at the very end of the circuit, with those two diodes, not at the second op amp (unless you turn the gain of the signal up so high that the signal tries to amplify above the supply voltage, then it will clip there too). So your circuit is basically Boost-Boost-Clipping diodes. It is a little redundant. The first stage will not really do anything different then the second stage.

and because i suck at making layouts so far lol, i often keep my perfboard layouts spaced out and confusing, using lots of jumper wires lol

so from i understand, i just use the same bias from the beginning of the circuit? and how does the values of the bias resistors affect tone?

Read my post in your other thread about bias. Changing the bias on an op amp won't really do much of anything. "Proper biasing" is critical on transistors because that's how they operate. "proper biasing" on op amps is not critical because as long as it is somewhere near 1/2 the supply voltage changing the bias won't make any difference in the sound. Biasing at exactly 1/2 the supply voltage is best because you have the maximum headroom on either side of your bias for the signal to swing to.

Now, your "bias adjustment" will do the following: As you bring the bias closer to the supply rails, eventually one side of the signal will have a lot less headroom then the other side and will start to hit the limit of the op amp voltage supply and clip. You will get a kind of asymettric clipping on your signal. Maybe you want it, maybe you don't. You'd have to breadboard it or something and see if you like that sound.

Using a single supply, you need to bring your signal up to the 1/2V+ bias. You do this by putting it through a capacitor where the other end of it is at the required bias. Capacitors cannot pass any DC, so your signal is the only thing that goes through it. Since there is 1/2V+ on the other side of the capacitor, this signal is superimposed on that DC voltage, it is "biased" to that voltage.

The op amp output will output the signal with the same 1/2V+ bias, so your signal does not need to be rebiased again for another op amp. It's already right where it needs to be.

At the end of the circuit, you want to eliminate the 1/2V+ voltage so that your signal is back at ground. You do this with another decoupling capacitor.



I hope I am not too discouraging!

[slacker]

The first stage will not really do anything different then the second stage.

That's not completely true, the way the gain pot is wired on the second stage as you increase gain it rolls off low frequencies, where as the first stage is a "flat" boost. So in theory setting both stages to a gain of 10 for a total of 100 will give a different sound than setting the first stage to 1 and the second to 100. Whether it's enough difference to be worth bothering with is another matter

[JKowalski]

The first stage will not really do anything different then the second stage.

That's not completely true, the way the gain pot is wired on the second stage as you increase gain it rolls off low frequencies, where as the first stage is a "flat" boost. So in theory setting both stages to a gain of 10 for a total of 100 will give a different sound than setting the first stage to 1 and the second to 100. Whether it's enough difference to be worth bothering with is another matter

Yes, that is true. But still, I personally don't think it would make enough a difference to warrant increasing the complexity of the circuit.

There is no more helpful tool for designing circuits then the wonderful breadboard. I strongly suggest you make use of one, it will allow you to compare changes to your circuit quickly and easily and troubleshoot it's operation so you are confident when you put it onto perf/vero/PCB as a final product.   On it, you can hear the differences, and that's ultimately what matters the most. If you think the dual boost configuration offers a versatility that you can hear and appreciate, then go ahead, nothings stopping you! If you find that it doesn't sound much different then a single op amp version, then you just saved some parts for the same product!

[TimWaldvogel]

ok i see exactly what your talking about now... heh, foiled again lol... SO HERES ANOTHER QUESTION. i was looking at this layout here for mark hammers chaos pedal. now he says he uses soft and hard clipping stages in this pedal...
is there a way to change the boost design in the beginning to an MILD overdrive circuit using soft clipping. so i can give it a pre-gain type deal before it hits the second op amp?

[TimWaldvogel]

what if i added diodes to the boost pot similar like people do to guitars for a mild overdrive, and instead placed the the 1meg pot in the feedback loop of the 2nd op amp to control gain differently. and end the circuit with a baxandall tone stack and a volume pot

boost( w\diodes)-> distortion control (feedback loop?)-> bass and treble controls->volume out

[TimWaldvogel]

i have been reading lots of things trying to understand what makes versatile distortion pedal, and i ran into something that says it you insert something like a 50k pot between the diodes to ground in the hard clipping stage, that it acts as a softness control for the distortion....
or after the diodes between ground which it says acts as a volume control for harmonics. has anybody experimented with these things at all???