Overdrive design - clean blend

[SprinkleSpraycan]

I'm using this schematic as a jumping off point for an overdrive. So far I've only really focused on the clipping and tone control. But I really want to add a clean blend like in a blessed mother. However this must be a little more involved than I thought. I ran a wire from input to a resistor and then to the output but this causes oscillation. How do I go about doing this? I want it to be independent of the gain so, not on a duel pot.

[marcelomd]

The output is feeding back to the input. You need a buffer to "protect" the input.
I'm not on my computer right now, but check the Bootleg Overdrive, or the Obsidian Preamp on the same site. They both have a working clean blend.

[t1redhands]

The "Triad" overdrive has an input buffer already there, so you can pretty easily add a clean blend using the JHS Moonshine or the Voodoo Labs Sparkle Drive as a guide.

[ElectricDruid]

If you're going to add a buffer because the passive mix doesn't work properly, perhaps the solution would be to put an active mixer at the end instead? That way, you don't need the buffer, and the proper mixer won't cause the feedback problem.

It's the same "one extra op-amp" either way though, so it's up to you.

[Fancy Lime]

The easiest and in my opinion often best sounding way to get a clean blend, is to stick a pot wired as a variable resistor in series with the clipping diodes. 10k to 50k should work best for this circuit. This may require some tweaking of the tone shaping afterwards for optimum results, depending on what sound you are after. But it's way simple and saves an opamp and most importantly, does not have any of the phase problems that haunt most clean mix implementations, so I suggest to try that first.

Andy

[SprinkleSpraycan]

The easiest and in my opinion often best sounding way to get a clean blend, is to stick a pot wired as a variable resistor in series with the clipping diodes. 10k to 50k should work best for this circuit. This may require some tweaking of the tone shaping afterwards for optimum results, depending on what sound you are after. But it's way simple and saves an opamp and most importantly, does not have any of the phase problems that haunt most clean mix implementations, so I suggest to try that first.

Andy

would you mind drawing this out? i tried it but it still oscillates. honestly everything ive tried oscillates. im totally into using a second opamp because i want try an active tilt eq so ill need another opamp anyways. thats a whole other issue thats vexing me but ill probably start another thread for that when i get to it. haha. thankful for all the input!

[Fancy Lime]

I used this idea here:
https://www.diystompboxes.com/smfforum/index.php?topic=127739.20#msg1245690

[SprinkleSpraycan]

So far this method is working. I think it could be better but I think maybe on the right track. Any thoughts?


Ignore the big muff tone stack. It was an idea I didn't like.

[antonis]

1M resistance in signal axis isn't recommendend..
(I know Andy implemented it but he is a rather of-the-wall guy.. )

Also, mixing pot should will suffer from crackling due to DC VREF across its wiper - lug 1..

[Fancy Lime]

1M resistance in signal axis isn't recommendend..
(I know Andy implemented it but he is a rather of-the-wall guy.. )

Also, mixing pot should will suffer from crackling due to DC VREF across its wiper - lug 1..

Aww, that's sweet, thanks! But wait, I did what? A megaohm resistor in the signal path of a solid state device? If I did, then it was probably a typo and I mixed up "M" and "k" again. Or are you thinking of a different Andy? There are loads of us...

Another issue related to the DC across the clean blend pot is that this will mess up the bias of Q2. Try changing the pot to 100k and connect lug 1 to Vref instead of ground.

Andy

[antonis]

But wait, I did what? A megaohm resistor in the signal path of a solid state device? If I did, then it was probably a typo and I mixed up "M" and "k" again. Or are you thinking of a different Andy? There are loads of us...

My bad..

I messed you up with some other guy who implements 1M for R2 in all versions of his "Eye of the Goat" OD design..
(I'm deeply sorry..)

[Fancy Lime]

Ok, now I'm super confused. I'm not good at the whole sarcasm thing, especially not in written form. And especially especially not when there are smilies involved 

So... what is R2? Did I actually put a 1M series resistor in one or several of my designs? I know I used a 1M bias resistor a lot on opamps that should have a smaller one, but only until you taught me why that's not a good idea. Thanks, BTW! With the exception or using deliberate bias current starving on 5532 to-rail clipping stages, which just sounds great.

[idy]

oops you do have a 100k mixing R there. Looking good.

[SprinkleSpraycan]

[/quote]
Try changing the pot to 100k and connect lug 1 to Vref instead of ground.
[/quote]

Gadzooks your right. So much better. Thank you thank you

[antonis]

So... what is R2? Did I actually put a 1M series resistor in one or several of my designs?

My bad..
(misread bias R2 resistor as clean signal blending series one..)

Honestly, I'm deeply sorry Andy..