how to blend clean with effect

[Milothicus]

I'm planning on building a distortion of some type to use with bass, but i want to blend a clean signal with the effected signal. what's the best way to do this? is it as easy as wiring a blend pot in parallel with the circuit?

[computerjones]

no.  the problem is that a paralell blend pot can transmit signal both ways, and one of those ways is a feedback loop.  if you look at it drawn out its easy to see.  a simple buffer will be your friend, and be sure to search for "splitter blend" on this forum.  surely you dont think we havent talked about that before?

[Milothicus]

I assumed you had, but my searches didn't come up with anything useful. for some reason, you can search either subject and message text, or just message text. it would be nice to search for just subject. too many results. didn't help much.

thanks for pointing me in the right direction.

[claydavis]

here's one way to do it:
http://www.runoffgroove.com/splitter-blend.html

it's a good starting point.

[MartyB]

Milothicus,

    I can't find the original source, but I've kept a download of the Joel Purkiss Buff 'N Blend pcb layout and wiring diagram.  Low component count .   Pvt msg me iwith your e-mail if you'd like a copy.

MartyB

[MartyB]

Okay, found the orig source!   Had to search the old forum archives.  It has layout, wiring, and schematic:

http://www.geocities.com/jrtookmyfalseteeth/


We'll have to ask Joel about that false teeth thing (!?).

MartyB

[Milothicus]

Thanks. i'm planning on building this into an effect pedal (my second pedal) and i have a pretty basic question:

can i run the effect and this buff-blend off the same battery? do i just attach this in parallel with the rest of the effect?

it makes sense to me to be able to do that, but im not positive.

[claydavis]

yeah, you can use the same battery. if you use the buff'n blend, just build the distortion circuit you want to use, and connect the input to where the "to effect input" jack is and connect the output to where the "from effect output" jack is. you might also want to change the input capacitor on the buff'n bend to something larger for use with bass.

[Peter Snowberg]

Here's another way to blend:



This circuit uses the super high input impedance of the JFET opamp to buffer a clean and an effected/affected signal. The output impedance of the two are the same which makes linear blending very clean and easy. The JFET input has an impedance of something like 10,000,000,000,000 ohms so you can really just ignore it. I didn't show any resistors to ground because the effect will probably have it build in, or it will be provided by the volume pot on the guitar/bass.

You can do the same thing with a single opamp or even a single JFET transistor too:



This uses fewer parts and less power, but you may have to play with the value of the blend pot. The only problem with the simple approach is that the output impedance of the opamp and the effect will likely be VERY different and the blending will be more of a hit or miss exercise. You might be able to remove the clean signal from the mix depending on where you have the output level of your effect set.

Take care,
-Peter

[Greg Moss]

Also check out the Bass Para-looper over at Moosapotamus' site.
http://www.moosapotamus.com/


It uses 4 op-amp stages. Works pretty well.

Greg

[sirkut]

Wouldn't using just a 1meg pot work? Tie the input to lug 1, 2 (2 being the center), then tying lug 1 to the input of the circuit. Lug 3 goes to output jack and output circuit. Recalling from memory.

[Peter Snowberg]

Wouldn't using just a 1meg pot work? Tie the input to lug 1, 2 (2 being the center), then tying lug 1 to the input of the circuit. Lug 3 goes to output jack and output circuit. Recalling from memory.

Depending on the impedances of the effect input, effect output, and the impedance of the next effect's input.... the answer is maybe, sort of. You'll lose highs for sure, but it will work in some cases with some effect knowb settings. It just won't be ideal if it does work.

take care,
-Peter

[12afael]

some day I will make a octave up with a distortion box with two outputs one clean and one with effect for use it when the guitar play the solo for not forget the rithm guitar (bass with effect)

[Tim Escobedo]

I guess the "proper" way to do this would be to use a old fashioned summing circuit. The classic summing op amp is perfectly suited for this.

I have several times gotten away with something like Peter's circuit with a pot connecting two op amp outputs. This usually works well enough for op amps, but like Peter says, can get weird if one of the paths has a different output impedance/level than the other.

[RickL]

I just finished building the Bass ParaLoop and can also vouch for it. I used a printed copy that I've had for a while (marked Bass Thru) and a layout marked BassParaLoop. The layout doesn't quite match the schematic but since I build using the 4ms CBCB method when a layout is available it was easy to allow for the differences.

The layout doesn't have the Filter Cut Off pot so I added it. The layout has an extra 0.22µF switched across the 0.047µF filter cap which I did use, and the layout uses a 100k feedback resistor in the feedback loop of the last op amp which I also used.

I've only had a chance to test it with a guitar but it seems to work pretty well. For the cost of a cap and a switch the 0.22µF cap was worth adding. I tried a couple of Dano mini pedals in the loop (a vibe and an EQ) and the blend pot seemed to work fine. I didn't get any bleed through of the loop effect when the balance pot was all the way to the dry side. There's lots of volume available - I got unity gain with the Volume control only about 1/4 of the way up.

I think I might add a simple distortion circuit (probably a Bazz Fuss) in place of the jumper between the Send and Return jacks that would be removed automatically when the jacks are used.

I haven't tried the configuration yet but it looks like this effect could also be used as an active splitter by just using the Send and Out jacks as the two sends or as a mixer by using the In and Return jacks as inputs.

[Peter Snowberg]

I think I might add a simple distortion circuit (probably a Bazz Fuss) in place of the jumper between the Send and Return jacks that would be removed automatically when the jacks are used.

I haven't tried the configuration yet but it looks like this effect could also be used as an active splitter by just using the Send and Out jacks as the two sends or as a mixer by using the In and Return jacks as inputs.

What a cool idea! ...and a great observation too!

Take care,
-Peter

[moosapotamus]

Rick - Yeah, the paralooper/bass-thru will work like that. Putting a bazz in there is a nice idea, too. But, from my experience, the output buffer will "tame" the bazz a bit, won't sound quite as nasty as it does on it's own.

I've been tinkering with the idea of putting a clean buffer/booster in parallel with a buzzbox, as a way to implement a wet/dry blend control while retaining the nasty character. But, I'm still trying to figure a good buffer/booster that will work well on bass, pass all the lows. Most of the ones that are great for guitar (stratoblaster, minibooster, etc...) tend to cut the low end. So, like I said, I'm still tinkering.  

~ Charlie