Bass distortion schematic

[Meanderthal]

 Hello all. I guess I'm officially de-lurkified now. Anyway, I've had this idea for what might be a great bass distortion. Here's what I'm thinking- there's lots of bass distortions and paralell loopers out there that allow you to blend your clean bass signal and keep your bottom end... Well what if you JUST want to blend in the bottom end? So I threw this together- it's a Tim Escobido Harmonic Jerkulator(I've built this and it sounds great on bass) with mods,  blended with a Hog's Foot. I guess in theory the IDEA would work. However, I'm not sure about things like impedance, Do I really need all those pulldown resistors, are my cap values way off the deep end, and maybe could I simplify this? I obviously went nuts with the cut-and-paste here.
If I made any stupid mistakes or shouldn't post any part of this let me know, but keep in mind I'm kinda new.

http://i86.photobucket.com/albums/k99/jprak1/bassdist.jpg

Let me know what y'all think...

[Meanderthal]

 I also wanted to add that this could probably work with a distortion+, fuzz face, BMP, or whatever your favorite bass distortion already is, I just used the Harmonic Jerkulator as an example, and I like tim's "font" so it was easy to cut and paste that way.

[Meanderthal]

Here's a variation which could actually be called a bass injector, and could be a pedal that you use as an add on for your distortion... if that makes sense...

[Bernardduur]

Nice man!

I LOVE the Jerkulator on bass; been using this unit a long time Like the touch of clean blend.

I now use a modded Splitter- blend for my clean blend because I have more pedals that need a clean blend

[Laus]

I don't know the jerkulator. What does it do on bass?

I built this a while ago:


According to values chosen one can vary the amplification. Now it's about 2.5. Which should be sufficient. This thing could be probably updated with 2 extra buffers but that could be overkill also. I only built the highpass filter on effect out. That does really good beacause the wahwah for example doesn't get the low B and give too much mud. The lowpass filter on the clean could be used, better with a buffer behind it I guess. I did't imlement the lowpass and I don't miss it.

To my opinion works very wel. Tried it with a whawha and some distortions.

Btw: corrections to my schematic are welcome..

[Bernardduur]

He Laus, would you know if I "cut" one line of your design, it would also cut the volume?

Right now I have the issue (with both the Splitter / Blend as the modded Splitter / Blend + GEOFEX Panner) that my end-signal is always the result of the adding up of both signals, so when I have only one signal on the volume is less then with both signals.

I could really need a fix for this

[Meanderthal]

 Hello Laus, yes, that's pretty much what I had in mind. (I figured I might not be first to try this) I like the simple lowpass filter you used instead of a Hog's foot circuit, which is pretty much an active lowpass filter. I'm glad to hear it works, I never tried it yet, just bits and pieces. The Jerkulater is an updated version of the Interfax Harmonic Percolater found on Tim Escobedo,s Circuit Snippets page. It's a distortion(with the diodes added as I drew it) and sounds pretty good for bass.

Bernard- I'm glad you liked it. The only thing is- I was trying to AVOID the clean blend, rather reduce the normally "clean" side to its fundamental frequency and allow the distortion to provide all the percieved harmonics. That way you shouldn't hear a clean bass and distorted bass mixed, but rather a distorted bass with MASSIVE bottom end and no mud. You (I hope) would hear the bottom end as PART of the distortion rather than as a clean bass WITH a distorted one.
I take it you've also built something similar(splitter, blender). Are you switching between sides or using a pot to blend?  I was thinking that the 5.6k resistors on either side of the 10k pot might cause exactly what you describe- always a somewhat blended signal.  I can't remember the circuit I genked this from(I know I should give proper gredit and all, please forgive me) but it looked liked a good idea because I wanted to deliberately have a little bleed-through. After all, why bother building this if I would want to dial one side or the other out completely!

[Laus]

Bernardduur:

In the "Lender" you use the 50K pots for the volume of each channel. They are FULLY separated. That means you can mute the clean or effect channel fully. Whel one pot is fully open, that channel gets a boost. So I think it could be your solution.

Meander: hog's foot could be interesting....

[tommy.genes]

Hello Laus, yes, that's pretty much what I had in mind. (I figured I might not be first to try this) I like the simple lowpass filter you used instead of a Hog's foot circuit, which is pretty much an active lowpass filter.
<snip>
The only thing is- I was trying to AVOID the clean blend, rather reduce the normally "clean" side to its fundamental frequency and allow the distortion to provide all the percieved harmonics.

I built a bass paralooper a while back (you can find info on that circuit, as well as my build report, with a search), and it used a single-pole, passive LPF in the "clean" loop. The passive filter only served to dull the clean tone, not create a strong fundamental like you are seeking. To achieve that, I'd strongly suggest sticking with the Hog's Foot or similar active filter.

-- T. G. --

[Laus]

you can boost the two channels in my schematic bij lowering the 39K after the pots. That way you can choose to boost one of the two channels extra.

[Meanderthal]

 Yeah, I have an old hog's foot and I really like what it does! Really goes a long way towards a pure sine wave sound! It seems to be THE thing missing from bass distortions. I wasn't aware of any looper circuits with filters (btw, Laus's highpass on the upper part is cool!), if I was I might not have had the hog's foot idea and just built one of the existing circuits instead.
Yeah, tommy, I think you're right. Active would allow me to ensure that I get a good strong fundamental, which is really what I'm after here! Passive might be a little weak, might just get overpowered by the distortion. Especially at the severe cutoff freq. range I have in mind, a passive filter might cause a big volume drop.

[DuncanM]

I might be wrong here but... I think you need to look at providing a split rail voltage, Vref (4.5v), and refering some of the op amp inputs to that rather than 0v - otherwise the op amps will only pass one half of the waveform.
Also the 1M resistors after the first op amp stage are probably redundant.

Just my 2¢ from a quick look...

[Meanderthal]

 Schematic updated. Ya mean like this? Thanks, that's what I'm lookin' for, I welcome any suggestions.

[Meanderthal]

How about the 10uf coupling caps after the input buffers? Maybe also redundant?

[Laus]

no, don't think so. Need them. Could be smaller. Looks nice the schematic.

[DuncanM]

I was thinking along the lines of:



You will need to do something to the input of U2a similar to U2b with a pullup resistor to Vref and a cap before it to block any DC shift.
Caps on the outputs of U2a &U2b would stop any crackle on the blend pot.

Just a quick analysis...

[Meanderthal]

Thanks man! That all makes sense. I upped the value you suggested for the U1B output coupling cap because of the nature of the hog's foot(it only boosts the lows it sees), but there's not much sense slamming it with subsonics. Plus I always keep running out of 10 uf caps...
This thing's gonna be a nightmare to perf...

[Meanderthal]

Oh yeah, forgot to mention- schematic updated again.

[Meanderthal]

 LOL! I just found the splitter/blender you were talking about bernard... apparently I had found this before as it looks real familiar and that's where I cut my "splitter" file from... I must have glanced at the fet 
stage and moved on... Anyway, After taking a (second) look at I see they have solved a problem I hadn't thought of- phase cancellation. So I've added their phase switch to the hog's foot side to make it more compatible with a wide range of distortion.

[Meanderthal]

 Ok, updated the "injector" schematic and named them both- The Hog Grinder and The Hog Blender. I did a brief search in google and here. The Hog Grinder seems to be some kind of vwoodworking device... but Found nothing else...
So I'm assuming I'm not stepping on anyone's toes? I hope not, I like the names...