A Bleeding Blend Control on Bass

BuddytheReow

BuddytheReow

Breadboard Baker
Hey Guys,

Since I got my bass last week I wanted to put together a simple little circuit for it, and I'm currently in the breadboard phase. At first I wanted to do a Bazz Fuss with large in/out caps with a simple volume control. Then I realized it would sound better to allow some of the raw signal into the mix for nice tweakability. The issue I ran into quickly is that there is a big volume difference between the two, so I want to put a clean boost instead of raw signal. I chose an lpb1. Both circuits work fine as standalones, but trying to blend the two is causing some issues. I want to have the signal 100% boost or 100% fuzz when the blend control is turned to the extremes, but I have a small amount of fuzz when i'm dialed into boost and vice versa. Lug 1 is the BOOST, lug 3 is the FUZZ, and lug 2 is output. I upped the blend pot to 1m and don't have a bigger value in my inventory. Is there a way to fix this or a piece that i'm missing? Maybe dump some signal to ground on both sides? I read somewhere that an input buffer may fix this?

1646743874412.png
lpb-schematic.png
 
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A few thoughts.

Often, for blend circuits it’s recommended to buffer before splitting to avoid interaction between the how the various circuits load your your passive pickups. In this case, neither circuit has very high input impedance. Also, in particular the bazz fuss loses a lot of it's power and sounds a lot different if it's after a buffer. This can be helped partially by adding series resistance between the buffer and bazz fuss, but it won't be exactly the same. All that to say, the 'proper' way for blend circuits is usually considered using a buffer at the beginning. Without a buffer, the input impedance of one circuit may affect the tone of the other. However, in this case, the interaction may end up not being bad, or may work for you, and for sure the buffer will change how the bazz fuss sounds. Basically, experiment, and if you find something you like, that's more important than doing it the 'proper' way. This does mean that the pedal will want to be first in your chain, not after a buffer so the bazz fuss can sound like it's true self. another option would be to use a different fuzz circuit that doesn't mind being after a buffer (like a big muff), but this increases the complexity quite a bit.


About the bleed, check out the JMK Panner build docs. The blend knob wiper goes to V-ref, so at extreme knob positions it mutes the unused signal. This concept apparently originally comes from RG Keen. Pedalpcb Fv-1 circuits use this method for wet/dry blend. As far as implementing the panner circuit in your build, you can ignore the input buffer, and insert the lpb-1 output at the 'S' node, and the fuzz output at the 'R' node, and go from there. It does need an opamp stage for recovery gain and low output impedance.

After typing all that I had another thought, are you keeping both VOL pots? Couldn't those be used to achieve blended sound? You'd want to include a resistor after each pot's lug2 before bringing the signals together, and an output buffer would be a good idea.
 
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phi1 said:
A few thoughts.

Often, for blend circuits it’s recommended to buffer before splitting to avoid interaction between the how the various circuits load your your passive pickups. In this case, neither circuit has very high input impedance. Also, in particular the bazz fuss loses a lot of it's power and sounds a lot different if it's after a buffer. This can be helped partially by adding series resistance between the buffer and bazz fuss, but it won't be exactly the same. All that to say, the 'proper' way for blend circuits is usually considered using a buffer at the beginning. Without a buffer, the input impedance of one circuit may affect the tone of the other. However, in this case, the interaction may end up not being bad, or may work for you, and for sure the buffer will change how the bazz fuss sounds. Basically, experiment, and if you find something you like, that's more important than doing it the 'proper' way. This does mean that the pedal will want to be first in your chain, not after a buffer so the bazz fuss can sound like it's true self. another option would be to use a different fuzz circuit that doesn't mind being after a buffer (like a big muff), but this increases the complexity quite a bit.


About the bleed, check out the JMK Panner build docs. The blend knob wiper goes to V-ref, so at extreme knob positions it mutes the unused signal. This concept apparently originally comes from RG Keen. Pedalpcb Fv-1 circuits use this method for wet/dry blend. As far as implementing the panner circuit in your build, you can ignore the input buffer, and insert the lpb-1 output at the 'S' node, and the fuzz output at the 'R' node, and go from there. It does need an opamp stage for recovery gain and low output impedance.

After typing all that I had another thought, are you keeping both VOL pots? Couldn't those be used to achieve blended sound? You'd want to include a resistor after each pot's lug2 before bringing the signals together, and an output buffer would be a good idea.
Click to expand...
So if I understand you:

Output buffer, yes. Input buffer, maybe. Ok, no problem to experiment on a breadboard
Bazz fuss might not be the way to go if after a buffer.
To fix the bleed just dump the unwanted signal to ground using the PAN control like below. This one makes sense.
Add the LPB1 right before the 'S' node and Bazz fuss output at the 'R' node. Hmm, I don't want the boosted signal to go into the Bazz fuss (or maybe I do?). I think instead of the LPB1 I'll just adjust the gain of the input opamp feedback loop in the schematic below to save on real estate when this goes to stripboard.

After seeing the Panner schematic I think may throw a volume trimmer in the output of the Bazz fuss to match the volume of the input section. Then after the output buffer I think I'll try adding a master volume to output and see how that sounds.

Depending on how deep this rabbit hole project goes I'm debating whether to socket the diode of the Bazz Fuss of simply make it switchable with a rotary.
1646752496815.png
 
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I took some time to draw out a schematic. I’m going to breadboard this shortly and would like to know any thoughts. My requirements are this:

-Make the input signal louder
-Add a fuzz circuit in parallel
-Have a BLEND knob to mix between the two. No signal bleed should happen at either extreme
-Unity volume for the two parallel circuits
-Little to no noise/oscillation

I’m considering making the input cap switchable between guitar and bass. I also need to tweak the feedback loop resistor and maybe add a small capacitor in there. I also don’t have 15k resistors in the PAN section so I’ll throw some 22s in there and see what happens. I’ll also be using a tl072
 

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cool, I like where this is going. In your sketch, you have the buffer feeding the bazz fuss (basically, like the planner circuit is drawn up). You can experiment, but buffer into bazz fuss changes the sound a lot in my experience.
 
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You could take the in jack straight into the Panner circuit, and also straight into the the BF. This way, you can still use the first op amp as your clean boost.
 
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phi1 said:
cool, I like where this is going. In your sketch, you have the buffer feeding the bazz fuss (basically, like the planner circuit is drawn up). You can experiment, but buffer into bazz fuss changes the sound a lot in my experience.
Click to expand...
I'll try it as drawn. I can always move the fuzz before the input opamp and keeping the return node as is
 
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You’re way off, I say you’re way off this time son!

LPB-1?


giphy.gif


Ahem…
Y’see, th’ prawblum is yer still thinkering lahk ah geetawrist, boy. Allow me to elucidate you with some bassification…

Whutchall neeed son is a Hog’sfoot/Mole. Ya playin’ BASS now boyo, gotta git that through yer noggin. You’re a smart kid, but always gettin’ in treble — I made a funny son and you’re not laughin’. Here’s your, I say, you listenin’ son? Fortunately I always keep a spare schematic in my locker — Here’s your bass-boost, boy:

moleschem2.gif


Why I’m workin’ on one on the breadboard right now, myself, gots it goin’ into a double Bazz Fuss (that’s a, I say, that’s a called a Buzz Box when there’s two of the little critters in there); but what you want for your bass-sick mutation of the clean blend (I’ve no such animal in my coop, I’m wallowin’ in the filth, y’see, like a Hog’s Foot — That’s another joke, I say that’s a joke son, I keep pitchin’ ‘em and you keep missin’ ‘em) …

Pay attention when I’m talkin, boy… y’all need a buffer-buster after the buffer but before your Bazz Fuss:

dbf.png


Consider a Tri, I say consider a Triad TY-250P instead of the 42TM018, for a fuller frequency spectrum — check the datasheets, do your Homework, son.

That ol’ fuzz dawg in the UK has a buffered bass blender you can take a gander at and add that to the possibilities of puttin’ it on your breadboard.

Here’s what I’ve been – I say, here’s what I’ve been telling you, boy!
- Buffered Bass blend
- Bass boost, none of this LPB-1 malarky
- Buffer-busted Basstastic Bazz Fuss

That’s all I’ve time for, son — less broad-roarin’ and more breadboardin’ to do — I’ve gotta go, like a race-horse that’s spent too much time at the waterin’ trough before post-time.


giphy.gif
 
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The transformer buffer buster is another option if you want the assurance of buffering before splitting. It also would allow this pedal to go anywhere in pedal chain, after other buffered pedals
 
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Feral Feline said:
A buffer-buster by any other name…

Guitar Pickups Simulation

Schematics & circuits for guitar effects with vacuum tubes and solid state electronics. FREE downloads of schematics such as TS-9, Fuzz Face and other classic rock devices.
www.muzique.com www.muzique.com
Click to expand...
Hmmm....is there a different, yet simple dirt circuit I could throw in there for bass that doesn't require the "buffer buster'? I'm trying to use parts I already have on hand
 
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The simplest fuzz circuits (this and FF) won’t like a buffer before. Some big muffs like GR are popular on bass, and could look around for other distortion pedals that folks like of bass.

Or, you could try what we talked about first (bazz fuss without buffer, clean side with buffer/boost) and see if that works well
 
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As mentioned, I’ve breadboarded a Mole into Buzz Box (into Ibby 850 tone/recovery) — I love the rasp, but the decay is basically non-existant.

It doesn’t sputter, it just cuts out, which I wouldn’t mind if it were more consistent on when it cuts out — either right away every time or a wee bit of sustain every time.

I’ll be revisiting all that tonight, see if I can get it more consistent.

Simple bass-friendly fuzzes…
Hmm…

Try tweakin’ PJP’s Photon, schem here. While you’re there you can also check these:

Colorsound One Knob Fuzz

EQD’s Bazz Fuss variant, the Bellows (Gpcb Fuzzstortion, IIRC).

Escobedo Lofomofo turned into a Phat Phuzz is dang good!

Mammoth is still fairly basic and you’d likely have everything on hand.

I’ll try to come up with some more later, got some work to do now.
 
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I'm going to start a new project development thread and loop this thread into the mix, but feel free for anyone to keep contributing here. This is definitely a good "from idea to schematic to breadboard to stripboard" build for me!
 
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