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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  bass boost pedal 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: bass boost pedal  (Read 2217 times)
sbgodofmetal
Posts: 25


giest riech


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bass boost pedal
« on: April 19, 2012, 12:49:53 AM »

Ok so going by the beginners project schematic it starts out as a simple boost, but by changing one capacitor it becomes a treble boost. By that same principal can it be made into a bass boost pedal, and could one be rigged with a rotary switch to change the one pedal to either of the three???
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Bill Mountain
Posts: 646


Re: bass boost pedal
« Reply #1 on: April 19, 2012, 06:41:05 AM »

Ok so going by the beginners project schematic it starts out as a simple boost, but by changing one capacitor it becomes a treble boost. By that same principal can it be made into a bass boost pedal, and could one be rigged with a rotary switch to change the one pedal to either of the three???

Not so much a bass boost but you could put in switchable input caps to let in different amount of bass.  Google the FAC control that Orange (and some fuzz makers) use in their amps and pedals.

Good luck!

Edit:  I was going to find an example and post a link but I'm having trouble remembering where I've seen an example of this lately but it's basically a rotary switch that selects between several input caps.  It will let in more bass but it won't cut highs on its own.  Hopefully someone will come along and post a link that would be more useful to you.
« Last Edit: April 19, 2012, 06:50:05 AM by Bill Mountain » Logged
Mike Burgundy
Posts: 1716


Re: bass boost pedal
« Reply #2 on: April 19, 2012, 10:59:04 AM »

A capacitor lets through higher frequencies more than lower ones - the lowest of low, 0Hz is DC ("Direct Current" vs AC-"alternating Current") and that is totally blocked. Think of it as a resistor which value is infinite at DC, and decreases with signal frequency, until it's low enough to be negligible. That "frequency-dependant resistance" is called "impedance".

Smaller values cap need higher frequencies to get to a certain level of impedance. Looking at it another way, a *smaller* value cap will have *higher* impedance for a given frequency, and therefor let through *less* signal.

This is how a treble boost works: have a cap in the signal path (in series) that's small enough to significantly increase in impedance at audible bass levels - it "blocks" bass, and only treble gets boosted. Smaller cap: even less bass. Even smaller: less mids too. Etc. Bigger cap: more bass, up to and including the point your booster is full-range. The cap's value is determined by math (Ohms law rules - literally) and depends on the surrounding circuitry - that's theory for later, now let's tinker.
Now, what happens if you use a BIG cap in series (to let in *all* bass - full range), and stick in a smaller cap to ground?
Remember, that smaller cap will want to let through higher frequencies. THOSE will be shunted to ground. Hey presto, simple bass boost.
Without math, I'd just try a working 1-tranny booster (full range version) and then perhaps stick a 100n from the transistors collector to ground, see what that does, and experiment from there. remember, larger values shunt lower frequencies to ground, higher values shunt higher freq's.
There's no rule you can't try it at the other end of the transistor either - you'll need a different value probably since circuitry conditions are different (there's that pesky theory stuff again).
 Build it on a breadboard and experiment.
hih

(edit: spelling)
« Last Edit: April 19, 2012, 11:00:52 AM by Mike Burgundy » Logged
sbgodofmetal
Posts: 25


giest riech


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Re: bass boost pedal
« Reply #3 on: April 19, 2012, 01:09:54 PM »

Ok let's say I just build the standard booster and insert a varitone unit in the end of the circuit just before the output would that give me the. Same effect I'm looking for or would I be better off hard wiring it to the transistor?
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Mark Hammer
Posts: 22228


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Re: bass boost pedal
« Reply #4 on: April 19, 2012, 01:54:57 PM »

The thing about boosters is that you want to retain definition and clarity.  In the case of a treble booster, configuring it as a combination highpass filter/gain stage with a gentle rolloff will achieve the boosta nd provide the needed definition.

Doing the converse - a lowpass filter and gain stage - will certainly get you more bass, but will lose you the definition.  If your goal is to make everything sound like a Gibson EB-0 fart machine, great.  If your goal is to simply add a little more oomph to a clear signal, that's not gonna do it.

One possible strategy is to do what many classic fuzzboxes have done to yield a big bottom with some sizzle on top: a midscoop filter placed after the boost.  Pull back on the selected mids, and let the bottom and some top come through.  Works like a charm.  Something like what you find on the Superfuzz or Shin-Ei FY-2 works great.
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Earthscum
Posts: 1932


David Edgar


Re: bass boost pedal
« Reply #5 on: April 19, 2012, 02:08:14 PM »

One possible strategy is to do what many classic fuzzboxes have done to yield a big bottom with some sizzle on top: a midscoop filter placed after the boost.  Pull back on the selected mids, and let the bottom and some top come through.  Works like a charm.  Something like what you find on the Superfuzz or Shin-Ei FY-2 works great.

I think that is one of the major reasons the Big Muff tone stack is such a widespread favorite. It can  give you that notch, with the ability to go from overly thick bass to screaming highs, centering around the notch.ble
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CynicalMan
Posts: 1613


Alex L. - Canada


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Re: bass boost pedal
« Reply #6 on: April 19, 2012, 03:14:40 PM »

Here's one trick to make a bass boost: http://sites.google.com/site/distorque/home/projects/fat-bottom
This goes from a shelving filter to a normal low pass filter, so you can get a bass boost without losing clarity.


Other than that, a mid cut or a Baxandall bass shelving filter would work well to get a bass boost that's not too muddy.
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Gus
Posts: 2774


Re: bass boost pedal
« Reply #7 on: April 19, 2012, 04:15:39 PM »

CynicalMan
Nice looking frequency response. 
Question how sensitive is the EQ to the drain resistor value?
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CynicalMan
Posts: 1613


Alex L. - Canada


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Re: bass boost pedal
« Reply #8 on: April 19, 2012, 05:12:58 PM »

Not bad. Looking at the sim results, I'd say that you're good with any drain resistance of 10k or more.
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sbgodofmetal
Posts: 25


giest riech


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Re: bass boost pedal
« Reply #9 on: April 19, 2012, 06:20:44 PM »

So what exactly would installing either a high bypass or low bypass buffer bring into the mix?
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Mike Burgundy
Posts: 1716


Re: bass boost pedal
« Reply #10 on: April 20, 2012, 05:35:51 AM »

  If your goal is to make everything sound like a Gibson EB-0 fart machine, great. 

Thanks Mark, been a while since something on the net actually made me laugh out loud. Played one of those, too.
+1 on the BM tone control. One tranny configured as high-gain booster, stick the tone control after, tweak. Treble boost, mid dip, bass boost all at the twiddle of a knob.
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