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Build a stomp box/plug in bass drum!

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Mar 09, 2010 6:37 AM GMT

Hi techies,

So I have a bunch of Piezzo elements (35mm) and also a bunch of old speaker cones, I cable them up - some I have buried in nice blocks of timber, some are porch board style - they sound fine but they the tone is too high! how do I get that bass tone? do I need to solder in a resistor or some such somewhere? Grateful for any and all advice. Thanks guys,


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Comments (9)

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Mar 09, 2010 6:52 AM GMT
Mondo Replied:

You need a low-pass filter to cut the highs. A combination of cap and resister with your tap between. Jig it up on a breadboard with variables so you can tweek it until you find the values you want. Then go buy the fixed units. Also, be mindful of your impedence.

You should be able to get a book on electronic projects that covers the subject.

Mar 09, 2010 9:49 AM GMT
HarpSkunk Replied:


Cool I am sitting with a dictionary and wikipedia to figure out what you mean but it looks good. Thanks,


Mar 09, 2010 6:25 PM GMT
Not a Replied:

Something like this ought to do it for you. It'll bleed the highs to ground, but let the lows through

piezo(hot leaqd)-----|---resistor(10kohm-1kohm)---------out(hot lead)
piezo(neg lead)------|-------------------------------------------out(ground lead))

Mar 09, 2010 8:27 PM GMT
HarpSkunk Replied:


OK I think I see, I shall order the parts and try the build. Let you know how it goes.



Mar 11, 2010 6:53 PM GMT
Not a Replied:

Actually, you can also place a 10k log-taper pot in series with the capacitor on the leg to ground. Just put it right before the cap. Leave the fixed resitor inplace (ie in series between the input and output, and right after the tap for the lead to the pot/cap combo to ground). Then it will be an adjustable treble-cut tone control. With that situation, you can basically vary the level of the highs without affecting the volume of the lows at all. I'd start with a cap value on the small end (0.0047uf) before moving it up. As you increas the capacitance, you are moving the filter notch DOWN in frequency (ie. you are intruding into lower and lower frequencies). And vice vera, if you find that 0.0047 cuts too much into the mids, make the cap smaller (0.003uf is a standard notch point for treble cut tone controls in amps). Probably the value you want will be lower than higher, since you want this to sound really bass heavy. That's why I suggested a lower cap value as big as 0.01uf, which would intrude significantly into the mid frequencies.

Mar 11, 2010 7:02 PM GMT
Not a Replied:

Additionally, you can take the fixed resitor and use a 10k pot there as well. That will act as a volume control. It will interact with the treble-cut filter a little (at high volumes, the treble cut will be a little less effective). If you find this effect to be to significant at high volumes, then put a fixed reistor in series with the voloume pot so that even at high volumes there is always SOME resitance to force the highs down the lead through the cap to ground.

Mar 13, 2010 8:48 AM GMT
Iggy K Replied:

I was putting an old mic element into wooden box, then i pluged into a amp over a boss oc2 pedal, and im getting a low bas tone. So if you have a extra octave pedal you can use it...

Mar 13, 2010 1:01 PM GMT
HarpSkunk Replied:

Hi Iggy,

Yep I did the same, and I must say the tone was perfect, but I want to make a stomp box for a friend and great guy though he is, i would rather keep the Octave pedal, I also like a challenge! Thanks for the post,


Jun 23, 2010 5:27 AM GMT
Maka M Replied:

I went the simple route andmade oa box out of 1/4" ply that was laying around. I just eyeballed the shape from a commercial stomp box on eBay. Its basically a box about 10" long, 6" wide and tapers from 2" to 3/4" inch thick.

I put my most expensive element in it (a telephone hearing - yep, hearing, not speaking - element from an old office phone - cost=$0) and taped it to the bottom then wired it to a 1/4" jack ($1.95) mounted in the back. Painted it all matt black (hides many woodworking deficiencies) and put a small rubber foot (4 for $2.95) on each corner on the bottom (stops it wandering and gives it some resonating space). A standard guitar cable into a PA (or even a bass practice amp) and you're in business.

Its got a big enough surface area on top to get quite a variety of tones, depending on where you tap. Hardness of footwear also makes a difference. For something a bit unusual, put a bit of cardboard under one of its feet and rock it back and forwards - two beats for one action if you're on a hard floor!

Good fun!

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