DIY Foot Drum

[jugglindan]

I am hatching a plan for a new pedal build, but something different this time.

I am thinking of picking up a cheap piezo transducer on eBay, and putting it into a wooden foot drum/stomp box sort of thing. I have seen people wire them as a passive circuit with just a volume pot which I will try first, but if I need to massage the output a bit more I will build a piezo preamp and wire it into the wooden box. This circuit might be overkill (https://tagboardeffects.blogspot.com/2017/05/barcus-berry-3000a-buffer-preamp-eq.html), but I have all the components and the volume, bass, and treble controls might be handy for shaping the sound.

I just wish my woodworking skills were up to making something fancy. I can probably manage something functional but ugly.


I only have one amp, and don't really want to use a mixer to blend this into my guitar signal so I am hoping that the preamp output will have a suitable level to go into the aux input on my THR. If not I could run a simple headphone amp after the pre-amp. Or I could build a 2 channel mono mixer, but I am worried about adding extra noise into my main signal.

Does anyone have any experience with this sort of thing? Any advice or suggestions?

DC

[Bakersdozen]

Cool project idea! I always wondering how these worked, but never got round to doing any research. I would have thought they would be better going into more of a PA rather than a guitar speaker. Something at least 12 inch, 15 inch being ideal as it is mimicking some of the sub frequencies of a kick drum.

[Simon Barden]

I really don't get the description of the preamp. It says it's designed to work with electret condenser mic systems, but those need DC power supplied to them and a low input impedance. Whereas a piezo hates DC and needs a high input impedance. Ideally 5-10 meg ohms for most piezos for the flattest response. As the input impedance is stated as 2.2 Meg, then it looks like a piezo design, but with some wrong descriptive words.

Some piezos work best with 1-2 meg ohm input impedances, some are better at 10 meg. I have no idea what makes the difference. But too low an input impedance and the bass end will be missing, too high and you get a lot more bass (which is really what you want with a kick pedal).

I'd suggest looking for a preamp with a mid control as well, as that is very important for shaping the sound. For a bass drum sound, you need a fair bit of low end, around the 80-100Hz area, and some high frequency punch around 3kHz, and a bit of a cut in the mids.

The high impedance means that the output lead is very prone to picking up noise, and any capacitance will roll off the top end quite quickly. So any wire should be kept as short as possible.

I'm not sure a guitar amp is the best amp to use for such a pedal, as a lot of bass and a fast attack transient could give a lot more speaker cone travel than it's designed for if used at any volume.

[jugglindan]

Thanks Simon,
I agree the description of that particular preamp is a bit off. I think it was written by marketing not engineering. It's pretty much a piezo preamp with two tone controls as far as I can tell. I might be able to tweak the tone filter values to shift the bass control into the low-mid zone, or I could go with a simpler piezo preamp (https://tagboardeffects.blogspot.com/2014/04/acoustic-piezo-preamp.html) and run the output of that into a separate 3 knob tone circuit.

Simon and BD, you have me thinking my amp won't cut it. This was meant to be a cheap project, but I might end up needing a bass amp. Better build a bass kit too then! Although my THR has a bass amp channel, so it should be safe but I think it must attenuate the bass frequencies a fair bit.

And yes, I could just buy a Peterman Recession Buster (https://www.peterman.com.au/music3/RB-Snare) for a bargain price, but where's the fun in that?

[jugglindan]

BD, I forgot to add that there are quite a few designs. Some of the pro models use piezo pickups but I am sure they have some sort of onboard processing, maybe digital in some cases, as well. Because I can't see how stomping on a box would sound like a snare, or hi-hat, or cowbells. The version I am thinking about is sort of like tapping on the body of an acoustic guitar fitted with piezo pickups.

Another interesting design uses bass pickups (https://diyguitar.ca/diy-gears/p-bass-stomp-box/).

[jugglindan]

Simon, thanks also for the tip about preamp input impedances. I can tune that so will breadboard the circuit first to get the values sorted.

Sent from my moto g(7) using Tapatalk

[Bakersdozen]

Yeah that's the sound I figured you were going for. I did always presume they were made from pickups [emoji16]

[JimC]

You might want to see about including a high pass filter in your circuit so you can filter out subsonics and near subsonics which are major speaker killers.

[Simon Barden]

It doesn't need to be a bass pickup. There's nothing inherently different between a guitar and a bass pickup except the number of coils and the coil spacing. Same magnets, same typical 42AWG wire. So a guitar pickup will pick up just as much bass end. Just use whatever's handy/spare/cheapest. Single coils will probably be better as they have less mid-range emphasis.

No need for a preamp or high impedance input then.

Most piezo-style kick blocks I believe are pretty solid as you really just want the 'thump' of the wood as your foot hits it. But a pickup style unit will need a thinnish top that can resonate - at least a bit. You don't want a long sustain and you don't want it so resonant that you get acoustic feedback when you apply a bit of volume.

[jugglindan]

You might want to see about including a high pass filter in your circuit so you can filter out subsonics and near subsonics which are major speaker killers.

Good idea. I could do that in the tone control stage after amplification. And the circuit I am looking at using (https://www.eleccircuit.com/acoustic-guitar-pickup-circuit-using-tl071/) (the Barcus Berry circuit has some errors so will use something simpler) has a 0.1uF input filter cap, which combined with the 2.2m half of the voltage divider going to ground should act like a high-pass filter as well. According to Jack Orman's R-C filter calculator (http://www.muzique.com/schem/filter.htm), it should attenuate below 0.7 Hz. Which is maybe a bit low. I think it's mainly intended as a DC filter. I could experiment with a lower value cap to raise the corner frequency perhaps. Or just handle it in the tone circuit.

[jugglindan]

It doesn't need to be a bass pickup. There's nothing inherently different between a guitar and a bass pickup except the number of coils and the coil spacing. Same magnets, same typical 42AWG wire. So a guitar pickup will pick up just as much bass end. Just use whatever's handy/spare/cheapest. Single coils will probably be better as they have less mid-range emphasis.

No need for a preamp or high impedance input then.

Most piezo-style kick blocks I believe are pretty solid as you really just want the 'thump' of the wood as your foot hits it. But a pickup style unit will need a thinnish top that can resonate - at least a bit. You don't want a long sustain and you don't want it so resonant that you get acoustic feedback when you apply a bit of volume.

Interesting. I do have a few spare pickups around. And I have an LM386 headphone amp that I built a few years ago that could maybe drive a speaker or the headphone input on my amp, at least for experimenting. And I found some piezo transducers for under $10 on eBay, so experiments seem likely.

Given my lack of a bass amp, I have a new idea. Make the wooden box large enough to house a small 386-based amp (like a noisy cricket or something modded for bass) and a speaker. A self-contained stomp box sub-woofer thingy.

[FrankenWashie]

Hmmm, I’ve all sorts of pallet wood, iron wood, blue gum, mahogany and ash scraps lying around the lab....if someone was to send me some dimensions for a box like thingy, Igor might be able to stitch, I mean, thtitch, something together....

[jugglindan]

Hmmm, I’ve all sorts of pallet wood, iron wood, blue gum, mahogany and ash scraps lying around the lab....if someone was to send me some dimensions for a box like thingy, Igor might be able to stitch, I mean, thtitch, something together....

I like the cut of Igor's jib, or whatever that hump is called. Give me time to move this project beyond the embryonic stage and I might well take you up on that offer!

[Ig0r]

I like the cut of Igor's jib, or whatever that hump is called. Give me time to move this project beyond the embryonic stage and I might well take you up on that offer!

Very kind of you to thay tho Marthter Dan, but it’th not my Jib. It belonged to my Couthin Igor and wath repurpothed after an unfortunate mithunderthtanding with an angry mob.

[jugglindan]

Very kind of you to thay tho Marthter Dan, but it’th not my Jib. It belonged to my Couthin Igor and wath repurpothed after an unfortunate mithunderthtanding with an angry mob.

Can't .... reply ... too busy .... la la laughing...

[McCreed]

I played in touring duos and trios that used a stompbox instead of a drummer. The best thing I ever heard was the Bigfoot by Wolftone. (now called Wild Dog following some lengthy legal issues)

My point is that (most) every other stompbox I heard, sounded real "clicky" with no real THUMP like you'd expect from a bass drum. The Bigfoot could sound huge and the guitar player ran it through a 10 band EQ into a 15" sub. We played pubs, theatres and festivals all around Australia and it always sounded great.
A lot of the DIY and old school stompboxes I saw were inconsistent in their performance, could be prone to feedback and as I said before, lacked big bottom.

I have no idea what the electronics were because the builder (from Byron Bay) would not tell anyone what the secret sauce was and drilled out all the screw heads after he assembled them.

I've heard the "Puck" ones and they still fell short of the Wolftone/Wild Dog brand.

[Simon Barden]

Piezo trigger playing back a sampled kick sound maybe?

[FrankenWashie]

I played in touring duos and trios that used a stompbox instead of a drummer. The best thing I ever heard was the Bigfoot by Wolftone. (now called Wild Dog following some lengthy legal issues)

My point is that (most) every other stompbox I heard, sounded real "clicky" with no real THUMP like you'd expect from a bass drum. The Bigfoot could sound huge and the guitar player ran it through a 10 band EQ into a 15" sub. We played pubs, theatres and festivals all around Australia and it always sounded great.
A lot of the DIY and old school stompboxes I saw were inconsistent in their performance, could be prone to feedback and as I said before, lacked big bottom.

I have no idea what the electronics were because the builder (from Byron Bay) would not tell anyone what the secret sauce was and drilled out all the screw heads after he assembled them.

I've heard the "Puck" ones and they still fell short of the Wolftone/Wild Dog brand.

They don’t miss, 200 for a smaller one up to 400 for one of the bigger ones, yikes!

[jugglindan]

I played in touring duos and trios that used a stompbox instead of a drummer. The best thing I ever heard was the Bigfoot by Wolftone. (now called Wild Dog following some lengthy legal issues)

My point is that (most) every other stompbox I heard, sounded real "clicky" with no real THUMP like you'd expect from a bass drum. The Bigfoot could sound huge and the guitar player ran it through a 10 band EQ into a 15" sub. We played pubs, theatres and festivals all around Australia and it always sounded great.
A lot of the DIY and old school stompboxes I saw were inconsistent in their performance, could be prone to feedback and as I said before, lacked big bottom.

I have no idea what the electronics were because the builder (from Byron Bay) would not tell anyone what the secret sauce was and drilled out all the screw heads after he assembled them.

I've heard the "Puck" ones and they still fell short of the Wolftone/Wild Dog brand.

Anything I build is likely to be very inconsistent. But then, so is my playing, so at least Stompy and I will have that in common :)


Piezo trigger playing back a sampled kick sound maybe?
Or a pressure switch? But yeah, you might be right. Maybe a lot of them don't amplify the stomp but instead just trigger a sample. Maybe if I get an old midi keyboard, program it for drums, wire one key to the stomp and hide the keyboard somewhere...nah.


They don’t miss, 200 for a smaller one up to 400 for one of the bigger ones, yikes!
Yikes indeed. It was looking at the prices that made me think DIY. That, and it sounds like a fun project to build. I can see two now. A small pedal, and something larger with the amp and speaker integrated. Maybe I could just buy an old combo amp and jump on that?

[Simon Barden]

Lots of old drum machines with a trigger input out there!

[jugglindan]

Lots of old drum machines with a trigger input out there!

While that would take a lot of the mad scientist fun out of it, it would also be pretty cool having the ability to program in different drum sounds.

[Andy40]

Out of this whole thread, I heard.....


I am hatching a plan for a new pedal build, but something different this time.

I only have one amp,......... Any advice or suggestions?



You need to build another amp and experience that radness.

[Woltz]

What size enclosure? I have some scrap timber which may be large enough and I have a possible solution for you for making the box.

Sent from my SM-G960F using Tapatalk

[jugglindan]

Thanks Woltz. I don't know what size yet, need to do some prototyping with books 'n stuff. Also trying to decide on the right profile. For playing seated I think a wide but fairly low box would work nicely, but should it be a wedge, or a flat rectangle?

This project will probably move fairly slowly since I have some other pedals and my tele to work on. I am getting very impatient with the tele, I really really want to play it! Oh, and I am also trying to find time for that other thing we do sometimes - playing guitar.

About the only other idea I have had for this one is the name. Either "Stompy", or "Monster Mash".

[jugglindan]

Out of this whole thread, I heard.....



You need to build another amp and experience that radness.

I was thinking about building one of the Lamington amps later this year, but it won't be for bass either.

[Simon Barden]

I'd go for a wedge shape myself. Something reasonably heavy to stop it moving around, as well as rubber foam underneath for grip.

[jugglindan]

I just tested using a few books I have around, and found one that fits perfectly under foot, is a comfortable height, and is high enough for the potential electronics and wiring.
35316

Two people have generously offered to help with the box construction, so please let me know if those dimensions are OK. Otherwise I am sure I can knock something together with BGS pine.

The generous size is so I can fit my whole foot on, and to leave room for a speaker.

Plan 1 for the speaker is to fit the piezo transducer, a small amp and the speaker all in the box, to see if an all in one solution can be made. I suspect the thump would be less than satisfying, but it might work for home use. Feedback might be an issue though. OK, ditch plan 1.

Plan 2 for the speaker is that some people have used a small speaker as the microphone instead of piezo pickups. Some claim they give a better thump. For example, here is a simple design (https://nzguitars.com//forum/viewtopic.php?p=527663#p527663) that doesn't even use a preamp. Not sure if they have something off-board or run straight to amp or mixer:
3531735318

[jugglindan]

For the electrical side of things, if a speaker works well enough without a preamp then I would probably fit a passive tone and volume control, maybe something like the Fender Greasebucket (https://www.premierguitar.com/articles/12311-mod-garage-the-fender-greasebucket-tone-circuit) - the high and low pass controls might be nice, but then it might be better to have separate pots for bass and treble.

If I use a piezo or if the speaker-mike needs an amp, then I will probably use a simple preamp on stripboard along either a 2 or 3 pot tone circuit and volume. The box dimensions should have room along the top edge (150mm) for 4 pots, DC jack, and 6.5mm output jack.

Or, I could keep Mr Stompy simple, and build a very cheap combo amp from this Ikea box and a noisy cricket:
35319

And yes, I tested that box as a stomp. It's much too high for comfort.

[FrankenWashie]

Those dimensions are not an issue, JD. There’s a couple of options for it, I’ve a couple of blanks that could be hollowed out to suit, or a spec box built to house what you want.
are you going to stick with the flat format or did you want to wedge it a bit for ease of use?

[jugglindan]

A bit of taper might be nice. Even 1 cm difference would work, so 50mm at the back and 40mm at the front.

I had no specific plans for how the box would be constructed, beyond "box, with lid screwed on the bottom". I think in my mind it was sort of a wooden pedal enclosure. But I know almost nothing about building things out of wood, so please suggest whatever you think might work.

[JohnH]

This is an excellent idea for a project. I have a whole box of cheap pickups kicking around in a box somewhere, and now I'm tempted to try the bass pickup version

[It seems my previous post vanished, so if you can all see two posts I apologise for the double post]

[jugglindan]

This is an excellent idea for a project. I have a whole box of cheap pickups kicking around in a box somewhere, and now I'm tempted to try the bass pickup version

[It seems my previous post vanished, so if you can all see two posts I apologise for the double post]

Just one post here. If you do build one I will be very interested in your results. This is pure experimentation for me.

[Simon Barden]

I'm not sure how well standard volume and tone controls would work with a speaker as a transducer. You're looking at 8 to 16 ohm for the speaker impedance, rather than 6+k ohms for a guitar pickup. So a much lower volume pot resistance would be required and you'd have to look at the circuit maths as to whether you could get a standard passive tone control to work at all. I suppose it should do.

[jugglindan]

I'm not sure how well standard volume and tone controls would work with a speaker as a transducer. You're looking at 8 to 16 ohm for the speaker impedance, rather than 6+k ohms for a guitar pickup. So a much lower volume pot resistance would be required and you'd have to look at the circuit maths as to whether you could get a standard passive tone control to work at all. I suppose it should do.

Good point Simon. The output from the speaker will be so much lower than a pickup, so the voltage drop across 250k might be way too much. It is hard to see how it could work well without a preamp. And if I have a preamp I may as well do the tone controls in that (apart from a simple low-pass filter after the speaker), or in the main amp.

My plan has evolved now into stomp box --> piezo preamp (should work well enough for speaker transducer as well I hope) --> cigar-box amp.

If the cigar box amp doesn't have enough thump, I might be able to cook something up from an old PC speaker sub-woofer. But now I can't decide between a Little Gem, a Ruby, or a Noisy Cricket. Will have to breadboard all three and compare.

[Cliff Rogers]

Not entirely correct.
Output to Input impedance matching is a subject not well understood.
Below is a link to a page on microphone impedance that may help you understand if you want to plough through it.

In a nutshell, low impedance output into high input works, high impedance output into low impedance input doesn’t.

It has more to do with the signal level presented to the input than the impedance of the output.

100K, 250K & 500K volume pots are better for matching small signals to a high impedance input than a lower value pot.

Here are some links.
https://mynewmicrophone.com/microphone-impedance/
https://sound-au.com/project01.htm

[jugglindan]

Not entirely correct.
Output to Input impedance matching is a subject not well understood.
Below is a link to a page on microphone impedance that may help you understand if you want to plough through it.

In a nutshell, low impedance output into high input works, high impedance output into low impedance input doesn’t.

It has more to do with the signal level presented to the input than the impedance of the output.

100K, 250K & 500K volume pots are better for matching small signals to a high impedance input than a lower value pot.

Here are some links.
https://mynewmicrophone.com/microphone-impedance/
https://sound-au.com/project01.htm

Thanks Cliff. That's why I love these projects and this forum: they help me learn things :)

I have used the sound-au pages for lots of other information, so I will start with that one.

DC

[JohnH]

That's great, thanks Cliff. Everything about this is confusing for me, but honestly the learning is most of the fun!

[Simon Barden]

A 500 ohm pot might work for volume. You don't want to add too much extra resistance in to the signal path at part-volume. If you keep a similar resistance ratio as a standard pickup e.g 8k to 500k, then 8 ohms to 500 ohms is about right. Whilst the pot acts as a voltage divider, and in theory the output voltage level should be the same with any pot, the current produced with a 500k pot compared to a 500 ohm pot will just be so much less, making it far more prone to picking up induced noise and making pot operation scratchy. The pot just needs to have a high enough resistance so that it doesn't 'load' the speaker, and a minimum 1:10 ratio is normally stated as being sufficient for that.

The pot resistance will form part of the input impedance seen by the speaker, but with a guitar amp impedance normally being around 1 meg ohm, the speaker will only really see the impedance of the pot.

A modern mic preamp will typically have an input impedance of between 1200 ohms to 3000 ohms. Older mic pre designs (and modern copies) tend to have impedances towards the lower end of the scale It would obviously be just as easy to make the input impedance a lot higher, but they don't.

A typical dynamic microphone will have an output impedance between 150 ohms and 300 ohms. So some dynamic mics may be slightly loaded by the lower input impedance mic pres, and in fact some stand-alone mic pre designs have adjustable input impedances so you can load the mic output for a different frequency response (less highs with lower impedances).

Speaker-based drum mics like the Yamaha Subkick (originally the LF driver from an NS-10M in a round enclosure), will run directly into the mic pre of a mixing desk, so will be running into that circa 3k input impedance. But that's a 7" speaker and the signal level produced by sticking that on a loud kick drum is going to be significantly greater than that made by a much smaller speaker resonating due to being given a small knock by your foot.

Personally I'd think about active controls, and look at getting say a cheap Behringer EQ700 pedal, stripping it down and mounting it in the enclosure. So you'll have level and tone shaping controls available. It won't take you to zero volume, but you won't need that. In fact you may welcome the ability to boost the output level!

[jugglindan]

I found this excellent article (http://www.muzique.com/lab/imp.htm) by Jack Orman that boils it down to voltage dividers and Ohm's law and finally it makes sense why low output and high input impedance is the way to go. The reverse leads to signal loss proportional to how large the mic impedance is relative to the input impedance.

Jack is talking about pickups and guitar pedals but that detail is irrelevant. It's really about a signal source and a sink. He also simplifies impedance to resistance by assuming it has a fixed value at all frequencies, but it still gets the concept across. And he indicates later how the effect is greater at higher frequencies.

As for EQ, building something is doable pretty much from parts I already have. I am not sure where to put the EQ, or how many to have. I can tack active 3-band EQ to the preamp built into the stomp, and the Noisy Cricket (or maybe a Ruby Tuby (https://tagboardeffects.blogspot.com/2014/10/ruby-tuby.html) if I get extravagant, although reviews are mixed) will also have some EQ in the cigar-box amp.

DC

[jugglindan]

I probably need to start a different build diary for this, but I went shopping at The Green Shed (not the Big Green Shed) but a place in Canberra next to the landfill site that sells reclaimed stuff for next to nothing. I was looking for parts for the cigar-box mini amp that I am building for the foot stomp (or other things).

For the princely sum of $5 I got this old Sanyo speaker:
3536935370

It's as ugly as anything I can imagine, but paint can fix that, and it's the right size and the 6" 5W speaker is usable. It likely won't give anything like a solid thump, but this mini amp might end up being used for a completely different purpose anyway.

I also picked up the chassis of a Kustom Sienna 30W acoustic amp, again for $5:
35371

It looks like someone let the magic smoke out of a cap in the power supply section:
35372

While I can replace the cap and fuse, I would be worried about why it blew in the first place and whether there are other faults. I don't have a chassis, and if I went to the trouble to build one, I would want to put a homebrew tube amp in, not this. So I might strip it for parts. I can salvage all the pots, the knobs, jacks etc. Most passive components are not worth enough to desolder, but there is a nice JRC13700 opamp sitting on an adapter board that is just ready to use in a pedal. There is also a spring reverb unit that looks OK. Too large for a pedal but I might be able to use it somewhere else, like in the mini amp.

[Ig0r]

Ethellent thtart Marthter Dan! Do you need any thpare electrodeth? I’ve a Jacob’th ladder and a lightning rod lying about that are thtill good for a few thouthand voltth or tho.

[jugglindan]

Why thank you Ig0r, but those Jacob'th Ladderth (uhum, sorry, got something stuck in my throat, hack that's better) scare me silly.

[Cliff Rogers]

It looks like someone let the magic smoke out of a cap in the power supply section:
35372

While I can replace the cap and fuse, I would be worried about why it blew in the first ......

Read the story of the capacitor plague.
https://en.m.wikipedia.org/wiki/Capacitor_plague

[jugglindan]

Read the story of the capacitor plague.
https://en.m.wikipedia.org/wiki/Capacitor_plague

Thanks Cliff, that was an interesting read. I don't know when the amp was manufactured, but at least I now know it's possible for the cap to fail catastrophically all by itself, and there may not be anything else wrong. Fortunately I haven't started tearing down the amp for parts (I got distracted testing a chorus/vibrato pedal by playing shimmery ambient stuff), so attempting a fix is possible.

DC

[Fretworn]

Ethellent thtart Marthter Dan! Do you need any thpare electrodeth? I’ve a Jacob’th ladder and a lightning rod lying about that are thtill good for a few thouthand voltth or tho.

Can we please get Ig0r an avatar.....
I’m voting for ....
http://2.bp.blogspot.com/-b8q9DWe-IOw/UJB3dbMAEXI/AAAAAAAAHOc/rbhKqpPQhf4/s1600/Marty+Feldman+Young+Frankenstein.PNG

Or

http://bestsimilar.com/img/movie/thumb/5b/15615.jpg

[jugglindan]

Definitely Marty Feldman. That's a great movie.

Sent from my moto g(7) using Tapatalk

[Ig0r]

There it’s thertainly a family rethembelenth, I think he ith (partth of) my thecond couthin theveral timeth removed.
Wathte not want not, ath the old thaying goeth.

[McCreed]

What hump?

[Sonic Mountain]

So we are making profiles for all our multiple personalities now? Oh boy, things are going to get crowded in here.

[Bakersdozen]

So we are making profiles for all our multiple personalities now? Oh boy, things are going to get crowded in here.This is what happens when @FrankenWashie is lax on changing the WiFi password periodically.

[jugglindan]

So we are making profiles for all our multiple personalities now? Oh boy, things are going to get crowded in here.

Ig0r isn't a multiple personality. Just multiple people.

[FrankenWashie]

So we are making profiles for all our multiple personalities now? Oh boy, things are going to get crowded in here.

Im sure he’ll limp off back into the shadows of the lab before long. There’s only so much lithping the keyboard can soak up.....

[Sonic Mountain]

I'm surprised he can type, what with the 4 thumbs, 3 index fingers and the repurposed monkey toes.

[jugglindan]

A monkey paw sure helped Bob Log. I wonder if Ig0r can play like that.

Sent from my moto g(7) using Tapatalk

[McCreed]

A monkey paw sure helped Bob Log. I wonder if Ig0r can play like that.

I had to google Bob Log... found some YT videos...

That's eight minutes of my life I'll never get back.

[jugglindan]

I had to google Bob Log... found some YT videos...

That's eight minutes of my life I'll never get back.

I saw him live a couple of times. His shows in person have a certain energetic charm, but I don't listen to his CDs. There's only so much frenetic slide guitar by a man wearing a helmet and singing into an old telephone mic that I can take.

[jugglindan]

Back to the original topic, I did some suck-it-and-see-engineering just now. Stuck a disk piezo transducer to the bottom of a small wooder crate and plugged it into my THR set to the bass amp sim. The output was low (no pre-amp) but the audio quality was apparent. Rather than the satisfying thump I am aiming for, I got something more akin to a tap, or a knock, with just a little bit of click mixed in. I don't even think EQ would help (I maxed the amp bass and adjusted mid and treble) since the low frequencies didn't appear to be there to start with. Maybe a different wooden box would help, or wearing boots instead of socks.

To compare, I then hooked the broken 6" sub driver up as a microphone and gave the cone a light tap. From the amp came the rich resonant thumpa thumpa I was looking for with this project. I tested again with the Sanyo speaker I got for the mini amp project, and again, a nice thump from the amp. It was not as rich as the sub driver, but it was still in the ballpark. The piezo wasn't in the ballpark. It wasn't in the car park. I don't even think it was in the right part of town.

I now understand why many of the DIY foot drum designs I looked at use a speaker as the transducer. In this application, more or less faithful reproduction of the vibrations isn't really the goal.

[JohnH]

Good to know. I have a couple of old speakers kicking around somewhere, maybe I should dig one out before I try playing around on the weekend

[Brendan]

OK - so here's one I built with my brother last time I was in Canberra. Haven't wired it up - hence front cover not sitting properly. Also need to clear coat it and chamfer the edges a little.

[jugglindan]

That looks awesome Brendan. Very close to the sort of thing I am working towards. I know it's not wired up, but what are you using inside as the microphone? Have you tested with temporary wiring? How does it sound?

DC

[FrankenWashie]

Back to the original topic, I did some suck-it-and-see-engineering just now. Stuck a disk piezo transducer to the bottom of a small wooder crate and plugged it into my THR set to the bass amp sim. The output was low (no pre-amp) but the audio quality was apparent. Rather than the satisfying thump I am aiming for, I got something more akin to a tap, or a knock, with just a little bit of click mixed in. I don't even think EQ would help (I maxed the amp bass and adjusted mid and treble) since the low frequencies didn't appear to be there to start with. Maybe a different wooden box would help, or wearing boots instead of socks.

To compare, I then hooked the broken 6" sub driver up as a microphone and gave the cone a light tap. From the amp came the rich resonant thumpa thumpa I was looking for with this project. I tested again with the Sanyo speaker I got for the mini amp project, and again, a nice thump from the amp. It was not as rich as the sub driver, but it was still in the ballpark. The piezo wasn't in the ballpark. It wasn't in the car park. I don't even think it was in the right part of town.

I now understand why many of the DIY foot drum designs I looked at use a speaker as the transducer. In this application, more or less faithful reproduction of the vibrations isn't really the goal.

Does that affect the dimensions for the box Dan?

[jugglindan]

Does that affect the dimensions for the box Dan?

Good question. At first I thought it wouldn't, since the 150mm width would be enough for a 4" speaker, or maybe a 5" depending on the timber thickness and internal dimensions. But I am now wondering how much height will be needed. I know speaker drivers vary a lot in depth. Today I will look up dimensions of some of the speakers I might use and get back to you.

DC

[jugglindan]

OK, I have a 5" speaker that has a diameter of 135mm once I include the metal surround. That will easily fit into the 150mm width even if the wood was no more than 6 or 7mm thick. But the speaker is 50mm high (measured with digital calipers). So it's too big, especially the taper from 50mm to 40mm plan. I am happy to keep the box as is, and obtain a smaller diameter speaker. Or the box could have 10mm added to the height (tapering 60 to 50mm). That's getting pretty big though, so maybe keep it as is and I will get a smaller speaker if the piezo doesn't sound right.

DC

[FrankenWashie]

Hmmm... I am pondering how to go about this.
if we make it more wedge shaped, the you might over come the depth issue some what. But we will still end up wit a chunky enclosure.

Out of interest what size piezo did you test?

[jugglindan]

I agree that the box shouldn't get any larger. The speaker I have is just too large (it's a 5"). I can get a generic 4" speaker from Jaycar for $5. It will easily fit into the current planned dimensions. I was just at Jaycar today getting some parts for my current pedal and amp builds. I should have picked up one of the speakers.

The piezo I tested is a 3cm disk. It probably wasn't a totally fair test though, as the box was a bit dinky, making it hard to stomp with my foot. A lot of people use piezo mics in these, so it should work. The box Brendan built looks too small to house a speaker, so I suspect it has a piezo inside.

[Brendan]

That looks awesome Brendan. Very close to the sort of thing I am working towards. I know it's not wired up, but what are you using inside as the microphone? Have you tested with temporary wiring? How does it sound?

DC

Nothing as yet - hence why I'm following intently. Didn't want to stuff it up with a couple of dinky piezo's and haven't really revisited to see alternatives...

[jugglindan]

Nothing as yet - hence why I'm following intently. Didn't want to stuff it up with a couple of dinky piezo's and haven't really revisited to see alternatives...

Ah, I see. Well, I am happy to be the guinea pig :)
There are three main designs I have seen: piezo, speaker, and a pickup mounted close to a metallic object under the stomping surface. I will try the first two.

[Brendan]

I've got an old p bass pickup kicking around - may see if I can rig that up inside without a full commit.

[jugglindan]

I've got an old p bass pickup kicking around - may see if I can rig that up inside without a full commit.

Great. I think I linked to a design or two like that back on page 1 or 2. I would be very interested to see how it works out, even though I don't have any spare pickups laying around. I like that it is less likely to need a preamp while I am pretty much committed to building a preamp into my mini amp as an optional input.

[FrankenWashie]

So the Lab got a bit busy this afternoon.

I needed to do some rip cutting on a large chunk of QLD Maple and some mahogany that has been laying about.

This involved passing an 8” wide board through my bandsaw, with a 20mm ripping blade on it. Slightly scary. Push sticks mandatory.

https://uploads.tapatalk-cdn.com/20200606/962426584abc333b3ab19f1a303aa7b7.jpghttps://uploads.tapatalk-cdn.com/20200606/fd01bfe5a27a00650c96ad2e566c149b.jpg

I’m building 2 enclosures, one is more or less to the basic box specified by Jugglindan, the other is a FrankenLab twist version.

I decided to use some of the beech I had for the box sides; on the square box for DC, the ends will be Merbau, on the FL version sides and ends are beech.

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The tops will be QMaple, the key decision for being 1/4” or 1/2” top?




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[FrankenWashie]

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[Simon Barden]

I'm just wondering if the tops might be a little too thick to resonate well enough to get a good 'thump' sound. You can but see and you can always thin it down if necessary.

[jugglindan]

Whoa, that looks amazing!

And I think that the 1/4" top is more than enough. I agree with Simon it needs to allow vibrations through to the microphone on the other side. But since this is all new to me, I don't know for certain.

I should get the amp stuff wired up in the next few days to test the electrical side of things.

FrankenWashie, I see you are building your own. Do you want me to build a piezo preamp in a box to send up to you? Or do you have something suitable already?

[FrankenWashie]

I'm just wondering if the tops might be a little too thick to resonate well enough to get a good 'thump' sound. You can but see and you can always thin it down if necessary.

I think that in the wedge form version, it will definitely need thinning to perhaps 1/8”, with the bigger box version it might be okay at 1/4”.
Waiting on some piezo discs to test that.

[FrankenWashie]

Whoa, that looks amazing!

And I think that the 1/4" top is more than enough. I agree with Simon it needs to allow vibrations through to the microphone on the other side. But since this is all new to me, I don't know for certain.

I should get the amp stuff wired up in the next few days to test the electrical side of things.

FrankenWashie, I see you are building your own. Do you want me to build a piezo preamp in a box to send up to you? Or do you have something suitable already?

I’m going to see what I can cobble together to fill that function DC. I’m playing with similar bits in the franken Reso build so it’s all good experience.


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[FrankenWashie]

I think that in the wedge form version, it will definitely need thinning to perhaps 1/8”, with the bigger box version it might be okay at 1/4”.
Waiting on some piezo discs to test that.

Okay if anyone is curious as to why it takes the FrankenLab forever and a day to get anything done, here is a good example.
https://uploads.tapatalk-cdn.com/20200607/920f5b4f9ea310516567a9dafe7d7bb1.jpg

We’ve got 3 or 4 differing thickness QMaple blanks to use as the skin for these two stomps. We hard right turn and slice up some rock maple into 4mm boards and laminate two together just ‘cause we got curious as to how that would sound.

We also chewed up an hour and a half because we had this idea about slicing up some merbau strips and using them as inlays in the corner of the stomp boxes, cause y’know, why not!

https://uploads.tapatalk-cdn.com/20200607/a012bfc4d35469c0246ec5ed98f69b52.jpg

ps: DC where do you want your jack mounted? Front of box or side or other?


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[jugglindan]

I am simultaneously laughing at your description of getting distracted, and gawping in admiration at your workshop as glimpsed in these photos.

Jack to the rear please, just where it looks like yours is drilled.

[FrankenWashie]

So some progress shots, here is the DC stomp in progress

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The Lab stomp is now mostly complete, bar the piezo discs, which I have now been advised won’t get here until August. In the interim I’m going to have a crack at mounting an old pick up in it and seeing how that goes.

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[Bakersdozen]

Fine skills there Boss

[FrankenWashie]

Fine skills there Boss

thanks BD. It’s been a nice diversion

[jugglindan]

Lookin' good :)

Also, I got three piezo transducers with the set I bought. They are currently wired in parallel on the one socket, but I was planning to snip two off anyway as I don't need all three. Happy to mail one up to you.

[JohnH]

An update on my attempts as I play along at home.

I tried a single coil with a thin metal sheet but couldn't really get it to sound any good. To be fair, I didn't spend a lot of time on it, but it wasn't really doing much for me.

Tried a piezo, but also found it made a tiny tap rather than a thud (probably unsurprisingly).

Raided my random speaker box and found I only had these three to choose from. The big guy is a 4" 4 Ohm, then there's a small 8 Ohm and the two small 4 Ohm speakers from an old bluetooth unit. After trying all three the bluetooth speaker gave the best result - a good thud, which was quite loud when I ran it through a boost pedal

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[jugglindan]

It's looking more and more like a small speaker is the way to go with these things. I have a 5" driver and can salvage some smaller 3" speakers from the remains of the PC speaker set that I got the broken sub speaker from.

[JohnH]

When the 4" one went thump it was impressive, but I really needed to give it a whack. I only had to tap the small one for a good sound, so that seems ideal for the application. Glad I salvaged that little bluetooth speaker from my old job!

[jugglindan]

Interesting, thanks.

[FrankenWashie]

http://youtu.be/HPruDtqPZzw

[jugglindan]

Awesome!!!

I had better crack on with the FS-808. Taking a break tonight. One too many Coopers Extra Stouts for good soldering :)

[FrankenWashie]

Umm, I might have gone a little OTT on sanding this afternoon.

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This result is particularly exciting, as the blank that generated the top and bottom of the enclosure came off of the plank that generated this puppy:

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I hadn’t thought to ask what finish you wanted on this before I started sanding, if you want to paint or clear it you’ll probably need to knock it back to 320 or 400, as opposed to the polished finish I’ve got it to.




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[FrankenWashie]

the image quality isn’t fantastic but hopefully it conveys how much grain feature has come up on this thing.



http://youtu.be/tSFlq7p4ON0

[jugglindan]

That looks fantastic. There is no way I could put paint over that. I have some satin poly, but maybe an oil finish of some sort would be better. I am open to suggestions.

I also love the connection to one of your other builds. Do you have a link to the build diary of that guitar? I made good progress on the FS-808 yesterday, and should be able to wire it up for testing tonight.

[FrankenWashie]

That looks fantastic. There is no way I could put paint over that. I have some satin poly, but maybe an oil finish of some sort would be better. I am open to suggestions.

I also love the connection to one of your other builds. Do you have a link to the build diary of that guitar? I made good progress on the FS-808 yesterday, and should be able to wire it up for testing tonight.

That build is just a body blank at this point, it doesn’t yet have a defined plan. And to be fair it is about 6th in the queue of things I need to play with. With the exception of this stomp diversion, build efforts are focusing on Build for a Mate and Igor gets the blues.

[jugglindan]

Igor gets the Blues

I like that!

[McCreed]

Those little 4 ohm ones just look thumpier :p

[jugglindan]

Applying the electrodes to this project now that the beautiful box has arrived in the mail.

The parts I need to finish building the preamp are still en-route from Tayda, so I loaded the Xtomp mini with some of the preamp patches.

First experiment: piezo transducers. I stuck one underneath the box top, and ran it through the xtomp and into my THR on the guitar input.
Result: the same unsatisfactory clicks and taps as before. Using a piezo pickup will require some serious EQ. The best sound I could get was with the Xotic RC Booster patch loaded into the Xtomp, with gain and volume maxed, bass maxed and treble to zero. And when I say best it still wasn't good. I tried the Aux input on the amp: less volume and clearer sound as it wasn't getting hit with the reverb. But still not what I am after.

Second experiment: A small speaker salvaged from old PC speakers taped to the underside of the box, wired through the RC Booster.
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Result: much better. The speaker only responds to the lower frequencies, so I get less of the stuff I don't want. With the same RC Booster settings as before this is much closer to a usable sound. I won't get the same result from the preamp I am building though. While I can boost the gain/volume sufficiently, it only has a passive EQ while the AC Booster is active so it can really push the low end.

Future experiments: Different speakers, an old bass pickup (once I can get hold of one).

Clearly more to these magic boxes than I first thought!

[jugglindan]

Revisiting the piezo option might be worth doing. This video shows a cigar box build with a piezo and simple passive circuit and it sounds quite good. I think the key difference is that it's plugged into a decent acoustic amp.

https://www.youtube.com/watch?v=7h1VF1fsTAw

[Simon Barden]

It doesn't have to be a bass pickup. They aren't any different to guitar ones except in relation to pole spacing and number of poles.

A bigger diameter speaker would probably give more bass end. And a low power one should have a softer speaker compliance than a higher power one, so the cone will move more for a given input.

[jugglindan]

Thanks Simon.

Yes, I definitely need to try different speakers. And I have the old set of Schaller active HSS pickups that I took out of the G&L. Should be able to hook one up with a battery to test it.

And here's another video showing an interesting build from an elm log that uses 2 piezo pickups. Although he does say at one point that the best result comes from cranking the bass on the amp.

https://www.youtube.com/watch?v=3hmltXZKHLc

All these videos give me confidence that eventually I will find a combination of electronics that will work.

[jugglindan]

Final bit of research for the night: found this showing how to modify a small speaker to get an improved bass response by adding weight to the membrane:

https://www.youtube.com/watch?v=a5dUmReP6ls

[Simon Barden]

In that position, technically his 'high-hat' is a 'low-hat' or 'low-boy'. That's the original position for them and they were known as 'low-boys' and weren't played with sticks, just a pedal. Then they got moved up a couple of feet to their now-standard position. One of the pieces of info I retained from a Carl Palmer drum clinic. #notadrummer

[jugglindan]

I didn't know that. Not planning on the whole cymbals thing, but I just tried taping a 20c coin to the small speaker and I definitely get a better bass thump. Boosting the signal and running through a low-pass filter and it's getting a bit closer to the sound I want. This time without the active EQ of the RC booster. Just a simple clean boost followed by the low-pass. This is progress because it's closer to what I can build easily.

Will need to ditch the piezo preamp circuit though, as it has a fixed gain of 2 (6dB). I needed maybe 18 or 20 dB boost. I will try replacing the fixed gain resistor with a pot, and if that doesn't work will just build a simple clean boost and add a low pass filter (standard passive bass control).

The roomy box has enough room to fit all this and a battery inside (switched by the jack) if the design works out.

[Simon Barden]

Technically a low pass filter isn't a standard bass control. It passes all frequencies below the filter cut-off (and actually some above, but it's rolling them off at the filter slope rate and will already be 3dB down at the filter frequency). A normal bass control is typically a shelving boost/cut, which only affects the bass frequencies. But a low pass filter should do what you want in terms of just leaving most off the bass and low mids, especially when paired with that boost to get the level up.

A kick drum normally has a low component and then a high-mid component from the beater that provides some definition to the sound in the 2-4kHz region. I don't know how much of those frequencies your weighted speaker produces, but I wonder if you could somehow pair the low-passed speaker with maybe a high-passed piezo signal to more closely mimic a real kick sound.

Again it's something you could test quickly out in a DAW after recording the two signals to see whether it would work at all.

[jugglindan]

Should I have said "standard tone control"? I was thinking of using a first-order passive RC low-pass filter, which I see in circuits a lot labeled as "tone". I guess "bass control" implies an active control that can boost or cut in a band. I did try a 5 band EQ, but it was easier to get a good result with a one-knob low-pass filter.

To do the piezo mix I would need the booster and low-pass filter on the speaker, and a piezo preamp with high-pass filter, then a 2 channel mixer (either passive or with an opamp) to blend. Sounds like a lot but it could probably all fit on a single stripboard. Maybe.

The DAW test certainly sounds easier than breadboarding all those circuits. Hopefully Audacity can do simple filters, because that's all I have.

But I might be able to get something decent using just the weighted speaker by pairing a Baxandall bass/treble tone control with a clean boost. Time to pull the Rat off the breadboard!

[Simon Barden]

Yes, probably a pedal standard tone pot. Though a standard, that LPF would probably be set a bit higher than what you'd require. You may not need piezo pre-amp if you just work with the sound it produces into a lower impedance input. The piezo preamp provides the high impedance required for a flat response if it's a single source transducer and needs to do full-range flat reproduction. But as a simple sound source, and with you 'throwing away' a lot of the sound it produces, and probably at a fairly low-level in the mix, you shouldn't need a special preamp for it.

Hence the suggestion to play with the two sounds in a DAW where you can adjust the LPF and HPF frequencies and mix levels to see whether you even think it adds anything extra or whether the speaker on its own is fine. As long as you record the two sounds at the same input gain level, you'll also find out how much relative gain one signal would need to the other.

Audacity should have LPF/HPF and shelving EQs available, so you can also test the Baxandall EQ and see what frequency settings/gain levels you'd need without having to even open your resistor box.

[jugglindan]

Still haven't recorded anything, but I built a mosfet-based boost on breadboard tonight. It's sort of a modified SHO (Soulsonic Crackle Not OK (https://tagboardeffects.blogspot.com/2014/03/soulsonic-crackle-not-ok.html)) set to max gain (no gain pot). Sounds quite good with guitar, and gets the level of the speaker transducer up high enough without too much noise despite being on a breadboard.

No bassy thump, but I haven't added a tone circuit yet. I think it would make an interesting boost pedal for guitar with the addition of tone and volume controls.

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