[DESIGN] Piezo-Piezo to Piezo-Switch Adaptor (by Keith Raper)

[PFozz]

Piezo/Piezo to Piezo/Switch Adaptor
by Keith Raper

DON’T MISS THE UPDATED INFO
BELOW THE ORIGINAL CONTENT 😉

The information provided here is freely available to all for NON-COMMERCIAL purposes only.

The schematics and information are provided ‘as is’, without warranty of any kind.

As everything provided on this website, the author (Keith Raper), EDrum For Free or any other party cannot be held responsible for any damages to yourself, others, or equipment while attempting
any of the projects listed on these pages.

Please use common sense.

---

Many of you and mostly members of the DTXPress Yahoo! group have heard about the “Magic Box” which will allow two pads to use one input on the DTXpress, and also combine two piezos from a single pad into a single piezo and rim switch signal for use on the DTXpress (some non Yamaha dual zone pads use two piezos instead of a single piezo and a rim switch).

As the original “Magic Box” was quite complex, I have come up with a simplified idea which should be within the abilities of anyone who wants to have a go. The components will only cost a few cents and the circuit is “passive” in that it does not use any external power (but has an “active” component).

Here are some schematics for various applications :

---

NB : Bear in mind that when combining two pads into one input you can only get one sound at a time (although you can get both if one hit is slightly after the other) so you need to choose your combinations with some thought (ie don’t combine the kick drum, snare or high-hat with anything).

---

Example applications :

– Mesh Head dual-trigger (piezo/piezo) to piezo/switch input (Dual mesh toms on the TD-8/TD-6V/DTXPress/…).

– Dual-zone cymbal made of 2 piezos (design by PFozz to come).

– Triple-zone cymbal made of 3 piezos (design by PFozz to come).

– …

For less “rim/edge sensitivity”, reduce the R2 value but DON’T replace it with a wire (100K to 1M is alright).

---

UPDATED (03/2006)
I have now made a PCB and am building up my DTXpander (for a small fee) for people who cannot do it themselves.

I am still happy for people to build their own, and here’s the latest circuit : http://edrum.for.free.fr/static/pictures/KeithRDTXpanderCheapB.pdf

The changes are minor :
1. putting a potentiometer for R1 to adjust sensitivity

2. Schottky diodes to reduce the voltage drop from the piezos (0.3V instead of 0.7V)

3. a jumper to allow one of the diodes to be shorted out.
These changes may help with systems not like my commercial DTXpress kit.

The Schottky diodes will help if the piezo signals are low – I have not noticed any difference with the DTXpress.
The option to bypass one of the diodes can help improve the signal from that pad if the polarity is wrong on the pad – the circuit works best with positive going pulses from the piezo.

Enjoy 😉

Keith Raper

(Key Design Electronics Ltd.)

http://www.kdel.co.uk

---

Excellent design, Keith!
Thanx for your contribution 😉
Best.

www.eareckon.com

Topic

[tazinnuedo]

does someone can tell me what is a schottky diode please???? is there a schematic about the new circuit with udpates? because i’m bad and i don’t understand where i have to insert a jumper…  ( the jumper is here to shorcut  one of the diodes???right???)
 
does the last photo represent the first schematic or the second???  i’m not sure but there there ‘s a lot af componant into the box and the second schematic no…
 
francois

[PFozz]

Hey François,
 
The schottky diodes are labelled BAT46 on the schematic.
The last photo is the built version of the 2nd schematic (PDF).
 
Best.

www.eareckon.com

[tazinnuedo]

and the pdf schematic is an update of the first one posted on the thread…  is that right????  (two mono pad in a stereo input…)
but, if i want to build a dual zone pad (for exemple tom’s input in a td10) i will have to start from the second schematic which is posted on the thread…and i don’t need to put some schottky diodes (just variable pot if i want)?? is that right???         (does the pot must be wired like in the pdf schematic???)
 
why in the first schematic it’s r2 which is changed to have less sensitivity and in the second  it’s r1 to adjust sensitivity?????

francois

[PFozz]

I haven’t tried the second schematic yet. The first version works like a charm into my 3-zone hihat (I’m using the schematic with the yellow/grey drawn piezos), and it should work for your tom aswell.
You may add a pot between the aux piezo (+) and R1 (instead of a pot before or after R2), if needed.

Best.

www.eareckon.com

[tazinnuedo]

so what is writen below the schema (with drawn piezos) isn’t good (or incmplete if we can put a variable pot near  r1):

For less “rim/edge sensitivity”, reduce the R2 value but DON’T replace it with a wire (100K to 1M is alright).  

    
 
similar question but not about this design…   if i put a resistance between the main piezo and the module, on the tip wire… does my sensitivity decrease?????  (on my module for the snare, sensitivity is at 2 or 3 / 32 scales… so i don’t have possibilities to have some fine adjustments) 
 
 

[PFozz]

I just edited my previous post (“around” was confusing and I replaced it by “before or after”) 😉
 
The comment about R2 isn’t wrong. Actually, you can reduce the “rim sensitivity” by decreasing the R2 value, but you must keep R2 above a minimum value. That’s why you may change R2 for a 100K resistor and add a pot before or after R2 but you can’t simply replace R2 by a pot. R2 won’t be less than 100k with a 1M pot and a 100k resistor in serial connection.
 
Adding a pot between the Aux Piezo (+) and R1 will have the same effect (it will reduce the “rim sensitivity”).
 
About the sensitivity of your main piezo… Yes, a pot between this piezo (+) and your module will reduce the sensitivity (and the tiny pot present on most Yamaha rubber pads provides this functionality, btw).

www.eareckon.com

[tazinnuedo]

[happy mode mode on] [happy mode off]
 
do you an idea about the resistance value i can put for the main piezo???? (or the max to have no sound…) 100kO 1mO 100mO….????
 
and if i have unsterstood evrerything of the design… if i want less sensitivity for my aux piezo, r2 must be decreased (but with a min resistance  (100ko)    and if i want more sensitivity, r1  must be decreased…

[PFozz]

1. I would try something between 10k and 100k (but that’s just a supposition).
 
2. I’m not sure about decreasing the R1 value…

www.eareckon.com

[elrules]

I have a doubt. Does this adaptor work for splitting the piezo/switch Roland TD6 inputs (i mean tom1 and cymbals) so you can connect 2 mono pads in one input?
Has anybody achieve that? In an spanish forum people tried your design but the told one pad had to be stroken very hard to get even a low low sound.
Please, help!

[PFozz]

The first schematic does what you described (2 mono pads into 1 piezo/switch input).
 
Though, I’ve built the piezo/piezo to piezo/switch adaptor only (2nd schematic). This one provides a way to plug a dual piezo/piezo trigger into a piezo/switch input (for example, a dual mesh head pad into a TD8 tom input) … and it works perfect for me 🙂
 
Best.

www.eareckon.com

[elrules]

Does anybody know which of the 3 circuit designs (1st schematic, 2nd schematic, boxed PDF schematic) is better? Pros and contras?

The 2nd schematic does NOT work with Roland TD6 module. You have to hit the rim pad too strong and the sound is soft 🙁

Maybe the 3rd schematic??

Does anybody have proved them with roland?

Where did you find info of how are the signals for the Yamaha triggers?
Can I find info of the signals for roland pads?

:'(

I need help!!

[PFozz]

Please tell us what you want to get.
Do you want to plug a dual mesh head pad into a piezo/switch input or would you like to plug 2 mono pads into such an input ?

Best.

www.eareckon.com

[elrules]

Hi again. What I want to do is conect two mono pads to one Roland TD6 input (for tom1 and crashes inputs, because tom2 and tom3 are able to do that without strange circuits)

I have tested connecting two PD-8 with all of your 3 circuits but none of them work. Circuit 2 (piezo/piezo to piezo/switch) divides but the sensitivity of the pad on the rim connector is awful, you have to strike it with a hammer to be able to hear something, nearly I can hear nothing. And circuit 1 and 3 (they are similar) replicate head sound in both pads so it does not divide.

I have been testing voltage coming from the PD-8 pad when I hit it on rim and head.
When I hit head, the tip and the ring give up to 30 mV. When I hit rim, the tip gives from 3mV to 5mV (less range) and ring gives from 0 to -2mV.

I don’t know what to do. I’m getting mad with all my failed attempts.

Maybe someone has achieved to connect 2 mono pads to roland dual inputs, please help me!

[PFozz]

Circuits 1/3 are what you need.
It seems the “rim detection” part of your circuit isn’t sensitive enough, though.
You may try to reduce the R1 value (replace R1 by a pot to do it progressively).
 
Best.

www.eareckon.com

[elrules]

circuit 1 and 3 (they are similar) replicate head sound in both pads so it does not divide

The circuit 2 is the one which does not give enough sensitivity. I have tried circuit 3, which has a pot in R1, none of the values in its range makes it better, the signal replicates in both pads. I mean, when I hit the pad connected to rim I get exactly the same sensitivity that with the head pad, but also the same sound, although I configured two different sounds for head/rim.

Maybe you could explain me how the circuit 3 works, saying what is the function of each component, and what is their goal. Maybe that way I can change their values so I can adapt the circuit to a Roland input, because it seems that it is designed for Yamaha inputs.

[Author]

Replies