Replacing Roland PD-120 pad piezos - rim piezo distance?

[glenn.szymanski]

Unfortunately my account must have gotten hacked a few days ago and Dmitri must have deleted it. So, I'm reposting this...

About 10 years ago I bought 3 Roland PD-120 pads (to use as snare, rack and floor tom) and a used Megadrum module from Ebay. After reading this forum I realized that the stock piezos in the Roland pads are considered "too hot" for the Megadrum's analog inputs. I had a friend solder in some resistors to cool the pads down, but I don't think he actually researched the value for the resistor so I'm taking the more extreme route and replacing the piezos with part 7BB-27-4L0 by a company called Murata from the distributor Mouser. I'm attaching 2 photos from the inside of the PD-120 and a page from the manual. I also watched a video on youtube of someone making their own DIY 2 zone mesh head pad and they also put the 2 piezos very close together (although isolated from each other with the center piezo raised up and underneath a foam cone). In the manual for the PD-120 it shows that rim hits will only be accurate in the very small area right above the input jack. I'm wondering if this was only an issue for Roland modules or if this would also be an issue for the Megadrum module. Since I'm using these 3 pads for snare, rack and floor toms, they all sit in different orientations on my rack. I'm wondering if it would be better to mount the rim piezos on the shell underneath where they will actually be struck. Or will this mess with the positional sensing?

[dazjam]

In the manual for the PD-120 it shows that rim hits will only be accurate in the very small area right above the input jack. I'm wondering if this was only an issue for Roland modules

Hi - this is literally about the position of the rim sensor dictating where strikes will be the most effective. Because this era of pad places the rim piezo on one side as opposed to in the centre (on subsequent era pads), the rim sensing is biased to one side.
On PD-100 pads that don't come with a rim piezo you can add one in the middle very easily which functions perfectly - I have done this a few times with great success - the pcb is the same board as the dual zone pads so it is a very simple upgrade. You can move the head sensor assembly by removing 3 screws. Then you can mount directly underneath to the metal bar.

If you move the PD120 rim piezo into the middle then you cancel the bias. Then it is a matter of tweaking settings to have the rim and head sensitivity balanced. Even if you don't you can use the rim as is successfully if you up the sensitivity a little. (This advice is from experience on roland modules but applies to all/adjust for megadrum settings).

You can definitely overthink all of this! The head piezo needs a good cone on top to make decent contact. Wiring should be non-frayed. When mounting the piezos don't stick your adhesive pad/tape right up to the edge, else you compromise the piezo working correctly.

[glenn.szymanski]

Thank you for the reply. I took a photo of how my kit is set up with the mesh heads taken off. I circled the area on the rims where I am most likely to hit them. They are much different than where the manual for the Roland PD-120 says hits are most accurately read. I feel like my options are to relocate the positions of the mounting hardware or relocate the position of the rim piezo.

[glenn.szymanski]

In the manual for the PD-120 it shows that rim hits will only be accurate in the very small area right above the input jack. I'm wondering if this was only an issue for Roland modules

On PD-100 pads that don't come with a rim piezo you can add one in the middle very easily which functions perfectly - I have done this a few times with great success - the pcb is the same board as the dual zone pads so it is a very simple upgrade. You can move the head sensor assembly by removing 3 screws. Then you can mount directly underneath to the metal bar.

If you move the PD120 rim piezo into the middle then you cancel the bias. Then it is a matter of tweaking settings to have the rim and head sensitivity balanced. Even if you don't you can use the rim as is successfully if you up the sensitivity a little. (This advice is from experience on roland modules but applies to all/adjust for megadrum settings).

Wiring should be non-frayed. When mounting the piezos don't stick your adhesive pad/tape right up to the edge, else you compromise the piezo working correctly.

I just re-read your reply. Now I see that you're saying that I should mount the rim piezo on the bar directly underneath the cone mount?

What do you mean by the wiring should be non-frayed? Also, I wasn't going to use tape, I was going to use glue of some kind.

[dazjam]

I just re-read your reply. Now I see that you're saying that I should mount the rim piezo on the bar directly underneath the cone mount?

What do you mean by the wiring should be non-frayed? Also, I wasn't going to use tape, I was going to use glue of some kind.

Hi

Yes, directly under the cone on the bar itself is the perfect placement. You want to be able to trigger the rim from any angle not just have one hugely biased spot. This is how roland make all their upper tier drum pads with rim piezo at dead centre.

Frayed wiring - check all the connections as you go - if a wire is degraded in some way, moving it for your modification can make it fray or break or even worse detach from the piezo. Solid connections = happy drumming.

Your rim piezo needs enough clearance for it to vibrate so be sure not to glue up to the edge or it'll give you compromised triggering.

You can get lost in detail but keep it clean and simple and follow the rules and it'll work just fine. I use double sided carpet tape myself and double it over to make a sticky pad no bigger than the ceramic centre disc, works great.

[glenn.szymanski]

Yes, directly under the cone on the bar itself is the perfect placement. You want to be able to trigger the rim from any angle not just have one hugely biased spot. This is how roland make all their upper tier drum pads with rim piezo at dead centre.

Thank you for the detailed reply.

Am I ok to use the same size 27mm piezo for under the cone and for the rim sensor? I notice that the stock piezo on the PD-120 for the rim seems to be a bigger size than the center one under the cone. Or does it not matter?