"Bridge resistor" needed for dual mono?

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mortennp
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Joined: Fri Mar 26, 2021 7:45 am

"Bridge resistor" needed for dual mono?

Post by mortennp »

Hi Rob

I have two single piezo pads. One I wired as "Drum Head" in the ED10 manual's "Dual Piezo Pad" diagram (Roland style). The other I wired as "Drum Rim".

I run the two pads through two standard TRS cables to a standard "stereo jack Y-splitter" (two female and one male) and into an ED10 input configured as "Dual Mono". It works fine!

However, I've become aware that some sources recommend using a "resistor bridge" for e-drum splitter cables, for example: https://studioscrapnsound.com/creating- ... and-td-11/. And drum-tec advertise their e-drum splitters as "built in resistor bridge": https://www.drum-tec.com/drum-tec-e-dru ... -mono-jack.

My understanding is a standard stereo splitter like the one I am using (not an "e-Drum splitter") does not have a resistor bridge. Should I be concerned I am damaging the ED10 or the piezos when running without a resistor bridge?

Best regards,
mortennp
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Rob
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Joined: Sat Aug 01, 2009 2:04 pm

Re: "Bridge resistor" needed for dual mono?

Post by Rob »

You do not need or want a bridge resistor. Using one on an eDRUMin will simply create unwanted crosstalk that the eDRUMin will ultimately need to filter out.

Roland modules can't really split an input into two separate inputs like eDRUMin can. On a Roland module the tip connection alone is responsible for detecting when a pad has been hit, so some of the signal from the ring connection needs to be transferred through that resistor to the tip in order for the module to begin scanning a transient.

Reading the voltages on piezos is the most time consuming thing any module needs to do, so designers want to minimize reading piezos as much as possible. By ignoring the ring piezo until the tip is stimulated, you effectively double the sampling rate of your module. eDRUMin does the exact same trick for inputs that are in stereo mode. But when an input is in Dual Mono mode on the eDRUMin, both the tip and the ring are continuously read and operate independently. To make up the difference, I just use more powerful processors!
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