Building: The Thomas Henry Mega Percussion Synth (MPS)

Oh boy oh boy. This one is very special to me. I was in a bad period in my life when I started reading the Noise Generator Cookbook by Thomas Henry. Reading it gave me a lot of rest and I learned a lot from it. I didn’t know that much about noise, white, pink, red, blue and the noise in my head, it all started clearing up. In this book Thomas Henry writes about the Mega Percussion Synth (MPS). Back in those days a lot of schematics where based upon 15volt. I always wanted to have a MPS but never found the time and skill to transfer his design to eurorack (12 volts)

Then Haraldswerk released the MPS, and put the gerbers online for building one. Sadly it was still 15 volts and with banana jack. Not typical for eurorack. I wrote about this in the topic Haraldswerk posted on modwiggler. And I wasn’t the only one hoping for a 12 volt version with 3,5 jacks. That started a discussion and.. well

Someone on the internet somewhere already converted the MPS schematics to 12 volts as a other user from modwiggler found out. So I was possible to convert the voltages. This lead to the possibility of converting Haraldswerk pcb’s to 12 volts. Only be a few resistors values that needed to be changed. A BOM was posted but…. I never asked Thomas Henry if we could do this and forgot to ask Haraldswerk too. Better late then sorry I mailed them both.

Many thanks to Haraldswerk whom did a lot of work designing the Panel and pcb’s. Many thanks also for Thomas Henry designing this module in the first place. They both give permission to try and convert it to 12 volts and 3,5 jacks.

I took the panel files Haraldswerk provided and just made the holes where the banana jack where a bit smaller so 3,5 jack would be hold in place with the jack rings. The where some holes in the pcb below them so I was hoping the jacks would fit without any other modification. The BOM was posted again this time with permission and boards where ordered.

It was a typical Haraldswerk board well designed and only 100nf capacitors as SMD. These are quite easy to solder. Here you can see the holes in the PCB where normally the banana jack fit in.

Just a few SMD parts (100nf Capacitors)

A straight forward build with no issues or strange stuff

Until I came to the jacks. These would fit the panel but weren’t pcb mounted. So I needed some wires to connect them.

Question was would the panel fit doing it like this

The panel fits. As you might notice the power for this module did not use a eurorack power header like a normal 10 or 16 idc header.
I always press my own power cables and though well just solder it onto the board, press the power connector on the other side and that should work..(hopefully)

Most issues where resolved but would the BOM be right, or where there any mistakes. Time to test it all.

The jack’s and panel would fit, the bom was correct and the module work. It was a joyfull moment when it all came alive. But it made a lot of noise.. Ok it’s based on noise generators but this was a little too much. What happed here. Hmm the jacks where connected to signal but not to ground. As the banana jack would probaply be grounded with the panel. An other wire and soldering it to a ground point on the pcb.

That seem to fix the noise issue and the module was now fully working making bass drums, toms, lasers and more.

Again and I can’t say this enough.. Thank you Thomas Henry for making this module. Thank you Haraldswerk for putting it on a pcb and releasing the Gerber files. A long wanted module is now sitting fully functional in my rack….time to build a second one

Oh and if you want to read the book also here you can find it. Also a link to the MPS on Haraldswerk site and some background on the module.

Leave a Reply

Your email address will not be published. Required fields are marked *