Tilting at Windmills aka DIY Plate Reverb

Inspired by Top Top over on the diystompboxes forum.

I am attempting to build a compact plate reverb. Based on Top Top's clips, it sounds so good. So I am endeavoring to build something similar. The quest is to build something comparable to the EMT 140 in compact form.

Yeah, fool's gold, I know.

Version .001

This version used a Hammond amp chassis cover plate with a thickness of approximately 1.12 mm. Secured to the cabinet with thick gauge steel wire cinched down tight.

Thin aluminum plate. Started life as a Hammond chassis bottom.

Built a wooden cabinet using my world-renowned lack of wood-working skills.

Cabinet stained and plate suspended by metal wire to screw-in eyelets.

Back view

Results: Complete crap. First test was using the unit with a single piezo transducer taped to the faceplate. This essentially caused the unit to act as a wide-field piezo microphone. I placed this front of my Fender Twin with the output going to a second guitar amp.

The result was an intensely unpleasant sound. There were also issues with feedback. I am going to chock this failure up to two things:

• The rigidity of the plate I used (aluminum sheet, 1.12 mm thick)
• I used steel wire to notch that sucker down tight

So on to Test #2. I moved the piezo transducer to the right of the plate. I then mounted a very small thin 8 ohm mini-speaker on the left. Guitar into Noisy Cricket, output to the 8 ohm speaker. Then the piezo off to the Twin.

Results: Sounds like a muffled plate microphone. Not that great, but much better fidelity by mounting both the driver and pickup transducers directly to the plate. Absolutely no reverberation in either test.

The plate I'm using is just to thick and its rigid mounting really creates a very metallic sound.

Version .002

I found some very nice thin copper sheets in one of my boxes of crap and will now work on using that as the plate, and change the suspension to something a bit more springy.

I added an input and output jack to the back panel along with some terminal strips to make it easy to test different input and output drivers

In order to eliminate the problems with version 1's stiff steel wire mounts. I opted for whipping twine with heat shrink-tubing to dampen and reverberation sound.

Front and back views of version .002

Ok, v.002 actually GETS A REVERB EFFECT!

The bad news is that it is faint, and only reverbs on the high-frequency side of the signal.

In order to move forward with a true compact plate reverb, there are two major tasks that I need to accomplish:

1. Optimize the transducers. This means going through endless permutations of ouput drivers and input pickups.

2. Optimize the plate material. The thin copper sheet works, but not great.

So, much work still ahead on this. If you decide to play around with this design and get interesting results, let me know!