DIY Plate reverb

[pitol678]

So I started building this plate last year before our twins were born, then it got set on the back burner. The part I thought would be most difficult ,the welding and fabricating, turned out to be fairly simple. However, Ive hit a HUGE snag with the electronics, the main reason is because Im a newb in this regard and am at a loss.
My question is:
What needs to come in between my DAW(using a Tascam 1800 interface) and/or Tascam 388 to the plate and from the plate. For instance right now, I have a Velleman 2w amp to boost signal to the driver from the DAW. However, I have to turn the signal down incredibly low to like -37 in my DAW (Reaper)for it not to distort. That being said, the signal coming back is very weak and un-useably low. Is there some impedence issues here? What can I do for that? I watched this video and thought I may even try and copy what they did for pickup preamps etc just to try and apply it to what Im doing but dont want to throw money away. Any help would be MUCH appreciated and Im glad to provide any additional info needed.

Ive gotten some help here and there on this forum but I really need it "dumbed down" for me. Im dying to get some use out of this thing finally!

 

[Rob Flinn]

if you intend to build the ampsfrom scratch the Ecoplate electronics are pretty basic.

http://groupdiy.com/index.php?topic=52701.0

 

[dmp]

You don't say what you are using for a driver or pickups - 
You can get it working using a powered speaker about a foot away at a normal listening volume.
For pickups, the plate should have piezo electric pickups adhered on. The pickups should go to a DI and then to a preamp with a moderate amount of gain. It will be apparent how to balance the driving volume with the pickup gain to be over the noise floor, but not distorting.
That should give you usable results and you can go from there on building dedicated amp / drivers.
If you don't get usable results there may be something wrong in the construction?

 

[musika]

Can you possibly post a photo of the plate reverb and amp - what you have built so far?

 

[pitol678]

if you intend to build the ampsfrom scratch the Ecoplate electronics are pretty basic.

http://groupdiy.com/index.php?topic=52701.0

I would love to and will give it a look, but I suspect that it may be too complicated for someone like myself who has very limited knowledge of reading schematics

 

[pitol678]

You don't say what you are using for a driver or pickups - 
You can get it working using a powered speaker about a foot away at a normal listening volume.
For pickups, the plate should have piezo electric pickups adhered on. The pickups should go to a DI and then to a preamp with a moderate amount of gain. It will be apparent how to balance the driving volume with the pickup gain to be over the noise floor, but not distorting.
That should give you usable results and you can go from there on building dedicated amp / drivers.
If you don't get usable results there may be something wrong in the construction?

So my pickups are piezos and my driver is a modified speaker. I have also connected a typical speaker and still got distortion at very low levels. Currently I'm running a TRS cable out from my Interface and using a guitar type input jack (it's what I had on hand and am not sure where to get a jack for a balanced cable) to connect to the Velleman amp. I'm suspecting that could be a problem? The DI makes a lot of sense, does it matter if it's active or passive? Thanks!

I can post photos when I get home

 

[dmp]

Probably an active DI would be better for a Piezo, but either should work. It sounds like you need to connect the Piezo pickups to DIs  and preamps to get a little gain on the return.

 

[JohnRoberts]

A decent bi-fet op amp will have high enough input impedance to buffer a typical piezo.

Surely there are plans and circuits around.

JR

 

[dmp]

Surely there are plans and circuits around.

Yup. Here is a a generic amp.
But I'm suggesting grab a few pieces of gear everybody has, plug them in, and see if the plate is working -- before building an amplifier.

 

[pitol678]

Surely there are plans and circuits around.

Yup. Here is a a generic amp.
But I'm suggesting grab a few pieces of gear everybody has, plug them in, and see if the plate is working -- before building an amplifier.

yep, that looks great Im sure, but as stated above, I seriously have no experience reading schematics. I mean I could try to do some research to build one, and will, but if I had issues I would be totally clueless. I guess the lesson I learned is that I didnt know, what I didnt know. Im not sorry I built it and will eventually sort it out.

From this thread Ive learned that:
1) I need to find a TRS female jack to connect to the amp.
2) get some active DI boxes to take the signal from the piezos to a balanced signal to the interface.

Any thoughts on the signal going from the interface to the amp? does any conversion need to happen prior to? Also, I assume I need a TRS jack for the balanced cable to go into the amp, anyone know where to get one? Does it matter? thanks

 

[pitol678]

Can you possibly post a photo of the plate reverb and amp - what you have built so far?

 

[pitol678]

Can you possibly post a photo of the plate reverb and amp - what you have built so far?

 

[critterkllr]

If you don't want to DIY the piezo buffer/preamp, you could pick up something like the Radial Piezo Stage Bug:

http://www.radialeng.com/stagebugsb4.php

 

[dmp]

That looks really great! Very impressive.
Are you going to add a damper plate?

 

[pvision]

The mechanics of the plate look great!

One thing that may help with distortion is to reduce the bass sent to the speaker and increase the treble. Then roll off the treble coming from the piezo pickup until the signal sounds OK

Reducing the bass will minimise large movements of the plate and help prevent mechanical noises. Increasing the treble should help reduce noise from the piezos

Nick Froome

 

[hitchhiker]

Here is the piezo preamp and  line driver scheme to what I have on my EMT 140 stereo plate.  I built this on  perf board and it works great.  The  piezo's pick ups are not original but Martin Sound replacements. The schematic is not what Martin Sound used.
I would say any decent fet input opamp will work.   

 

[dmp]

Here's a tip
I have four pickups on mine that I blend into a stereo return. Having more blended together sounds better.

 

[Bill Wilson]

I have two pcb's made specifically for a hi impedance pickup. The pickup is fed to the gate (input) of an FET impedance converter. The output of the FET drives a Beyer Mike input transformer low impedance input; the secondary feeds a Bi Fet opamp, that drives a pair of 2N3904 & 3906 transistors that forms a buffer that provides up to + 18dbm. There is a volume control at the input of the Bi Fet opamp. I have two of these boards specifically designed to amplify high impedance pick up on a reverb plate. Just connect a low noise +- 15volt power supply & you are in business> Asking $45.00 each. I only have two from my days as a manufacturer.