Plate Reverb pickups

[pitol678]

Nearly finished my frame for my plate this week and am pretty stoked. Ive noticed that on platereverb.com that there a stereo pair of pickups for $50 and although I may eventually get those the price seems a little steep. Does anyone have a suggestion of where to get a pair of piezo pickups that are a bit less expensive but also good quality? I would like to eventually upgrade and get the parts from JCC but currently cant spring for all of the most expensive parts. Thanks for any suggestions.

Edit: I also see that JCC appears to not be taking orders at the moment so any suggestions as to where to get any parts would be great!

 

[usekgb]

Have you tried attaching bare piezo elements? 

 

[joaquins]

Some music stores have piezo pickups for guitar which stick to the front, (contact mics) They are very cheap, already with some protection, adhesive and wires, I don't know if they are any better than the bare element. You could also get ones for string instruments like a clip that attaches to the bridge, but they would need a hack.

In any case you should try attacking the bare piezo as usekgb said at least as a first run, some double sided tape and you are up and running in no time messing with this. Then when you find everything is working you start to play with mic replacements, but I wouldn't worry about that in the frame state of the project. 

Very nice! let us know how that's going, I really want to build one but I already know this summer will be impossible, maybe next.

JS

 

[abbey road d enfer]

See te radio Shack piezo element there
https://www.youtube.com/watch?v=Gkezlp-eI-I

 

[pitol678]

Thanks for the replies everyone. I actually got to "hang" the plate onto the frame yesterday although I need still to tension it and of course install all of the electronic elements. it appears that piezo elements are fairly inexpensive which is why I was curious what justified the 50$ price on the JCC ones and if there was anything comparable.

I spent a good deal of time and effort on just the frame and the plate because those are the more static portions, then I figure I can experiment with the electronic components until I find what I like. I would really like to build dedicated input and output amps and have seen schematics online but they seem way over my head at the moment. For the time being, I'm going to use a headphone amp to send the source to the plate, then some CAPI preamps and EQ to boost/filter the signal coming back. I tried this on a very crude prototype I built and it worked, but I'm sure it will take quite a bit of experimentation before I settle on something, but that's the fun part!

 

[joaquins]

You need to take care two things, the first is impedance, your headphone amp is probably fine to drive 30Ω but if your load is 8Ω coil it probably won't like it, a small power amp is probably a good start, the power stage of a small guitar combo would be my first try probably, I don't know what you have as element. Same for the preamps, piezoelectric elements will have many pF output impedance, mic preamps are optimized for many ohms, and your pF will be many mega ohms at LF, so you have a problem there, probably a get input would be a better match for it, with properly high input impedance.

The second one is the usual power amps used in plate verbs have a particular filter, for compensating the losses. I attach a file for a plate reverb with some schematics, you can avoid from there the line receiver at the power amp and the line driver at the preamp, but I recommend to use a power amp as stated there, with a similar filter and a high impedance non inverting amplifier for the piezo. You only need 1 NE5532 and 1 LM1875 (20W TO220 amplifier)  for the driver and one LF356 (opamp with 1G input resistance) for the preamp. You shouldn't have problems to find those around, then you can add later a line receiver and line driver so you can run longer wires balanced without more noise or losses, since you usually want to have your plate reverb away from the mixing room, specially if you are mixing loud. But not need to do it as a first approach since you will be working with your verb close because you are tweaking it.

The power amp you probably want to have it close to you, since you have tone and level control, the preamp will be probably better close to the piezo pickups, to avoid picking up noise in the way to the preamp. You will find a spot on the level where it works good and leave it there, and control the verb level from your power amp, or have a separate output level in a stage after the preamp, so you have the return control closer to you.

JS

 

[pitol678]

You need to take care two things, the first is impedance, your headphone amp is probably fine to drive 30Ω but if your load is 8Ω coil it probably won't like it, a small power amp is probably a good start, the power stage of a small guitar combo would be my first try probably, I don't know what you have as element. Same for the preamps, piezoelectric elements will have many pF output impedance, mic preamps are optimized for many ohms, and your pF will be many mega ohms at LF, so you have a problem there, probably a get input would be a better match for it, with properly high input impedance.

The second one is the usual power amps used in plate verbs have a particular filter, for compensating the losses. I attach a file for a plate reverb with some schematics, you can avoid from there the line receiver at the power amp and the line driver at the preamp, but I recommend to use a power amp as stated there, with a similar filter and a high impedance non inverting amplifier for the piezo. You only need 1 NE5532 and 1 LM1875 (20W TO220 amplifier)  for the driver and one LF356 (opamp with 1G input resistance) for the preamp. You shouldn't have problems to find those around, then you can add later a line receiver and line driver so you can run longer wires balanced without more noise or losses, since you usually want to have your plate reverb away from the mixing room, specially if you are mixing loud. But not need to do it as a first approach since you will be working with your verb close because you are tweaking it.

The power amp you probably want to have it close to you, since you have tone and level control, the preamp will be probably better close to the piezo pickups, to avoid picking up noise in the way to the preamp. You will find a spot on the level where it works good and leave it there, and control the verb level from your power amp, or have a separate output level in a stage after the preamp, so you have the return control closer to you.

JS

Wow, thanks for all the info! Im afraid I may have underestimated this portion of the project. I have done some small electronics projects but have no experience when it comes to reading schematics. I had assumed that since my headphone amp worked in the prototype that I could just use it again.

 

[joaquins]

You could use it, but you will have two problems, one is higher distortion which probably isn't a big deal, but you still need the curve in the driver, which you could get in digital domain if you are using it from the DAW, setting some curves close to the ones in the graphics could be a place to start. If your preamps have FET DI input you could probably use them, maybe increasing the resistor which bias the get (the one after the cap going to the FET gate to ground) which probably is around 1M, make it a few times higher, not a problem to get resistors up to 10M so something in the middle should be fine, but only ig you are having LF rolloff too soon, if not you will be fine.

JS

 

[Rob Flinn]

The pickups that plate reverb.com were selling are like the link below.  I'm not sure of the exact diameter used because it is 5+ years since I did an upgrade for a client, but out of the options available 27mm seems about right.  They are glued on with some adhesive that is used to stick rear view mirrors onto windscreens/shields, which is supplied in the low noise kit that they used to sell.  See links below

http://www.ebay.co.uk/itm/5x-Piezo-Element-Pickup-Drum-Trigger-Transducer-27mm-/110919648087?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item19d3538357

http://www.ebay.co.uk/itm/Evo-stik-evo-stick-stick-car-windscreen-rear-view-mirror-adhesive-320130-new-/281371881599?pt=UK_Crafts_Cardmaking_Scrapbooking_Glue_Tape_EH&hash=item418312307f

 

[joaquins]

Rob, you are saying 5 of those go out for 1£ instead of 50$ per piece? I believe you, just doesn't sound fair...

That's about 25nF so you will be fine with 1M loading there, probably they are about that, the element is about 300k @20Hz so 1M load you are totally fine still with lower capacitance (smaller) ones, I was wrong with my first guess.

JS

 

[pitol678]

The pickups that plate reverb.com were selling are like the link below.  I'm not sure of the exact diameter used because it is 5+ years since I did an upgrade for a client, but out of the options available 27mm seems about right.  They are glued on with some adhesive that is used to stick rear view mirrors onto windscreens/shields, which is supplied in the low noise kit that they used to sell.  See links below

http://www.ebay.co.uk/itm/5x-Piezo-Element-Pickup-Drum-Trigger-Transducer-27mm-/110919648087?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item19d3538357

http://www.ebay.co.uk/itm/Evo-stik-evo-stick-stick-car-windscreen-rear-view-mirror-adhesive-320130-new-/281371881599?pt=UK_Crafts_Cardmaking_Scrapbooking_Glue_Tape_EH&hash=item418312307f

Great, Thanks! thats exactly what I was looking for. Any suggestions on a driver Rob? My plan thus far is just to use a small stereo speaker.

 

[Rob Flinn]

I have only ever dealt with EMT & ecoplate plate reverbs, & I have never had the need to experiment with alternative drivers, so I can't help you with this from any personal experience.  However. the original drivers are very like a loudspeaker voice coil & magnet, so that is a good starting point. You could probably use an old speaker. The voice coil attaches to the middle of the plate & the magnet to the frame.  You will need some way to move the magnet so it is concentric with the voice coil.  If you could get a look at the real thing I think it would make it easy for you to work it out.  You may be able to to get some pics by searching. I can't help you with pics of mine right at the moment because it's in storage.  I think I saw a youtube clip where some studio owner was showing this sort of stuff & how to move the magnet so it doesn't rub the coil.   

You probably don't need to worry too much about how to excite the plate, because in my opinion the tuning and filtering are what makes the biggest difference to whether it sounds any good.    Most of the people I know who have experience of a lot of different plates say they aren't too worried if it's valve or solid state so long as the plate is in tune. 

 

[pitol678]

I have only ever dealt with EMT & ecoplate plate reverbs, & I have never had the need to experiment with alternative drivers, so I can't help you with this from any personal experience.  However. the original drivers are very like a loudspeaker voice coil & magnet, so that is a good starting point. You could probably use an old speaker. The voice coil attaches to the middle of the plate & the magnet to the frame.  You will need some way to move the magnet so it is concentric with the voice coil.  If you could get a look at the real thing I think it would make it easy for you to work it out.  You may be able to to get some pics by searching. I can't help you with pics of mine right at the moment because it's in storage.  I think I saw a youtube clip where some studio owner was showing this sort of stuff & how to move the magnet so it doesn't rub the coil.   

You probably don't need to worry too much about how to excite the plate, because in my opinion the tuning and filtering are what makes the biggest difference to whether it sounds any good.    Most of the people I know who have experience of a lot of different plates say they aren't too worried if it's valve or solid state so long as the plate is in tune.

Thats great info Rob! Ive seen every video I can find on plate reverb and I think I may have seen the one you are talking about. I have seen some examples of DIY projects where the builder has used a piece of a wooden broom handle which sits on both the voice coil and on the plate in order to excite it. I realize that you have used the real EMT/Ecoplate parts, but in your estimation, do you see any disadvantages of wood as opposed to metal for this purpose? I have no way of knowing yet but it would seem to me that metal of some sort may be better, just because :

1.) It appears that the original EMT used thin brass or metal which was attached by a screw to the plate (at least this is the best I can tell from the pics Ive seen)

2.) in my thinking, wood may dull the sound coming from the driver resulting in less highs in regards to frequency response?

Of course I have no way of knowing for sure, and I am in no way a pro at recording. And given that you said "You probably don't need to worry too much about how to excite the plate, because in my opinion the tuning and filtering are what makes the biggest difference to whether it sounds any good" then properly tuning the plate will likely be the best place to focus my efforts for the moment. Just wondering if you or anyone else had any thoughts on this. Thanks again for the valuable info!

 

[dmp]

So you can get started by just using a speaker next to the plate - 12" away or so.
Mine is setup with a speaker like this, and I use the speaker most of the time. It is a small speaker and just cuts the lows in comparison to the attached driver.
And you can get started using a DI on any preamp for the gain recovery on the peizos as well.

 

[L´Andratté]

There´s one method I heard of using a power amp into the 8 Ohm secondary of a reversed output transformer and drive the piezo with high voltage of the primary side (like 100 V), because piezo´s like high voltage (I didn´t try, tip by Nic Collins). Also there are bigger diameter piezo elements which are rumoured to produce better results.

It´s not that complicated, if you´re not aiming for better than the best (some people here do). Definitly try your headphone amp, I bet it will still be usable/mid-fi for a start. 
In my piezo experiments I was using OPA2134 and 4M7 input resistor with good resuts and no bass loss at all...

Also the speaker driver method:http://ionosonderec.blogspot.de/2013/04/diy-plate-reverb.html

And have you thought about a ´damping´ plate like in this?
http://ekadek.com/?s=plate+reverb

 

[Rob Flinn]

As DMP says, you could just use a speaker in close proximity.  Or maybe glue a lightweight tube inside the cone of the speaker & somehow attach it to the plate.   

You are right about the brass coil former on the EMT but it might be riveted rather than screwed onto the plate (again I can't remember).  I think they used a different metal on the ecoplate, but its a few years since I swapped mine out for an MCI desk, so can't remember precisely.    I don't think wood is a bad idea for coupling.    Give it a try, if you don't like it, swap it for something you do !

You could very easily copy the ecoplate electronics, there's not anything special about them, but they do incorporate the right filtering.    The circuits diagrams are readily available & easy to build on veroboard.    They are mainly chip based with some transistors for the driver amp output.  That would put some people here off, but in practice I liked the ecoplate I had a lot. It was brighter sounding than the EMT because the plate is stainless steel.  I wish I still had it, but I have a great little desk now in place of it.

For tuning, some people say tune as tight as possible until you break clips (EMT).    Personally I don't think it's necessary to go that tight to achieve a good sound.    I'm wary of tightening too much, because the EMT clips get expensive if you break too many.    On the other hand the ecoplates have much tougher clips, & you are probably more likely to tear the plate if you over tighten them.

With regards to the damping plates.  I offered to re glue all the tiles on a friends EMT damping plate because they had fallen out.  He said not to bother because he only uses it wide open anyway.  on the other hand I didn't like the ecoplate completely wide open because I found it swamped the mix to much.  Maybe ok on a slow ballad  though ...

 

[abbey road d enfer]

There´s one method I heard of using a power amp into the 8 Ohm secondary of a reversed output transformer and drive the piezo with high voltage of the primary side (like 100 V), because piezo´s like high voltage (I didn´t try, tip by Nic Collins).

  That would be using the piezo-elements as drivers. That wouldn't work because the piezo elements weigh close to nothing compared to the weight of the plate. Piezo are (relatively) good at driving air, not metal.

Also there are bigger diameter piezo elements which are rumoured to produce better results.

Being larger, they produce more energy, so the signal-to-noise ratio is potentially better; they would also pick up a larger area of the plate, which would change the character of the sound, increasing lows and decreasing highs, which would make it warmer or duller, depending on one's taste.

 

[abbey road d enfer]

I have seen some examples of DIY projects where the builder has used a piece of a wooden broom handle which sits on both the voice coil and on the plate in order to excite it. I realize that you have used the real EMT/Ecoplate parts, but in your estimation, do you see any disadvantages of wood as opposed to metal for this purpose? I have no way of knowing yet but it would seem to me that metal of some sort may be better, just because :

1.) It appears that the original EMT used thin brass or metal which was attached by a screw to the plate (at least this is the best I can tell from the pics Ive seen)

2.) in my thinking, wood may dull the sound coming from the driver resulting in less highs in regards to frequency response?

The nature of the rod is almost irrelevant as long as it's not unduly heavy or floppy (lead and rubber wouldn't do), but the way the rod is mounted has a certain significance.
The wood rod would sit o, a larger area of the plate and so would damp it somewhat. It is important that the area where the rod joins the plate be as small as can be reasonably.

 

[ddt]

Here's what I've bought to use as a driver, haven't tried it yet though.

http://www.ebay.co.uk/itm/Vidsonix-Sonic-Ghost-3-Tactile-Transducer-Hidden-Vibrate-Waterproof-Speaker/281366153987?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28111%26meid%3D2ecb3b2c4d6b40caa6c5c9796d26a029%26pid%3D100011%26prg%3D11472%26rk%3D2%26rkt%3D10%26sd%3D271190285865

 

[pitol678]

Here is a pic of my progress so far. I have it tucked away in its permanent space near my practice/mixing room so I wont have to move it much. However, I still have to construct the damper, the encasement, install the pickups and find a suitable driver. The speaker I have on there, as a trial, doesn't have enough volume. Although, I have no clue as to how much sound the driver needs to put out.