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Spring reverb shielding
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Spring reverb shielding
Todai
Presently working on a Soundbox / Noisebox project incorporating a spring reverb.

Since this might incorporate an Arduino and the general rule seems to be 'keep the spring tank away from anything digital' my options seem to come to either

-make the box BIG

-shield the spring tank

I'd clearly prefer to shield it.

So the challenge is...how can I effectively shield it from the RF (?) noise?
Dave Peck
One fairly good way to do this for one-off custom products like a modular synth would be adhesive-backed copper tape, which is designed especially for this purpose.

But something to note - Another option is to shield the device that is producing the RF, rather than the device that is sensitive to that RF. And if that device is much smaller than the reverb tank, it may be a lot easier to shield that device rather than shield the reverb tank.
Rigo
Place the spring reverb outside the box ? Gives some extra noise making cool
Todai
Dave Peck wrote:
One fairly good way to do this for one-off custom products like a modular synth would be adhesive-backed copper tape, which is designed especially for this purpose.

But something to note - Another option is to shield the device that is producing the RF, rather than the device that is sensitive to that RF. And if that device is much smaller than the reverb tank, it may be a lot easier to shield that device rather than shield the reverb tank.


Good point about shielding the circuits instead of the tank!

I guess the best way to go is to gather the parts still missing, get some of that copper tape / foil and test for sufficient shielding.

I'm booked on an 'Introduction to Arduino' workshop, tomorrow. I'm not settled on the Arduino, but the possibilities of using various controllers seems...tempting!
Todai
Rigo wrote:
Place the spring reverb outside the box ? Gives some extra noise making cool


That clearly is an option...rubbing, pinching, what-not...

But it's not the direction I'm heading. Aesthetics call for a a tank inside the box... cool
Graham Hinton
Todai wrote:
-shield the spring tank

I'd clearly prefer to shield it.


The tank is already shielded, the trick is in how you connect it.

The output coil is low level and gets amplified so treat it like a microphone. You need a balanced amplifier and you can either make your own based on an instrumentation amplifier topology or use a dedicated mic amp IC. Use a screened twisted pair cable from the tank output with the screen connected to the metal case, i.e. just like a dynamic microphone: a coil and a grounded case. Usually the terminals are on an insulated board even if they are RCA phono so just connect the pair to those.

Dave Peck wrote:
Another option is to shield the device that is producing the RF, rather than the device that is sensitive to that RF.


All digital circuitry should be screened. The cavalier way that controllers and DSPs are scattered amongst analogue circuitry shows a complete lack of understanding or care of the realities of RFI and EMC. There is "good practise" and then there are legal regulations, you can't buck either for long.
Revok
Graham Hinton wrote:
Usually the terminals are on an insulated board even if they are RCA phono so just connect the pair to those.


You can use the tank code to verify if they are insulated or not. Typically it is the 5th digit in the code. For Belton tanks you just knock off the BL or BS from the front of the code ie BL2AB3C1B

A - Input Grounded / Output Grounded
B - Input Grounded / Output Insulated
C - Input Insulated / Output Grounded
D - Input Insulated / Output Insulated
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