Double Bass How to shield piezo pickups?

[JtheJazzMan]

Is there a way to reduce hum? particularly Im getting a low frequency hum from an underwood pickup.

As a point of reference, Ive tried my NS and electric bass guitar in the same input and theres no noise or interference that I can hear.

 

[RustyAxe]

Is there a way to reduce hum? particularly Im getting a low frequency hum from an underwood pickup.

As a point of reference, Ive tried my NS and electric bass guitar in the same input and theres no noise or interference that I can hear.

Are you running through a DI or preamp with a DI? The impedance mismatch could be the source of your noise.

 

[Uncletoad]

The underwood is already as shielded as it can be. Hum can sometimes occur when it fits to tight. It could also be broken internally.

 

[JtheJazzMan]

I used the underwood both through a 10 mega ohm impedance preamp, and the underwood straight into the input on the pedal

The preamp isnt the problem, I dont think. I tested that with my other instruments and theres no noise.

Interesting I just tested the underwood and preamp into an amp, and the noise isnt there.

So it seems to be there with underwood, or underwood and preamp, only when going into a gt10b pedal? I tried the ground lift on the pedal and that didnt do anything

 

[Uncletoad]

I used the underwood both through a 10 mega ohm impedance preamp, and the underwood straight into the input on the pedal

The preamp isnt the problem, I dont think. I tested that with my other instruments and theres no noise.

Interesting I just tested the underwood and preamp into an amp, and the noise isnt there.

So it seems to be there with underwood, or underwood and preamp, only when going into a gt10b pedal? I tried the ground lift on the pedal and that didnt do anything

Sounds like the UW doesn't get along with that pedal.

Try a BassMax if you have to use that pedal.

 

[Mark Perna]

I'm trying to understand what's going on.

You get the noise with UW+preamp+pedal into the amp.

You don't get the noise with UW+preamp directly into the amp.

I'm unclear if you tried the NS and EB with or without the pedal.

Do you get the noise with the NS or EB into the pedal into the amp? Without the pedal?

Do you use the same instrument and patch cords when you run the NS, EB and UW? Does the pedal run on batteries or AC? Does the preamp run on batteries or AC?

mark

 

[JtheJazzMan]

I think I figured out what the problem is. I wasnt using the pedal with an amp, I was setting it up for some studio work where I dont have to take an amp, I just use my underwood straight into the recording desk.

When I plugged the pedal into an amp, the noise went away. So it seems the pedal isnt properly grounded, which would make sense as its only a 2 pronged plug. Ill have to earth it.

Having said that, do any electronic wizards know why this happens?

 

[Uncletoad]

I think I figured out what the problem is. I wasnt using the pedal with an amp, I was setting it up for some studio work where I dont have to take an amp, I just use my underwood straight into the recording desk.

When I plugged the pedal into an amp, the noise went away. So it seems the pedal isnt properly grounded, which would make sense as its only a 2 pronged plug. Ill have to earth it.

Having said that, do any electronic wizards know why this happens?

You are not explaining yourself very well. Can you try to be clearer. Under what conditions is it noisy and under what is it not?

The pedal being grounded or not should be irrelevant.

If you plug the UW into the sound board without an impedance friendly preamp it will sound bad. If you plug the UW into the pedal without a preamp it will sound bad. If you plug the UW into an amp without the pedal or the preamp it may sound ok.

 

[JtheJazzMan]

Ok, Im using a GT10B pedal as a standalone unit ie

UW -> Pedal with headphones

or

UW -> Preamp -> Pedal with headphones

Under these conditions theres a low frequency mains hum, verified by both listening to the headphones or unplugging the headphones and watch the volume graph on the pedal.

As soon as I plug the pedal into a combo amp the hum instantly stops. The only thing I can think of is that the pedal has a 2 prong plug ie, no ground, whereas the combo amp is grounded.

Plugging the UW or UW+preamp directly into the combo amp (no pedal at all) is also silent.

The pedal acts as a tone shaper and amp sim, and Ill be blended with a mic too. It just occurred to me that the connection to the main desk would probably stop the hum in the same way

 

[Uncletoad]

That sounds like a ground loop vs. a lack thereof.

What happens when you plug the pickup into stuff without the pedal?

I'm thinking you should loose the pedal in tracking, track a clean dry signal, and add whatever it does in the mix.