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Radio Interference - Can't solve it
- Thread starter BaileyMan
- Start date
Two thoughts:
1) The NTMB3 schematic diagram shows where wires come of of the pre-amp module. The orange wire comes off just before the 2.2 K resistor and the gray wire just after this resistor. Both of these wires are just before the tone controls. Determining exactly which is the correct orange wire will take some more research. The gray wire can be identified from the picture below. I am not sure which wire/s is/are ground for connecting a capacitor between the gray wire and ground. It is possible that the RFI is entering through one of the wires that comes out of the pre-amp module, so adding a small ferrite may actually be possible.
This picture may reveal more details.
2) Pictures of the actual shielding installed in the control cavities of your active basses may reveal an area where the shielding needs to be modified. This is in line with your finding that Faraday cages may not always provide 100% isolation. Back in college, a Faraday cage was used for biofeedback research. The walls and door were made with solid sheets of copper. Electricity for lighting inside the box was powered by DC voltage. I seriously doubt that the shielding inside the Bartolini NTMB3 pre-amp meets the same standard for as that Faraday cage. I have seen buildings manufactured supposedly as Faraday cages, Tempest certification, that used wire mesh instead of solid metal sheets. So the definition of shielding varies by the customer and installer.
1) The NTMB3 schematic diagram shows where wires come of of the pre-amp module. The orange wire comes off just before the 2.2 K resistor and the gray wire just after this resistor. Both of these wires are just before the tone controls. Determining exactly which is the correct orange wire will take some more research. The gray wire can be identified from the picture below. I am not sure which wire/s is/are ground for connecting a capacitor between the gray wire and ground. It is possible that the RFI is entering through one of the wires that comes out of the pre-amp module, so adding a small ferrite may actually be possible.
This picture may reveal more details.
2) Pictures of the actual shielding installed in the control cavities of your active basses may reveal an area where the shielding needs to be modified. This is in line with your finding that Faraday cages may not always provide 100% isolation. Back in college, a Faraday cage was used for biofeedback research. The walls and door were made with solid sheets of copper. Electricity for lighting inside the box was powered by DC voltage. I seriously doubt that the shielding inside the Bartolini NTMB3 pre-amp meets the same standard for as that Faraday cage. I have seen buildings manufactured supposedly as Faraday cages, Tempest certification, that used wire mesh instead of solid metal sheets. So the definition of shielding varies by the customer and installer.
I'll play around with some things. Someone else suggested I wrap the preamp in copper tape and connect it to ground.Two thoughts:
1) The NTMB3 schematic diagram shows where wires come of of the pre-amp module. The orange wire comes off just before the 2.2 K resistor and the gray wire just after this resistor. Both of these wires are just before the tone controls. Determining exactly which is the correct orange wire will take some more research. The gray wire can be identified from the picture below. I am not sure which wire/s is/are ground for connecting a capacitor between the gray wire and ground. It is possible that the RFI is entering through one of the wires that comes out of the pre-amp module, so adding a small ferrite may actually be possible.
This picture may reveal more details.
2) Pictures of the actual shielding installed in the control cavities of your active basses may reveal an area where the shielding needs to be modified. This is in line with your finding that Faraday cages may not always provide 100% isolation. Back in college, a Faraday cage was used for biofeedback research. The walls and door were made with solid sheets of copper. Electricity for lighting inside the box was powered by DC voltage. I seriously doubt that the shielding inside the Bartolini NTMB3 pre-amp meets the same standard for as that Faraday cage. I have seen buildings manufactured supposedly as Faraday cages, Tempest certification, that used wire mesh instead of solid metal sheets. So the definition of shielding varies by the customer and installer.
I have a Bartolini XTCT preamp with an added MCT (mid frequency) module. Certainly the schematic would be different, but maybe I could apply your ideas based on the NTMB to it. The mid knob seems to affect the RFI signal, while the volume, bass, and treble do not. Maybe it's the MCT module and I could look at putting a ferrite clip on the wires to it.
https://bartolini.net/wp-content/uploads/Docs/TCT_Wiring.pdf
I'll play around and post back up.
Last edited:
Thought I had posted an update, but it appears I only did so in my mind...
I've not been able to eliminate the interference and I don't expect I will as long as I'm living in this house. I think I mentioned in a previous post here that one of the guys who came over to help troubleshoot turned out to be the guy who built the radio tower. He's been doing this work for close to 50 years. I'd say he knows what he's doing.
He said given my proximity to the tower and the fact that one of the antennas is pointing directly towards our house that there's not really anything I can do about it. I've exhausted pretty much all the possibilities.
I have found some positions that I can hold my bass in that minimize it, but it doesn't go away completely in my active basses. Thankfully I've got some great sounding passive basses too.
I've not been able to eliminate the interference and I don't expect I will as long as I'm living in this house. I think I mentioned in a previous post here that one of the guys who came over to help troubleshoot turned out to be the guy who built the radio tower. He's been doing this work for close to 50 years. I'd say he knows what he's doing.
He said given my proximity to the tower and the fact that one of the antennas is pointing directly towards our house that there's not really anything I can do about it. I've exhausted pretty much all the possibilities.
I have found some positions that I can hold my bass in that minimize it, but it doesn't go away completely in my active basses. Thankfully I've got some great sounding passive basses too.
