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Preamp / Powerline weirdness


geoham
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Had a bit of strange one today. The wife bought me a Bartolini NTMB pre-amp for my birthday (today!), and I proceeded to fit it in to my Lakland 5501. It was straight forward enough, but when I plugged it in to try it out, there were some fairly loud clicks & pops. These faded when switching to passive mode, and vanished altogether when I took the battery out. I rechecked every bit of soldering, pulled the whole thing out and tried it outside the bass - the problem persisted. Two hours I tried everything I could think of! 

Eventually, I tried unplugging a powerline adapter from the socket adjacent to the one my amp was plugged in to and the problem stopped altogether. I can't quite figure out what's going on. I've always used the bass amp on this socket - none of my passive basses nor the previous preamp in the Lakland had this problem. I get that the powerline has the potential to bleed interference into an audio-signal - however, I can't quite understand why it's only occurring with this pre-amp and when it has a battery in it.

Any suggestions?

Thanks,

George

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Check if the battery contact is soldered the right way (grounds are connected after the plug is put in).

Is there any DC going to the amp input? Should not.

Clicks and pops may be a hint of faulty grounding. Is the bridge wire and all other grounds connected well (sort of electrically "tight") together? Check with a DMM. Everything (like any string to the output ground) should be less than 1 ohm.

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41 minutes ago, itu said:

Check if the battery contact is soldered the right way (grounds are connected after the plug is put in).

Is there any DC going to the amp input? Should not.

Clicks and pops may be a hint of faulty grounding. Is the bridge wire and all other grounds connected well (sort of electrically "tight") together? Check with a DMM. Everything (like any string to the output ground) should be less than 1 ohm.

Thanks, a few bits for me to double check. I still can’t fathom how this only presents itself when the powerline is plugged in - but I suppose earthing is a logical place to start.

It’s a pre-wired harness, so my working assumption that everything is wired correctly may be worth revisiting! 

Here’s all I did...

- Removed old harness, keeping only pickups and battery box from existing wiring

- Snipped battery connector from new harness

- Fitted new harness, attaching old battery box red/black cables to those on the new harness.

- Soldered pickup white cables to the centre lugs on the blend-pot, pickup earths to an earthed lug on the pot. 

- Soldered bridge earth and additional earth wires from pickup cavities (presumably connected to shielding) to a common earth point on the back of a pot.

George

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Well, this sounds like a well thought plan and execution. A photo might be a nice addition.

Long soldering times (excess heat) may ruin the pots, but other than that and grouding there should not be any major problematic places. bartolini even provides reasonably legible schemas.

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Just to close this off (I hope!), I gigged with this last night and it was absolutely trouble free. The only time I encounter the problem is when my amp is plugged into the socket next to the powerline adapter. 

Google is full of people reporting audio interference with powerline adapters, so I’m happy to put it down to that.

I would like to understand exactly why the problem occurs, but it’s not too important.

George

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I had a similar problem (link to thread below). One of my Trace heads was picking up weird pulsing interference. My other heads were fine, but this particular head seemed really susceptible. As far as basses go, my old Status was the worst. Quiet as a mouse with my other amps but with this particular one it was noisy as hell - fine anywhere else but in the house.

I bought a conditioner which helped but I’ve since ditched the powerline adaptors completely.

 

https://www.basschat.co.uk/topic/334731-power-conditioner-to-overcome-dirty-powerpower-line-ethernet-interference/

 

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17 hours ago, Deedee said:

I had a similar problem (link to thread below). One of my Trace heads was picking up weird pulsing interference. My other heads were fine, but this particular head seemed really susceptible. As far as basses go, my old Status was the worst. Quiet as a mouse with my other amps but with this particular one it was noisy as hell - fine anywhere else but in the house.

I bought a conditioner which helped but I’ve since ditched the powerline adaptors completely.

 

https://www.basschat.co.uk/topic/334731-power-conditioner-to-overcome-dirty-powerpower-line-ethernet-interference/

 

Glad I'm not the only one to be having problems!

I just need to practice elsewhere in the house, or unplug the powerline (which is only in our spare room to give a faster than wifi internet connection to the kid's Xbox).

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