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Neve portico 5012 - Right channel hums
Old 10th March 2021
  #1
Here for the gear
 
🎧 10 years
Neve portico 5012 - Right channel hums

Hi everyone,

While playing around with one of my preamps I noticed something strange today: The 2nd (right) channel of my Portico emits a hum to the sound card (Focusrite 18i20).
I noticed the hum when layering multiple vocal tracks.

To investigate the cause, I disconnected everything in the system so that only the sound card and the portico are connected.
No mike and no other cable. The cable was also swapped, as was the input on the card. So it is definitely due to the Neve or the combination of the sound card. Monitored through headphones.

It remains the same: If the right channel is connected to the sound card, it hums quietly.
So, now it's going to be wild. It buzzes even when the Neve is not connected to the electricity! If it is switched on, it is less!
I've also found that the hum is loudest when the preamp is above the right side of the Focusrite. If the preamp is further away, the humming becomes quieter.

My guess: there is an interference of the Focusrite NT on the Neve circuit which is successfully suppressed when the circuit is switched on.

But: Why is that only on the 2nd channel?
And why does a studio converter interver so much?

Oh yes, a power conditioner bought specially for analysis did not help here. But it was almost clear that the Neve has a switching power supply.


Thanks and Greetings,
Randy
Old 5th April 2021
  #2
Here for the gear
 
🎧 10 years
Hi everyone,

after further tests I found out that the humming is the Result of the left monitor adam a7. Its powerunit emits a field into the neve.
It gets better as farer i put ot away from the monitor.

Unfortunately there is no useful position in the setup where the humming is not noticable.

Du you have some hints?

Thx
Randy
Old 11th April 2021 | Show parent
  #3
Here for the gear
 
Quote:
Originally Posted by Randy666 ➡️
Hi everyone,

after further tests I found out that the humming is the Result of the left monitor adam a7. Its powerunit emits a field into the neve.
It gets better as farer i put ot away from the monitor.

Unfortunately there is no useful position in the setup where the humming is not noticable.

Du you have some hints?

Thx
Randy
Maybe you've already tried these, but I'd want to make sure that the humming is not related to the power source, so I'd:
1. try a different power outlet and verify hum
2. swap left/right input cables and verify hum (eliminate cable shielding)
3. if still same hum due to electromagnetic field:
3a.use aluminum foil to shield the outside of the speaker (the side facing the Neve). If that works, unplug the speaker, open it up (ONLY IF YOU KNOW ENOUGH ABOUT ELECTRONICS. THERE ARE LIKELY LARGE CAPACITORS IN THERE, AND THOSE NEED TO BE DISCHARGED), and use copper tape to properly isolate the same side. Alternatively, ask an audio engineer to shield the inside of the speaker for you.
3b. try shielding other things, and good luck!
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