Tips for removing induced noise

[Loquah]

Great suggestion re running a cord from elsewhere, grufti. I'll give it a go and report back.

[Jim R.]

Just curious if you have an outlet tester?  If so, does the office outlet look to be wired to code?

Also, if you do find the interconnects to be the problem, you may want to try the BH interconnects as they are fully shielded from end to end.

And how close to the amp does the video cable from the laptop to the monitor run?

Definitely try a long extension cord to an outlet outside the room and if the hum disappears, do check that the outlet in the office is wired correctly.  You wouldn't belive how common this is even in a house where one guy did all the wiring.

-- Jim

[4krow]

I second the wiring reversal thing. I will have to admit making some stoopid mistakes with wiring, all by myself.

[Loquah]

Hi all,

I've been gone a while and completely re-arranged my office in that time which worked a treat... at first.

After being able to use my Crack perfectly last week, I made 2 small changes this morning and when I powered up there is worse 50Hz noise than ever.

What I changed: placed Playstation 3 on shelf next to DAC and Crack. Moved HD650s and headphone stand to shelf below the Crack. (Connections to PS3 are optical (to DAC), power and HDMI)

When I noticed the noise had returned, I unplugged the PS3 (power only) to see if this was the cause, but the noise remained.

How could this occur?

[Loquah]

Sorry about the immediate addition, but thought to roll the tube to see if this had any effect. It seems my beloved Mullard 6080WA was the cause.

Will it rectify itself or does this mean dead tube?

[4krow]

I recommend gently placing the tube on the floor and stomping on it just once. If it survives, keep it. It may have magical powers. If it doesn't make it through this test, it's better that you found out now, 'cuz as soon as it went to the dark side, it would come back with a vengance and take out all the circuitry it could.  No joke.

[grufti]

Congratulations on finding the culprit.

Somebody else will have to come up with a good answer to your question about the tube's fate. One thing your story does remind of however, is that problems will more often be found in the circuit that is misbehaving rather than "being induced from the outside".

The usual demons: SMPS, CFL, normal fluorescents, transformers, displays, ... should not be able to cause really bad noise in a well designed and correctly built circuit. They sometimes do anyway.

You might want to shake your troubled tube rather than stomp on it. I'm worried about your foot.

[Paul Birkeland]

When I find dead tubes at the shop, I will put them in a plastic bag and hit them with a hammer.

This is after Josh insisted on taking home some dud 9 pin tubes for display (duds have a habit of making their way back into the pile for lab use).

[Loquah]

Well thankfully I didn't take the stopping or "hammering" advice. I decided to try the 6080WA one more time and it's fine. There must have been a poor contact between the tube and the socket (despite no movement or anything). I guess some mild oxidation or something.

Either way, re-seating completely fixed the issue and I have my audio heaven back ;-)

Thanks for all the advice and suggestions everyone!

[earwaxxer]

I'm still too retentive to get rid of a questionable tube. I put them back in the box and mark it with an 'X'. I guess I'm hoping for a healing. Maybe a 'rest' will help. Dont know, they are just too pretty to throw away.

[Grainger49]

Break the glass and file it down with a diamond file.  Then you can see/display all the intricate innards.