Seduction hum (how much is normal?)

[denti alligator]

Thanks, Desmond. I see now how it's supposed to work. I might as well try it.

[denti alligator]

Star grounding sounds simple, at first, but then I get lost and wouldn't know how to proceed with the few pieces in my system:

http://www.geofex.com/article_folders/stargnd/stargnd.htm

http://www.aikenamps.com/StarGround.html

http://www.lh-electric.net/tutorials/gnd_loop.html

[denti alligator]

Unfortunately, the Hammond box won't fit, but only because I have switched out the caps for somewhat larger ones that woudn't fit in the only 1.77" height.

Another potential clue to the source of the hum: if I *just* put my finger on the Sed ground, the hum is only reduced very, very slightly. Only when I also touch the *wooden* base at the same time is the hum reduced significantly.

I've experimented with this, touching the chasis and ground, other amps and ground, other amp bases and ground, etc. Only touching the wooden base and the ground lug does the trick. (This is why holding the amp and touching the ground lug made such a difference.) NBot sure if this helps figure out the source of the hum. To me it suggests a grounding issue, not RF.

[Grainger49]

Sam,

I have seen pictures of a Seduction with holes drilled through the box so long leads could be used on the capacitors.  The cap leads were fed through the holes, soldered on and then the box screwed to the top plate.

It might work for you.

[howardnair]

sam-- when you touch sed ground and chassis thus reducing hum is your turntable plugged in --is the turntable on the same outlet or string of outlets from one circuit or are they on different circuits--the same question for sex and seduction-turntable

[Paul Birkeland]

(Maybe I'm being overly sensitive. The noise isn't that audible, if at all, at normal volumes through speakers. Only with quiet music turned up to a high volume on 'phones can it be heard. I'm testing without music and with volume turned way up with 'phones on, so the hum can sound pretty dramatic.)

You'll drive yourself nuts doing that, turning things all the way up without signal just amplifies the noise floor to its maximum potential, often times "testing" a scenario that you would never encounter while listening. 

[howardnair]

sam--if you google --regap3-24 hum problems there is info-some say the tt is picking up hum from amps-others say maybe bad ground in turntable-also google ground loop hums there is info there

[denti alligator]

sam-- when you touch sed ground and chassis thus reducing hum is your turntable plugged in --is the turntable on the same outlet or string of outlets from one circuit or are they on different circuits--the same question for sex and seduction-turntable

It's not the TT. With and without TT plugged in = same effect.

I'm gonna learn to be less anal and live with it, knowing I don't hear it most of the time, anyway.

[Paul Joppa]

Two thoughts-

1) Your hand may be providing a radio frequency shield around the side of the box. The ground plane made up of the chassis plate does provide some shielding, but is most effective on parts and wires that are closest to the plate.

2) There is a bit of residual hum in the tube closest to the power transformer; this is the magnetic field of the power transformer affecting the tube, or perhaps bending the electron stream. I don't remember (if it was ever posted) what your cartridge sensitivity is, but that hum is usually OK with carts of 3-5mV or greater. That's because with a higher output cartridge you turn the volume at the amp down.

[denti alligator]

What's an effective DIY RF shield that I can use to test with the Sed, before going with the Hammond box, which really will be a pain to install given my cap upgrades?

[2wo]

You could take a few sheet of heavy duty aluminum foil and fold them into a box shape. And of course, duct tape to hold it together. 

Somewhere along the line you mentioned, that if you touched two components, the hum was reduced. Have you tried using a jumper wire to replace your body?     

[Paul Joppa]

I haven't suggested aluminum foil because of the risk that a high voltage might touch it. Be careful!

Hammond and others do make 6"x10" boxes 2" deep, which can replace the wooden base. The lip may need some trimming, depending on how wide it is, but it does have a better chance of accommodating the large caps.

Understand, this is low level hum we're talking about. There is no guarantee than ANY particular solution, including this one, will be the right one. Hum busting is pretty frustrating.

[Paul Birkeland]

Hum busting is pretty frustrating.

Not as frustrating as mutton bustin!

Have you tried clip leading the chassis of all your gear together?  Sometimes I can discover the issue by doing that.

-PB

[denti alligator]

I'm having a tough time finding a Hammond that's deeper. If anyone could point me to one or an equivalent, I'd be grateful.

[Grainger49]

Start on this page:

http://www.hammondmfg.com/scpg.htm

The first type goes to 3.98" deep.