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eligilam
Advanced Member
Username: eligilam

Post Number: 302
Registered: 2-2006
Posted on Wednesday, February 16, 2011 - 6:30 am:   Edit Post

Hi everyone.

I'm nearing completion of a soundproof "jam room" in a building separate from, but nearby, my house. Everything is done except the floor...so last night I moved my bass rig and PA out there to sort of break the room in and test out the "soundproofness."

The soundproofness is great (and I expect it'll get even better after we put in the floating floor), but my rig now has a horribly loud hum. I assume it's RF interference related. Note that I live in a rural area without any close neighbors. The nearest visible power lines are about 100 feet from the jam room building.

The track lights (nonfluorescent) in the room are on a dimmer, and the hum "cycles" and changes pitch when the dimmer is turned. There are no fluorescent lights in the room. The only other electrical devices in the room right now are a small air recirculator and a ductless AC/heating unit. The hum does not appear to change when either of these units is on or off.

My rig is made up of: Rickenbacker 4003-->SansAmp RBI rack unit-->Line6 POD BassProLive rack unit-->GK 700RB-->GK 4 x 10 Neo cab--> Furman power strip rack unit.

I know that the hum I'm describing is a fairly common problem, but it's putting a crimp on my otherwise jubilant feelings of this jam room finally becoming functional.

(Note also: I appreciate that this is the ALEMBIC Club, and I do own a SCSD bass...however, I'm not braving "the room" with my crown jewel axe until absolutely everything is done. Then she will be introduced with much fanfare!)

Thanks in advance for your advice, comments, suggestions, and expertise.

Will
dadabass2001
Senior Member
Username: dadabass2001

Post Number: 1545
Registered: 6-2002
Posted on Wednesday, February 16, 2011 - 6:57 am:   Edit Post

That sure sounds like an old dimmer is introducing garbage into the AC, rather than RF interference.
My 2 - replace the dimmer with a new one after explaining your problem to the local hardware guru. Alternately you could just turn the dimmer off and bring some stand and desk lamps in for lighting.
Mike
eligilam
Advanced Member
Username: eligilam

Post Number: 303
Registered: 2-2006
Posted on Wednesday, February 16, 2011 - 7:22 am:   Edit Post

thanks mike
I should add that the hum is still present even with the track lights turned off

I should also add that I have individually removed each of the rack units listed above from the signal chain and the hum persists

I'm wondering if it could be a shielding issue with the ric
eligilam
Advanced Member
Username: eligilam

Post Number: 304
Registered: 2-2006
Posted on Wednesday, February 16, 2011 - 7:26 am:   Edit Post

oh and the dimmer switch I mentioned is brand new just installed last week
lbpesq
Senior Member
Username: lbpesq

Post Number: 4750
Registered: 7-2004
Posted on Wednesday, February 16, 2011 - 7:29 am:   Edit Post

Will:

Does the hum change as you adjust the dimmer? Is it present with the dimmer turned full on?

Bill, tgo
eligilam
Advanced Member
Username: eligilam

Post Number: 305
Registered: 2-2006
Posted on Wednesday, February 16, 2011 - 7:58 am:   Edit Post

hi bill yes the hum changes as you roll the dimmer dial

and yes it is also present with dimmer fully on and also switched off ....although it seems to be not quite as bad with the dimmer fully on
terryc
Senior Member
Username: terryc

Post Number: 1505
Registered: 11-2004
Posted on Wednesday, February 16, 2011 - 8:40 am:   Edit Post

Could be earth fault on the lighting circuit, are all connections properly grounded to the centre pin on plugs, switches and lights??.
When the dimmer is turned down the coil is loaded so the hum will increase, when it is at min resistance(full on) there is no load.
Best get a PAT test(or whatever you USA guys call it)
sonicus
Senior Member
Username: sonicus

Post Number: 1622
Registered: 5-2009
Posted on Wednesday, February 16, 2011 - 8:55 am:   Edit Post

I would get rid of the dimmer completely and wire a standard light switch instead. It would also be prudent to check your AC wiring and make sure that hot , neutral, ground are all correct. Make sure that your AC is well grounded ,sometimes it is a good idea to install an 8 ' NEC code (national electrical code) Supplemental ground rod to your AC service. I would NOT use a dimmer in an audio studio at all to be honest with you. I have installed all LED lighting in my studio with excellent results.
eligilam
Advanced Member
Username: eligilam

Post Number: 306
Registered: 2-2006
Posted on Wednesday, February 16, 2011 - 9:13 am:   Edit Post

yeah it's looking more and more like the dimmer is probably the culprit ... which makes me a little sad since I was really enjoying the mood lighting
sonicus
Senior Member
Username: sonicus

Post Number: 1623
Registered: 5-2009
Posted on Wednesday, February 16, 2011 - 10:01 am:   Edit Post

You can still have mood lighting, I totally understand!

You can divide the switch leg circuit in to 2 or more legs to power different sets of lights . There are a few ways to make this work with out the dimmer.
cozmik_cowboy
Senior Member
Username: cozmik_cowboy

Post Number: 883
Registered: 10-2006
Posted on Wednesday, February 16, 2011 - 2:01 pm:   Edit Post

Dimmer = hum, unless you completely isolate the 2 circuits. I concur with everything Wolf said.

Peter

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