The 60 Cycle Hum on an STR 7

[cbk]

I just bought a used STR LS748. Everything sounds good, except the 60 cycle hum when one pick-up is favored over the other. If the bass is moved away from the amp, the hum fades somewhat; however the "spot" is hard to find and the hum is extremely loud.

I would appreciate any suggestions as the clock is ticking on my time to return the bass.

Thanks everybody for your input.

cbk

[line6man]

Sounds like normal single coil hum to me, and there is nothing you can do get rid of it.

You either need to keep the pickups at an equal volume, or replace the single coils with humbuckers.

[fleabee]

like line said...nothing you can do about it...shielding yada yada wont change anything..its the nature of single coil's

[cbk]

Thanks for the input. Although, that is not what I wanted to hear!

cbk

[svirfnebli]

Thats correct. Most likely the pickups are wound RWRP which cancels out the hum when put together.. The two single coils become a humbucker because the coils are out of phase with each other. When you favor one pickup, the individual pickup comes back into phase and you pickup electromagnetic interference.

There is no way around it.

svirf

[line6man]

Originally Posted by svirfnebli

When you favor one pickup, the individual pickup comes back into phase

Incorrect.
The hum is coming in equal from both pickups, but on opposite phases. (Equal and opposite waveforms cancel each other out...)

When you favor one pickup, the hum is no longer equal on both pickups (one waveform is louder than the other) so one phase is stronger than the other and it cannot cancel itself out.

[cbk]

It makes sense that they cancel each other until one is favored.

I like the sound of the bass, but it is a shame not to be able to get the other tone shades because of the hum.

Thanks everyone for all of the input.

I may return the bass and continue the search for the tone ...

cbk

[lowendfriend]

Originally Posted by line6man

Incorrect.
The hum is coming in equal from both pickups, but on opposite phases. (Equal and opposite waveforms cancel each other out...)

When you favor one pickup, the hum is no longer equal on both pickups (one waveform is louder than the other) so one phase is stronger than the other and it cannot cancel itself out.

+1....exactamundo

[lowendfriend]

Originally Posted by cbk

It makes sense that they cancel each other until one is favored.

I like the sound of the bass, but it is a shame not to be able to get the other tone shades because of the hum.

Thanks everyone for all of the input.

I may return the bass and continue the search for the tone ...

cbk

Look for a used Warwick Corvette Double Buck ($$) as each pickup cancels itself, so to speak and then you can do parallel, series, solo and blended tones, not to mention where you pluck or pick strings. I love that span of control on mine.