5E3 and single coil pickups

[Leevi]

I have noticed that 5E3 circuit based amps can easily hum depending on the guitar position.
This is very common with guitars having single coil pickups.

What might be reason for that? Does the Cathodyne PI have some meaning in this?
/Leevi

[pompeiisneaks]

Humbuckers are named that for a reason :).  Single coil pickups always add hum.  Some amps may make it worse.  From my understanding of cathodyne's, they're actually very clean and often used in hifi as well due to having a very high quality, low noise type of operation.  (I've been reading Merlin Blencowe's preamp book and I'm in the cathodyne chapter right now :D )

I think willabe was telling me yesterday that the older amp layouts sometimes were more noisy, and as they progressed the designs they made them better with respect to avoiding grounding loops etc.  (I've also learned a ton about grounding this week alone :P )

I think you could possibly try to update the grounding in the 5E3 in some way to make it cleaner, but not sure.  Maybe some here on the forum have already done it.  Usually, its just best to move single coils away a few feet and try rotating them slightly off axis as well. 

I've had that problem with single coils on many amps over the years... :)

~Phil

[Ed_Chambley]

Not the PI, but some thing to check.  Does your chassis have a shield covering it like a piece of metal?  Are the flourescent lighting on the same circuit as the amp is plugged?  Is the cavity of the guitar shielded well?

My 5E3 does hum a little more with single coils, but it is very little.  Shielding the chassis of the amp and cavity of the guitar helps a lot.

[Leevi]

I think the grounding is ok since there is not any background hum.
The hum that comes from the guitar/guitar cable disappears when you find the "right" guitar position.
The guitar works like an antenna.


I have built lot of amplifiers and think the problem is related to the amp type.
E.g. VOX and Marshall-type amps (or preamps) are not that sensitive.


Shield covering might help, have to try.


/Leevi

[uki]

Dummy coil !!  http://www.cavalierpickups.com/frettech/dummy/index.html

[jjasilli]

Guitar / amp, maybe, maybe not.  Ambiance factors: fluorescent lights, dimmer switches, & fan speed switches have induced hum into some, but not all of my amps, equipment - with no apparent rhyme or reason.  Took a long time for me to trace the cause.

[HotBluePlates]

I have noticed that 5E3 circuit based amps can easily hum depending on the guitar position.
This is very common with guitars having single coil pickups.

What might be reason for that? ...

... The hum that comes from the guitar/guitar cable disappears when you find the "right" guitar position.
The guitar works like an antenna.

I have built lot of amplifiers and think the problem is related to the amp type.
E.g. VOX and Marshall-type amps (or preamps) are not that sensitive. ...

I disagree, but based on a subtle distinction. You already know the problem is the guitar, because it only appears with the guitar plugged in, and only with single-coils.

Indeed, the single-coil pickup is acting as an antenna. It it my guess/opinion that the single-coil is picking up noise from the power transformer. I wonder at times about contribution from the rectifier or choke, as I think I hear the "buzzy hum" of ripple (120Hz rectified, non-sinusoidal, with harmonics of 120Hz). If you bring the guitar/pickup close to the amp's power transfor4mer, the noise will get louder. If you get far enough away (while also staying away from other noise sources like flourescent lights, computer monitors, etc), the noise will be very much less.

Rotating the guitar (and therefore pickup) does strengthen/weaken the coupled noise. What you're doing is changing the relative angle of the pickup winding to the magnetic hum field, which changes the degree of coupling into the pickup coil. No different than rotating transformers 90-degrees on the chassis to minimize coupling. Except you can very easily rotate the guitar along 3 axes and immediately hear the change in hum coupling.

So why does the tweed Deluxe make more noise (seemingly) than a blackface, Marshall or Vox. It's my opinion this is due to the tone circuit of the amps you hear as having less noise. They all have a steep midrange scoop. Look at a plot of that curve with the Duncan Tone Stack calculator; compared to the peak of Bass frequencies, there is significant and increasing cut from 120Hz up to at least 500Hz. So that's a reduction of the ripple and its harmonics, and in the range of hearing where ears are most sensitive. By comparison, a tweed Deluxe is flat in the midrange (which sounds like "mid boost" compared to the other circuit) and ripple/buzz is not reduced.

That's my theory anyway, and I have a lot of confidence in it based on playing single-coils with original tweed & blackface amps (and my copies) since the mid-90's. 

[Willabe]

Makes sense to me HBP. 

[Tubefiend]

I've got a 76 Strat that did that when I bought it new (I'm friggin OLD!). I was using a modified Bandmaster head at the time, with four 5881's and that guitar was terrible for noise. One day I opened it up, and using a shielding kit that included a brush on conductive paint, I insulated the entire pickup cavity, and the problem when away. Years later I replaced the entire crappy 70's Fender pickup and guard assembly with a DiMarzio Area  I think it was called, and that's the way it still is, quiet as can be.

Pete

[HotBluePlates]

A guitar can be improved with respect to noise by proper shielding.

I've even go so far to have opened up single coil pickups in a strat and shielding the coils with copper (after also shielding the entire cavity, jack cavity and running 2-conductor+shield wiring between). All this reduced noise considerably, but didn't eliminate it. And I could still pick up noise from the amp's PT or from lights if I had the guitar near them and in a certain angle.

As pompeiisneaks said in the 1st reply, that's why humbuckers have their name (though there are many ways to buck hum while having a single-coil sound).

[Leevi]

So why does the tweed Deluxe make more noise (seemingly) than a blackface, Marshall or Vox. It's my opinion this is due to the tone circuit of the amps you hear as having less noise. They all have a steep midrange scoop. Look at a plot of that curve with the Duncan Tone Stack calculator; compared to the peak of Bass frequencies, there is significant and increasing cut from 120Hz up to at least 500Hz. So that's a reduction of the ripple and its harmonics, and in the range of hearing where ears are most sensitive. By comparison, a tweed Deluxe is flat in the midrange (which sounds like "mid boost" compared to the other circuit) and ripple/buzz is not reduced.

Very much possible


/Leevi

[PRR]

If you can "aim" the guitar for more/less hum, it is probably magnetic pickup, not electric pickup.

More tin-foil and grounding inside the guitar won't fix this.

Your pickup is supposed to pick up the 82Hz-440Hz vibrations of your strings.

The wiring in your walls is "vibrating" 50/60Hz. The pickup can't actually sense "vibration", only "variation". Power line is a "valid" signal. Your PT has the same, plus harmonics.

Putting the pickup in an iron box would block the hum and also the strings.

The partially open iron shell favors near-by vibration over distant vibrations, but isn't perfect.

Humbuckers pickup string+hum, and mostly-hum, subtract to get mostly-string. Not perfect, and less treble, but a good improvement.