[Nadim]

Just this weekend I got my Gilmore V2 kit and put it together. Everything seemed to work great (and there was much rejoicing!). However, I brought the amp into work today, and noticed that I could hear a distinct buzzing sound when the amp was on. This was strange, as I didn't hear it when I was testing the kit at home...of course my computer room ain't exactly quiet. Anyway, the buzzing was independent of volume (i.e. same loudness with volume at midpoint, or even all the way turned down), and independent of input (i.e. it didn't go away, even when I disconnected the interconnects from the input). I brought the amp back home, and just tried it in various outlets in the house. It definitely seems that the buzzing is louder in some outlets, and quieter (almost gone) in others. I tried this both with and without the power cord grounded (using a 3-2 prong adapter), and that didn't seem to make a difference.

I'm not sure how to proceed...I'm not sure if there is something wrong with my building job, although I followed the instructions, tied the rca jacks, headphone jacks, pot, and case screw all to ground, I'm not what I may have missed...If that's the case, I'm curious about approaches to track down what's wrong. Or maybe the amp is just sensitive to bad power, and needs some sort of RF filter or something. Any thoughts /suggestions would be greatly appreciated!

-Nadim

 

[dd3mon]

My buzz was eliminated by reversing the polarity of the power - perhaps you connected them opposite? If not - proceed with caution, I have no idea the consequenses of reversed polarity in your amp

-dd3mon

 

[Nadim]

Hmmmm....Interesting. Now that you mention it, the instructions for hooking up the back of the IEC power connector didn't match the connector itself, so I just took a crack at which way it went. Well, if you hook it up backwards, and neutral is treated differently inside the power supply circuit, I could see a ground loop being created (since neutral is tied to ground at the circuit breaker box), but then the buzzing should still go away if you hook up the amp with a 3-2 prong adapter and cut out the ground. I dunno...does someone with more experience on this subject care to weigh in?

-Nadim

I may try reversing them anyway and seeing what happens...

 

[Nadim]

Well, I was playing around with the amp, and noticed that the hum disappeared when I took the top off. Strange. Then I got a message from Antness suggesting I rotate the toroidal transformer a bit to tweak the hum, and sure enough, after loosening the bolt and playing around with different positions, I noticed that some positions hummed with the top plate off, and some with it on, and eventually I found a position where, with the top on at least, it was dead silent. Tighten the bolt, screw on the top plate, and voila, fixed.

Now, my EE training is certainly rusty after these years of doing software, but I'm very curious to know exactly what effect causes this... Is the transformer inducing an electric field in the aluminum top plate? Perhaps in some positions it induces it in the sides or bottom as well, which would explain the hum in some positions when the top is off. In any case, why would turning the transformer affect this, since it's toroidal, not the "wrapped iron figure 8" style? Or am I missing something more obvious...

-Nadim

 

[dd3mon]

Gotta be some sort of electrical/magnetic field being added in if moving it can change or eliminate it. What exactly is the creator and receiver of this rogue field is anyone's guess (although toroid is obviously involved).

-dd3mon

 

[flashbak]

The problem is the position of the transformer! Make sure the transformer's colored wires group (not the ones covered in yellow tubing) exit out the transformer at a position between 6:00 and an 11:00 oclock position. Rotate the transformer until that colored wire group is exiting at a 7:00 position, and if necessary increase to 8:00, 9:00, 10:00 etc, until the noise disappears. Same problem here and mine was completely gone at a 9:00 oclock position.