Not sure what a VF is but what I have is a high intensity lamp with a skinny cylindrical bulb that should not be touched by humans under penalty of death or first degree burns. When the lamp is on "high" I could fry an egg on its cover. I need to get a flat plug extension cord to fit into tight space behind my desk. Hopefully it will be a $3.99 solution.

Or I could spend no more money and just turn the dang thing off when the amp is on.

Well, to demonstrate how strange causes of hum in one's amp transformers can be, here is the latest.

The high intensity lamp I have on my desk is the cause of my hum. I plugged it into a several different outlets on my several power strips. No change. I plugged it in by itself into a separate wall outlet (yeah, probably in the same circuit as the rest of the stuff) and no change.

Then remembered there is a circular switch on the lamp cord that provides a "high" "low" and "off" setting for the lamp. The "low" setting produces the hum. The "off" and "high" settings do NOT produce any hum. Voila!

Now all I have to do is get a lower wattage bulb so the high setting doesn't blind me.

It is likely that the switch is causing some RFI to be generated and interferes with some circuit in the 2150. The switch may not be making good contact thus creating some small arcing issues. Power companies of old used to drive around with the AM radio tuned to a white noise channel listening for the same sort of interference to tell them when the connections on a power pole were needing repair.

I'm sure it would be a lot cheaper to get a lower wattage bulb (if I wanted to reduce the brightness) or even to buy a new lamp than to buy a device to reduce the interference (if such device even exists).

This lamp just uses a rotary switch to dim it, I guess by just using a resistor?

There's a lot out there on RFI caused by dimmer switches. Technically this is probably conducted emissions because most likely the interference is on the power wires not radiated through the air.

Go with the lower wattage bulb and run it full power.

BTW Because I used a lot of them in the past I say VF (Vacuum Fluorescent) when referring to CFLs(Compact Fluorescent). Sorry for the confusion.

No, not a compact fluorescent, but a halogen. And when I used the term "high intensity" I meant "halogen." Sorry for my confusion too. This is the bulb. So do you think it is the bulb or the switch or the wire that generates the transformer noise in the amp?

Unless needed for a portable heater I would think a halogen bulb and the associated power supply needed would be the last thing I want plugged in near audio gear.

Look at the LED types available. You should find something that will be fine for your lighting needs without the high current power supply. Most anything you could choose would be an improvement over the halogen.

Yup, it does make a great heater, and to fry my eggs in the morning now that I keep it on high. Seriously, now that I know it is the culprit, I will keep it off 90% of the time. It is just a local task light.

Thanks for all the encouragement to keep troubleshooting.

I bet it does. I have never seen one used inside before. We used to use them in flood fixtures for parking area security lights.

Happy for you that you discovered the cause of the problem.

I would keep it off just because they use so much power. I have a work light that draws 900 watts when all the bulbs are on. It has two 150 watt low power bulbs and two 300 watt high power bulbs. It doesn't interfere with my radio I use in my shop so I would suspect the dimmer switch is the culprit. You could try some contact cleaner on the switch.