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Does it happen with other guitars as well? What about if you take them somewhere else? It sounds to me like you might have noisy electrical in your house. Have you tried a power conditioner? Try different guitars or guitar cables? I'd be curious if they make the same noise at someone elses house.

This happens with or without anything plugged into the input, so different guitars have no effect. It has also occurred in at least 5 different locations.

I should mention I've never encountered this issue on 3 channel rectifiers, which leads me to believe there must be a design difference.

That's really strange. I have only ever had 3 channel versions.

snave said:

On all five 2-channel Dual Rectifiers I've had (1993 to 1998 productions), there has been a constant hum/buzz noise that's affected by several variables but never goes away completely.

First off, it's a constant volume level (i.e. it does not change with volume or gain control changes). It's present on both channels. The ground switch does not get rid of it.

I've found it gets louder with either the bold or silicone diode modes, and much louder on modern modes. The noise also seems to be louder when using EL34 tubes vs. 6L6. This leads me to believe it has something to do with internal voltages, since all of these settings (except for modern I think) increase the operating voltage.

Since this has been a trait of all 2-channel Rectos I've owned (including a Tremoverb), I've assumed it to be normal.

Does this happen to anyone else here, and is there any fix for this issue? Is it something a recap or preamp tube change will get rid of?

Click to expand...

Necro bump of this thread. I have the exact problem described by the OP (I used search, what a novelty!).

Mine is an old 'G rev' 2 channel. Sounds great apart from the hum.

Has anyone found a solution? I assume its quite common.

It sounds similar to my 2203KK after my attenuator packed up when I was using it as a load box biasing the amp.
Is the hum coming from the speaker or the PT side of the amp?
I know I've stressed my PT and it's that which is humming. Nothing alters it or changes it's pitch.

Nicklotsaguitars said:

It sounds similar to my 2203KK after my attenuator packed up when I was using it as a load box biasing the amp.
Is the hum coming from the speaker or the PT side of the amp?
I know I've stressed my PT and it's that which is humming. Nothing alters it or changes it's pitch.

Click to expand...

It's from the speakers.

If I remove all preamp tubes the amp is silent. Adding the PI (v5?) reinstates the hum, so I think it's not in the power stage. Swapping different PI tubes doesn't alter the hum so it's not the tube either.

As with the OP bold has more hum as does setting the rocker switch to clone orange to red (two modern channels).

Clearly it's not the power transformer then mate. As you say, it's obviously happening at the pre-amp stage. Without getting elbows deep into the thing it's beyond my scope to ascertain what's causing it. Given that you've experienced the problem on 5 amps. It's obviously a flaw that you're noticing more than most people. Or you'd read about it more often.

Nicklotsaguitars said:

Clearly it's not the power transformer then mate. As you say, it's obviously happening at the pre-amp stage. Without getting elbows deep into the thing it's beyond my scope to ascertain what's causing it. Given that you've experienced the problem on 5 amps. It's obviously a flaw that you're noticing more than most people. Or you'd read about it more often.

Click to expand...

I'm not the OP, I posted because his problem sounded identical. Was curious if the OP had a solution.

I never had a guitar amp that was noise free, even the solid state amps will generate noise with no input signal.
Mark V makes the most noise on the lowest gain of the clean channel. Both RA100 will generate noise as well as the Roadster. My old Mark III and Mark IV did that as well.

The hum or buzz I would believe to be in the 120Hz range. Some power tubes will generate some noise as the heaters are typically AC sourced. Power tubes will also generate noise as well. You can pull all of the preamp tubes out of your amp and still hear some noise as the bias voltage may have some current ripple in it that may affect the power amp even with the PI tube removed. This may be the condition of quiescent point of operation as there is current flowing in the power tubes with no input signal on the grid. If the noise is excessive but with the tubes removed except the power tubes, it would be the tubes I would suppose. What level of noise or hum is not normal in a tube amp? Usually I can ignore the white noise or slight hum if the magnitude is not noticed when playing though the amp. If it gets annoying, I usually start tube rolling but may move the amp first in case there is EMF pickup from electrical lines in the wall or floor.

I'm sure you've checked this and would know the difference ... But presumably the fan has to whir away quite a bit.