Stereomour II Noise (or lack thereof)

[benzxc]

I have a Stereomour II (with all 3 upgrades) in my system for almost 5 years now and only recently switched amplifiers. I never noticed any noise with the Stereomour II even though it is located right next to my Wifi router.

With my new amp, there is clearly audible buzzing that is caused by the wifi router, which is understandable and easy to solve.

My question is what is the Stereomour II doing that is blocking all that noise so I have a total silence even with the wifi router right next to it? I'm very curious to know as I would like to look for that in future amps I get.

Thanks!

[Paul Birkeland]

What is the new amp? 

Typically I would expect an amp like the Stereomour to be more sensitive than most! There are some ways to make tube amps more susceptible to this, but it would be somewhat concerning if a solid state amp picked up this gunk. 

-PB

[benzxc]

Hi Paul, the new amp is Audion Silver Night 300B. It sounds great but I was surprised that an amp costing roughly 2 to 3 times the cost of the Stereomour II (with all upgrades) was susceptible to such noise when the Stereomour II was dead silent. 

[Paul Birkeland]

If you have the 6922 version, you could try shields on the driver tubes just as an experiment.  If you have the 5687 version, I might have to do some head scratching about that!  I don't see a spec for input impedance, if you set your meter to measure resistance and measure across one of the input RCA jacks, what value do you see?

[benzxc]

I use the 6H1N driver tubes. The input impedance, according to the manufacturer, is 50k ohms.

[benzxc]

Weird (but hopefully easily salvageable) thing happened with the Stereomour.

I was playing music and all was fine but when I tried to turn the volume down using the "coarse" volume pot, the sound suddenly became very loud and at the same volume regardless of the volume pot (the sound would return to normal when I pressed down on the volume pot itself but as soon as I release the pressure, the sound shoots back up). I played with it a bit and now the red and white connecting wires between the "fine" and "coarse" pots have snapped. I will re-solder them together but how do I deal with the original issue (volume issue)?


 

[Doc B.]

Get those wires properly reconnected first and see if that changes anything. Also inspect the switches closely to be sure you don't have any bare wires touching that shouldn't be.

[Paul Birkeland]

I was playing music and all was fine but when I tried to turn the volume down using the "coarse" volume pot, the sound suddenly became very loud and at the same volume regardless of the volume pot

Definitely do not intentionally push down on the switch.  An issue with the coarse switch mechanism will make the sound cut out completely.  What you're describing is either a resistor or a ground connection that's intermittent, and when that happens you will get the full volume out of the coarse switch regardless of the position of the knob.