Tracking down a hum.

Today when I powered up my system, I noticed a hum from my tube pre amplifier, a Rogue Audio Model 99 (line stage only). It is worse when first powering up. It is absent through my headphones, (using an external headphone amp and the record button on the pre-amplifier)  Listening to speakers the noise is present but diminishes and eventually goes away as the system warms up.
I'm using the Rogue to send a signal to a Musical Fidelity X-P200.
I don't think the issue is the tubes as I'm using Tung-Sol 6sn7 tubes with less than 300 hours on them.
I bought this Rogue used and had to take it back to get it fixed as one channel kept cutting out because of a bad solder in the out put jack. Maybe something else failed?


A bad solder joint would not surprise me. I bought this thing used and it had a bad solder joint in the left channel variable output. Got that fixed no problem.Hopefully they'll get it fixed. If they don't I'm going back to a solid state integrated amp.

I had an intermittent noise problem on my main system that I originally attributed to a bad tube. I replaced all the tubes from phono stage, to the recherché rectifier for the phono, to the line stage (old stock DR 6h30s, no fun to source), to everything on the Lamm ML2s. Still the noise intruded. Sent one long interconnect back to Joe Kubala to be reterminated- XLR. That didn’t fix the problem either. Found a wanky tube socket on the Allnic phono stage and replaced it. Nope. Glad I did all this stuff, it was due, but still the noise.

Talking to Vytas from Veloce-- he said swap the battery backs in the line stage and see if the noise changes sides. Well, pulling up one pack, there was a feather of dust on the contact plate. I cleaned it, swapped channels/battery packs-- noise eliminated.

Moral of story for me- it’s usually something stupid.

Good luck- by the time you are done sussing it out, you will have given your system a good going over. Back when I was a car guy, they’d sort it out this way-- get the car to a place where you can open it up- floor it-- if something breaks, you’ll know. If it blows out black exhaust and then starts singing at full chat, you have performed what I learned to call the "Italian tune-up." (With respect). :)

Well today I swapped emails with the people at Rogue. They found a faulty SW 5 switch. This is in addition to replacing 5 capacitors earlier. I need to get a new battery for my multi meter, and a set of precision screwdrivers so I can get at the battery. This in order to check the voltage coming from the outlets. I should have it back early next week.Wednesday most likely.

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Well I plugged everything into a different outlet. So far so good. I'll have to give it some time to see if that really was the problem. As whart said. "It's usually something stupid."   It appears jond was right as well.