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AUDIO FORUMS >> General Discussion and Support >> Questions-tubes and transformers.
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Message started by Robert Hart on 02/11/20 at 19:32:54

Title: Questions-tubes and transformers.
Post by Robert Hart on 02/11/20 at 19:32:54

I have a new rogue Cronus magnum 3 and the input transformer hums loud enough to be a problem during movie dialogue.
It’s plugged into the wall, is there anything that can be done to reduce or eliminate it? My listening position is 9’ from the transformer, in a well padded room. I am thankful I can get the house this quiet for a few hours a day.

I had a Cary SLI80HS with kt88’s. One striking feature was the bluish purple glow of the power tubes. My Kt120’s Don’t do this.

Is there a particular tube type /manufacturer that displays this behavior particularly well, I can use kt120’s and smaller .

Title: Re: Questions-tubes and transformers.
Post by Lonely Raven on 02/11/20 at 21:06:33

When tubes show a lot of purple glow, it's because the vacuum isn't perfect in the tube, and the atmosphere in the tube is ionizing. It's not a feature, it's probably a flaw in manufacture. Some power tubes may have a light purple glow from stray electrons hitting the glass, this is normal. Some tubes, like voltage regulators may use an alternate gas in the tube such as neon or argon and will glow purple or pink...but with power tubes no glow usually means an excellent vacuum during manufacture.

As for the transformer hum - assuming the amp doesn't have any manufacturing flaws, it's probably some stray voltage on the ground. If this is in a media room (which I'm guessing it is since you mention movies), try disconnecting the Coax cable (assuming Cable TV) and see if it goes away. That's often the culprit. If it doesn't go away with the cable disconnected, try disconnecting different gear in your setup and see if the hum suddenly stops with a particular piece of equipment removed.

If my guess is right, and it's some voltage on the ground, you might need an isolation transformer or other filter. Or if it's the cable companies line, call them and tell them to get out and fix their poor ground.

Title: Re: Questions-tubes and transformers.
Post by Robert Hart on 02/11/20 at 21:19:14

Thank you, Ill try eliminating plugs. There is no coax; cable (wireless node) and tidal (pc)are WiFi.
I have silence in the speakers which is great... and I’ve turned off everything in the house. The one socket everything is plugged into is split between the amp and a budget line conditioner (livewire pc900)