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I’m getting a hum in my integrated tube amp and it’s bugging me alot

Hi - first of all, here’s my system:

- Rogers High Fidelity EHF-200 mkII integrated tube amp

- Magico A5 speakers

- Merging NADAC + Power DAC

- Audience T2 power conditioner

- Purist cabling

I love the sound of my system. BUT…….I have been noticing a hum after about 10 minutes of use from my amp. There are two switches on the amp - POWER & OPERATE - that need to be turned on in order to listen to music. (The Power switch needs to be turned on about 30 seconds prior to switching on the Operate switch). With both KT150 and KT88 tubes (all matched), after about 10 minutes I hear an audible hum from the amp that is apparent from my listening position about 10 feet away. If I turn off the OPERATE switch, the hum disappears (but of course, then I can’t listen to music). I have contacted Roger (the company owner) who said it was noise from old tubes. But my KT88’s have less than 100 hours on them and they hum as well as the KT150’s (maybe a few db’s softer than the 150s’). 

 

Does anybody have any ideas about what causes this and how it might be fixed? Is this an issue that is endemic to tube amps? FYI - if this requires new tubes, then I need to switch back to SS as I’m not willing to invest approx $800/year in new tubes. 

 

I turn to the great wisdom of this forum to help.

 

Thanks - Matt

mwsl
minorl
1,016 posts
 

Try this.  Unplug everything from the wall and just plug in the amp and connect the amp to the speakers.

Disconnect all interconnect cables also.

If, with the amp the only thing connected you don't hear hum, then connect the DAC to the amp/speaker combination and see/hear if you detect hum.  keep going until the hum appears.

If the hum is present with only the amp connected to the speakers and nothing else is connected and plugged in, then it is the amp.

I'm glad you are sending it in for evaluation, however, I didn't see in the previous responses if you tried to isolate all component to see what is actually causing the hum.

What you don't want is to send the amp in for evaluation and they don't find anything wrong with it, and it turn out to be another component in your system.

enjoy

 

builder3
758 posts
 

Sounds like transformer hum, to me. If so, it will always be the same level, won't change with high or low volume. Disconnect the speakers (and everything else), if you still hear the hum, it's obviously the amp, and likely transformer noise.

roxy54's avatar
roxy54
8,007 posts
 

He already said that he's sending it back to the manufacturer guys.

builder3
758 posts
 

Read that, didn't see any harm in sharing my own experience with this.

perkri
907 posts
 

Since the hum appears after the tubes warm up, and not immediately, it sounds like a tube issue to me. Is the problem in both channels, or just one?

And just to confirm, the sound is coming from the speakers, and not from the amp. Is that right?

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