Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: oltmb on November 28, 2016, 07:45:01 AM
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Hi,
I finished my BeePre Limited Edition last week. I added several sound damping extras like Dynamat on the inside and 4TUBE absorber feet. I also placed the preamp on a wall mounted rack to reduce any vibration from external sources. I added a Rothwell balanced 10dB attenuator before feeding the signal into my Hegel Power Amp.The sound is great!
However there is still a continuous audible hum in the left channel. I found out that exchanging the 300B tubes moved the hum from the left to the right channel.
Can this be a tube problem and not something in the preamp itself? How can I correct it?
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Sounds like a tube problem. If you are using new tubes, the problem might go away with time as the tube breaks in.
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Ok. I will wait for a few days and see if it improves. Forgot to mention that I am using High Density Silicone Tube Vibration Dampers from Levytubes.
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I did not want to wait as after several hours the hum stayed and it was very annoying. I went to the local tube store (www.tubeprofi.com) and purchased a pair of JJ 300B tubes. That immediately improved the level of microphonics and there was no hum. The JJ's have internal silicone damping and it works well. I don't need to use the external damper rings.
I don't like that one of the EH 300B tubes that was delivered with the kit was not working 100%. I guess there is no warranty.
There is just a little bit of 100 Hz hum, but only if I put my ear next to the loudspeaker. For the rest everything is fine.
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I don't like that one of the EH 300B tubes that was delivered with the kit was not working 100%. I guess there is no warranty.
I don't know why you are assuming this. All you need to do is contact us about returning the tube for a replacement. Email Eileen at [email protected] and she will help you with the return.