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Background noise

Hello folks. I have a Shindo Monbrison, a wonderful preamplifier, with a wonderful phono section. That said, I noticed a fairly high level of background noise when I turn up the volume without playing music (and this doesn't change by unplugging the interconnects). When the volume control is at its maximum level, you even listen to a little whistle.

Is it normal for a tube preamp or do you think there is a tube problem or another issue? I never experienced this problem in the past, but I've always used SS phono sections.

thanks.
ggavetti
ggavetti OP
143 posts
 
there is no noise I can hear from the other inputs, even at maximum volume levels. Just to give you a better sense of the loudness of the noise, I just set it at the maximum level, stepped out of my listening room, moved to another room that is approximately 8 meters away from the listening room, and could still hear it.

BTW, I bought the Monbrison 3 months ago from someone who bought it in October. Called Shindo and they told me that the warranty is not transferable...weird policy for a luxury product, if you care about keeping your customers. That said, the Monbrison is just wonderful
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rcprince
3,075 posts
 
Sounds like it could be tube rush from the tube(s) in the phono stage. If you have enough gain from your cartridge/phono stage combination, it may not be noticeable in ordinary listening. Could also be a noisy tube, though, in which case you'll probably need to get your replacement from Shindo, I think they use some unusual tube types in their gear, at least the amps.
ggavetti OP
143 posts
 
I think the hypothesis that this is tube rush is sensible. The gain is ok but not great: I use a MC Sumiko Blackbird through the MM phono section. The Blackbird is 2.5 mV, and the Shindo dealer says the minimum MM should be 3 mV. Despite this slight mismatch, I find the combination to be wonderful...except that I can hear some noise when I turn up the volume level during music reproduction.

I'll find out what tubes are used for the phono stage and see if I can find a replacement. Thanks
swampwalker's avatar
swampwalker
5,138 posts
 
I use a MC Sumiko Blackbird through the MM phono section. The Blackbird is 2.5 mV, and the Shindo dealer says the minimum MM should be 3 mV.
OK, now we are getting somewhere. You probably have a noisy tube or tubes that is exacerbated by being below the minimum recommended input voltage, therefore needing to crank up the gain. Its also possible that you may have a loading mismatch by going into an MM phono stage (typically 47k ohms), but I'm not sure what that would sound like. See if you can get some phono grade/v, low noise tubes from a reputable dealer and report back.
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