Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: oltmb on April 09, 2017, 04:10:19 AM
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My Limited Edition is running fine with Shu Guang PS-300B-Z/2 tubes. I have upgraded my power-amp to a NAIM NAP100. This amp has no on/off switch at the front, just a switch at the back and the manufacturer recommends to leave the amp powered on as it only uses 7W in idle state. The problem arises when I switch on my Beepre while the power-amp is already on. I see my loudspeaker concusses moving excessively, most likely due to a DC swing.
What to do? I can disconnect the interconnects until after the Beepre is in a stable state and then connect them. It works but is not a nice solution. The other option would be to put a switch in the output channel. Does that create other problems?
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You can use a DPST switch to ground the outputs of the BeePre until it's warmed up. This isn't all that uncommon in other tube preamps, and is generally labeled as a muting switch.
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Thank you! I used one of the available holes on the chassis to put in the mute switch and it works fine. There were a lot of tips on the web using relays that do the switching automatically, but that involved additional circuitry and I chose your recommendation which is very efficient.