How long are tubes lasting in your BHK 250. I have 1127 hours on a new set I purchased from PS Audio direct and though they still sound good I am now getting a pop when I put the system on standby. This is the condition I have seen with every set of tubes that I have used in my BHK 250. It seems odd to me that this should occur so quickly without any other sonic degrading going on.
Does the pop occur on both channels?
Right now it is just in the Right Channel but in the past I have heard it on both! A new set of tubes clears it right up!
This is not a lot of hours for a small signal tube.
How long did it take for the earlier tubes to exhibit this behavior?
Have you always used stock/OEM tubes?
I have had 3 sets of OEM tubes all purchased direct from PS Audio and Two sets of tungsrams that came with the amp from Kevin Deal. None of them lasted very long. The amp went to PS Audio when this issue first showed up they checked it out put in another set of tubes and said they only reseated the card. Before my amp went in to be serviced I had sent the Preamp in as directed by the techs . They replaced the main board in the preamp but that did not clear the noise. That is why they had me send the amp in.
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I have found that the tubes in my BHKpre and BHK300’s need to be replaced by 2500 hours. They start to lose SQ at that point. More importantly, this last time I pushed it, and once they were over 2900 hours “bad things” started to happen which were resolved when replacing them all. They started to periodically pop and have background static. So I go 2500 hours and out they go.
I’m with Elk, 1127hrs seems a bit shorter than what I would expect. I saw that you picked up some new tubes. 
that does the trick!!
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James,
Yes I did order a set today. I am now using the Tungsrams and they do not make a audible of a pop when I put the system in standby. They are quiet in the amp and sound good. I can’t take the noise they make in the preamp though.
With last 3 sets of tubes (replaced in both amps even though issue was only with one) same issue: intermittent POP when Audio Research LS28 MUTE pressed on or off (which usually happens only after system has been on a couple of hours). The first set with left BHK300 only, the last 2 with right BHK300 monoblock only. First set was replaced after only 1,024 hours (POP was severe enough to cause left channel BHK300 to go into protection mode). Second set replaced at 780 hours. Current tubes have only 380 hours. All tubes were matched sets directly from PS Audio. With the last 2 sets POPs only - not causing BHK300 to go into protection. Each time tubes were replaced the problem went away, only to return 100 or so hours in.
Any thoughts, James? Would you run this by the guys in engineering? Thanks.
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But this is only happening when you throw the pre in and out of mute? Nothing when you put the amps in and out of standby?
If that’s to me, yes only with MUTE, Turning system on and off (using 12v trigger) no POPs. System is always in MUTE when turning on or off. Haven’t tried pressing STANDBY without MUTE on.
If you talk to engineering, this may be useful:
LS28 uses a relay mute right at the output, if there is DC at the INPUT of the BHK300 (coming from the amp, not the preamp), when the LS28 mutes it will cause a pop since it is shorting the signal lines directly to ground.
It does it with mute too, only audible without music playing.