I did a quick search but didn’t see a previous post on this… For the BHK250 amp, how long a “gap” in listening would recommend going into standby mode? e.g., if one knows it would be 2 hours? 6 hours?
Thanks
As a BHK 250 owner and someone who wants to save electricity, I’ve thought about the same question. I find that it takes 2 to 3 hours for the cold amp to start sounding its best. I tend to listen in the evenings. So I turn the amp off before I go to bed and usually turn it on in the late afternoon. That way it’s ready by about 7 o’clock or so. Of course this will vary for different people depending on one’s individual listening pattern.
Recovery from standby mode takes 30 minutes, maybe less; only the tubes are turned off in standby so there isn’t much to warm up again. Putting the amp into standby saves relatively little power so I think it’s important to turn it off if I’m not going to listen for several hours.
Edit: re-reading my post, I realize that I went off on a tangent, addressing a different issue of when to turn the amp off completely. Sorry, not thinking clearly.
Since Standby turns off both the filament and high Voltages to the tubes, I think I’ll be switching my pair to Standby for absences of maybe a half-hour and longer… I expect the tube circuitry reaches thermal equalibrium in maybe a half-hour but that the amps sound fine in maybe 5 minutes, and saving tube life seems…hmm…
…one hour might be only 1/2000th of the life of the tubes… If a quad of Genelex 6922 tubes costs maybe $200 (delivered) from Tubedepot.com, one is consuming 10 cents of tube life per hour… What’s that worth to you? If you’re using original-type tubes, perhaps very little… If you’re using rare, expensive tubes that cost mayby $800 per set, that hour turns into 40 cents… Perhaps more importantly, those tubes that were difficult to find this year might be imossible to find two years from now.
Only you can judge what all this is worth, but still I’ll turn mine off if I planned to be away at least a half-hour.
FWIW, I’ve ordered my '250s, but they won’t be here for a couple more weeks… However, I already have on hand a quad of the Tungram PCC88/7DJ8s from Upscale and also well-tested quads of British-Amperex ‘A-frames’ and British-Mullard dimpled-disc-getter ECC88/6DJ8s that I accumulated for a prior amp.
FWIW, Brent Jesse has LOTS of info on 6DJ8/6922/ECC88 tubes here…
http://www.audiotubes.com/6dj8.htm … I’m just a satisfied customer. 
I turn mine on when I get home from work, off when I go to bed, and leave in on all weekend/holidays etc. Set-o-tubes last me about 1 year.
Same here.
I never concern myself about how many hours the tubes have been used. I am still on the stock tubes and I took delivery of the BHK 300’s in August 2015 ! In July 2016 I took delivery of the BHK preamp and a BHK 250, they too are still on stock tubes… All the equipment is permanently powered up - only powering down when away from home on holiday - I just switch the tubes off at bed time. Going from past experiences with other equipment I’ve owned, low voltage input tubes can, and do, last for years hence I only replace tubes when I hear a degradation in performance. I once renewed the tubes in a preamp I was selling on, the originals were 4 years old and sounding as good as the new ones I’d just installed…
The perfect way to test, compare new to the old.
Small signal tubes easily last 10,000+ hours.
Interestingly, most people I know with tube equipment never throw tubes out. They declare certain tubes are worn out and must be replaced, but they never toss the old tubes declaring they still have life in them. Which is it? 
Elk saidInterestingly, most people I know with tube equipment never throw tubes out. They declare certain tubes are worn out and must be replaced, but they never toss the old tubes declaring they still have life in them. Which is it?
Exactly ! Just audiophile paranoia !
Indeed.
I have experienced a few tubes which have gone bad, they developed noise or otherwise failed. Outside of this, I have replaced tubes only out of curiosity, such as swapping in KT88 for EL34 power tubes to hear the difference and sound. I, of course, keep the replaced tubes as they are perfectly fine.
Guilty as charged. 
I usually replace small signal tubes after about 2,000 hours. The fresh tubes do seem to sound better (perhaps a bit louder), although I wouldn’t swear I could tell the difference in a blind test. I keep the old ones in case there is a sudden and drastic shortage in availability of replacements. Not that I’m paranoid or anything.
Thanks, all. I have adopted the same pattern as Woot and Stevem2… weeknights and all days over the weekend. I wasn’t so much concerned about cost of tubes (though I appreciate that additional factor), but was idly thinking about the possible “shock” of turning the tubes on and off vs. leaving them on as far as overall life of any tubes (so cost is a factor… but more perhaps the hassle of having to replace them).
I do appreciate the comments… thanks again.
jeffreybehr saidI know that I had posted on this subject before but I can't find it so I will do it again.Since Standby turns off both the filament and high Voltages to the tubes, I think I’ll be switching my pair to Standby for absences of maybe a half-hour and longer… I expect the tube circuitry reaches thermal equalibrium in maybe a half-hour but that the amps sound fine in maybe 5 minutes, and saving tube life seems…hmm…
It is not true that standby turns off both the filament and high Voltages! In both the amp and preamp, the high voltage is always on when the back panel power switch is turned on. So the tube filaments are turned on when the unit is taken out of standby. One advantage of this is that the high voltage regulators are always on and warmed up.
Hmmm … I seem to recall that somebody (not B) posted that “if you’re worried about tube life, just put the BHK’s in standby”.
So, assuming the tubes are being used 24/7 then, when would it be sensible to replace them … 6 months? 1 Year?
And another question: What is then the benefit of standby [other than the output to the speakers are switched off]?
Using standby does save wear and tear on the tubes since the filaments are not powered. I change my tubes after about 2,000 hours, as measured by the counter in the BHK Pre. That works out to about a year for me. Others change more often and some don’t change tubes until they fail.
BHK saidBascom,jeffreybehr said Since Standby turns off both the filament and high Voltages to the tubes, I think I'll be switching my pair to Standby for absences of maybe a half-hour and longer.. I expect the tube circuitry reaches thermal equalibrium in maybe a half-hour but that the amps sound fine in maybe 5 minutes, and saving tube life seems...hmm...I know that I had posted on this subject before but I can't find it so I will do it again.It is not true that standby turns off both the filament and high Voltages! In both the amp and preamp, the high voltage is always on when the back panel power switch is turned on. So the tube filaments are turned on when the unit is taken out of standby. One advantage of this is that the high voltage regulators are always on and warmed up.
Thanks for this clarification. That makes sense as the HV light does stay on even when the unit is in standby.
Also thanks for mentioning your vanishing post. I had posted just before yours, refreshed and saw a blank post from you… then refreshed again a few hours later and your blank post and mine had both disappeared. Mystery not solved, but at least I now have confirmation of what I remembered!
The key thing I said was that my impressions are that while the BHK-250s sound decent after about 5 minutes out of standby (as JeffreyBehr said), to my ears and in my systems, I hear continued improvement until just a bit after an hour of on-time. After that, they are peak BHK & I hear no change.
I’ve been trying a number of tubes and so far the Tungsram 7DJ8 (mine are from the PartsConnexion as I was already placing another order with them) are the winners. I have several sets of the Voskhod 6N23P tubes here and have yet to go through all of them along with some other current production tubes and NOS options (including some 61NP’s and iFi’s GE5670’s in their special adapter). BUT I could happily live with the stock tubes and am happy I have gotten some spares.
I’m also in the camp of hearing the ‘magic’ diminish in a set of tubes long before they stop operating properly. My early tube gear was from NYAL & Counterpoint through the late 80s & 90s & Alta Vista Audio upgrades of Counterpoint & a Bottlehead Seduction phono preamp in the late 90s & 2000s. My experience of this was consistent across the 4-5 pieces I’ve had over the years. That’s one of the reasons I keep spares of my favs around… and also why I don’t go after the super-high-$ super NOS tubes. I have some here from when one could get them for a song at hamfests in the 80s… and they are GOOD. But they are all doomed… I save them for prime listening experiences with special gear and go with what I can get nowadays for most of the time.
YMMV…
My 2 cents…
Greg in Mississippi
plcomp saidIn addition to the filaments being off, the output stage operates at reduced power.What is then the benefit of standby [other than the output to the speakers are switched off]?
The specifications state that power consumption at idle is 175 watts and standby is 75 watts.
So save 100 watts and the unit runs cooler.
st50maint saidplcomp saidWhat is then the benefit of standby [other than the output to the speakers are switched off]?
In addition to the filaments being off, the output stage operates at reduced power.
The specifications state that power consumption at idle is 175 watts and standby is 75 watts.
So save 100 watts and the unit runs cooler.
And in addition, which is important, the high voltage and output stage regulators are all on and the whole solid stage circuit is ACTIVE but with reduced current in all of the active devices. This way, the circuit will take less time to get up to full sonic quality when set into operate mode as opposed to starting from a total cold start and putting into operate mode right away.
BHK
Bascom, or anyone,
Do the filaments come on instantly or do they ramp up to full voltage slowly? I assume that they ramp up slowly, no sudden surges. My experience is that tubes usually fail when turned on, without the ramp-up. Thanks
“My experience is that tubes usually fail when turned on, without the ramp-up.”
Fail as in the filament opens up?
I decades of playing with tubes, I can not recall one with a burned out filament.
The BHK Pre by default goes through a warm-up that takes something like 45 second before becoming active. Not sure what all goes on during that period.