What I do is buy two sets of tubes for my pre-amp --- using one set as if they were my only tubes and the other as back-ups and to test for the degradation of my primary set of tubes. After about a year, I swapped out the tubes that were in for a year for the other set (that were the same type & stock and had maybe 10 hours on them). I played with the second set for a week and determined that the 1st set with a year on them sounded the same. So I put the 1st set back in and played them another year.
At the year 2 mark I tried again the back up set and realized that my 1st set (with 2 years on them) sounded a little grainier and had a little more noise and did not sound as "lively." So... I deemed the 1st set to have lived the life out and trashed them. My back-up tubes then became my primary tubes and I buy a new back-up set.
A side note... I have had tubes blow on my power amp and cause much damage. I have entirely gone away from tube amps and do tube preamp w/SS amp.
Finally... tube rolling --- if you have the $ and the time to play around can be anything from fun and advantageous to kind of a waste of time.
A tube tester is always a good way to tell.
In our gear, it tends to move towards a sleepy sound if the tubes are shot.
I am just a moderate tube user these days, but first thing I check for is any audible noise or hiss. Also if anything sounds unusually different in any way, tubes are one of the first suspects. I keep a few spares around so that I can a/b regression test individual tubes at a minimum and replace if not sure.
Noise is easy to identify but other sonic anaomolies not so much. A good quality tube tester like Atmasphere recommended is probably the only way to be sure. Not as common anymore these days, but depending on where you live, in lieu of owning and using a tube tester yourself, there might be shops nearby that keep a tube tester around and might be able to test them for you.
I would replace the two 6550 in the power supply after 2000 or 2500 hours. It is cheap insurance against the possible damage a blown power tube could do. The 6h30 tubes are not going to do any damage if one fails.
I also have a complete set of backup tubes for all my tube equipment. That way I always have a spare in case of failure.
BTW I own an Audio Research Ref CD7, Ref 110, LS27 and PH8
The only 6H30 tube rolling option I'm aware is 6H30-DR and they are expensive and tough to find plus you need 8.
Caveat Emptor buying 6H30-DR off Ebay located in Russia. I heard many received fakes.
There are rolling options on 6550. Since you only need one, you can try NOS TS, NOS GE ...
I believe your Einstein rolls 6922 so you got lots of options.
My experience is similar to Atmasphere, SQ gets softer as tube ages that will signal time to replace.
According to Kalvin @ARC, all power tubes (KT120 and 6550) regardless of position should be replaced @2000 and 6h30 @4000 hours in my amp so probably same as your pre.
I'm not taking any chances and replace all at the recommended intervals.
I find the comments very useful.I will follow Lostbears recommendation and replace the 6550 in the power supply.
Thanks for all the replies.
I say use your ears, and have backup tubes around from your god damn tube hoarding fetish...oops...got carried away there...there is NO way anybody else can suggest when to change the tubes on an amp they're not personally listening to so stick the backup tubes in as a reference when you suspect aging... I got about 8000 hours from a set of KT120s with great performance until I fired them (laid them off?) for getting soft, and until my KT150s arrive I'm enjoying the hell out of my backup 88s and 6550s. Note that all of this depends on how hard your amp drives these things, and power tube explosions aren't any more likely than SS amp failure...it happens, but rarely in well designed amps. I recently replaced my 12AX7s after rolling my various tubes around and found that my previous ones were also a bit dull...new set of Gold Lions put that right. This is the fun part of tube amps...love my Flashing Mullards...great band name...
Wolf - Seriously? 8000 hrs on power tubes?? I'm impressed.
Regarding 6H30s...did recently replace some Sovteks in my pre-amp with EH
gold pins. The Sovteks had hours on them but tested strong. Noticeable
improvement in sound quality with the EHs installed, however. I wasn't
expecting much and was pleasantly surprised given these are out of the same
factory, gold is just cosmetic, blah blah blah. Very reasonable prices on the EH
6H30 gold pins too.
Maintaining a listening log is a good way to keep track of hours on power tubes.
When they go, they can do damage.
When it comes to power tubes, I'm more concerned with catastrophic tube failure than SQ. Following the recommended tube maintenance schedule is dependent on the amp and manufacturer.
I've had power amps where the tube just gracefully dies but with ARC, I'm definitely following their recommendations.
I didn't count the hours on my 120s but it was about 2 and a half years of
use...even 5 hours a day (I have my rig on more than that usually) is over 5000
hours, and they still held their bias and sounded fine until that last couple of
I really AM impressed, WG.
Heck, almost any triode power amp can log 10,000 hours on the power tubes, the exception being the 6C33. We had one of our amps log 22,000 hours on the power tubes before we finally had to replace one (there were 16 power tubes in that amp, FWIW...).
I had the same tubes in my '60 Fender Deluxe for over three decades.
Wolf, Why did you go for the KT 150's instead of just replacing the KT 120's? Double the $$ double the pleasure?
They became more affordable and now cost about the same as 120s on a weight basis (it might take 5 120s to equal 4 150s), they could last a ling time, and they're larger than any other tube that will fit in my amp (!)...I was listening to a great live jazz CD (Fred Hersch) tonight and the 150s sort of woke up and now sound even better than yesterday...they sound large.
So da big question is should I go with 120's or 150's when I replace the original Tungsol 6550 on my Jolida 502 p? I have about 1500 hours on them I would guess.
The cheapest price I see on ebay for 4 kt150 is about $130 more for a set of 4 than kt 120's. You got a hell of a deal.
LONG time...not "ling" time...my retired 120s were about 100 bucks less than the 150s I just bought (they're still available by the way), and when you adjust for inflation, "present value" of money, Russian raw goods indices, jo mama, gross weight, groceries, Albert Grossman, the savings on heating your hut, the cost of cooling your hut (!), and labor used in wiping fingerprints from the glass, it's not too bad a deal...
I would check with the manufacturer prior to replacing a 6550 with a KT150!
If the filament considerations are tight on the power transformer, it could lead to failure.
Yes indeed Atmasphere. When the KT120 came out i wanted to drop them in my ARC Classic 120 (8 tubes per amp) Chris Ossana said to me you do that at your own risk and peril and make damn sure you report back thereafter.
I kinda got the stern warning and stayed with my trusted 6550 Winged C's.
Good point Atmasphere. Wolf did you check with Jolida re using KT150's @ the 502 p amp?
Once again, the risk of transformer failure from wildly careless drunk and clearly insane risk taking tube rollers raises its ugly head. I did an informal study of this issue a couple of years ago (this study is ongoing by the way) and determined...ahem...that NO TRANSFORMER FILAMENT HEATING RELATED FAILURE HAS EVER OCCURRED (or has been reported anywhere I've seen) from using 120s or now 150s (although it's early for these...be warned!) EVER in the history of the entire audio world. None. Zero. Also, Jolida techs have approved 150s (and previously 120s) for use in the 502p, I use them now (somehow the amp is surviving, although it could BLOW UP any second) after replacing 120s that got old, and, again, no issues for me or anybody else I've ever read about anywhere...in spite of warnings all over the place. It's possible it's happened, but data on those happenings is nil, nada, none, zilch...still I'd check with yo' mama before going outside, you might get wet.