Can you do anything to make power tubes last longer ?

No… luck as I inherited the MAC which i abused as a young punk… The Music Reference connection born of my experience selling gear Roger designed and built w Harold Beveridge… also imo a genius… RIP….

mulveling,

Could you suggest particular Amperex EL34 that I might want to try later ?

Perhaps, I should also try Sylvania 12AU7 black plates from 50s as well. What difference would they make compared to RCA black plates from 50s, I wonder ?

Mke sure there all biased correctly.enjoy the tube sound.

Found them ! Matched quad of Mullards EL34 XF2 is coming this way. It's a little risky because they are not new and the exact number of hours on them is unknown, though supposed to be low enough. Test as strong NOS, as the seller with excellent feedback says. It's always a gamble with tubes to a degree, I feel fine about it.

Found them ! Matched quad of Mullards EL34 XF2 is coming this way. It’s a little risky because they are not new and the exact number of hours on them is unknown, though supposed to be low enough. Test as strong NOS, as the seller with excellent feedback says. It’s always a gamble with tubes to a degree, I feel fine about it.

Nice! Enjoy - great tubes. Don’t worry about the exact hours on ’em. A meaningless metric, now. "They don’t make ’em like they used too" applies, etc and yada yada...

For Amperex / Hollands I’ve only used the xf4 and xf5 models, both with the brown/red-base. They both sound equally great - I’ve even mixed them in quads (matched pairs), with no problem. The older metal base Philips / Holland version is supposed to be extra special - I’ve almost pulled the trigger on these in the past, but never did.

Perhaps, I should also try Sylvania 12AU7 black plates from 50s as well. What difference would they make compared to RCA black plates from 50s, I wonder ?

Why not? I expect 1950s black plate Sylvanias should be very good. I generally prefer these over any RCAs, though I haven’t tried the 12AU7’s. You can do 5814, 6189 and 5963 subs too. The 5963 tend to be microphonic, so those should be relegated to amp driver slots only (NOT the preamp or phono slots).

RCA black-plate 5963 was the favorite 12AU7 sub for early 2000s-era VAC power amps.

@inna I wouldn't say that I recommend choosing an amp that is easy on tubes so much as I recommend against an amp that is hard on tubes.  How do you know which is which?  

I'd say avoid an amp that gets more power than normally attributed to that tube--unless I needed that power and was willing to buy tubes.   And I'm fine with that. Personally I don't think tubes are expensive compared to the rest of the audio equipment we all have to purchase.  I buy tubes when I don't need them.  A nice pair of Hytron 801As showed up yesterday. 

There is a trend now to make higher power tube amps to drive lower sensitivity speakers.  I like higher sensitivity speakers but if you're married to your 92-95dB speakers and want to drive them with a tube amp, you need more power.  So they are making more push pull, parallel SET, and High power SETs with the higher output tubes.   if you buy some of these, recognize you'll have to replace tubes more often.  (not saying push pull amps are hard on tubes, unless designed that way).

If I'm looking at a 300B SET and the OEM says 8 wpc, and 300b's generally do 6 wpc, I'm going to wonder about tube life.  (or else the marketing talk is exaggerating and it really is a 6 wpc amp).

I've found that if you go with an amp builder with a lot of experience and knowledge, they are likely to design their amps conservatively.  And if you call Aric or Apollo and order and amp, if you tell them to use conservative parameters to promote long tube life, I'm sure they can do that.

jerry

Jerry, you are right.

Anyway, the best way forward is to have more spare tubes !

mulveling, I think I am done with audiophile expenses for this year, But..let me see..maybe I can cut the expenses somewhere else. This is a disaster.

I saw those Sylvania on ebay but I will wait - currently installed RCA black plates from early 50s work very well, no complaints.

Now that I am going to have better Mullards, I suppose I will not accept anything less in the future. It is either XF2 or XF1 Mullard or perhaps Amperex Holland.

@inna For longest tube life:

1) keep the tubes clean and free of fingerprints.

2) keep them biased properly, if you can run them a little below spec. This works only if the sound isn't adversely affected.

3) use the Standby switch to warm up the tubes. If you don't have one on your amp consider getting one installed. A standby switch cuts off the B+ (DC high Voltage) for the tube. As its warming up, if the plate supply Voltage (B+) is present, you get a phenomena called 'cathode stripping' where the cathode coating gets eroded over time. So a standby switch can prevent this.

4) don't push the amp hard. In a class AB amp (most EL34 amps are class AB) the harder you push the amp the hotter the tube gets and heat causes it to wear faster. So make sure your speakers are easy enough to drive that the amp is loafing nearly all the time.

5) make sure you have adequate ventilation. Again, heat is the enemy of the tube.

6) Make sure your speaker is connected to the right output transformer taps. So a 4 Ohm speaker should never be on the 8 Ohm tap; that would cause the load on the power tubes to be much lower, causing some of the power they make to be dissipated in the tube rather than the speaker- so yes, they will run hotter, put out less power and make more distortion.

7) make sure your line Voltage isn't running high. 120V is normal now and the line is not supposed to exceed 125V for more than a second. But I've seen situations were 125V was normal and unsurprisingly the customer was going through power tubes a lot faster.

8) the controversial and last thing: Some amps push power tubes harder than others so go through tubes faster. You might want to take a thermal camera to see how hot the tubes are running and compare that to other EL34-based amps, or use the internet to see if there's a correlation with certain amps that tend to go through tubes faster.

Follow these suggestions and your tubes will last longer.

inna, you can bias amp’s output stage for 20% less current, and use 120<=>110V step down transformer. These two steps will increase tubes life time significantly, est. 30%+. 

Ralph, thank you.

It appears that I do everything right. There is no standby switch. Voltage is regulated by the regenerator, I hope it is. Ventilation is excellent from all sides. The amp seemingly drives the speakers with ease, no stress that I can perceive. The tubes are clean, no fingerprints. I might try to lower the bias a little and see what I hear.

atmasphere

... make sure your line Voltage isn’t running high. 120V is normal now and the line is not supposed to exceed 125V for more than a second. But I’ve seen situations were 125V was normal

If you’re talking about the US, you are mistaken @atmasphere. Nominal voltage in the US is 120VAC $$\pm 5\; percent,\; so\; anything\; between\; 114VAC\; and\; 126VAC\; is\; normal.\; That\; is\; established\; by\; ANSI\; C84.1\; standard.$$

$$Note\; that\; the\; spec\; is\; measured\; at\; the\; service\; entrance\; -\; it’s\; common\; to\; have\; some\; voltage\; drop\; at\; the\; AC\; receptacle.\; That’s\; something\; dedicated\; lines\; can\; help\; limit.$$

What is "normal" is not necessarily ideal for tube electronics, particularly vintage gear that was built for lower voltages that were prevalent when they were made.  As I mentioned above, my local dealer who only sells tube amplification often has customers measure their outlet voltage and then orders the right transformer for them to use on the outlets supplying their amp and other tube gear.  He prefers to run the gear at much lower voltages than is common.  This is usually the cure for premature tube failure.  He also has his customers bias amps on the conservative side.  This is consistent with Atmasphere's recommendation.  

My normal voltage has been, for the longest time very steady at 117 volts at the outlet, but has recently crept up to 119-120.  My amp is cathode biased so I cannot do adjustment, but typically, cathode biasing means conservative levels.  If my voltage rises more than this, I too will consider a transformer.

If you’re talking about the US, you are mistaken @atmasphere. Nominal voltage in the US is 120VAC $$\pm 5\; percent,\; so\; anything\; between\; 114VAC\; and\; 126VAC\; is\; normal.\; That\; is\; established\; by\; ANSI\; C84.1\; standard.$$

@cleeds I stand corrected. 

However if the line Voltage is consistently 126V you'll find that tube life is curtailed with many tube amps and all if they are vintage. 

I recently worked on an Eico tube amp that was 'eating tubes'. The amp was built when '110V' was the norm. The output tubes were conducting way too hard. They were cathode biased so I was able to change the cathode resistors and calm things down. 

The only thing that can come to mind about making your power tubes last longer would be to set their bias a little under than the recommendation for the amplifier. This will not hurt the amp or the tubes in any way. The manufacturer has a recommended set point for where the power tubes should be biased to get the best sound and operation from the amplifier but by adjusting the bias to your liking, you might be happier. And by dropping it down a bit under the recommended set point the tubes with be running a bit cooler and should last a little longer. . Some people choose to run their tubes hotter which burn them out sooner and others run their cooler which makes them last longer. You’ll also hear a difference as you adjust the bias. I’ve experimented with this on my Canary 301 mk 2 300b amplifier yrs ago. 

In other words, I can set the bias as low as I want to until the point when I hear the deterioration of the sound quality. Setting bias by the ear not by manufacturer's recommendation.

The designer and builder of our monoblocks uses the same Dodd Balanced Power Supply to power his builds that we use to supply power to our system. They makes exactly 120 volts at 60 Hz. The 75 lb. laminated core transformer takes whatever comes from the wall outlet and makes a +60v and a -60v rail, both at 60Hz, and then joins them at the outputs. The amps are optimized for KT77 output tubes and can run no other type of output tube. I foolishly tried all of the usual suspects, even though I was told by the designer/builder that it wouldn’t work; he was right, can’t get any other output tube type to bias correctly. Had a lot of Octets for sale for a while :).

Anyhoo, I feel very lucky about the amps being designed and built based on the same power supply; apparently, pretty darn optimal. Accordingly, I’ll say again, for tube amps, it’s worth using a Balanced Power Supply (or, I think, a power regenerator) to assure that your amp(s) see 120v at 60Hz.

It's been a while since I ran amps that required biasing, but my approach was to start at the low end of the builder's recommended range.  Then, in part because I'm lazy and because I want to be gentle on the tube.  I would just leave things be and not bother to check the bias.  As the tube ages, the current flow drops on its own so the bias point drops.  By not changing the bias to compensate for the drop, i am actually preserving the tube, albeit with a small loss in output power.  

Put the Mullards XF2 in. Great tubes, probably need a little of burn in time. So much better than SEDs. Hold the bias perfectly. Should’ve bought them when I bought the amp. Noble, balanced sound.

When I don’t listen to music, all power off.

Power on, standby, etc...., I don’t do that.

When I want music, I just all power on. After 5 minutes, almost full performance comes out.

24-hour-on mode does not give much better performance than 5-minute-wait mode.

If you doubt it, just do the both ways. You will realize my opinion is CORRECT!

I'd say, in the case of my VAC it is 10 minutes of warm up minimum, I usually do a little more than that for critical listening. And VAC's manual says the same - 10 minutes before tubes warm up fully, especially if you want to check the bias before you go.

This is a situational maybe.  In South Florida especially during hot weather in densely populated areas we experience fairly large voltage fluctuations.  During peak demand hours at my location voltage can range from ~105-120 VAC.  Power tubes were constantly needing to have bias adjusted.  Like weekly.  I bought a power regenerator, originally a PS Audio P10 later a P20.  Tube bias requirements dropped almost to nothing, like once every 6 month I check but almost never need to adjust, and tube life at least doubled.  So if you live in an area with high peak power demands and consequent voltage fluctuations taking steps to regulate your power supply could extend power tube life.  

@billstevenson -good point. In Austin, we get 110F for days and weeks on end in the summer. The utility sends out constant warnings about potential rolling black-outs as a threat to turn down the A/C and conserve power. I simply don't turn the big system on during the summer, not b/c of the heat indoors- we are well insulated and have very efficient new HVAC, but because of power quality issues. 

I thought about buying a pair of Valvets (solid state amps) to use in lieu of my Lamm SETs, but everything else in the chain is tube as well (except a modest digital front end and the woofers/subwoofers and turntable). So, the idea of regeneration might make good sense. I haven't heard one since they were first introduced. We had very "clean" power here even without the big Iso transformer (10Kva) I installed as p/o an electrical subsystem for the main hi-fi, but given the growth and power demands, I consider it a risk to play this gear when the grid is "iffy." When I was in NY, along the Hudson, we had very antiquated power infrastructure, and could lose power easily. 

I'm thinking I might take up ice sculpture or some other hobby during the summer, which is brutal. (Though right now, the weather is perfect, the blue bonnets will soon come out and there are an awful lot of great things about living here).  I guess no place is perfect. 

We aren't constrained to live here, I'm retired, my wife will retire in a few months. And I may have one last move in me, but that's a constant topic of discussion-- where?

(to be continued, perhaps in another thread).

PS: I'd live abroad for no reason other than the excitement, history and challenge but that's a hard sell to my spouse. She loves traveling, but also likes being in proximity to friends. I'm different: I could live out of a good hotel in a safe place that had good food, a village or town full of life and proximity to the things needed- health care, an airport and a little culture. I did so for many years when I was on the road.  Oh, and no more winters, which is why I'm here, rather than the NE. 

Bill, I hear you. How about Montpelier, France or Tuscany, Italy ?

You could try PS Audio's biggest regenerator, I guess. Who else makes this stuff ?

Then there is a German company that makes some very expensive batteries to use with audio equipment, forgot the name.

There is also Accuphase but it's not a regenerator, I think.

How would you Lamm amps react to all that, I wonder ?

@inna, don’t know. There’s the Definitive Audio/Living Voice folks who used to (maybe still do) work out of an old Edwardian factory in England. They have a very substantial battery system, inverter, etc. Yeah, that would be even better, but I wonder what dealing with the batteries would be like.

We did do a whole house back-up generator but I went to some lengths to have the electricians feed the hi-fi subsystem from the main panel, then moved all the generator supported stuff, lights, appliances, gas furnaces and main floor AC to a separate feed. That, in turn has the ATS for the generator and a 24 breaker box of its own, so only the circuits directly hooked up to the ATS/service panel get generator power. This was done to separate the hi-fi power subsystem from the ATS in light of Framer’s complaints. I tapped into Rex’s expertise on that- he helped on Fremers’ project, which also implicated some other issues, only reinforcing my belief that, at least in single family dwellings where you have control from the meter, an "audit" of your existing electrical system should be done starting at the meter, before adding "improvements."

Obviously, living in an apartment has limitations in that regard.

I saw an article about 833A triodes that says they last longer with the cathode run at 9.5 Volts rather than the full 10 Volts, and there is no loss of how they sound. Also, these tubes are built to last because they are used in AM radio stations as transmitter tubes. Running them at 1000Volts on the plate rather than pushing them so hard that they have a red glow spot will make them last indefinitely. The drivers I use are 45 globes that cost about $75 to replace on ebay and they last for years. I keep spares. Some claim that solid state requires less maintenance because you never have to replace tubes, but changing a tube is so simple that finding a bad transistor is far more complicated. Also, if you can use metalized polypropylene filter capacitors in the high voltage to run the tubes, you have indefinite shelf life and better ESR than the slightly cheaper electrolytic filter capacitors on tube amps costing five figures. This is why I build my own tube amps and preamps.  

Some claim that solid state requires less maintenance because you never have to replace tubes, but changing a tube is so simple that finding a bad transistor is far more complicated.

This is true. Across probably hundreds of components I've used in my time in this hobby, once you eliminate simple "replace the bad tube" issues, I've had decisively more failures with Solid-State - and they're far more frustrating and difficult. Especially when the transistors you need are long OOP and counterfeited like crazy.

Bill, there was a lot of electrical work done in your house and still the current is not good enough, especially, as I understand, in summer.

Batteries can limit the dynamics, I guess, but maybe some companies overcame this, I have no idea.

I use old PS Audio regenerator in my system, everything is plugged in it. By comparison, without it the system is unlistenable, and this is not exaggeration. The dynamics too is much better.

I think, wall current is the biggest problem in audiophile world. And increasingly so.

Good tube equipment will last for decades with only occasional tube replacements. The only problem, two problems in fact, NOS tubes will be getting more expensive and more difficult to find. But some transistor equipment is also very reliable, think Gryphon and Accuphase, as an example. If not tubes - that's what I would have.

It is VAC Avatar SE integrated.

Good tube equipment will last for decades with only occasional tube replacements.

Hmmm . . . decades?  I don't think you will get decades out of output tubes unless you skip using your amp for a decade or so.

Of course, not, just replace tubes as needed.

safebelayer, I think you can only use el34/6ca7 power tubes.

The system sounds underpowered in triode mode with my speakers, and I hear nothing positive, anyway.

Yes, it's 60 watts in Ultralinear and I think 37 watts in triode.

You just align the needle with a black dot, no red/green lights.

These Mullards are not excessively warm, though of course on the warm side. Just as my entire system is, including the speakers. So the match appears to be perfect.

Good points by @atmasphere and a couple I want to comment on.  My current amp has a warmup relay to warm the tubes up before applying B+.  What he suggests with a warmup switch is easy to do and a great suggestion.

Avoiding high voltage is important.  The designer was very careful to provide the correct voltages and if your voltage goes up 120 to 125 (mine varies from 117 to 124 and that is just what I have seen) then the increase goes right through the power transformer to every voltage in the amp. 

A good way to regulate voltage to 120 (I have mine set to 119.9) is with a regenerator.

Jerry

@inna congrats on finding the Mullards at hopefully not too an outrageous price. I’m sure you’ll be very happy you did. I had similar experiences, though different amps but the same tubes, and found that the SED never gave me as good an experience as true Mullards. Ralph brings up a very good point of warming up the tubes slowly at the outset. It’s probably (at least one of) the reason he builds his amps the way he does.

marco1, thank you.

Yes, so now I have 12AX7 Mullard long plates in the preamp, 12AU7 RCA black plates in the driver and Mullard EL34 XF2 power tubes. This is done. Now I will have to think/experiment what to put in the phono stage, since I don't care much for the Brimars that are currently there.

The price was reasonable. A little more than new SED tubes cost.

I’ve always liked the RCA 12au7 black plates. I remember discussing them on another thread with you and Mulveling. I’m currently using RCA 5816A black plates as a driver in one of my amps. They’re a little more refined and warmer than the 12au7 and although I’ve never used them in combination with Mullards EL34 I think they would compliment the Mullards nicely.  Something else to spend your money on if/when you get the itch 🤑

Next year maybe, I spent enough already. I would be cautious to take the sound in  warmer direction compared to how it is now, that would also probably be the case if I replaced the RCA black plates with Mullards for the driver.

Yes, we discussed it before. You and mulveling helped me  choose 12AU7 tubes.

"Next year maybe, I spent enough already. I would be cautious to take the sound in  warmer direction compared to how it is now” yeah, next year you will be one year older, and hopefully everything around you will be “warmer” LOL

@inna 

That was one of the reasons I went with Hybrid stuff. I currently have PS Audio.  The BHK preamp that uses two 12AU7’s and the mono blocks are currently using 6922’s.  All of which can be affordable and last a fairly long time.
My downstairs mono blocks use 4, 6HB5’s in each and they starting to get expensive to replace. I’m still using an ARC SP9 MKll Hybrid preamp with them and it uses 6922’s also.

Yes, not inexpensive. I made approximate calculations. Unless prices for NOS or near NOS tubes go much higher I will need about $40/$50 per month on tubes. This is no problem. But I need only four power tubes. Excellent NOS 12au7 tubes from a reputable source or ebay can be had for about $50 each. 12 AX7 are often two/three times more expensive. Well, the NOS 12AX7 long plate Mullards that I have in preamp were $450 for a matched pair. But they should last for a very long time, so no worries.

Coconut oil

Now I wonder how Mullard XF1 and the earliest ones with metal base would sound in my amp..