Can tube amps mess up your headphones?

Where did you hear that?

By now I've gone through quite a number of tubes, in quite a number of amps, both speaker & headphone. I've had tubes die in various ways, and had a bad tube send some nasty pops to the speaker, but never yet anything that took out a driver. Well, there was ONE time I had a tube headphone amp kill a nice pair of Sennheiser Jubilee, but that's because the output caps were wired INCORRECTLY by the amp maker; had nothing to do with the tubes (or the amp, were it wired correctly). 

 

I don't think your worries of damage-inducing clipping are a likely consequence of dying tubes. Here are some of the varied signs of dying/bad tubes I've encountered:

• Tube gets noisy; "rustling leaves" sound, or static-type noise
• Heater dies, in which case the music just fades out in that channel
• Tube just starts sounding bad - e.g. dynamically dull and flat; a mushy diffuse sound. Keep some spare tubes on hand for comparison, in case you think you're dealing with this kind of issue.
• Loud random "pops" sent through the speakers/headphones - these DO suck and you should remove the tube(s) immediately!
• Had a KT90 power tube short-out in one of tube monoblocks. NOT FUN. Fireworks, smoke. Took out a resistor in the amp. No damaging transients were sent to the speakers; they were were unharmed. In the future, I'll be buying KT tubes from sellers that test them at realistic voltages AND fully burn them in, first!

 

In summary, I think a poor amp design, poor implementation, or critical parts failure (e.g. output caps, output transformers), is more likely to damage your speakers/headphones than failing tubes. And as always, simply OVERpowering your headphones speakers (read: USER error) is the most likely cause of all. 

Edited by mulveling - 5/21/11 at 7:39pm

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Thank you for that highly-informative post.  Must keep these things in mind.

 

Who told you that, OP?

No, tube amps aren't any more dangerous than solid state. The biggest risk is DC offset, but that's only a threat in a poorly-designed circuit. Tubes or chips, DC offset kills.

Tube failures aren't a problem. If a tube stops working, it's like turning the amp off. No danger.

Also, there's generally zero maintenance for tubes. Yes, tubes die and are a wear item, but you know that going in. Besides, just about everything else inside an amp is a wear item. Caps and resistors go out of tolerance after a certain amount of heat and hours of use. Go to Digikey or Mouser and pull up the datasheet for a cap or resistor. You'll find the MTBF (mean time before failure) listed in terms of hours. Keep in mind that failure doesn't mean a smoky meltdown. It can be a resistor that goes from 100 Ohms to, say, 300 Ohms. The amp will still work but it won't be in tolerance.

The only parts with long-term stability are transformers, mica caps, wirewound resistors, and air gap capacitors. Everything else ages, usually a victim of heat. Heat kills everything in time.

The maintenance you might have heard of for tube amps is probably biasing. As a tube ages, the amount of voltage it needs to maintain the correct bias voltage changes. Some amps are auto-biasing, which means that you never have to adjust anything. The vast majority of tube headphone amps autobias. If you do have to bias, it's a cakewalk. My tube power amp has to be biased. I turn a small screw until a LED comes on. Then I slowly back the screw off until the LED goes out. I showed my six year-old nephew how to do it. Piece of cake.

So stop worrying about the tube myths. I've been running tubes daily for something like 14 years. Tubes are a robust, rugged technology where the bugs were mostly ironed out 60-70 years ago. I'm much more cautious with chips. When you DIY with chips, a slight touch of static electricity will kill them. Tubes laugh off static electricity.

Well before transistors there were vacuum tubes. Now ask your elders if vacuum tubes failure ever caused those things you claim.

 

 

 

 Wow.... wow  how did they not catch that before sending it out?

Just for the record I've left my vacuum tube amp on many times on week ends from Friday to Sunday over 48 hours. The transformers get warm and the tubes glow and hot but they don't blow up. Because they were designed to be like that.

 

 

 

 

This gem was thanks to Mikhail of Singlepower - enough said! There are folks who work on & build tube amps that don't have a clue what they're doing. Such amps can be dangerous - live and learn!

 

I've now got a local tube tech/tube amp designer I can trust. He fixed that headphone amp for me (simple replacement of output caps to the higher, proper voltage rating, and fixed some cold solder joints), and restored some vintage tube amps for me as well. Once safe, it was a fantastic sounding amp.

 

Well engineered, well implemented tube amps are indeed quite safe. That, and I just can't go back to the sound of sand.

 

Edited by mulveling - 5/21/11 at 10:50pm

I doubt the life of tubes is as annoying as say, replacing a comply foam eartip every 1-3 months. I imagine it varies from model to model, but remember reading on Schiit's website that the Lyr's tubes last 5000 hours. I'm not going to make any variables up or anything but think about it; thats a pretty decent amount of time. Schiit's waranty is only 90 days for the tubes but for the average user they should easily last a few years. Again, this isn't from experience though...

But how did they get that number?

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Dunno, maybe that's the manufacturer MTBF?  The Lyr doesn't use NOS, it uses JJ tubes that are currently in production if I'm not mistaken.

No idea, all I could find from there website was this statement: "Lifespan: 5,000 hours typ." 

 

Edit: The same is said for the Russian NOS tubes in the Valhalla, perhaps its just a generalization.

 

Edited by Sylverant - 5/21/11 at 11:56pm

That's a lot of hours. Lets say your Lyr amp is on 5 hours a day * 365 days = 1825 hours/year, that's over 2.5 years.

 

 

Depends on the tube, and how hard the circuit in question is running them. Good quality American/European small-signal tubes are typically said to be good for 5,000-10,000 hours. Power tubes maybe 2,000-3,000 hours or so, though I'm sure there are specific examples of certain classics (e.g. Mullard EL34, Tung-Sol 5881, Genelax KT66) running for MUCH longer. The Russian 6H30-DR "supertube" (in vogue with high-end preamps) was rated at 20,000 hours lifetime, IIRC.

 

Early failure is a risk for all tubes, though possibly less so for the old classics, as compared to new production tubes. I've heard my tech complain of bad runs of new production stuff, for example lots of JJ power tubes, and the EH KT88 in particular (of which he presented a box FULL of failed tubes). I wouldn't trust the reliability of the new stuff to match that of the old tubes, though I must admit some of the new power tubes are at least starting to sound pretty decent for the $$ - when they work. I thought the EH EL34 sounded pretty darn excellent for dirt cheap, and I never experienced a problem with them.

 

You can look at/inside the nicer American/European vintage tubes and see certain qualities and attention to detail that just aren't there yet in the new Russian and Chinese stuff - though they are getting better. Some of those vintage tubes were an artform. Of course with a non-NOS vintage tube, the question is always how much abuse and mileage they've taken before getting in your hands. A tube tester doesn't always give proper insight, here. 

 

Just like with phono cartridges - sure, they're a wear item, but the better ones will usually last a long time with proper care, and they're so worth it.

 

Edit:

Heh, I just remembered that today I just saw an uber-premium $$$ Czech 300B tube (current production) where its PLATE structure had come loose and was rattling free inside the bulb. Sure it probably happened in shipping, BUT that thing was packed extremely well, encased in inches of foam. Supposedly it sounds way better than the Chinese alternatives, that is when the plates aren't loose...

 

 

Edited by mulveling - 5/22/11 at 12:17am

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Thanks for the info.  I remember Jamato8 also mentioning that the older tubes were built for reliability, as they were used for military applications and such.  I guess cheap mass-produced tubes nowadays just aren't up to snuff.

 

And IMO, NOS tubes sound better, though YMMV.  I very much prefer my Amperex 6922 to the stock JJ.