[Necrolic]

I'm maybe picking up a WA6 some time soon, and I have no experience whatsoever with tube amps at this point in time. I realize there is some maintenance required to keep them performing at their best, but I have no idea what this maintenance consists of.

Are there any guides around here that would tell me what I need to know (what to do to keep it performing well, how often to do it, etc.)?

 

[Spareribs]

From time to time it's probably good to check your connections and keep spray some of a deoxit to prevent anykind of oxidation. Also, IMO, it's not good to tube roll excessively because it is possible to wear out the tube sockets. I would say after maybe 20 years or so, you can check to see if the caps are not bloated. If they are replace them.

 

[Skylab]

Most headphone amps are self-biasing. Some big tube power amps (for speakers) require you to bias the tubes. But the WA6 is self-biasing. So unless you hear some sort of distortion or static coming from the amp, that might indicate a tube going bad, there is no required maintenance. I do agree with Spareribs that one has to be careful not to do TOO much tube rolling, or socket replacement could become needed.

 

[rosgr63]

skylab could please explain in simple terms how the self-biasing works?
Do you recomend the use of Silclear (silver grease) to treat tube pins?
How can one clean a tube's metal base (6SN7W for example) without causing any damage to the markings and/or base?
Sorry If I digressed a bit.
Thanks

 

[Uncle Erik]

Tubes are biased at a certain voltage to get the optimal performance according to its design.

Without getting too complicated, tubes have to run at a certain voltage, and then the voltage goes up and down depending on the signal.

A tube cannot go negative. If the bias was zero, it won't go to, say, -25V when the signal dips that low. You have to set it (for example) at 200V. That way, when the signal dips -25V, it'll go to 175V, and also swing back up to 225V in the other direction.

If you look at tube curve charts, you'll see that a tube can be biased at a variety of voltages. Each voltage produces a slightly different curve - some more linear than others. Where the amp's designer sets the bias changes how the tube will operate in the circuit.

Now, as the tube changes with age and use, the bias point also changes. On some amps, you have to turn a knob connected to a potentiometer that changes the voltage going into the tube so it keeps operating at the optimal bias point selected by the designer.

Other amps, however, are designed so the circuit biases itself with tube age, to keep it operating where it should.

As has been pointed out, most headphone amps do not require this bias adjustment. I can't think of a commercial model that requires you to bias it. Even if you find an amp that requires biasing, it's not a big deal.

My Conrad-Johnson MV52 (speaker amp) has to be biased. All I have to do is turn a screw until a LED turns on. Then I back it off slowly until the LED goes out. It takes about five minutes and is as easy as it sounds.

As for other maintenance, there ain't much. Don't leave it on when you're not using it. Tubes aren't the only components that age with use. Capacitors and resistors have a finite lifespan, too, and you don't want to wear them out before their time. Heat is the enemy of all electronics - the more heat they're exposed to, the shorter their lifespan. That, and you'll eventually have to change tubes. It's about as tough as changing a lightbulb.

So don't worry and enjoy your tubes.

 

[rosgr63]

UE If you have a 6SN7 driver tube and the sections are not matched, would the amp "balance" them?

 

[spritzer]

If you are using a dual differential amp then there is almost always some way of balancing the output of the two sections. This is certainly true with most electrostatic amps be they SS or tubes. Most of the adjustments are with regards to DC offset though and not the true operating point of the tubes as is with many old school tube designs.

 

[Necrolic]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Most headphone amps are self-biasing. Some big tube power amps (for speakers) require you to bias the tubes. But the WA6 is self-biasing. So unless you hear some sort of distortion or static coming from the amp, that might indicate a tube going bad, there is no required maintenance. I do agree with Spareribs that one has to be careful not to do TOO much tube rolling, or socket replacement could become needed.

So the deoxidization spray stuff I've heard about really isn't something I need to worry about?

 

[Skylab]

I wouldn't fuss with any of that on a new tube amp. If you bought a vintage amp, that's a different story (assuming it needs cleaning). But for a new amp, don't worry about that.

If you are buying vintage TUBES, though, it's a good idea to clean the pins gently before using them. I do use Caig Pro-Gold for that, and sometimes some very fine steel wool first if they are really dirty.

 

[atbglenn]

I agree with Skylab. I never use any protective coating on new tube amps. I do however clean my tube pins with Flitz metal polish, and then some 90% isopropyl alcohol to clean off the residual polish if the pins look oxidized.

 

[AcousticDreams]

Quote:

Originally Posted by atbglenn /img/forum/go_quote.gif I never use any protective coating on new tube amps. I do however clean my tube pins with Flitz metal polish, and then some 90% isopropyl alcohol to clean off the residual polish if the pins look oxidized.

This is the standard procedure for your NOS tubes, but not for a brand new gold pin.

 

[atbglenn]

Quote:

Originally Posted by AcousticDreams /img/forum/go_quote.gif This is the standard procedure for your NOS tubes, but not for a brand new gold pin.

Tubes that have indirectly attached pins such as most 8 pin bakelite or metal based tubes usually don't need attention. NOS non gold 9 pin tubes almost always need attention from my experience..