TUBE F.A.Q.
A few general all-too-frequently-asked vacuum tube questions from the manleylabs.com F.A.Q. as found on
our website are answered here in case you don’t have internet access (which we don’t doubt because after all
you bought vacuum tube amplifiers, didn’t you?):
(Don’t take that comment personally. EveAnna still drives air-cooled Volkswagons...)
FAQ #16. Do you sell tubes?
I don’t know what you’re talking about.
FAQ #16a. I need to retube my Manley amplifier. Do you sell tubes?
Sorry. Just kidding. Yes, of course we do. We have about 100,000 tubes in stock of the several major types we use.
FAQ #16b. Why should I buy tubes from you?
We are only as good as our worst tube. We are very selective about which tubes we use in Manley products and we
have several different testing and burn-in jigs to test for certain parameters which will be most important for that
tube in a given circuit. We will test and select a tube set for you that will be optimized for your Manley piece of
gear and in most cases, your tube set will actually be tested in another one of what you have.
FAQ #16c. Are tubes expensive?
Not especially. Although I might have made a killing in the stock market had I invested the money, I instead put
it into finding and stocking these large quantities of tubes twenty years ago when the USA military was dumping
its stocks of NOS JAN vacuum tubes. Seriously, there is the stocking cost to consider in the cost we must charge,
development charge of the computerized test jigs we built, then more importantly the time it takes one of our guys
to run a little tube through its qualification procedures. Remember, a given tube cannot be improved during testing.
It is the way it is, and one hopes it stays that way. It can only be selected, and in selecting that tube that will work
really well for your piece of gear, we probably had to throw away several. In some cases we might have had to go
through 30 tubes to find the quietest one, or the one with the lowest microphonics, or the one with the best internal
matching, depending on what parameters are important for that circuit. That is all factored into the cost somewhat,
but no, overall, we don’t charge enough for replacement tubes.
FAQ #16d. NOS? JAN? What does that mean?
New Old Stock. Joint Army Navy. Yes, our military used to use vacuum tubes. As long as the glass doesn’t break,
tubes are impervious to a nuclear explosion’s electromagnetic pulse unlike little silicon devices whose little junc-
tions would go poof!
FAQ #16e. Good to know. How long do tubes last?
Some of them are dead out of the box. Some tubes don’t make it through burn-in and after a few days they just go
noisy or quit. Sometimes UPS sabotages our shipments and after all our testing efforts the tube arrives broken at
your place. Sometimes a tube decides to end it all early and intentionally misbehaves after a few months. Other
tubes are real troopers (like my 98 year old neighbor) and run strong for 30 years. We have documented cases of
power tubes in Manley amplifiers going over 60,000 hours non-stop in recording studios 24/7/365 without a re-
tube. In one case in particular, the amplifiers were never turned off and had their own dedicated air conditioning for
the amplifier rack they lived in. This certainly contributed to their long life.
FAQ #16f. Should I turn off my gear between uses?
While power cycling is a factor for ultimate tube life, there also is a fixed number of electrons that can ultimately
jump off the cathode. In general we do recommend if you aren’t using the gear for more than a few hours you
should power it down, or in the case of your Stingray iTube just put it in “Standby” mode with the little blue button
on the front panel.
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Summary of Contents for Stingray iTube
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