Manley STINGRAY original version rev.2 6/2005 - 9/2009 MSTX - Manual (Page 16)

TUBE FAQ
A few general all-too-frequently-asked vacuum tube questions from the manleylabs.com FAQ
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... We're not perfect either.)
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 into
finding and stocking these large quantities of tubes ten years ago when the USA military were dumping their 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 junctions 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.
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