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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