Ver. 1.1 - ©Phædrus Audio Ltd. 2011 All rights reserved.
Slovak Republic under JJ Electronics brand name (formerly Tesla).
12AU7 or ECC82
The 12AU7 is a popular, miniature 9-pin medium-gain dual triode valve
(tube) and is used in many instrument and hi-fi amplifiers. Both
triodes are used, in cascade, in the Phædrus Audio PHI product. The
12AU7 is also known in Europe under its Mullard-Philips tube
designation ECC82. This tube is widely available both new and NOS
and a number of special quality equivalents are available. Current
production of 12AU7 takes place in Russia, Slovakia, and China.
Phædrus Audio selects and recommends the long anode (plate) version
of the ECC82 (ECC802S) or 12AU7 valve for application in the PHI
DI-Box.
Valve (tube) lifetime
You should replace the valves in the tubes in the Phædrus Audio products only when you start to
notice changes in the sound quality. If the gain of the preamplifier decreases noticeably, then this
is certainly evidence of the onset of valve (vacuum tube) failure. Before this, the tone may become
"dull" and transients may be become "blunted".
That said, the lifetime of a valve (tube) is largely determined by the lifetime of its cathode
emission and the small-signal valves (tubes) used in the PHAB, PHAME and PHI use oxide cathodes,
which can provide adequate cathode emission for 100,000 hours or more. That's over eleven year’s
continuous use. So do not replace valves (tubes) just because they have seen a few years service.
Phædrus Audio Ltd. can provide suitable valves (tubes) as spares which, after a burn-in period, are
screened for best performance in your Phædrus Audio product. These are available as line items:
PHAE-12AU7
– Selected 12AU7/ECC82 type valve
PHAE-ECC88
- Selected ECC88 type valve
PHAE-EF86
- Selected EF86 type valve
Please contact your dealer or Phædrus Audio Ltd. for current prices.
Chapter 5 - Instructions for use
Phædrus Audio’s PHAB, PHAME and PHI products employ valves (vacuum tubes) as the ONLY
ACTIVE DEVICES in the audio path. Valves (vacuum tubes) and their associated circuitry need
time to reach an electronic equilibrium before they will operate at optimal specifications. Please
therefore allow these products to warm up for, at least, 5 to 10 minutes before using them in your
signal chain. To prolong the life of your valves (tubes), it is recommended that you turn off these
units when not in use.