Ver. 0.1 - ©Phædrus Audio Ltd. 2011 All rights reserved.
humi di ty; or the uni t does not operate normally or ex hi bi ts a marked change i n
per formance; or the uni t has been dropped, or the enclosure has been damaged.
Chapter 4 - About Valves (Vacuum Tubes)
Valve (tube) types
The Phædrus Audi o PHAB and PHAME preampli fi ers and
the PHILTER equali ser employ an EF86 pentode i nput
valve (tube) and an ECC88, or E88CC, valve (tube) as the
output devi ce. Posi ti ons for the valves are very cl early
marked on the PCB si lkscreen as i ndi cated i n the
i llustrati on. The valves (tubes) that ar e i nstalled i n
Phædrus Audi o’ s products duri ng assembly ar e selected
to gi ve the best possi ble per formance. We offer v ersi ons of all products wi th NOS (rather than
current producti on) valves. But thes e must be chosen car efully, and be pr e-screened. Replaci ng the
suppli ed valves (tubes) wi th di fferent, collecti ble, or “hi gh-end” valves (tubes) types may not
affect any i mprovement and mi ght cause deteri orati on of per formance.
EF86
The EF86 i s a low noi se pentode, ori gi nally manufactur ed by many di ffer ent factori es and
branded by Phi li ps, Mullard, Telefunken, Valvo, and GEC, TESLA and Si emens/RFT. Many
NOS valves are sti ll avai lable. Equi valents i nclude the CV2901 (the UK servi ce desi gnati on
for the EF86) and the CV4085; a s peci al quali ty versi on for mi li tary use. The EF86 tube i s
sti ll bei ng produced i n Russi a and i n the Slovak Republi c under JJ Electroni cs brand name
(formerly Tesla). Chi nese close equi valents are also s ti ll bei ng manufactur ed.
ECC88
The ECC88 i s a frame-gri d, sharp cut-off, tw i n (dual) tri ode wi th an i nternal,
separati ng screen. The valve w as ori gi nally desi gned for s ervi ce i n the front ends of
VHF radi o recei vers. The ECC88 (E88CC) tube type i s equi valent to the Nor th
Ameri can 6DJ8 tubes and the (rare) mi li tary branded CV2492. The transposi ti on of
the fi gures from ECC88 to E88CC w as Mullard's w ay of denoti ng a speci al quali ty
bui ld and i s equi valent to the US 6922. Russi an 6N1P tubes and the Chi nese 6N1
tube ar e NOT equi valent.
NEVER install a 6N1(P) in the Phædrus Audio PHAB,
PHILTER or PHAME prod uct
. The ECC88 valve i s si ll bei ng manufactured i n Chi na
and i n the Slovak Republi c under JJ Electroni cs brand name ( formerly Tesla).
12AU7 or ECC82
The 12AU7 i s a popular, mi ni ature 9-pi n medi um-gai n dual tri ode valve (tube)
and i s used i n many i nstrument and hi -fi ampli fi ers. Both tri odes are used, i n
cascade, i n the Phædrus Audi o PHI product. The 12AU7 i s also know n i n
Europe under i ts Mullard-Phi li ps tube desi gnati on ECC82. Thi s tube i s wi dely
avai lable both new and NOS and a num ber of speci al quali ty equi valents are
avai lable. Current producti on of 12AU7 takes place i n Russi a, Slovaki a, and