VAC Phi "Kappa 30i" - Manual (Page 23)

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Tips: Output Tubes
Your VAC Amplifier uses the 300B filamentary triode. It is strongly recommended that replacement
tubes be purchased only from VAC. If, however, you want to customize the sound to your tastes,
be aware that as with interconnects and speaker cables, each tube manufacturer's 300B tends to
have a distinct sound, as well as its own reliability profile.
Tips: Low Level Tubes
The Voltage Amplifier/Phase Splitter, driver, and line stage gain tube type used in the Phi is the 6SN7
medium mu octal twin triode. Your amplifier is fitted with the current production VAC Tested 6SN7
from China, which we find superior to the NOS types we have tried. There are dozens of versions
of this tube available in new old stock (NOS) from a variety of sources. It would be impossible to
characterize them all.
Other equivalent type numbers are 5692, 13D2, B65, ECC32, QA2408, QB65, and CV1988.
The phono tubes and line stage output tubes are type 12AX7, also known as 12AX7A, 12AX7WA,
ECC83, E83CC, 7025, and CV4004.
We strongly recommend obtaining tubes as sets from VAC.
Tips: Impedance Matching
We strongly suggest that you experiment with the three available impedance connections for the
best sonic match with your system. Since no loudspeaker represents an unchanging impedance at
all frequencies, it is impossible to assert with certainty which output tap is appropriate to use. In
many systems an amazing difference in sound will exist between the various impedance taps.
The available connections on your Phi are: Labeled Use with speakers of
8 ohms 4 to 8 ohms
4 ohms 2 to 4 ohms
2 ohms 1 to 2 ohms
Since the impedance of most loudspeakers vary over a wide range experimentation is essential.
Most speakers have a rated impedance of 4 or 8 ohms. We recommend starting with the 8 ohm
connection; after you know the sound if that connection, try the 4 ohm connection. Choose the
connection that sounds best to your ears.
If you bi-wire your system (run separate speaker leads from the amplifier to the high and low
frequency transducers) you may discover that two different impedance taps work best.
Contrary to popular misconception, no power is lost due to unused output taps.
For more information consult VAC Technical Monograph 90-9.