VAC Renaissance 140 - Manual (Page 10)

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TJ (mesh anode):
Manufacturer indicates that it can not withstand full 300B specifications; therefore not recommended.
Please note that firms such as Gold Aero, RAM, and Penta do not design or manufacture their own 300B tubes.
Various US companies marketed 300B tubes during the 1950's. Not much is known about their quality.
A Word About Low Level Tubes
The Voltage Amplifier/Phase Splitter and driver tubes in the Renaissance Seventy/Seventy is the 6SN7 medium
mu octal twin triode. Your amplifier is fitted with the current production British/Chinese Golden Dragon, 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. The usually are not
terribly expensive, and may be worth experimenting with. VAC welcomes your comments.
One NOS variant worth mentioning is the RCA "Special Red" industrial version 5692. These represent the
pinnacle of RCA's tube knowledge.
Other equivalent type numbers are 5692, 13D2, B65, ECC32, QA2408, QB65, and CV1988.
A Word About 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.
Since the impedance of most loudspeakers vary over a wide range experimentation is essential. We often find
that matching a speaker's minimum impedance is more important than matching its nominal (average)
impedance.
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. For example, with early production
Martin Logan Sequel II we find that the bass speaker is best matched with the 4-8 ohm tap, while the
electrostatic panel is best controlled by the 2-4 ohm tap. On later production Sequels we use the 8-4 ohm
connection to both drivers.
Contrary to popular misconception, no power is lost due to unused output taps. Also, the amount of negative
loop feedback in the amplifier does not change, being set by the front panel switches. For more information
consult VAC Technical Monograph 90-9.