VAC Vintage High Power User Manual
Page 11
SPECIFICATIONS
The VAC System has been developed with the critical ear as the major arbiter of quality, with both conventional and
unique measurements providing insight and guidance as necessary. The lack of emphasis on measurements is due to
the fact that engineering's arsenal of equipment and techniques do not operate on the pattern recognition principals
that control human perception of sound.
In the immortal words of Daniel von Recklinghausen, if it measures good and sounds bad it is bad. If it measures bad
and sounds good you've measured the wrong things.
For those concerned with test bench performance, the following describes typical measured performance of a Vintage
High Power operated at 120 VAC, 60 Hz.
Power Output:
98 watts continuous average power at 1 kHz with less than 1% THD into 6.6 ohms
connected to the 8 ohm tap. Triode mode reduces power to 57 watts.
Frequency Response:
down 0.5 dB at 5 Hz and 95 kHz, ref 0 dB = 1 watt @ 1 kHz.
(Note: response peaks will be observed at approximately 68 kHz and 190 kHz. Such peaks are
present in all tube type transformer coupled power amplifiers, and are normally suppressed by the
use of a phase compensation network in the negative feedback loop. VAC has deliberately avoided
this technique, finding that it is sonically inferior to the slight ultrasonic peaks encountered with an
excellent output transformer. The compensation technique looks good into a resistive load, but falters
in the real world. Interested audiophiles should see Some Defects in Amplifier Performance Not
Covered by Standard Specifications by Norman H. Crowhurst, published in the October 1957
Journal of the Audio Engineering Society.)
Power Bandwidth:
down 0.5 dB at 14 Hz and 56 kHz, ref 0 dB = 90 watts @ 1 kHz.
down 3.0 dB at 9 Hz and 92 kHz, ref 0 dB = 90 watts @ 1 kHz.
Distortion:
< .2% THD at 1 kHz 10 watts
Noise:
S/N ratio > 85 dB
Sensitivity:
.6 volts input for full power output
Negative Feedback:
Loop feedback is fixed at approximately 8 dB regardless of output tap selected.
Absolute Polarity:
Does not invert signal polarity.
Fuse:
Slo-Blow type, 5A for 100 & 120 Volt configuration, 2.5A for 220 & 240 V.