Muting Provisions; Servicing; Output Tube Bias Adjustment; Cleaning - Audio Research VSi55 Owner's Manual

Model VSi55

Muting Provisions

The VSi55 has several provisions to help protect against
misuse of the exceptional dynamic range and wide band-
width that it offers. It is not subject to damage itself, but
some speakers are more limited in their ability to with-
stand signal extremes. These provisions, both manual and
automatic, are designed not to interfere with the listening
experience, while giving reasonable protection against
warm-up surges and power line interruptions. However, for
absolute protection of associated equipment some operator
understanding and responsibility are required.
Initial "s e t t l i ng" time of all circuit parameters within
the VSi55 requires approximately 5 to 10 minutes. The au-
tomatic muting circuitry timer is adjusted for about 30
seconds. (This is because recurrent interruption "s e t t l i ng"
time is much less. You would not want to wait for 5 to 10
minutes each time such an interruption occurred.)
The Mute/Operate switch allows manual disabling of the
VSi55 inputs during the switching of equipment. Use of
this switch will minimize stress on your VSi55 and other
components. It is also highly recommended that manual
muting be employed during turn-off for maximum protec-
tion.
The automatic muting operates as follows:
1. The automatic muting always disables all inputs and
overrides any manual settings. (The "O p e r a te" position
of the manual Mute switch is functional only when the
unit is not in the automatic mute mode.)
Not e : Power supply regulation of the VSi55 is effective
down to 100VAC (120V units) without serious sonic
degradation.
2. The automatic muting of the VSi55 is designed to be
effective only against power line interruptions and
power line failures. It will not mute against subsonic
signal transmissions from your input source. Proper
fusing of speakers is essential to protect against
excessive audio signal levels.

Servicing

Because of its careful design and exacting standards of
manufacture, your VSi55 amplifier should normally require
only minimal service to maintain its high level of perfor-
mance.
C A U T I O N: The VSi55 integrated amplifier contains suffi-
cient levels of voltage and current to be lethal . Do not tam-
per with a component or part inside the unit. Even with
the power turned off, a charge remains in the energy stor-
age capacitors for some time. Refer any needed service to
your authorized Audio Research dealer or other qualified
technician.
4
VSi55 Manual / 3-03 /
The vacuum tubes in your VSi55 should not need to be
changed for approximately 2000 hours of use. Replacement
vacuum tubes should be of equivalent quality and are avail-
able through your authorized retailer or directly from Audio
Research Customer Service. For best performance, the
6550EH output tubes should be matched pairs.
Additional questions regarding the operation, maintenance
or servicing of your amplifier may be referred to Audio
Research Customer Service at (763)-577-9700.(CST)

Output Tube Bias Adjustment

As shipped from the factory, the output "bias"
adjustments are set for a nominal 65mA per 6550 tube.
Under these idle conditions the tubes are each dissipating
approximately 27 watts of their 48 watt rating (42
watt plate, 6 watt screen). This point of operation provides
"enriched" Class AB 1, and will satisfy the most critical
listener.
For best results, operate and adjust the VSi55 at 120VAC.
Adjustment must be made under zero-signal conditions
after at least 15-20 minutes of uninterrupted stabilization
time.
A digital voltmeter capable of accurate measurements with
0.lmVDC resolution is preferred for accurate adjustment
(must have 3 / digit display). Use the plastic alignment
1
2
tool provided to make the adjustment. The measurement
points are banana test jacks at the rear of the VSi55. Adjust
the "bias" for an average voltage reading of 65mVDC (.065
Volt DC) between test jacks, four places.

Cleaning

To maintain the new appearance of this unit, occasionally
wipe the front panel and top cover with a soft, damp (not
wet) cloth to remove dust. A mild, non-alkaline soap solu-
tion or dilute isopropyl alcohol may be used to remove
fingerprints or similar smudges. Cleaners containing abra-
sives should not be used as they will damage the anodized
finish of the front panel. A small, soft paint brush is effec-
tive in removing dust from bevels, the recessed nameplate
and other features of the front panel.
2-17-03