VAC DAC Mk II User Manual

VAC DAC Mk II Instructions

0.DO NOT OPEN POWER SUPPLY OR DAC CHASSIS - NO USER SERVICEABLE PARTS
INSIDE. DO NOT REMOVE TUBE CAGE UNTIL UNIT HAS BEEN SWITCHED OFF FOR 5
MINUTES. TUBES BECOME HOT IN USE. DO NOT EXPOSE EITHER CHASSIS TO
MOISTURE. DO NOT PLUG INTO AN AC SOURCE UNTIL ALL CONNECTIONS ARE
COMPLETED.

1.Complete all connections, including the two power supply to DAC power cables, before connecting
the AC cord to the wall outlet.

2.The associated preamplifier should be set to mute and/or its gain controls turned fully down.

3.The associated CD or DAT transport should be switched on and emitting a synch signal (playing).

4.Switch the DAC on and allow 1 minute for warm up.

5.Select a digital input (1 and 2 on coax, 3 for AT&T optical). For AT&T, read the special section
later in this manual.

6.The green "magic eye" indicator shows three possible shadow angles. The approximately closed
position indicates that the DAC is not receiving a synchronization signal from the selected input. The
approximately 45 degree angle indicates that the DAC is receiving a synchronization signal and is
not applying deemphasis (this will be the most commonly observed condition). The approximately
90 degree angle indicates that the DAC is receiving a synchronization signal and is applying high
frequency deemphasis.

If the shadow is seen to vary rapidly the unit is hunting for a signal, and the output might be an
unpleasant sounding hash. If this occurs, make certain that the input selected has good connection
to a correct, switched on, and playing digital source. Then cycle the input selector to a different
digital input, leave it there for 5 seconds, and switch it back again to the desired input. If the
symptom persists, switch the source off, the DAC off, switch the source on, start the source playing,
switch the DAC on. Persistent problems indicates bad cabling (most likely), a bad source, or a fault
in the DAC (least likely).

7.Switch preamp to MUTE before switching the DAC on or off. Continuous operation of the DAC is
recommended for best sound and longest tube life.

8. Allow the system to sit switched off for 10 minutes before disconnecting the DAC from the power

supply.

9.The phase invert switch functions in a true push-pull differential circuit and does not add additional
devices to the signal path in either mode. It is a true phase reversal control. Output is non-inverted
when the control is set as marked.

10.The XLR balanced outputs are in conformance with the EIA standard, whereby pin 2 is non-inverted
and pin 3 is inverted. Please note that a surprising number of manufactures fail to conform to the
standard.

11.In some systems it may be found advantageous to connect an insulated lead (16 gauge or larger)
between the ground binding posts on the power supply and main DAC unit.

12.Tube compliment is:

V112AX7A/E83CC
V212AU7A/E82CC

Low noise types are not required. However, V1L&R should be matched section for section. V2L&R
should be matched section for section. Matching is important for channel balance in a zero global
feedback circuit such as the DAC employs.

13.A digital output is provided for connection to the SP-DIF input of a DAT or CD-R recorder. Care
should be taken to not select the recorder on the main input when it is in the record mode or digital
source monitor mode, as feedback oscillation may occur. Such feedback could damage parts of your
system.

14.Please call us with any questions you may have. It is better to ask than to guess. A full owners
manual will be sent to you as soon as it is completed.

15.Your equipment is warranted for a period of thirty (30) days from the date of purchase. In addition,
if the registration card(s) is received by VAC along with a copy of your sales receipt from an
authorized VAC dealer within this thirty days, a service contract will be extended to cover your
equipment for three (3) years (except tubes which are covered for 90 days). Receipt of your
registration card will be confirmed in writing by VAC: it is important that you call VAC if you do
not receive this confirmation.

This warranty applies only to units sold to and operated by private individuals in the United States
of America through authorized VAC dealers. For warranty information outside of the U.S. contact
the importer of VAC equipment for your country. Units sold outside of the U.S. should still be
registered with VAC.