VAC-in-the-BOX
Instruction sheet
Thank you for purchasing the Audio Alchemy VAC-in-the-BOX (VITB),
external
Phono
Preamplifier. You obviously care about the quality of the music you listen to on your home
audio system. In order to be sure that you obtain the best possible performance from your new
purchase, please read the following instructions before operating your VAC-in-the-BOX.
IMPORTANT - READ FIRST!!
• Do not plug
anything
in until we instruct you to do so.
• Your Turntable may utilize either a moving magnet (MM) or moving coil (MC) phono
cartridge in order to use VAC-in-the-BOX.
• VITB is a full phono preamplifier, not just a head-amplifier or pre-preamplifier.
Therefore, it puts out a
line-level
signal. It must plug into an auxiliary input on your
preamplifier,
not
a phono input.
• In order to use VAC-in-the-BOX you will need two pairs of high quality RCA cables;
one from your turntable,
the
other to your preamplifier. Contact your Audio Alchemy
dealer for assistance in selecting appropriate cables.
INSTRUCTIONS
1.
Unpack your VAC-in-the-BOX and power supply and place them each in convenient
locations; VITB near your turntable, power supply on the floor or shelf near an AC power
plug within about six feet of the VAC-in-the-BOX.
Do not plug the power supply into the AC
mains yet.
To perform the gain and loading settings on VITB, the board must be removed from the
chassis. Do this by removing the knurled ground nut on the right side, and the one Phillips
screw on the left side. Remove the back panel. To remove the PCB, flex the board up in the
middle and slide it out. Reverse this procedure to install the PCB back in the case. See the
attached illustration for details on this and each of the next two sections.
NOTE:
Always remove power from VITB before changing any of these settings.
2
. Phono cartridges require the correct resistive (and if moving magnet, capacitive) loading
for optimum performance. The instruction manual for your cartridge will tell you what the
correct loading should be.
All MM and some high-output MC cartridges use 47K Ohm loading which is VITB's default
condition; therefore remove all jumpers from positions 3 through 6 of both J6 and J7. The
correct capacitance for MM loading can be determined empirically or by calculation. By
subtracting your input cable capacitance from the specified optimum load capacitance you
will know
the
ideal capacitor value to add. We provide 100 pico Farads (pF) in position 1, and
270 pF in position 2. Use one or both (totaling 370 pF) to get within 10 % of the ideal value.
Should you need a value other than these, a capacitor of your choice (polystyrene type
preferred) can be soldered into position 3 and the attendant jumper installed to select it. Too
low a capacitive value will sound slightly "bright" while too high will sound "dull".
