F300 The VAC Phi Three Hundred Stereo/Mono Beam Power Amplifier Operation & Maintenance Information Valve Amplification Company Manual issued 03/15/2006 Revised 11/14/2006
PLEASE READ CAREFULLY Your Phi Beam Power amplifier is fitted with a unique output tube monitoring circuit. Rather than directly contacting the audio path, and thus contaminating the pure sound, the temperature of a small cathode resistance is sensed. The four bi-color LED’s on the front panel indicate the tubes’ conditions. If the idle current of a KT88 output tube drops below nominal limits, the LED corresponding to that tube will light green.
CAUTION THE AMPLIFIER AND POWER SUPPLY CONTAIN NO USER SERVICEABLE PARTS. DO NOT REMOVE THE BOTTOM PLATES OR CHASSIS COVERS. LETHAL VOLTAGES ARE PRESENT WITHIN THE CHASSIS. DO NOT OPERATE THE UNITS IF THEY ARE WET. VACUUM TUBES BECOME HOT ENOUGH TO CAUSE SERIOUS BURNS. NEVER TOUCH A TUBE WHEN THE UNIT IS ON. IT MAY TAKE SEVERAL MINUTES FOR THE TUBES TO COOL DOWN AFTER THE UNIT IS SWITCHED OFF. IT IS STRONGLY RECOMMENDED THAT THE TUBE COVERS BE LEFT IN PLACE AT ALL TIMES.
INTRODUCTION The Phi 300 is a unique power amplifier, and the most power and detailed in VAC’s history. Featuring a new direct-coupled input & driver circuit, extremely fast and vivid sound is achieved from both single-ended and balanced sources. The Phi 300 may be used as a 150 watt/channel stereo amplifier, or as a 300 watt monophonic amplifier, as determined by the rear panel switch.
UNPACKING & ASSEMBLY Your amplifier has been shipped with the side and front glass in place. The following steps show how these are installed, in the event that you ever need to change them. Remove the screws that secure the aluminum top frame to the chassis pillars. Turn counterclockwise to remove. Take care to prevent the tool from scratching the chassis. Remove the top frame. From each of the four columns remove the tape, which prevented the nylon setscrews from coming loose during shipment.
The front glass has the etched VAC logo. Install this between the front pillars. Take great care not to scratch this glass. The front glass fits into a small channel in the front plate. Tighten the white nylon setscrews that secure the side glasses. Turn clockwise to tighten. There are four setscrews for each glass plate. Do not tighten the setscrews for the front glass yet. Install the six aluminum blocks at the top of the side glasses.
Set the beveled glass top into the aluminum top frame, oriented so that the two holes are on the left and right side. To prepare a Phi for shipment, follow these steps in reverse order. When loosening the metal and nylon setscrews, be careful not to back them all of the way out of the holes! If a metal screw falls into the amplifier, contact VAC for service directions. NOTE: Do not remove and connect input cables or speaker cables while is amplifier is running.
INSTALLATION 001) Install the vacuum tubes. Each tube or its box has a “V” number, which corresponds to the labels on the top plate of the amplifier; these indicate where each tube should be installed. Fit each tube into the matching socket, first removing any sticker from the amplifier and/or the tube. Tube Placement - VAC Phi 300 V9 When inserting and removing tubes, handle them by their bases, not by their glass bulbs.
10) Do not place in a completely enclosed cabinet. Do not stack other equipment on top of the VAC unit. 11) Do not operate on carpet or any other surface that might block air flow. 12) The chassis and glass will become hot in normal use. 13) Do not allow the chassis to touch any metal parts, such as the frame of an equipment rack. This might create a parallel ground path that could degrade the sound of your system.
OPERATION By time delay, sound will begin approximately 60 seconds after turn on. As with all high fidelity products, the sound characteristic of the VAC changes somewhat as it warms up. Best sound will be achieved after about one hour of operation. We advise against leaving the equipment on at all times for safety reasons (see Safety Notice at the front of this manual), and because of the attendant acceleration of output tube wear and power consumption.
TRIODE & ULTRA-LINEAR MODES Triode amplification is the oldest form of amplification known, while partial triode ("ultra-linear") operation of pentodes and beam power tubes dates back to 1937. Both modes of operation are available with your VAC Phi amplifier via a single switch on the top plate.
INSTALLING NEW OUTPUT TUBES Output tubes are type KT88. Replacement output tubes should be purchased from VAC. It is important that the tubes be checked for any tendency to mechanical or electrical shorts (see Safety Notice at the front of this manual). It is desirable that tubes be in matched quartets for each channel, and be close to the "bogey" values for the major parameters. Make certain that each tube fits firmly in its socket. ALL POWER MUST BE OFF.
CHECKING OUTPUT TUBE CONDITION As described at the beginning of this manual, the Phi is equipped with the KT88 Sentry circuit, which continuously monitors each output tube to ensure that it is operating within normal limits. Each tube has a corresponding indicator light on the front panel. A green indicator light will be seen as the amplifier warms up, or when a tube’s idle current is less than normal.
REPLACEMENT OF LOW LEVEL TUBES All power must be switched off. Allow tubes to cool down. Remove the top glass cover. Remove and replace with new tubes of the appropriate types. Note that these tubes have a central platic shaft with a locator ridge on one side; this ridge must be aligned with the slot in the socket. Replace the glass cover before operating the amplifier. Replacement tubes are available from VAC and other sources.
TIPS & ADVICE SECTION A Word About Tubes in General It is true that each brand of tube sounds different in a particular high resolution circuit. This is because no two manufacturers make a tube type in quite the same way, and the central tendencies of the performance parameters will differ slightly with each maker. To emphasize the point, examine the plate structure of any two 6SN7 from different manufacturers will probably find that they may not even the same shape and size.
Tips: Output Tubes Your VAC Amplifier uses the KT88 kinkless tetrode. It is strongly recommended that replacement tubes be purchased only from VAC. If, however, you want to customize the sound to your tastes, be aware that as with interconnects and speaker cables, each tube manufacturer's KT88 tends to have a distinct sound, as well as its own reliability profile. Tips: Low Level Tubes The Voltage Amplifier/Phase Splitter and driver tubes in the Phi is the 6SN7 medium mu octal twin triode.
Tips: Impedance Matching We strongly suggest that you experiment with the 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.
Tips: Audio Grounding Systems incorporating single-ended interconnect cables (“RCA cables”) are prone to a problem known as “ground looping”, which can result in extraneous hums and buzzes audible through the loudspeaker. If this occurs in your system, you have to attempt to minimize the ground loop. To minimize the buzz using the normal RCA input jack, there are several steps you can take: 1) Use the shortest interconnects possible. 2) Use interconnects with good shielding properties.
SPECIFICATIONS The VAC Phi 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.
WARRANTY Your equipment is warranted for a period of thirty (30) days from the date of purchase. In addition, if the registration form 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 (tubes excepted).
