Phi 300.1a
Phi 300.1a
Power Amplifier

The groundbreaking Phi 300 pioneered the unique direct-coupled Class A triode input and driver circuitry that allowed VAC to get closer to the sound of the recording studio or concert hall than ever before. This consummately musical performer is also extraordinarily flexibly, with settings for fully balanced or single-ended input, selectable front panel attenuators, 150-watt/channel stereo or 300-watt mono modes, and triode or ultralinear output operation. The visual celebration of tubes behind the thick front glass is a fitting match for the joyous sound.

Phi 300.1a
  • Its eight beam power output tubes yield 300 watts in dedicated mono mode or 150 watts/channel in stereo mode at the choice of the user. Front panel level controls may be engaged to aid in balancing biamplified systems.

    Both balanced XLR and single-ended RCA inputs are provided. The chassis is machined aluminum, with the tubes beautifully showcased behind 0.75” glass. Also included are standard 12-volt triggers. The Phi 300.1 is based on our direct coupled input & driver circuit Both single-ended and balanced (fully balanced amplifier mode) inputs are provided.

    The chassis is custom machined 0.25” aluminum welded into a solid unitary structure, finished in metallic black paint. The 1” thick aluminum front panel is finished in hand rubbed silver metallic lacquer, with bias meter and tube adjustors that make it easy to maintain and optimize. Output matching taps are provided for 2, 4, and 8 ohm speakers.

  • Wattage

    150 - stereo

    300 - mono


    36 dB, SE/stereo

    30 dB, balanced/stereo

    37 dB, SE/mono

    31 dB, balanced/mono

    Frequency Response

    4 Hz to 75 kHz

    Power Bandwidth

    13 Hz to 70 kHz


    Single-ended input via RCA jack, non-inverting

    Balanced input via XLR jack, non-inverting relative to pin 2 (“pin 2 hot”, traditional EIA/RCA broadcast/recording standard).


    Connections to precisely match loudspeaker loads of 2, 4, and 8 ohms


    8x KT88

    4x 6SN7

    Residual Noise

    Typically, 700 microvolts at the speaker terminals


    May be factory configured for operation at 100, 120, 220, or 230/240 volts

    Power Cord

    Detachable power cord, standard IEC power receptacle

    12-volt Trigger



    Illuminated logo may be switched off


    Hand-rubbed gold-flake gloss black lacquer with chrome knobs standard.

    Hand-rubbed metallic gloss silver lacquer with chrome knobs special order with additional cost.


    Two years parts and labor, excluding tubes (USA, see manual for full details)

    Dimensions (H x W x D)

    (Not including knobs or connectors) 9.75 x 17.8 x 18.25 in. (24.8 x 45.2 x 46.4 cm.)

    Shipping Weight

    128 lbs. (58.2 kg.)

    *Specifications subject to change without notice.

  • “It is critical in manufacturing perfectionist speakers to use related components that reveal all that’s possible; especially in resolution, tonality, dynamics and sound-staging. To this end we’ve evaluated and tried a vast array of the highest end equipment available. VAC’s amplifiers and preamps have turned out to be references of the highest order, and not coincidentally, terrifically enjoyable to listen to.”
    - Alon Wolf, Owner, Magico Loudspeakers