Whitestone Audio Instruments Company, USA Introduces P331 Tube Loading Amplifier At Winter NAMM 2018

Whitestone Audio Instruments Company, USA Introduces 

P331 Tube Loading Amplifier at Winter NAMM 2018

January 19, 2018, Ringwood, NJ:  What began as a custom line amp project for the studio of three-time Grammy® nominated mastering engineer Kim Rosen (Bonnie Raitt, Bettye LaVette, Aimee Mann, Joe Henry, The Milk Carton Kids) the Whitestone Audio Instruments P331 Tube Loading Amplifier evolved into a versatile tone shaping instrument for professional mastering, tracking and mix engineers.

“So much of the way I work is exploiting input and output stages in my analog gear to enhance the energy of a track without leaving too many fingerprints behind.”, says Kim. “We were looking to design a piece of gear for my room that started as a beautifully clean tube line amp but with controls that could introduce subtle enhancements to the signal as needed. We’re thrilled to be offering it to other professional engineers and excited to hear how it enhances their projects as it has mine.”

To nail that big, clear and open tone Kim desired, the designers chose to build the P331 around a pair of 6sn7 vacuum tubes. The 6sn7 octal double triode tube is relatively rare in pro audio designs, but heavily relied upon in high-fidelity audiophile stereo preamps.  First introduced in 1939, and still available as new production stock, 6sn7 vacuum tubes were chosen for this amplifier due to their lower distortion capabilities that exceed that of the standard and ubiquitous 12A*7 variety. Notwithstanding, ultimate circuit topology can bring out more second harmonic characteristics than usual with any tube design. Hence the impetus for the variable circuit topologies within the P331 Tube Loading Amplifier to allow the user to do so as necessary or not at all.

Features of the P331 Tube Loading Amplifier:

LOADING CIRCUIT

The LOADING circuit is part of the fully differential (balanced) Class-A tube amplifier. It was designed to coerce an audio signal to hit the tube at different points on its response curve.

POWER SUPPLY

High voltage plate/anode tube power supplies start at around 320V DC and are filtered (up to 6 times) and smoothed with active regulators. It only uses film capacitors and real inductors (chokes) to remove ripple and noise.

LIFT CIRCUIT

The LIFT circuit is a gentle parallel filter that enhances the highs, lows or both the highs and lows of the signal.

TRANSFORMERS

The P331 is designed to run fully transformerless in its default state. However, the operator may switch in output transformers and select two optional settings, loading them in different ways.

SOLID STATE OUTPUT GAIN

Low distortion, fully balanced solid state amplifier for the output gain section.

PERFECT L/R MATCHING AND RECALL

Front panel rotary and toggle switches commanding 84 sealed precision relays. No audio runs to the P331’s front panel and the finest components are used throughout the audio path.