GMI Public Address Systems 33F6 35W 2x12" Dual-Channel Handwired Tube Guitar Amplifier Stack

The GMI Public Address Systems 33F6 is a boutique, American-made 35-watt tube amplifier developed in collaboration with Troy Van Leeuwen of Queens of the Stone Age. Designed and handcrafted by amplifier builder Sean Romin, the 33F6 combines the unmistakable character of vintage tube amplification with modern reliability, versatility, and road-ready construction.

Drawing inspiration from the legendary circuits of vintage Fender, Marshall, and Peavey amplifiers, the 33F6 delivers an exceptionally articulate and harmonically rich tonal response. From expansive, full-bodied cleans to aggressive, saturated overdrive, this amplifier captures the dynamic sensitivity and musical complexity that make classic tube amplifiers so desirable.

Its four-input design provides a versatile range of tonal possibilities, from rich, responsive overdrive to exceptional clean tones with generous headroom for pedals. A Lar-Mar-style post-phase-inverter master volume allows players to achieve expressive, driven tones at more manageable levels, while the defeatable tone stack provides additional flexibility in shaping the amplifier's response.

Built around a fixed-bias, push-pull tube circuit utilizing 12AX7 preamp tubes and 7581/6L6-family power tubes, the 33F6 offers impressive clarity, touch sensitivity, and harmonic depth. Its carefully selected components and meticulous handwired construction reflect GMI's commitment to boutique craftsmanship and long-term performance.

Developed and extensively road-tested with Troy Van Leeuwen, the 33F6 was created to withstand the demands of professional touring while retaining the inspiring character of a great vintage amplifier. Equally suited for recording studios, live performances, and discerning collectors, the GMI 33F6 is a distinctive modern amplifier built with an uncompromising vintage philosophy.

Key Features

• 35-Watt All-Tube Design: Fixed-bias, push-pull circuitry delivers rich harmonic content, dynamic response, and excellent tonal clarity.

• Troy Van Leeuwen Collaboration: Developed with the Queens of the Stone Age guitarist to meet the demands of professional touring and studio recording.

• Four-Input Configuration: Offers a versatile range of tonal characteristics, from full-bodied cleans to expressive overdrive.

• Handwired American Construction: Individually built in California with carefully selected premium components.

• Lar-Mar-Style Master Volume: Post-phase-inverter master volume provides precise control over output level and amplifier saturation.

• Defeatable Tone Stack: Allows players to bypass the tone-control circuit for a different response and tonal character.

• Premium Tube Complement: Three 12AX7 preamp tubes and two 7581/7581A/6L6GC-family power tubes.

• Vintage-Inspired Voicing: Combines the headroom and warmth of classic Fender designs with Marshall-inspired drive and Peavey-style attack.

• Road-Ready Construction: Engineered for dependable performance in demanding professional environments.

• Boutique, Limited-Production Design: Hand-built using specialized components and traditional amplifier-building techniques.

• Two 12" speaker cabinet: This stack comes equipped with one 12" Warehouse Blackhawk speaker and one 12" Warehouse ET90 speaker for two unique voices when mic'd individually. 

Technical Specifications

• Brand: GMI Public Address Systems

• Model: 33F6

• Type: Boutique Tube Guitar Amplifier Stack

• Output Power: 35 Watts RMS

• Amplifier Configuration: Fixed-Bias, Push-Pull, All-Tube

• Inputs: 4

• Preamp Tubes: 3 × 12AX7

• Power Tubes: 2 × 7581 / 7581A / 6L6GC

• Rectifier: Solid-State

• Master Volume: Lar-Mar-Style Post-Phase-Inverter

• Tone Stack: Defeatable

• Construction: Handwired

• Country of Manufacture: USA

• Voltage Options: 120V / 220V / 230V / 240V

• Amplifier Head Dimensions: 19" W × 10" H × 8.5" D

• Amplifier Head Weight: Approximately 30 lbs

• Artist Collaboration: Troy Van Leeuwen – Queens of the Stone Age

• Application: Studio Recording / Live Performance