The technical specification sheet for your vintage 1960s Harmony Model H306C two-channel tube guitar combo amplifier is detailed below. Built in Chicago, Illinois, this highly regarded studio and recording amplifier is famous for its shimmering clean headroom and bias-modulated tremolo circuit. Top Control Panel LayoutThe blue control panel features a dual-channel design with top-facing chicken-head knobs: Missing back panel.

• Channel 1:
• • Two 1/4" inputs (labeled for Instrument/Mic).
  • Independent Volume, Bass, and Treble knobs.
• Channel 2:
• • Two 1/4" inputs.
  • Independent Volume, Bass, and Treble knobs.
• Vibrato Section (Tremolo):
• • Speed: Adjusts the rate of the pulse.
  • Modulation: Controls the depth/intensity of the effect.
  • Foot Control: 1/4" jack for a remote footswitch toggle. 
• Power & Safety (Right Side):
• • Power toggle switch and a red indicator jewel light.
  • Standard screw-cap Fuse holder.
  • Electrical rating panel badge: 110–120 Volts, 60 Cycles A.C., 0.6 Amps, 65 Watts Input (stamped with the vintage CSA/UL safety logos).

Tube Complement (Valves)The hand-wired chassis architecture relies on a five-tube array: 

• Preamplifier / Tremolo: Two 12AX7 dual-triodes (providing input gain and driving the tone stacks).
• Power Amplifier: Two 6V6 (or 6V6GT) beam power tetrodes configured in a push-pull circuit design.
• Rectifier: One 5Y3 (or 5Y3GT) vacuum tube rectifier supplying high-voltage DC plate current. 

Audio & Output Performance

• Power Output: Rated at approximately 15 to 18 Watts RMS.
• Speaker: Standard internal 12-inch Jensen speaker (typically a ceramic C12R or alnico equivalent, running an 8-Ohm load).
• Circuit Characteristics: Warm, touch-sensitive compression at lower volumes that breaks up beautifully into vintage grit when pushed past noon. 

Physical Specifications

• Cabinet Material: Solid pine construction wrapped in charcoal/black textured tolex faux-leather.
• Dimensions: Approximately 22.25" Wide × 17.5" High × 9.5" Deep.
• Weight: Light and portable at roughly 24 to 25 lbs (approx. 11 kg).