Tube Amp Doctor Redbase GZ34-STR

Tube Amp Doctor Redbase GZ34-STR is a high-quality rectifier vacuum tube (rectifier) ​​intended for powering tube amplifiers. It is ideal for guitar and hi-fi amplifiers that require a stable B+ voltage with a reliable start and minimal oscillations.

Technical characteristics

• Type: rectifier tube, GZ34 / 5AR4, indirectly heated (soft-start)
• Base: octal (8-pin)
• Heater: 5.0 V / 1.9 A
• Maximum DC output current: up to 250 mA
• Max. peak reverse voltage (PIV): ~1500 V
• Typical voltage drop: ~17–25 V at ~200–225 mA
• Recommended maximum value of the first filter capacitor: up to 60 µF
• Gain: N/A - rectifier tube, does not amplify the signal
• Compatibility: replacement for GZ34/5AR4 in most projects and schemes

Sound characteristics

Objectively, the GZ34-STR provides a solid and stable B+ with lower internal resistance compared to the 5U4, which in practice is heard as defined bass, faster attack and less "sag". Dynamic range remains wide, with good transient control and low noise and mains ripple, contributing to the amplifier's clean and precise sound.

Compatibility and application

Suitable for guitar amps requiring the GZ34/5AR4, including classic designs such as the Vox AC30, Marshall JTM45 and many Fender models from the blackface era, as well as hi‑fi power supplies in EL34/6L6 push‑pull or single‑ended configurations that provide for the GZ34. Before installation, check the service manual or schematic to confirm the compatibility and allowable values ​​of the filter capacitor.

Condition and maintenance

Condition: used, excellent. Visually preserved, without observed physical damage. No service history attached. Recommendation: after replacing the rectifier tube, check the B+ voltage and, if necessary, re-adjust the bias of the output tubes; use the correct filter capacitor values ​​and ensure adequate ventilation for a longer life.

Price: 30 EUR