GZ33 AMPEREX BugleBoy by Mullard Blackburn Halo Getter Made in Great Britain '64

GZ33 AMPEREX BugleBoy by Mullard Blackburn Halo Getter Made in Great Britain '64

Description:

Rare GZ33 rectifier tube produced in 1964 at the historic Mullard factory in Blackburn , and branded AMPEREX Bugle Boy for the international market. This unit is tested with very strong values, fully in line with those of a NOS tube. It is therefore a tube with very few hours of actual use , ideal for those looking for an original Mullard GZ33 without having to pay the full price of the NOS NIB.

The internal structure is the classic one of the best British GZ33s: ring-shaped getter (halo getter) , generous black plates , robust construction, thick, slightly burnished glass. The Bugle Boy branding is still clearly visible, confirming the authenticity of the Mullard production for Amperex.

Timbral characteristics and sound behavior

Bass:
Deep, controlled, and with great authority. The GZ33 is known for offering extremely stable power, resulting in precise and well-defined low-frequency extension.

Medium:
Transparent and neutral. Compared to tubes like the GZ34, the GZ33 provides a more solid and colorless behavior, ideal for those seeking maximum tonal balance.

Highs:
Clean and never harsh. Even with complex loads, the top end remains airy and defined, without overemphasizing the brilliance.

Dynamics:
Excellent current reserve, with stable dynamic response. Ideal for systems requiring a rectifier capable of handling even heavy loads without compression.

Soundstage:
Stable and well-focused soundstage, with excellent instrument separation. The soundstage is wide and solid, especially in push-pull configurations or with high-power amplifiers.

🎧 Use in Hi-Fi amplifiers

Ideal for high-end power amplifiers, especially tube push-pull amplifiers , where power supply robustness plays a key role in dynamic handling. Also perfect for preamplifiers or driver stages that require high voltage stability.

🎸 Use in musical instrument amplifiers

The GZ33 is a rare but excellent choice for boutique applications, such as custom guitar or bass amplifiers with point-to-point architecture. It is less compressed than the GZ34, providing greater headroom while maintaining definition even on clean or crunch sounds.

🎯 Note for audiophiles and technicians

The Mullard GZ33 is one of the most respected rectifiers in audio: hard to find, even rarer if marked Amperex Bugle Boy . This example, although used , has very strong test values and a well-preserved aesthetic. An excellent choice for those who want original Mullard performance , at a more affordable price than a NOS NIB.

Test Results:

Tubes tested on FUNKE W19 Tube tester:

• Test Conditions: Va = 60V, Vf = 5V
• Good from: Ia = 55 mA
  
• Average 100%: Ia = 100 mA
  
• Test Result: VERY STRONG

Plate current:

Valve:

• Section 1: Ia = 94 mA
  
• Section 2: Ia = 94 mA

Additional Tests

• Microphonics: Standard. Tested and approved for use in hi-fi and guitar amplifiers.
• Output Quality: Excellent – Very strong and stable output, no fluctuations.
• Short circuits and GAS: Absent.

Conditions:

• Conditions: Vintage Valves - Tested and in perfect working order - Supplied in original box.
  
• Functionality: Fully functional.
  
• Cosmetic condition: Excellent – Excellently preserved lettering, minimal signs of wear. See photos for details.
  
• Manufacturing Code: rs1 B4D1 - Manufactured at the Blackburn factory - 1st week of April 1964