12AX7 / ECC83 NOS MULLARD – Blackburn 1959 – Matched Pair – Short Gray Plates – Halo Getter – Same Data Code – AMPLITREX Tested

12AX7 / ECC83 NOS MULLARD – Blackburn 1959 – Short Gray Plates – Halo Getter – Matched Pair – Same Data Code I61 B9K – AMPLITREX Tested

Description:

This matched pair of NOS Mullard 12AX7/ECC83s , produced in the historic Blackburn (Great Britain) factory in 1959 , represents one of the most appreciated configurations of the British Mullard production.

The valves have the classic internal structure:

• Short Gray Plates
• Halo Getter
• Mullard Blackburn production
• identical data code: I61 B9K

The I61 code identifies the famous Mullard structure for ECC83 with short plates , while B9K confirms the Blackburn 1959 production, one of the most sought-after periods by enthusiasts.

The specimens are NOS (New Old Stock) and are presented in showcase aesthetic condition , with perfectly preserved silkscreen prints and internal construction.

Both tubes have been thoroughly tested in our laboratory with the AMPLITREX AT-1000 , verifying emission, stability and operating behavior. They also proved to be Low Noise & Microphonics , qualities that make them suitable even for the V1 position in the most sensitive circuits.

Sound Characteristics

Mullard Blackburn ECC83s are renowned for their natural musicality and warm, engaging character, which has made these tubes a favorite among audiophiles and musicians.

Bass: Deep and well-controlled. The low end is full and authoritative, with an excellent balance between body and precision.

Mids: The strong point of the Mullard tradition. Vocals sound rich, three-dimensional, and very natural, while acoustic instruments and harmonics emerge with great presence.

Highs: Sweet and refined. The highs are well-extended yet elegant, with a fine texture that encourages long, relaxed listening.

Dynamics: Very fluid. Dynamic variations are reproduced naturally and seamlessly, always maintaining great musicality.

Soundstage: Wide and stable soundstage, with nice depth and very credible instrument separation.

🎧 Use in Hi-Fi Amplifiers

Mullard Blackburn ECC83s are among the most sought after tubes for:

• tube preamplifiers
• phono stages
• hi-fi amplifier drivers
• high-end vintage audio equipment

Thanks to the low noise and reduced microphonics , this pair is perfectly suited even for the most critical positions of the circuit , including V1 .

🎸 Use in Music Applications

In the world of musical instrument amplifiers, the 1950s Mullard ECC83s are considered a benchmark.

They offer:

• rich and musical mediums
• very expressive dynamic response
• excellent timbre definition

Features that contribute to a warm, articulate and very musical sound.

🎯 Note for audiophiles and technicians

• Mullard–Blackburn (Great Britain)
• Year of production: 1959
• Structure I61 – Short Gray Plates
• Halo Getter
• Identical Data Code: I61 B9K
• Matched Pair
• NOS – Showcase condition
• Low Noise & Microphonics – also suitable for V1
• AMPLITREX AT-1000 Tested

An authentic 1959 Mullard Blackburn pair , with identical production numbers , built in one of the most iconic factories in vacuum tube history. A combination of build quality, musicality, and historic appeal that continues to make these ECC83s among the most sought-after by vintage audio enthusiasts.

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Test Results:

Valve tested on AMPLITREX AT-1000 Tube Tester:

• Test Conditions: Va = 250V ; Vg = -2V
• Average 100%: Gm = 1600 ; Ia = 1.2 mA
• Test Result: STRONG

Valve #1:

• Section 1: Gm = 1500 ; Ia = 0.9 mA
• Section 2: Gm = 1800 ; Ia = 1.2 mA

Valve #2:

• Section 1: Gm = 1500 ; Ia = 0.9 mA
• Section 2: Gm = 1800 ; Ia = 1.4 mA

• Microphonics: Low. Tested and approved for use in hi-fi, including phono stages and guitar amplifiers. Also suitable for V1.
• Noise: Low and well-controlled. Silent operation in hi-fi and music amplifiers in the intended positions.
• Output Quality: Excellent – ​​Very strong and stable output, no fluctuations.
• Short circuits and GAS: Absent.

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Conditions:

• Condition: NOS - New Old Stock - Tested and working - Supplied in our custom box for optimal protection.
  
• Functionality: Fully functional.
  
• Cosmetic condition: Excellent – ​​Excellently preserved lettering, minimal signs of wear. See photos for details.
  

Manufacturing Code:

• I61 B9K→ I6x indicates an ECC83 with the sequential progression of x, where the increment of x indicates the production changes - B9K B → Mullard, Blackburn - 8 (over three figures) → 1959 - K → November
  

Find out why our valves are different →