Mazda / M.B.L.E. Brussels EF86 6267 NOS Matched Pair – Low Noise, Silver Mesh

Condition and presentation

A carefully selected vintage M.B.L.E. Brussels EF86 / 6267 pair with closely matching construction and strong measured performance. Both tubes were marked NOS when acquired; those temporary exterior inventory markings were removed during careful cleaning before photography.

Tube #1 tested at 2,150 µmhos and 2.7 mA. Tube #2 tested at 2,050 µmhos and 3.0 mA. Both were verified low noise, with no microphonics detected, no shorts detected, and no abnormal leakage detected.

The original commercial brand stencils are no longer present, Tube #2’s etched production code is faint, and the pins show normal vintage surface patina. These details are clearly shown in the photographs and are reflected in the fair asking price.

The buyer receives the exact documented pair shown, supplied in new white replacement boxes marked #1 and #2, together with the matching VTubeAudio test record.

Vintage M.B.L.E. Brussels EF86 / 6267 NOS matched pair

A carefully selected pair of vintage EF86 / 6267 low-noise audio pentodes, manufactured by M.B.L.E. in Brussels, Belgium, within the Philips/Mazda production family.

These tubes were chosen as a pair for what matters most: matching internal construction, closely matched transconductance, strong measured performance, low noise, and freedom from detected microphonics.

Both tubes were marked NOS when acquired. Those temporary exterior inventory markings were removed during careful cleaning before the final photographs were taken. Both tubes test at or above the Triplett 3444 average-new reference.

The glass now has a clean, understated appearance. The commercial brand stencils are no longer present, and the pins show normal vintage patina. Those cosmetic details are fully visible in the photographs and are reflected in the fair asking price.

The value here is in the quality of the pair: authentic Brussels construction, strong testing, careful matching, quiet performance, and exact-tube documentation.

Why these two tubes belong together

Both tubes share the same distinctive internal construction:

• Fine diamond-pattern silver mesh shields
• Matching polished silver upper internal cuffs
• Top halo/O-getters
• Closely matching getter-flash patterns
• Matching internal electrode geometry
• Matching support structure
• B9A nine-pin miniature bases
• Closely matching glass-envelope proportions

The side-by-side photographs show the unusually close construction relationship between the two tubes.

Philips-family production codesTube #1

• Type code: 8YC
• Factory/date code: L9G1
• 8Y identifies the EF86 tube family
• L identifies M.B.L.E. production in Brussels
• The code is consistent with the first production week of July 1969

Tube #2

• The original type-code line is no longer visible
• The lower factory/date code is faint and partially legible
• The visible characters appear consistent with L9G1
• Its construction closely matches Tube #1

Tube #1 provides the clearly readable production reference. Tube #2 is presented honestly as a probable same-period Brussels companion based on its faint code and closely corresponding internal construction.

Triplett 3444 test resultsTube #1

• 2,150 µmhos transconductance
• 2.7 mA plate current

Tube #2

• 2,050 µmhos transconductance
• 3.0 mA plate current

Triplett 3444 reference

• Minimum reference: 1,300 µmhos
• Average-new reference: 2,000 µmhos

Both tubes test at or above the Triplett average-new reference.

The pair differs by only 100 µmhos. Based on the pair average of 2,100 µmhos, this is an approximately 4.8% transconductance spread.

Both tubes were individually checked and verified:

• Low noise
• No microphonics detected
• No shorts detected
• No abnormal leakage detected
• Stable measured performance

The exact measured results are shown on the included VTubeAudio test record.

Made for sensitive audio work

The EF86 was developed as a high-gain pentode for amplifying low-level audio signals. It has earned a long-standing place in musical-instrument amplifiers, professional studio equipment, microphone electronics, phono stages, tape equipment, and high-fidelity audio circuits.

Compatible applications may include selected versions of:

• Original Vox AC15 and early EF86-equipped Vox circuits
• Matchless C-30, DC-30, HC-30 and related EF86-channel amplifiers
• Matchless C-15 and other EF86-equipped Matchless designs
• Dr. Z Z-28
• Dr. Z Route 66 and KT45
• EF86-equipped boutique guitar amplifiers
• Neumann U 67 and related EF86-based microphone circuits
• Vintage phono and audio preamplifiers
• Studio, tape and broadcast equipment

Please verify that your exact equipment requires the EF86 / 6267 tube type. Microphone applications can have particularly strict selection and operating requirements, so installation in valuable studio microphones should be handled according to the manufacturer’s service information or by a qualified technician.

The sound people seek from the EF86

The EF86 is respected for combining high gain with a musical, expressive presentation.

Owners, builders and specialist tube dealers commonly describe good vintage EF86 performance with terms such as:

• Rich and detailed
• Warm and liquid
• Clear and dimensional
• Natural through vocals and midrange
• Sweet on clean passages
• Harmonically engaging when driven
• Responsive to playing dynamics

In guitar amplifiers, an EF86 front end can deliver clear, sweet cleans and a lively transition into complex, harmonically rich overdrive. In hi-fi and studio circuits, the appeal is often the combination of detail, space and natural tonal body.

Sonic results always depend on the circuit, operating condition, associated equipment and complete system. These descriptions represent commonly reported listening impressions rather than a promise of one fixed sound in every application.

Honest presentation and fair value

Cleaner branded Brussels pairs are currently offered at higher prices. This pair is intentionally priced more accessibly because the commercial glass stencils are no longer present, one production code is faint, and the pins show normal vintage aging.

That gives the buyer an opportunity to own a carefully documented, closely matched and verified low-noise European EF86 pair without paying an additional premium for decorative branding or original printed boxes.

This is a performance-first pair for someone who intends to use and enjoy the tubes.

Included

• M.B.L.E. Brussels EF86 / 6267 Tube #1
• M.B.L.E. Brussels EF86 / 6267 Tube #2
• New white replacement box marked #1
• New white replacement box marked #2
• Matching VTubeAudio test record
• Exact tubes shown in the listing photographs

The numbered boxes correspond directly with the measurements and listing photographs.

Carefully packed for secure shipment.

Exact pair documented in this sales listing. Results reflect measured performance on the Triplett 3444 at the time of testing. Supplied by VTubeAudio.

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