Mullard EF86 6267 Tube Pair Blackburn 9r2 B0B + SDX2 Triplett Tested

Listing details

Vintage Mullard EF86 / 6267 and SDX2 EF86 Pair — Triplett 3444 Tested

For the listener, musician, technician or restorer searching for a strong, quiet vintage EF86 pair, these tubes provide the important information up front: clear photographs, actual numerical test results and an accurate identification of each tube.

THE PAIR

Tube 1 — Mullard Blackburn EF86

Mullard BVA shield logo

EF86 / 6267 low-noise audio pentode

Made in Great Britain

Etched production code: 9r2 / B0B

Short fine-mesh shield construction

Top O-getter

Cross-seamed glass dome

The Philips/Mullard coding system identifies 9r as the EF86 production type and B as Mullard’s Blackburn factory. Based on the code format and construction, B0B is consistent with Blackburn production in February 1960.

Tube 2 — SDX2-Marked EF86

Clearly marked EF86

Additional white SDX2 stencil

Short fine-mesh shield construction

Top O-getter

Cross-seamed glass dome

Internal construction closely matches the coded Mullard tube

No readable Philips/Mullard factory or date code is currently visible on the SDX2 tube. It is therefore accurately described as a construction-matched vintage EF86 rather than guaranteed as Blackburn manufacture.

TRIPLETT 3444 TEST RESULTS

Mullard 9r2 / B0B

Transconductance: 2,150 µmhos

Plate current: 2.5 mA

SDX2 EF86

Transconductance: 2,000 µmhos

Plate current: 2.2 mA

The tubes are within approximately 7% of one another in transconductance, making them a closely balanced Gm pair.

Both tubes were also checked with:

No shorts

No noise observed

No microphonics observed

The actual numerical readings are provided so the buyer can make a confident, informed decision rather than relying on appearance or a vague “tests good” description.

COMPATIBLE EQUIPMENT

These are standard EF86 / 6267 nine-pin audio pentodes intended for equipment designed for the EF86 tube type.

Compatible examples include:

EF86-equipped vintage Vox AC15 circuits

Dr. Z Route 66

Dr. Z Z-28

Dr. Z KT-45

Dr. Z M12

Matchless DC-30 / C-30 / SC-30 / HC-30

Matchless C-15 / HC-15

Matchless Phoenix 35

QUAD II and QUAD II Classic monoblock amplifiers

Other microphone preamps, tape equipment and audio amplifiers specifically designed for EF86 / 6267 tubes

A QUAD II Classic monoblock uses two EF86 tubes, so this pair supplies the correct EF86 quantity for one monoblock. A stereo pair of QUAD II monoblocks requires four EF86 tubes.

Equipment revisions can differ. Buyers should confirm the tube chart, schematic or owner’s manual for their exact equipment before installation.

Whether selected for a careful restoration, a vintage British amplifier or a high-quality EF86-based audio system, this pair offers strong measured performance, close balance and quiet tested behavior—the qualities that matter most in this sensitive audio position.

Both tubes will be supplied in clean new white replacement boxes and securely packed for shipment.

The photographs show the actual tubes the buyer will receive.

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