ECC88 / 6DJ8 SYLVANIA AMPLITREX Matched Pair Tubes Made in USA

ECC88 / 6DJ8 SYLVANIA Halo Getter Tested Tubes Made in USA '60s

AMPLITREX Matched Pair – Low Noise & Microphonics – Vintage American SYLVANIA Production

Test Results

Tested on AMPLITREX AT-1000 Tube Tester

Voltage Test:  Va = 90V ; Vg = -1.2V
Average 100%: Gm = 12.5 ; Ia = 15.0 mA
TEST RESULT: VERY STRONG

Tube #1:

• Section 1: Gm = 12.91 ; Ia = 14.9 mA
• Section 2: Gm = 12.30 ; Ia = 14.7 mA

Tube #2:

• Section 1: Gm = 12.20 ; Ia = 12.6 mA
• Section 2: Gm = 12.71 ; Ia = 14.4 mA

Description:

A unique pair of American-made ECC88 / 6DJ8 Sylvania tubes, dating approximately to the 1960s and featuring Halo Getter construction. The two units belong to different Sylvania commercial series: one retains the gold Gold Brand marking, while the other is from standard production and has completely faded lettering. The internal structure and main construction features are nevertheless consistent.

The presence of one Sylvania Gold Brand unit gives the pair additional interest. This designation identified the premium commercial line offered by Sylvania, while the second unit uses standard American production branding. This is therefore not a pair that is aesthetically identical or from the same series, but two tubes selected together based on their actual electrical performance.

Tests performed with the Amplitrex AT-1000 indeed highlight a particularly precise match. The first tube has an average transconductance of about 12.61 mA/V, while the second reaches about 12.46 mA/V: a difference of just over 1%. The average plate currents, equal to 14.8 and 13.5 mA respectively, also confirm good overall consistency between the two units.

Individual transconductance values are between 12.20 and 12.91 mA/V, being very close to or above the nominal reference of 12.5 mA/V. The first tube shows particularly uniform sections; in the second, there is a more evident difference in plate current, while still maintaining stable behavior and being fully suitable for applications where absolute symmetry is not required.

The 48-hour burn-in confirmed the stability of the parameters with no fluctuations. The pair features low microphonics and low noise, absence of gas, and no short circuits, making them suitable even for the most sensitive audio stages.

These tubes are suitable for hi-fi preamplifiers, line stages, buffers, headphone amplifiers, and other circuits compatible with ECC88/6DJ8, as well as musical instrument amplifiers. The close transconductance matching makes them particularly valuable in stereo equipment where it is important to maintain uniformity between the two channels.

Sonically, Sylvania production is appreciated for an open, dynamic, and natural presentation, with a transparent midrange, defined and airy high frequencies, and precise, controlled bass. The excellent electrical matching promotes a stable soundstage, good imaging, and consistent response between channels.

A unique offering for those looking for a vintage American Sylvania pair from the '60s, consisting of two units selected to offer very close electrical values: two Halo Getter tubes with strong emission, low microphonics, and stable operation, tested individually and ready for use.

Conditions:

• Conditions: Vintage Tubes - Tested and perfectly functional. Supplied in our custom box for optimal protection.
  
• Functionality: Perfectly operational.
  
• Cosmetic Condition: Small difference in manufacturing series between the two units: one unit is part of the Gold Brand production, the other is standard production. The construction and identifying characteristics are consistent, however. One of the two units has completely missing lettering. See photos for details.
  
• Manufacturing Code: Code undecipherable. Production attributable approximately to the '60s based on construction characteristics.

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