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Nice pair M8137 (ECC803S) twin triodes, Excellent condition, made by Mullard in Blackburn, UK
This is a pair M8137 tubes produced by Mullard in the sixties and seventies in Blackburn, United Kingdom. The tubes have so called box plates, which is considered superior to the conventional construction; see pictures.
The M8137 is the military long life ECC83 that was specially designed for the British forces.The tubes both look unused and measure new ; see test data! Very healthy tubes in deed with NOS specs! Tubes with matching systems; see test results.
Sonics
The Mullard M8136 is highly regarded. This version of Mullard is known as a very fine ECC83; with a liquid, creamy and very detailed sound image. I refer to the many threads on the web for more information. Excellent preamp valve, very low noise, very smooth extended highs, very good in phono stages. Balanced and smooth sounding with liquid midrange, recommended!
Note from the web: “The overall tonality of Mullard Mitcham tubes is warm and lively with a very spacious sound stage. “Like a warm British jacket of the finest tweed, these glorious tubes have an attractive sweet warmth in their midrange and lower regions.” This is how the experts on audiotubes.com describe the sound signature of British-made Mullard tubes. The top end is silky and pleasant and doesn’t get rolled off. They retain a fine sense of “air” at the top, and the upper midrange is smooth and liquid. These tubes reproduce the human voice, especially female voices, with haunting realism. The British made Mullard tubes are also known to have an attractive sparkle at the top with rich bass…now we know where that “warm British jacket” comes from!
Note: if your system is to “warm sounding’, this tube is not a first choice. Philips Holland made ECC83 tubes are to be considered in that situation.
The tube is thoroughly tested and has excellent test values that match the factory specifications of a new tube very well and with balanced systems. See test results below.
Test method & results
The tubes have been tested carefully with the official Telefunken test set-up and our sophisticated test equipment. Please read our testmethod for the ECC83 tube family. The measurement data below show that these tubes meet the factory specifications of a new/NOS tube.
| Valve 1
V95 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
1,3/ 1,2 mA
1,8 /1,7 mA/V OK |
= NOS / NOS
= NOS / NOS
|
| Valve 2
V231 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
1,4 / 1,4 mA
1,7 /1,6 mA/V OK |
= NOS / NOS
= NOS / NOS
|
Where NOS is : Ia = 8,7 to 12,5mA, Gm= 1,9 to 2,7 mA/V. Ia = 10,6 ± 1,9 mA. (Telefunken factory specification see test page)
Short description
| Tube type | M8137, (ECC803S) |
| Quantity of Tubes | One pair |
| Brand | Mullard |
| Manufactured in | Mitcham, UK |
| Dates | Date codes:641 R 6F3 & r41 R 5C51) |
| Construction | Box plates |
| Getter Construction | Halo getter |
| Print Condition | Nice; see pictures |
| Box included | White box |
| Equivalent tubes: | 12AX7WA, E83CC, ECC803S, 13D8 |
| General test results | NOS |
