Description
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. I refer to the many threads on the web for more information. Very musical preamp valve, balanced and sweet sounding, softened without losing detail with liquid full midrange, recommended!
From the internet: The valve produces the most detailed mid-range response of any ECC83 type ever made. This trademark sound has led many audio reviews to state that this is the best of its type ever made. The valve has a super warm sound with plenty of mid-range detail. Indeed in our test reports the female vocal and string sections were simply stunning. Verdict of a buyer: The sound is excellent – tight, spacey and clean, well balanced with a smooth top end.
Test results*
| Valve 1
V175 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
1,3/ 1,2 mA
1,6/ 1,6 mA/V OK |
= NOS
= NOS |
| Valve 2
V177 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
1,2/ 1,2 mA
1,6/ 1,6 mA/V OK |
= 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 data sheet)
Short description
| Tube type | M8137, (ECC803S) |
| Quantity of Tubes | One pair |
| Brand | Mullard |
| Manufactured in | Mitcham, UK |
| Dates | Date codes:641 R 9C3 & 641 R 7J1) |
| 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 |
