Description
ECC33 Mullard UK production matched pair !
This is a pair of NOS ECC33 tubes made by Mullard, UK. The properties of this tube are legendary and widely known. I refer to the many threads on the web for more information.
I was able to obtain a number of these tubes, therefore I could select nice matched pairs. The tubes do have the typical rounded plates and a bottom D-getter with a beautiful flash.They are thoroughly tested. Both tubes have excellent test values that match the factory specification and balanced systems (see test results below).
The type/date code on the tubes is 5K2 B 3D4; which imples that they are made by Mullard UK. This code is not anymore completely readable on all tubes.
Sonics
Excellent preamp valve, super linear, low noise, very smooth extended highs, very good in phono stages. Open and airy top end.
> one of the best vintage 6SN7 types ever made.
Test method & results
Tested with: AVO Mk IV, AVO Valve Data Manual 23rd edition 1981, Utracer 3+, Philips 1532, RFT stabilised power supply, 2x Korad KA3005P programmable power supply and 2x Keithley 2700. Gas and shorts tested with: AVO Mk IV. Ia & mu are tested with the official factory test setup: Va = 250V and Vg = – 8V. Precision of the test voltages 2%; measurement after 10 minutes stabilization.
Test results*
| Valve 1
V55 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
9,2 /8,7 mA
3,6 /3,4 mA/V OK |
= NOS / Strong
= NOS / NOS
|
| Valve 2
V58 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
9,3 /9,7 mA
3,6 /3,7 mA/V OK |
= NOS / NOS
= NOS / NOS
|
(Ia new is: 9 mA, Gm: New is 2,5-2,7 mA/v)
* For test methods and factory specification read the tube testing page.
Short description
| Tube type | ECC33 |
| Quantity of Tubes | One pair |
| Brand | Philips Miniwatt / Mullard |
| Manufactured in | Mullard, UK |
| Date codes | 5K2 B 3D4 (hardly readable) |
| Construction | Rounded plate |
| Getter Construction | Bottom D-getter |
| Print Condition | See pictures |
| Box included | Generic white box |
| Equivalent tubes: | 6SN7, 5692, CV2821, B65, CV3942 |
| General test results | NOS |
