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In Reply to: Valvo Red Series E88CC vs. white label posted by mb-de on January 12, 2004 at 06:44:44:
You are right that red series or any valvo label tube could be from Valvo Hamburg or Heerlen or other Philips sourced tubes.However, color codes meant something is the jist of the posts in this thread. The point here is that VALVO RED and other color codes related to different specs, and THAT IS an indicator of the quality parameters like mtbf etc.
At one point, my friend who retired from Valvo offered to send specs of different color codes. I may be able to get it from him if you are interested.
Follow Ups:
Hello cbes!I do not dispute that the colour code was used in the early 1960ies for depicting a set of properties of Philips/Valvo SQ valves.
BLUE was used for valves for aviation applications.
RED was used for valves for industrial applications.
YELLOW was used for valves for PTT and generic telecom applications.
GREEN was used for valves for computing applications.E88CC were meant to be used for industrial applications and therefore colourcoded red.
CCa - which are electrically equal to the E88CC - were meant to be used for long duration PTT apllication.
Both types were manufactured to the same specification on the same machines. The difference was in the batch testing and burn-in which was much more stringend for the CCa, to fulfil the PTT reliability requirements.
In the second half of the 1960ies the colour coding of the stamps was abandoned and all Valvo SQ valves were stamped white again, as it was done before the introduction of colour coding in the 1950ies).
The properties (longlife and/or interface layer free cathode, tight tolerances, vibration resilience, long life and/or high reliability) of the valve types involved were retained anyway, with or without the colour coding.
If you need confirmation for that, use similar sources to mine:
(1) Valvo Valve databooks 'Spezialroehren', various versions published between 1954 and 1972.
(2) An extensive stock (hundreds) of Valvo SQ valves from various sources and production batches, acquired between the early 1970ies and now.
(3) Philips typecode lists
(4) Valvo application notes
Regards,
You are right that the color coding was abandoned in 60's and other identifiers were used to specify tubes. Most old tube hands are aware of that.
I'm concerned as to tube life and any possible effect on sound. If you think others would enjoy the specs, then, by all means.
For example, low noise parameter is something you can relate directly to the sound. Others may be less relevant as far as the so-called "sound" is concerned.Perception of sound, and psychoacoustics is a complicated and controversial subject. Some people seem to perceive differences with different things like the tube architecture; Cryo treatment, era, color of the plates and even getter type etc etc., and others do not.
Best judge of the "sound" is you and your system.
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