DIY tube, you could probably spend a few years and end up with microphone.
This is a update I received from the engineers over at TechTube trying to start up the making of Mullard tubes like at the Blackburn factory.
Quote:
ItR17;s now been three months since our last notice and activity has been frantic and very productive but as yet the elusive solution is not quite ready for public unveiling. Despite the economic downturn our drive to launch the new TechTube™ valve technology is not diminished. We still have full management backing and are getting closer to the specification we have set ourselves.
Our target for the E813CC valve is to have every triode and consequently every valve with an Ip current within a band from 0.8mA to 1.2mA. We targeted this band after benchmarking several competitor valves. The benchmark analysis showed that current valve production has Ip ranging between 0.7mA and 1.6mA, even though the data sheet specification is 1mA! Within a valve, the triode to triode variation ranges from nothing (both triodes having the same output) to 0.5mA difference between triodes.
NOS valves perform better having Ip varying between 0.7mA and 1.3mA. Mullard NOS (Blackburn production) have excellent within valve (triode to triode) variations of less than 0.1mA against a norm of 0.25mA. Sovtek have a slightly wider triode to triode variation of 0.25mA but valve to valve they are very consistent with all the valves we tested falling between 0.95mA and 1.4mA.
Currently, our Ip ranges from 0.75mA to 1.5mA, too much variation considering our claim that we are benchmarked against the Blackburn Mullard valve. We continue to work on the factors that give this variation and are near to a resolution.
The other characteristic that we needed to improve upon according to feedback from the September show is microphony. Again we benchmarked several valves already in the field, both current production and NOS. Once again the variation seen was incredible. It’s no wonder end users complain about inconsistent performance!! Over the months the team has been working on this problem, we have come to know how valves shake, rattle and role in intimate detail. Our use of high speed cameras, differing construction techniques and numerous mechanical designs has led us in several directions. Unfortunately even though most were successful in removing microphony they created problems with other characteristics of the valve and consequently they have been scrapped. The down side of this process is that time moves on. Our knowledge base is rapidly increasing but that elusive solution that can be industrialised and automated is still to be found. We continue with numerous parallel paths and the team continues to work hard.
As a result of these factors we will not be in a position to launch the web sales to our plan of April this year. The team continues to work hard on the problems and we will keep you informed as we move through April and probably May.
