This blog looks at Supermatch and supplying quality output valves
We work to supply our customers with best matched matched output valves. The benefits are that the output is nice and balnced on the amp. This applies to not only matched pair but also to matched quad valves.
When we receive a shipment of output valves and lets take the example of a big batch of our mos popular output valve the 6L6GC from JJ Electronic in Slovakia.
We first run every valve through our digital tester which tests for the obvious such as shorts, functionality and in this test we grade each of the valves according to its overall performance. Valve specifications are very wide ( it is old technology ! ) and the values in the data sheets are only typical. Therefore, taking the results of this test while it is automated enables us to put them in groups according to the actual performance of the valve.
Next we use our valve characterisation tester to accurately measure under fixed data sheet conditions, what the actual current that is flowing through the anode of the valve. This is a good measure of the emission quality of the valve. We then measure the u of the valve which is the mutual conductance of the valve .
When we receive your order we take 6L6GC’s and ensure they are within 1mA of each other on anode current and work to get them to within 5% on the gain.
This is time consuming as we need to test a number of valves in the same group to find ones that meet this stricter requirement.We need to let the valves truly warm up to temperature. The EL84 ( 6BQ5) takes more than 5 minutes to settle at its working conditions so you ccan see that we can only test in reality 11 EL84 valves an hour maximum on one set of test gear!
One advantage of the characterisation tester is that it runs them at full voltage so they get a good stress test.
In all of this testing, you might wonder if we get failures. In the case of 6L6GC’s we see a very few and JJ Electronic always analyses them which helps them learns from these very few weak ones. We prevent our customers fro receiving valves like this !
In every product no matter what it is, there will be ” infant mortality” where the product stops in its tracks after a few hours of operation. In the case of the JJ 6L6GC, we have only seen one where this occurred at a customer and of course we supplied a replacement matched kit as we stand behind our 120 day warranty.
We have sold a LOT of 6L6GC’s so while it is a good record, we want customer failures to be zero. In the real world there will always be the very occasional valve that fails . It is old mechanical technology and even with improvements in manufacturing it still happens. But we will always replace non -mechanically damaged units under warranty
Good News for you
The good news is that with the exception of one failure at a customer, we ensure that you receive product that has been tested at the factory, overall parameter tested and finally hand selected for the best match. You can be assured your output valves have been well checked before you get them !
