Im learning as I live, with tube rolling.
Recently I replaced my no-brand chinese valves in my pre-amp for military specification Philips.
There was a rise in volume and depth and clarity of sound.
However, the tubes are also microphonic, so you get a 'ping' whever you touch the volume control or rap the top of the pre. They pick up noise very easily.
Starting over, I should have bought valves which had been tested for low microphony, whatever the type.
When buying vintage valves like mullards and philips, often these tests and others like them arent carried out, so in my case a sovtek, chinese or other valve that measured very low on microphony and well in other areas may have provided a better result....just as of course a vintage valve that had been tested may be better.
Perhaps its like buying wine - a vintage bottle may be superb, or perhaps its become corked, and the results will be very poor. A mass market cheap bottle of wine may be excellent, or may be very poor, consistancy is the problem with both!
In the future I will be more careful!
