Orange do the cheapest and most versatile valve tester that I know of, but it's still expensive and worthwhile only if you do a lot of amp servicing. Don't know what the valve supply situation is like in Australia, but there area a couple of UK suppliers (probably more but these are the biggest outlets) that pre-test the valves and match them up, often into low, medium and high gain sets. It's often variations on the standard valves that end up having the lowest microphonics or highest gain. A valve spec for a 12AX7 valve means it should have a maximum gain of 100, but often ends up less. And even the same manufacturer's valves will have a variation in actual gain. Here's a site I just found that does a good comparison of the different available types of 12AX7s. https://www.amplifiedparts.com/tech-...ent-made-tubes
Worth noting how many of the different brand's offerings are all the same Chinese-made valve, with the same electrical and sound characteristics. So you may as well find the cheapest brand you can find if you decide to try one of those valves.
Last edited by Simon Barden; 06-02-2017 at 12:20 AM.
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