Jon S Thanks for your input. We know Matsushita had Mullard tooling but what about quality control on metals. I wonder why two of your tubes measure 29 mA and two measure 33 mA. Guessing they were made around the same time and packaged together. Why are you seeing a difference?. If materials were consistent wouldn't we get tighter tube measurements? Just a thought.
No... That's not how it works... Tube manufacturers try to maintain consistent quality in their tubes but it is impossible to manufacturer all their tubes with the same measurements. The MaxiMatcher manual states that typical EL34 tubes plate voltage can vary between 22-50 mA, but usually a manufactured tube will vary only by about 10-15 mA. My Psvane Legend EL34PH quad measures between 24-36 mA, pretty bad matching. I have five Mullard reissued EL34 quads and they measure between 43-59 mA. I also have six quads of Electro Harmonix 6CA7s and they measure between 41-59 mA (but each quad measured only a couple per cent of each other, the quads were bought separately and the vendor matched them together for me. BTW, half of these tubes were gifted to me when the owner went to KT88 amplifiers).
Normally, independent tubes sellers will receive a case of 48 tubes from the manufacturer. They will then measure and sort out the tubes by their values. That's why they will state "matched" tubes. They will sell a quad that have closely matched values, they don't just grab any four from the box. For example, I have a total of five quads NOS Groove Tubes (that I got at a great price if I bought out the remaining stock) that was matched by the seller. The quads measured 30.7-31.0, 32.2-32.9, 34.9-35.3, 35.5-35.8 and 29.3-30.5 mA (excellent matched values, BTW). The vendor tested all the tubes and sorted them into closely matched quads.
Do not believe that the manufacturers measure and sell their tubes in matched sets, especially Chinese tubes. My TOTL Psvane 6CA7-T3 "matched" quad measured between 31-36 mA and my Psvane EL34-Z measured between 34-40 mA. Viva Tubes buys the Psvane tubes in bulk and will measure and sort the tubes by value. That's why the EL34-PH tubes they sell do not come in the nice box that Psvane sells the tubes in. Viva Tubes sells them sorted in Psvane's OEM generic tube box. In fact, if you order the same tubes later, you can specify the values for the plate current, that way all the tubes will have the same value.
If you buy tubes from Amazon direct or other large resellers, you really don't know what you are getting. Amazon receives hundreds of tubes from the manufacturer at a time. If you buy a quad from them, they will just grab the tubes from their boxes and send them to you. You don't know how closely matched the tubes will be. The only safe bet when buying from Amazon is if the tube resellers (e.g. Viva Tubes) are selling through Amazon's store front as they will usually match the tubes prior to shipping. Psvane sells through Amazon direct, so you won't get the same tube matching service. Don't believe that Psvane pre-tests the tubes before shipping to Amazon. I have read horror stories of how the Psvane Horizon tubes were either DOA or noisy out of the box even though Psvane says they burn-in and test the tubes for 24-hours before shipping.
