I have to buy matched pairs of 6S45P?
when plugging 32 ohms Grado's- It's better to set the impedence to 30 or 100?
I would say tubes with the same year of production are fine. I have a few sets of tubes, and I use the ones together with the same years.
Interestingly, just last night I put in some tubes that were NOS of older production. The tubes I was running had dates of 1990, so I rolled in some from 1980. I wanted to see if older tubes sounded better. One of them hummed like crazy and didn't play any music through that channel. I waited a few minutes to see if the tube would come around, but it never did. Dead on arrival. Bummer.
The NOS Russian 6S45P tubes I have found come in bulk and do not come matched, and I have not seen a tube tester that can test them, so while it might be a nice idea to have them "matched", it's probably not going to happen except by happy accident.
I have a bunch of 6S45P tubes that date from 1985 and 1990. They sound pretty much the same. I bought some from 1980 on eBay to see if they sound different. Well, one was dead on arrival, and it seems like I'm not going to get a refund from the seller. Oh well, such is life.
Anyway, the point of this post is to say I got some Reflector tubes from 1974 delivered yesterday. There's a seller on eBay selling a bunch of these tubes dated from 1974, which are the oldest I can find. There is a very slight difference in sound. Sure, they are new and still burning in, but I can already tell they have better bass than the other tubes. It could just be batch variation, or it could be because they are of older production (16 years older than the tubes they replaced).
If anyone is looking for a hint more bass from their amp, try the 1974 Reflector tubes. They really are more bassy, at least to my ears.
Also bought some Reflector tubes. My first tube roll. Haven´t done any real comparison to the old but after a heavy start with big imbalance it has automagically solved itself???
At first fresh out of the box it measured over 3 db difference on two different headphones and it was clearly audible and repeatable by changing the left and right driver tubes. However now I don´t detect anything and my SPL metre suggest then less then 1db if anything at all. Hope it stays this way. They look identical to the Sovtek tubes and appear to use the exact same material and parts. Lettering is different and the pins not being quite as shiney. Make you wonder if you been scammed but I guess there is no point scamming on cheap tubes like this. I suppose Sovteks bought the reflectors factory and blueprints?
Waiting for a Brimar rectifier next :)