Hi Andy, Your Tweaker will have Ruby's in it because both are made in China and because it was the best tube available to them. Ruby's have a reputation as a gainy valve and as a result they are also known as being noisy and have a problem as they age with microphonics. JJ's are your best bet as a good replacment, they work very well in rocky sounding amps with tight lows and clean strong mids and will be more reliable than the Rubys. JJ's are made in the Czech Republic so are readily available and cheep in the UK. You can get very giddy about valves, but if you can not find the valve you want or your best valve is susceptable to duff batches!. My Renegade came with Ruby's and were noisy and were changed for a full set of JJ's first thing. If you change your valves, your preamp valves V2and V3 need to be "phase tested" that just means that both sides of the valve is working at the same strength and will be twice the cost. the valve in the V1 position can just be a cheep factory tested one. your power valves need to be a "pair". I've been using JJ's for years and never had a duff one.
