I've been down the Mullard road & haven't liked them any any of three different pieces (CDP, preamp, & an integrated) they've been in. One of the pieces is a Jolida 100. Too soft, mushy, & slow...the tubes, that is.
One nice tube in the Jolida 100 is the Sylvania (JHS or JAN) 5751 NOS. Refined & clean on the top with good bass. I think tube depot has them at a fair price. Also give tube depots Tung Sol gold pins a look. I haven't tied them, but heard they are worth a look. I ran a pair of Raytheon 5751 3-mica black plates for a couple years & they are VERY nice. Clean on top with plenty of well defined bass on the bottom. When I bought them they were considered one of many 5751's worth a try (I liked them better than the GE or RCA 3 mica that was the rage then). I had one of the Raytheon's blow recently & went to look for another set....the world woke up & now the Raytheon is a HIGHLY sought after tube...and they are basically gone from most dealers. When you do find them they are pretty pricey. I ran a pair of cryo'd EI 12ax7's until the last few weeks. Very nice tube for a current production model. I'm now running a pair of Amperex 12ax7's (about 1967 vintage from Heeren) and like them the best over what I've mentioned here. They may not be as punchy in the bass as the Raytheon's but the mids & highs are extremely refined. A pleasure to listen to. The Sylvania 5751's are very close to the Amperex tubes, you'll have to really listen to tell them apart, on the top end at least. I'd expect Amperex bugle boys to be very similar. I have at least one more set of tubes I'd like to try..if they pan out I'll report back.
FWIW...keep your eyes open on the Telefunkens. From what I've been reading (and seeing) there are a ton of Teles being dumped on the market from eastern EU that are not the match of the older Teles that made their reputation initially.
