Rolling Mullard 6DJ8 into GE 5670 Application

I would ask the manufacturer or the distributor before I would ask here. I recently considered a different brand tube DAC that ran the same tube. I searched on line and saw the adapter and the recommended 5670 replacement tube. In my situation the E88CC was not compatible nor was the 6DJ8. Also in rolling that value tube ( I have a significant stash of nos ), the Mullard was dark and veiled and not to my liking. I realize YMMV , but I had better results with Tekefunken, Siemens CCA, Tungsram, and Tesla. Even the better Russian tubes beat the Mullard. I have dabbled with Rogue gear and they recommend Mullard, but it’s generally used to tame a harsh sound. Although the premium NOS Mullards are well received. But I’d really verify compatibility as I guess it’s not. Also in searching that topic the Westinghouse did seem to be the most poplar substitute. And the price is reasonable. Finding and buying premium medical grade Telefunkens is expensive and ugly these days. I worship my black coated G73-R’s . And I really do like Mullards for a rectifier or power tube. Happy Listening, Mike B. 

Based on the additional info it sounds like you’re on the right path. My system tends to be bright and I’ve avoided any silver in my interconnects to correct that problem. The tube “ Sound “ description on the Brent Jesse site is extremely accurate. My pre uses 12AU7’s and the sonic change is very similar to the E88CC change in my power amp. I was fortunate enough to be in your position some years back and nos tubes were not at astronomical prices. My experience with the German tubes is an improvement across the entire spectrum and that appealed to me. It has also been a plus to have a selection to roll with. I recently tried some KT 150’s for the first time and after some break in, wasn’t feeling it. So I rolled in the hottest rectifier tube I had ( a Mullard ). Now I had too much bass , so I changed the E88CC from a Tekefunken to Amperex to bump up the treble. In retrospect I’ve managed to be able to really tune my systems sound by tube rolling, but like stated above I acquired a bunch of tubes. It’s been a pricey but fun experience. Unfortunately I’ve had to attend Tube Addicts Anonymous after my wife saw my credit card charges. 😆 But seriously, Happy Hunting and good luck, Mike.