Tubes for Marshall Bluesbreaker RI

Speaking from experience, you might as well just buy yourself a set of Mullards and be done with it. If you don't get them right away, you'll always be thinking "What would it sound like if ....." If cash flow is a problem, get at least 1 good one for V1. I personally also really like the Brimar CV 4004s and I know a bunch of Marshall fanatics who like the Brimars as well as, if not more than, Mullards.
I also like the Mullard CV 4004s that have an extended high and low frequency range. I bought a couple from Upscale Audio for $65 each (their preferred stock grade) and really dig them in my Marshall and an old 18 watt Magnatone. I also use NOS RFTs, an East Germany made tube that goes into distortion sooner than a Mullard and has a very fat tone.

 

In terms of bang for your buck, changing the pre-amp tubes to Mullards will make a great difference - go for it.

 

The Mullards are really good in the pre. I`m using the Valve Arts KT66`s too and really like them. I just bought some Mullard KT66`s too, so I`ll let you know how they sound when they get here. I also put an OEI Plexi 50watt OPT in, and it`s a bit more aggresive sounding. I also had Rob at Trutone make me a deeper cab with only a porthole back, so it punches like a SOB. I also did all the mods here: http://www.raw-sewage.net/jtm45ri_mods.html
And the final touch was the Weber Alnico Blue Dogs with light doping to prevent cone cry. Great amp to mod to however you like it. Good luck!

 

Food for thought on this subject...
I've recently gotten a rash of these in for upgrades, complete with all the component changes, and OT changes and varying stages of this whole process.
The most interesting one belong's to one of the top player's here in the city. As with most amps he uses, he wants to change things to suit his needs. (I'm all for that!) Probably no less than 100 misc. amps later. (Fender's, Mig's, Sovtek's, HK's and numerous other companies). He finally got one of the Marshall BB RI's.

He came to me with the usual request's, (only this time they were actually feasible) but the direction the amp took is actually way different than what most are doing.

After a considerable amount of time and effort, and the usual OT swaps, tube swaps and then back, etc...
It ended up with EL34's, and modded the first input to resemble the 1959 design using a .68uf cap and the 2.7k cathode components for the V1b. All of this with the original transformers and minimal component changes.
Changed the mix resistors to 270k, as usual, and the amp really took on what I remember the BB to sound like. (Of course, 17yrs later, that recollection may have faded slighly).

FWIW, he's happy! (still would have been simpler just to get a Plexi, but whatever..)

The thing is, none of the other BB RI's I've done really sounded like this, with all the component changes done. They weren't bad, just different from what I remember it sounding like. ( the original one I had, that is..)

just FWIW,

Jeff Seal