[sounddog]

I'm hoping someone out there can help me choose a 5AR4 (or 5U4GB) rectifier tube to roll in my Modwright LS100. I have a 1960s NOS Amperex black base, but have the itch to look for something better. I've read some people rave about the Mullard metal base, but even I, as crazy as I can get chasing better sound, have to gulp many times before contemplating shelling out the $400-$500 those tubes now cost (let alone ever telling my wife!). I've also read that the Phillips/Mullard brown base (which may be labeled as CV1377) may be almost as good but at a much lower cost (though still not cheap - maybe $150-200). Finally, I read a reviewer say that the RCA 5U4G is a very good and inexpensive tube, but I think the LS100 would only accommodate the RCA 5U4GB (around $50).

BTW I'm using NOS RCA 6SN7 tubes in my LS100 and really like them a lot; just a bit of liquid warmth but without losing any details.

So, has anyone heard the Mullard metal base, the Phillips/Mullard brown base, or the RCA 5U4GB, either in the LS100 or any other model? And has anyone been able to compare any of those tubes to the NOS Amperex/Mullard black base?

Thanks for any help!

[toddc2]

I had a nice Mullard GZ34 (1965) installed in my LS100. I had a chance to listen to the much more expensive Mullard metal base and honestly couldn't hear a difference.

I agree with your love of RCA signal tubes. I really liked the red base RCA's and the military 1940's variant but struggled to get a quiet pair.

[S Clark]

Check out the Sylvania fat boy.  Not as cheap as they once were,, but nothing is.

[danabunner]

I own about 10 5U4GB, 274B, and GZ34 rectifiers.   I cannot hear any difference between any of the 5U4GB & 274B tubes.  Even between rare, expensive NOS vs common $10 vintage 5U4GBs.   A subtle difference when switching to my GZ34 tubes.   As this tubes convert voltage, as long as they are operating to specifications there really isn't much difference within a type.  Unlike your other tubes, through which the audio signal is passing.  I know some people claim to hear differences, but most of the tube equipment owners I know profess that they don't hear them.   

I definitely hear differences between different 6SN7 tubes.   I've spent a lot of time comparing them. 

[RPM123]

You can always ask Dan at MW to find out what he thinks. The 6SN7's probsably have a more noticeable impact than the rectifier tubes. However, the metal base tubes are supposed to have a vey long life span - some 10,000 hours or more. PM if you are interested, as I may have some tubes for your LS 100.

[sounddog]

Thanks for your comments. I have only tried 2 rectifiers in the LS100 thus far and did hear some differences in sound (though not big differences, like those I've heard with different signal tubes). I will follow up on some of your suggestions. RPM123, I've sent you a PM.