2. amps-preamps
  3. 119835-68004

Swapping 5AR4 rectifier for 274B in a PrimaLuna Preamp

Long time lurker, first time poster.
I have recently acquired a PrimaLuna Dialogue Three preamp.  (not the new 'premium' preamp, the original Dialogue Three)  It's a fantastic unit and sounds incredible.  I've achieved some very nice results tube rolling some of the other components I own(ed).  I am contemplating switching the OEM 5AR4 rectifiers with a pair of mesh plate 274B's from Sophia Electric.  
http://www.sophiaelectric.com/pages/se/274b.htm   
While allegedly pin compatible, I understand the life of the rectifier might run short.  To quote Sophia Electric's site:
"The 274B is direct heating tube. The indirect heating 5AR4 may turn on slower, however, people who buy 274B is for its superior sonic performance. To fully utilize its benefits, it may require first stage capacitor (capacitor input) to be less than 10MFD, or would shorten the 274B life span (very much like smoking is bad for your health). It would not be a problem with common choke input. Please consult to your amplifier maker or refer to a tube manual.
The maximum current capability for Sophia Electric 274B mesh plate tube is 90ma, suitable for tube pre-amp. "   

I was hooked on the SE 274B when I saw that Woo Audio was offering the 274B as an upgrade to their WA6 headphone amplifier.   Further research turned up a couple of great reviews for the tube in other amplifier and preamp applications.

PrimaLuna / Upscale Audio have given great recommendations for the Phillips 5R4GYS in my preamp.  In all probability I'll find myself buying & trying both and selling whatever comes in 2nd place.  

I'm pretty new to the tube game, but learning fast. 
I would welcome the opinions of those with more experience and finely tuned ears.  


128x128t-bon3
analogluvr
800 posts
 
Sophia tubes have reliability problems and I would stay away if I were you. I've blown about 4 tubes in my life and they were all sophia. 
t-bon3's avatar
t-bon3 OP
15 posts
 
I phoned Upscale Audio and spoke to Kevin Deal. He made a compelling argument for the Phillips 5R4GYS, particularly in the Prima Luna Dialog preamp. I placed an order and should have a pair soon.

Thanks to all who responded - you gave me some great advice.
aolmrd1241
759 posts
 
t-bon3,let us know how you like the Upscale Phillips 5R4GYS  tubes when you get a chance...

bradf's avatar
bradf
288 posts
 
Can you please advise Kevin's technical reasoning for the above recommendation, i.e. why better specifically for the PL, and advantages / disadvantages over the Blackburn GZ34. I would be interested in learning the technology.
t-bon3's avatar
t-bon3 OP
15 posts
 
bradf - I am sure Kevin would be willing to explain his recommendation to you.

My 5R4GYS tubes arrived this weekend.   I swapped one channel so that I could compare the OEM PrimaLune 5AR4 tube on one channel to the 5R4GYS on the other.  I liked what I heard.  

I'm not a Audio journalist so my vocabulary is somewhat limited; however I can give you a concrete example of the difference the tube swap made.

A few weeks ago, I was listening to Sarah Mclachlan's "Surfacing" album - a 180gr Music on Vinyl release.  I wasn't satisfied with the separation I head on a few of the tracks.  It seemed like the vocals were lost in the instruments - the vocals should have stood clearly apart and airy against the music.

When I swapped tubes and listened to the same album and the same tracks - the "veil"  that I felt covered the vocals was gone.  I got the sense of space and separation that I was chasing.  

It was a pretty significant change, not subtle at all.  Even a neophyte audiophile like myself could hear the difference.

I can't say how they compare against something like the Mullard GZ34.
More to discover