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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
rodman99999
5,988 posts
 
Have you ever tried the Mullard(Blackburn factory) GZ34(NOS, of course)? Long life and they deliver excellent sonics.
bradf's avatar
bradf
324 posts
 
I replaced the stock rectifier tubes in both my Primaluna PL3 and PL8
with the Phillips 5R4GYS. I would say the improvement was significant.
I bought the Phillips from Upscale at the time for $40.00 Ea. They have since increased in price over time, and currently run $110.00 - $115.00 each. I liked the tube so well, I purchased NOS spares thru E-Bay for a considerable savings. There are a few international sellers that have them. There not hard to find internationally. Of course there are pros and cons of purchasing from Kevin and Internationally.  I was also recommended by rodmann99999 to try the GZ34. I search for quite some time before I gave it up. All I could ever find were sellers claiming there used tubes tested like new and I wasn't going to settle for anything other then new.  If you can find them (and can afford them) I would jump on the GZ34 Mullard (Blackburn factory) GZ34(NOS, of course). I had a Woo H/phone amp that the power supply used a B274 Mesh. There was a significance difference between the 274 and the Russian rec. tube supplied with the amp. Never used one in the Primaluna. I wasn't able to find enough info to satisfy me that they were usable with the Prima Equip. 
I included a couple of links below to Vendors on E-Bay selling Phillips Rec. Tubes. Also found a vendor from England that has several Blackburn NOS GZ34. Not a bad price considering the recent increase in value of the US dollar. You may want to get these, you don't see NOS Blackburn Mullards come up very offend now days.


http://www.ebay.com/itm/NOS-PHILIPS-5R4GYS-5R4GY-Military-rectifier-Single-tube-Original-new-box/322...


http://www.ebay.com/itm/Philips-5R4GYS-5R4GY-rectifier-CV717-Dutch-army-tube-NOS-same-datecode-/2015...

http://www.ebay.com/itm/GZ34-MULLARD-5AR4-F32-B5C2-BLACKBURN-NEW-OLD-STOCK-VALVE-TUBE-O15C-/39129999...~
t-bon3's avatar
t-bon3 OP
15 posts
 
Outstanding information!  Thank you very much!
mhwalker's avatar
mhwalker
18 posts
 

Like t-bon3, I am new to the wonderful world of tubes and am also learning fast.

 

Regarding rectifier tubes, from what I’ve been able to piece together after significant research on the ‘net, is that the sonic differences between rectifiers is mostly caused by the “voltage drop” of each different tube model/design. This voltage drop is called “sag”. Apparently, under peek demands, some rectifiers will “sag” more than others, and this impacts how the rest of the amp performs with this brief drop in voltage from the rectifier tubes. From what I’ve found online, the 5AR4 / GZ34 family of tubes has the least amount of voltage drop, whereas the 5R4 family have the most (yet, many listeners prefer rectifiers with larger voltage drops – go figure):

 

Rectifier Tube Voltage Drop Chart:

 

http://www.300guitars.com/articles/rectifier-tube-voltage-drop-chart/

 

http://www.fourwater.com/files/fullrect.txt

 

From there, the story gets a little cloudy as to exactly what sonic differences are created between different rectifiers, and of course, how each one will perform in different circuit designs, with other pre and driver tubes, with your particular speakers, and your personal taste. Enter the ubiquitous “YMMV”.

 

I found a great article that describes the basics of how rectifiers work on the “Guitar Player” website:

 

http://www.guitarplayer.com/miscellaneous/1139/all-about-rectifiers/16429

 

Lastly, I’m not ashamed to admit, those “mesh plate” rectifiers like the Sophia 274B’s that t-bon3 mentioned (along with others), are darned seductive just to look at, and I’m considering installing a pair in my Cary SLI-80 just for their looks alone regardless of their impact on the sound [as I duck to avoid things being thrown in my direction ;-) ].

 

 

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