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...~
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...~