Substitute 5V4G tube for 5AR4 tube


I have mostly PrimaLuna equipment, I.E. Prologue 3, 5, and 8
The diode tubes in the Prologue 3 and 8 are 5AR4 tubes (Chinese). I would like to know what sonic changes others may have found by substituting either 5V4G or 5Y3 in place of the 5AR4 diode tube. The 5V4G tubes I am considering are NOS RCA's. All signal tubes, 12AU7 and 12AX7 are Tungsram.
I have rotated RCA cleartops and BB's and still go back to the Tungsgram tubes, although I recently aquired some 12AU7 Slyvaina Gold Brand triple mica, extra rod, that I am experimenting with. I need more time to see which unit they may sound best in, but I did get as far as pluging them into the cd player and noticed right away a focused, stronger base.
128x128bradf
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Thank You very much Viridian. You have been very informative. I will probably look further into the 5963 and 6680 tubes.
The owners manual of the referenced components states that the 5V4G tube can be used in place of the 5AR4 tube but to expect sonic differences. If your interested you can review said owners manuals by going to www.upscaleaudio.com. You will find a special section on there web site for PrimaLuna components, including the manuals.
Thanks again for your help.
Brad
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While the 5V4 and 5AR4 can be interchanged in your circuit; you'll find the 5V4 less dynamic. A NOS Mullard(Blackburn Plant) 5AR4 will provide long life, dynamics, and a clean/smooth presentation(no sacrifices). ie: (http://cgi.ebay.com/MULLARD-GZ34-5AR4-CV1377-rectifier-tube-NOSNIB-/270598619300?cmd=ViewItem&pt=Vintage_Electronics_R2&hash=item3f00ef40a4) Many others on eBay as well.