If you want the best possible rectifier for your PrimaLuna, then spring for a pair of vintage NOS Mullard GZ34s. The price may seem off-putting, but they will literally last a lifetime in that preamp, and offer the best possible sound, IMO. For maybe $500 you will get a $2K upgrade in the sound of the preamp. No modern GZ34, and I mean NONE, even remotely compares to the quality of a NOS Mullard.
Crucial TUBE question
I placed a KT 150 power tube into a Prima Luna Evo 300 preamp rectifier slot. I know. But what happened was surprising. The sound was, well, magnificent glorious. Nothing burned out. No smoke. No arc lights. I asked Upscale Audio to advise me as to what damage I may have done or could have done to the PL. They only said they would not advise placing anything but the original tubes in the slot. They would not commit to whether or not that power tube could be used in place of a rectifier to tube. So, is it an absolute or not? If so, why? I’d appreciate feedback (please, no slams) from anyone having any experience with this. Thanks!
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Just checked-out what’s available for NOS GZs. You’re right, they fetch a hefty price. I’l l just put it out there that since I can’t use them, I’m willing to do a straight swap of the essentially brand new Tung-Sol KT-150s (cryo/matched), for a pair of used good matched and balanced pair of the NOS GZ34s. |
Sounds like @dogearedaudio found the connection between pins 7 and 8 that allowed it to work. I also agree with his recommendation of the Mullard GZ34. Jerry |
I wish I were smart enough to know how the filament voltage made it through the diode to power the filaments, but I'm not. ;-) It worked somehow. "I don't know what it is that makes power tubes in the rectifier position have such a big bold sound." Well, you're only getting a half-wave supply (one diode) as opposed to a full-wave supply (two diodes in the 5AR4). It would be noisier, but if there's anough filtering it would work, I supposed. Also reduced voltage at the output, which would change the sound. Mainly, though, I'm having trouble imagining why a manufacturer would suggest, or even allow, replacing a twin-diode rectifier with a single-plate power tube, unless it were a 6080 or similar twin-plate regulator tube. Another possibility is that the unit uses SS diodes and the tube rectifier is just a buffer to provide a slower turn-on. In that case I guess a power tube could work. But most power tubes aren't designed the handle the amount current that rectifiers can. So it seems like a risky thing to me. ;-) |
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