Crucial TUBE question

@dogearedaudio,

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.

I don't know what it is that makes power tubes in the rectifier position have such a big bold sound. I have a unit that can use power tubes in the rectifier position, it just plugs into a 5ar4 rectifier socket.

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. ;-)

Also, it's likely that a schematic wouldn't indicate that pin 7 is used as a tie point, so you'd still be scratching your head. ;-)