Tube swapping question

[trumpus]

I just recieved a new set of preamp tubes and tube rectifier for my SF Vibrolux Reverb. I am planning on having the amp biased and new power tubes installed as well (next week). Is it ok if I put the new preamp tubes in now, before the power tubes are replaced (and amp biased).

On Mike's site he mentions that the PI should be changed whenever the power tubes are changed - is it ok to put a new PI in but NOT new power tubes (yet)?

Finally, the amp calls for a 5U4GB rectifier, but the previous owner has a 5AR4/GZ34 installed right now - is it ok for me to install my NOS RCA 5U4GB without having anything else done to the amp (ie new power tubes, biased, etc)?

I've got a box full of new/NOS tubes and i'm itching to install 'em! Please let me know what you think.

Brian

[rockon1]

You can swap out any of the 12AX7's including the PI to your hearts content without worry. Not sure about the retifier. It may mess with the voltage /biasing . Bob

[trumpus]

Anyone know about the rectifier?

[slider313]

If the amp was biased with a GZ43/5AR4 and you put in the 5U4, your B+ will drop and the tubes will be biased cooler or cold depending the setting.

[trumpus]

Thanks man! I'll hold off for a bit.

Brian

[devbro]

The whole PI relationship to power tubes thing might be voodoo science. I've read pro's and con's about the importance of buying a matched PI tube and replacing whenever you replace power tubes but can hear no difference (at least with my untrained ears) either way. In fact, some say that a slight mismatch adds to the "swirl" effect of the amp and adds character. Again, could be an urban legend and gigabytes have been written on the subject here and elsewhere.