GZ32 Rectifier Tube in a JTM45?

[DNeafsey]

Its been a while since I have been around here. I just scored some cool NOS tubes. In the batch is a perfect never used GZ32. Is this tube a pop in replacement, or would I need to make changes. From what I understand, the GZ32 simply drops the voltage in the amp a bit, is that correct?

Thanks for your input.

Dan

[demonufo]

Yes and no.
It also has lower current delivery at higher voltages.

[DNeafsey]

What do you think that would do the amp? Would it have any negative effect on the PT? I thought I read somewhere that this tube will give you more breakup at a lower vol but I can't remember if it was reliable source or not. If it increases the voltage that may not be so good for my preamp tubes right?

[demonufo]

It's not going to hurt the PT or increase the voltage at any time, it's just that at higher voltages the current is more limited than with the GZ32. This may end up sounding a little mushy when cranked. Or maybe really mushy. I've never tried a GZ32 in a guitar amp as yet. Used to have a nice set of Quad II's though and briefly tried GZ34's in them, but not for long, since I was assured the GZ34's would push the power transformer over the edge, since they were pretty much on their limits.
Did notice things seemed a little tighter with the GZ34's though. Don't ask me the brands though, I wasn't all that savvy back then.

[EFK]

I use GZ32 in place of 5V4 in a number of old Supros (50s) and in a number of circuits derived from these amps that I've come up with. Think of the GZ32 as a 'pumped up' 5V4: it drops around 10 more volts at idle vs. GZ34, but it has much more sag as these tubes are meant for lower voltage/lower current. I use GZ32 over a 5V4 when you have a bigger input capacitor, as 5V4 specs 10uF max (although you can get away with around 20-22uf most of the time) but GZ32 allows for more. It will definitely give you a saggier, browner amp. One thing to consider - these tubes are supposedly much more sensitive to hot-switching than a GZ34, and a JTM45 is basically the definition of hot switching if you use the standby switch. There is a reason a lot of those old amps were built without standby switches, and being as 5V4/GZ32 are indirectly heated, you don;t need them anyway as by the time the tube starts conducting, the filaments will already be heated anyway.