5y3 GT in 6G2 Princeton

[distorto]

Hello,

I have a 1964 Princeton (transitional white knob model) and it has a 5AR4 rectifyer in it. Shouldn't it be a 5Y3 GT? Can I use one in this amp safely?

Thanks

[Rob Mercure]

While the Princeton came with the 5Y3 the 5AR4 won't hurt anything and will give you a slightly "hotter" B+ voltage. I guess if you amp hasn't had the filter caps replaced - and it should at that age - then the higher voltage that the GZ34 produces (lower voltage drop across the rectifier to be more exact) will add to their eventual demise. And it does stress the output tube a tad more. But with good condition filters it really shouldn't hurt (unless it's a Chinese GZ34 which are known trouble makers - after all the Chinese invented fireworks and they still put great arrangements into their rectifiers).

Rob

[distorto]

Thanks for that,

The 5AR4 is a NOS USA tube. All caps etc are a-ok. What I really want to do is replace the 5AR4 with a 5Y3 GT and was wondering if it's ok to do. I poked around further and found that it should be alright. I think the amp is a little stiff with the 5AR4 and was hoping to loosen it up a tad. While it sounds pretty good as is, it doesn't quite have the growl that I recall from the brown 6G2s I've played. The tremolo on this thing ROCKS by the way.

Thanks again for the info

Chris

[Amp Kat]

Power tubes and preamp tubes have lots to say about the old blackface amp tones. I worked on some amps (Fender,Vox,Gibson) that still had old blackplate and original parts and they sounded unbelievable and had beautiful tone unlike anything with todays current production tubes could produce.

[distorto]

The Princeton has RCA 6V6s as well as RCA preamp tubes. I was just wondering if it was safe to stick a 5Y3 GT in it to see if that gives me a tad less "tightness" to the overall sound.

[Amp Kat]

No problem sticking the 5Y3 in there at all and it should loosen it up a tad especially at higher volumes or more compressed if you want to say. Those are nice tubes in it so it should sound pretty hot with the 5Y3.

[distorto]

Thanks for all the info so far.

So I popped a 5Y3 (borrowed from my Tweed Champ) in the Princeton and it gave me exactly what I was looking for. It has a little less volume but is a lot more smooth and dynamic and gets nice and crunchy at 7 and above. I ordered a NOS 5Y3 for it.

I bought this amp about 12 years ago and It always had the 5AR4 in it. I just recently discovered that the schematic called for a 5Y3. My question is: do I need to re-bias the amp for the 5Y3? I had the amp serviced about 3 years ago from a reputable tech. They replaced some noisy resistors and put a 3 prong cord on it. They said everything else looked great. So I'm guessing they checked the bias with the 5AR4.

Is this something I need to think about?

Thanks again for all your help.

Chris

[MWJB]

"I bought this amp about 12 years ago and It always had the 5AR4 in it. I just recently discovered that the schematic called for a 5Y3." Late model 6G2s came from the factory with a GZ34/5AR4, Fender just never updated the schematic...it's pretty common for amps to have been updated but the schematic to not have been redrawn/altered.

If the amp has worked fine with the GZ34 and you're getting reasonable tube life then it is not really necessary to rebias for the 5Y3 AS LONG AS YOU LIKE THE SOUND. I guess since it's giving you "everything you were looking for", that you do.

It's more likely that the GZ34 was causing high plate current, which will come down some with the 5Y3.

[distorto]

Thanks for that. I can't recall how long those 6V6 tubes were in there (Sylvania and not RCA as I previously stated) They've been in there at least 3 years maybe even considerably longer.

I do like the sound a lot. Like I've said, Ive had this thing for over 10 years and while it never sounded bad, I always kind of wondered why it didn't sound quite like the brown Princetons I've played. I always kind of attributed it to the fact the most of the browns I've played had Oxford speakers (mine has the original ceramic Jensen) but after dorking around with amps and browsing the wealth of info here I believe I found why.

It's like havin a new (old) amp.

Thanks again!

[distorto]

"Late model 6G2s came from the factory with a GZ34/5AR4, Fender just never updated the schematic...it's pretty common for amps to have been updated but the schematic to not have been redrawn/altered"

Interesting. The tube chart in my amp is torn on the left side so I can't read what they have listed for the rect. tube. The GZ34/5AR4 that is in the amp is a brown base GE. It's nice to have the extra clean headroom it gives available to me but for now I'm totally digging the warm grit from the 5y3.