Rectifier Tube question

[MacLoud]

Hi Gentlemen

Sorry if this a silly question but what will be the result of putting a GZ34 (5AR4) rectifier tube in a 5E3 clone (mojo) instead of the existing 5Y3. Will it result in more power or headroom?

Thanks

Delta macLoud

[pdf64]

Should do both, but will probably put the 6V6s over 100% plate dissipation. Increasing the cathode resistor to reduce dissipation will cause crossover distortion at high signal levels. Leo generally took things to the max and then some, one step beyond him is a step too far, by and large. Peter.

[cminor9]

I have a bit of experience with this. Short answer is yes you can, provided you upgrade some other components.

All the caps rated for 25v, up them to 50v. Increase your cathode resistor to something like 330 or even higher. If you're gonna run it full tilt, I'll bet you'll put out over 15 watts. So if you have a 15 watt speaker, beware. That last bit I am not sure about, though. I'd imagine more power in = more power out, but then again I am still kind of new at this. All I know is that my B+ was about 60V higher than spec. Since that was about 18% over spec, I'll bet that means 18% over 15W.

Long story, but I got a 5Y3 that was actually a mislabeled GZ32 according to one guy on this forum (http://music-electronics-forum.com/s...ead.php?t=7092) When I measured the voltages in my 5E3 clone, they were way over spec. I couldn't figure out why my amp had so much headroom. Wrong recto, duh!

I got the right recto, but kept the "wrong" one. I upped the 25-25 caps to 25-50 and can now run a hotter recto if I ever need the extra headroom. I also upped the value of the cathode resistor to something like 330ohm. Anyhow, having the option to switch a recto for more headroom really seemed like a good idea. With the fake "5Y3", the general character of the amp is the same, except that the breakup start to occur at a higher volume.

All that said, I never use it. The 5E3 with a 5Y3 is loud enough and then some for my band. I take the other recto to all gigs just in case. But if you want the extra headroom...you can upgrade a few parts and make it work. Unless Enzo comes on here and tells you I am wrong, of course.

[tubeswell]

5Y3GT gives a B+ in VDC about 1.1 x one side of the VAC HT winding and supplies 120mA - requires 5V 1.9A rect winding

5AR4 gives a B+ in VDC about 1.3 x one side of the VAC HT winding and supplies 250mA - requires 5V 2A rect winding

As the others have said, higher B+ with 5AR4 means you possibly need to change some of your cap ratings and output stage bias, and once all this is said and done you might be better off running beefier output tubes (depending of course on what particular output tubes you already have in there and what B+ and tube current you end up with)

[calis]

If you're gonna run it full tilt, I'll bet you'll put out over 15 watts.

Just a quick side note... Despite a change in rectifier tube, the amp should put out more than 15 watts when dimed. Generally, amplifiers are rated at X number of watts when the amplifier is running clean. When dimed and pushed over the edge into power tube distortion, the amplifier is putting out more than it's rated wattage. So, despite a change in rectifier tube, I would not recommend using a 15 watt speaker with a 15 watt amp if you are going to dime it.

[MacLoud]

Hi Gentlemen

Thank you all for your replies.

MacLoud