Using a 5Y3, your B+ voltage to the output tubes probably drop around 40V DC more compared to the GZ34. (This is assuming about 140mA at idle from the B+ Plate supply.) The amp is rated at around 16 Watts per channel as designed (w/ GZ34). So you are probably only losing a watt or two when using the 5Y3. With that said, you will be hard pressed to hear any difference when operating within the normal region of the amplifier.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
If you are really pushing the amplifier, so you get some compression on the transients, that is where you may hear some difference.
- To try and hear a difference, start with the GZ34 in the circuit. Turn the amp up to the point where you just start to hear the compression/distortion. Then turn it down just a tad to the point where the amp sounds clean again.
- Now, leaving your levels the same, turn off the amp, let it cool down, and then swap out the GZ34 for the 5Y3. Turn the amp back on, and give it a listen.
For Hi-Fi amps, you will probably never hear a real difference during normal operating conditions (with a self bias/cathode bias circuit). When dealing with guitar amps, etc... where their normal operating conditions are pushing the amps well into the non-linear region, and you actually send the output tubes into saturation, the difference between rectifier tubes can be fairly obvious.
Also, is you are running a fixed or adjustable biased amp, the drop in B+ voltage may require you to re-bias the output tubes. Before the re-bias, you may be running the tubes colder (less bias current) than before. In this case, you may be able to hear an increase in distortion. But once the tubes are biased properly, there will probably no audible difference between rectifier tubes.
For replacement tubes, you may have a hard time finding anything other than Groove Tubes in Indy. You might find some Fender or Mesa branded tubes too. I have always ordered new tubes online. I have had good luck with Triode Electronics (http://www.triodeelectronics.com/), Tube depot (http://www.tubedepot.com), and Antique Electronic Supply (http://www.tubedepot.com). Around $14 for a JJ 5AR4. Kevin Silva at Uncle Alberts may carry a variety of tubes, but I'm not sure about that.
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