A 5AR4/GZ34 tube rectifier (stock on Sunns with tube rectifiers) will take a little while to warm up itself, so if you don't use the standby, it still won't hit the tubes with full power. A solid state rectifier or a 5U4 warms up immediately (ss) or fast (5U4) so you should always use your standby switch and give it at least 5 minutes. The tube hi-fi amps with no standby have controlled warm up circuits, it's not the same as just turning on a guitar amp with the standby switch in the on position.
I mention the 5U4 because a couple of people have posted about picking up a used 1960s Sunn that had a 5AR4 stock and found a 5U4GB had been installed by the previous owner. It seems to work OK, might even be a good idea if you have high line voltage.
I still stand by what I said earlier.......guitar amps don't
NEED a standby, and there are others who agree with me who are quite well known.
For example:
Q: Can I get the bias voltage to remain on the tubes when my Power Scaled amp is on standby?
A: Standby (SB) switches are not really needed on guitar amps, but your question brings up two points. One, is that in the Power Scaled amp the bias voltage tracks actual screen voltage. If Vs disappears, then -Vb disappears, too, unless the standby switch is wired according to the PSK notes. These notes suggest using the SB to interrupt the voltage feed to the tube screen element - and preferably to ground the screen during standby - while the voltage feeding this switch is tracked by the bias regulator. The second point is that the SB can be used to create a "bias standby". In this circuit, the raw bias supply must be very high - at least -80V in most amps. Most amps do not have this much bias voltage available, but an easy mod will fix that: either adjust the stock supply or add an auxiliary bias transformer as shown in The Ultimate Tone Vol. 5 (TUT5). The SB is simply wired across the pass element of the bias regulator. The 'operate' position has the switch open and the bias tracks as it should. In standby, the regulator is bypassed and the full -80V is applied to the tubes, turning them off.
That is from the FAQ on Kevin O' Connor's website. He goes into much more detail in his books.
That said, it certainly doesn't hurt if a standby switch is on the amp, but 5 minutes is a little excessive if you are doing that to avoid cathode stripping. My 5E3 Fender Deluxe that I mentioned earlier does not have a standby switch and uses a 5Y3 rectifier, which is a directly heated type, and these type supply B+ voltage pretty quickly, yet Fender never warned anyone to avoid using the amp for fear of problems. Moreover, the tubes last a long time in the amp too, even with hard use. Standby switches are handy for stage use and the amp will probably sound and perform better when the tubes are at operating temps, but if your main worry about using a standby switch or not, and how long to leave it on standby, is because you are worried about cathode stripping, then you don't really have to worry about it.
Greg
