Tube life in preamp. Please help

The ARC SP9 series of preamps do NOT have your typical "standby" mode that some preamps have. Most "standby" modes reduce the voltage to the tube(s) and only keep the heater warm.

The SP9 preamp has only an on & off and a mute & operate toggle switch. The mute switch just mutes the output, but keeps full current to the tubes.

I agree with everyone above, if the SP9 had a real standby circuit, but it doesn't. I turn my SP9MKII on 30-45 minutes before I'm really ready to use it, then it takes an additional 30 minutes or so to warm up to full potential.

If even you keep it on full time, the tubes should last 5000-10,000 hours so you would need to replace them once a year or so.

"I liked the original MKI and the MKIII best. I did not like the MKII."

I was an ARC dealer for many years and have personally owned about a dozen different SP9 preamps. I keep going back to this unit because it really is a great preamp. I know others disagree, but I've had a massive amount of experience with these units and still find them wonderful.

I've had (2) MKI, (7) MKII and (3) MKIII.

IMHO, the MKII is the best. Just personal taste, but it seems to provide the best mix.