tubed preamp off and ss amp left on?


Why can't I leave my my ss amp turned on with the tubed preamp turned off? Loud hum occurs through speakers with this condition. When I had a ss preamp I could leave the amp powered all the time with the pre off. I would leave all powered up but concerned about the preamp tubes wearing prematurely. Is it a reasonable conclusion that I could leave everything powered on all the time and just change the tubes once per year?
twc
I don't know what your problem is but I leave my amp on 24/7 and turn my pre off with no problems.ARCLS26 and 300.2 amp. Don't leave your tube pre on 24/7.Along with burning out the tubes it could present a hazard.
It might be helpful to know what equipment you have, including cables. I have a Belles 21A tube/hybrid pre with a Belles Reference 150A SS power amp and I leave my power amp on and turn off my pre and never have had a hum.
I would not leave a tubed pre on 24/7 and only leave the amp on when you are going to be around it and in general not over night. I do on occasion leave my ss amp on overnight but as a general rule I turn it off. Having said that you should not get a loud hum when leaving the amp on with the pre-amp off. For qualifiers I have a cj tubed pre amp and cj ss amp.

If the preamp has a mute feature, switch the preamp to mute before you shut it down. See if that helps.

Otherwise you best turn off the power amp first then shut down the preamp.
Hm, some say that turning tubepre off and on is what kills the tubes prematurely.... preamps differ significantly in regards to how long their tubes last, where some reportedly should be turned off, others not. Knowing what your preamp is might help with answers. My tubes have been on for a year, and going strong (ECC 82).
Set your volume to maximum low and turn off your amp first and wait for a minute or two and then turn off your pre-amp.Result will be dead quiet.
I can't figure out the possible reason for your hum, but be patient. There will be a 'goner that will set you free. Fortunately (shortens my waiting time for optimum sound) my SET rig has a standby/idle feature on both the amp and the pre. The amp is good to go after the 845s have 30 minutes on them and the pre just has to wait for the amp/845s to catch up. Idle would be a nice feature on all tube pre amps and amps.
Funny, I had posted a similar question a few weeks ago, having come back to seperates after over 20 years. If the volume is down on the preamp, should it matter which you shut off first? Nowhere in my amp or preamp manual does it say to be certain to shut off first or last. I think volume down on the pre is the answer?
I had the same issue with a given combination of components, and never really resolved it. My preamp had mute, volume down, etc - all these things didn't stop the hum when the amp was on and the pre was off. Also, this didn't occur on all amps, just one. And that one amp didn't have the problem with other pre's. I really don't know. Have you tried floating the ground on various components? Unplug all the sources from your pre and see if the hum goes away. Then float the ground on your pre with a cheater and see the same thing. Please let us know what works, if you find it.

Best, Peter
Sounds like some type of grounding problem to me...Ir would be interesting to see what would happen if you lifted the ground...Just a thought
12-17-06: Warrenh
Funny, I had posted a similar question a few weeks ago, having come back to seperates after over 20 years. If the volume is down on the preamp, should it matter which you shut off first? Nowhere in my amp or preamp manual does it say to be certain to shut off first or last. I think volume down on the pre is the answer?

When the power switch is turned off a voltage transient spike may pass thru the preamp outputs thru the ics to the Amp. Result, a loud pop. This will happen even if the volume pot is all the way down.

My Sonic Frontiers line One preamp, when placed in standby before shutting down the preamp, apparently shunts the outputs of the preamp thus preventing the voltage transients. That is the reason in my earlier post I suggested trying the mute function if the preamp has one. The mute circuit in the preamp may shunt the outputs, thus, no transient spike leaving the preamp thru the ics to the amp.....
Thanks for the responses. I just rechecked and the loud hum when pre is off and amp on is gone. Why? I do not know. I have made many changes lately trying to get rid of a low level hum in speakers when nothing is playing. This hum is still present. I have tried cheater plugs on two of the 3 components and the low level hum persists. Audible out to 2-3 ft from speakers. I have one more pair of interconnects to change. I doubt it helps but hopeful it will. If not I am going to change back to my old amp and see. BTW, the pre is lector zoe and amp is belles 350a reference. Other amp is aloia st15.01. What are the symptoms of an impedence mismatch? Can tubes create hum? I don't remember having this problem with stock tubes. May put them back in also. Thanks again.
Do you still have the hum when the preamp is disconnected entirely (with no cable attached to the amp inputs)? Are the pre and power-amps connected to the same outlet ? Just ruling out possible sources of ground loops.

also how old is the amp ? If it's old it could be failing power supply capacitors ? Just a wild guess.

The low frequency hum is almost certainly mains frequency (60Hz), so it's either coming through the amp's power supply, or via poor grounding somewhere.
cheers
Twc, if your cable tv is nearby, you should also try disconnecting the coax cable tv wire at its first point of entry and then turn your rig on and see if the hum is gone. If there's no more hum, you need a ground loop isolator which will take care of this issue for you.
Thanks. I will try disconnecting the preamp at the amp's inputs tomorrow as Mang53 suggested and see what happens. I hadn't thought of that. The amp is pretty new so I doubt it is the ps caps. I think I have had both pre and power pc's connected to the same dedicated outlet at some point but are on different dedicated outlets currently. No cable or sat. tv connected. Will post back tomorrow evening. Thanks again.
Make sure you power down your amp before you disconnect the interconnects!!!
Progress maybe. I disconnected the preamp at the amps inputs and the strangest thing happened. The left channel was silent yet the right channel had the same hum and at the same level. I then plugged the interconnects back in and the hum returned to both channels. What could be happening and what is my next logical step? I have some more speaker cables that I can try, so I think I will start there. Your help in troubleshooting is most appreciated. This is a great forum.

Audio can be compared to women as a source of great pleasure and much frustration.
have you tried what I suggested earlier? about the cable tv....
I disconnected the preamp at the amps inputs and the strangest thing happened. The left channel was silent
You have the Amp isolated from all other outside input sources. Only the 120Vac power could corrupt the amp. But as you stated the left channel was silent . Jmho that would rule out the AC as the problem.

yet the right channel had the same hum and at the same level.
Sounds like a problem in the right channel. Time to take it to the shop for repair. Did you check if the manufacture has a ask a question website?

I then plugged the interconnects back in and the hum returned to both channels.
Almost sounds like the input jacks do not share the same signal ground.

I can't see how a speaker could cause your hum unless they have powered LF drivers.

If you want to rule out 100% a speaker causing the problem, switch the right and left speaker cables at the Amp. If the hum moves to the other speaker,(still the right channel) it has to be the amp's right channel.

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