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mixing tubes and transistors

I'm considering getting a tube preamp in an otherwise all solid state system. The solid state gear is designed to be left on all the time. The tubes in the preamp wouldn't last very long if left powered up all the time. Here's my dilemma: the power amp owner's manual says to power down the components in sequence from the speakers "backward" to the source. The preamp is in the middle of this chain. If I turn off the preamp (to extend tube life) while leaving the amp and sources on (to keep the transistors thermo-electrically stable) am I creating any electrical hazards for my equipment? Please advise, and thanks.
prospersol7a6a
jcaudio's avatar
jcaudio
237 posts
 
Many tube pre-amps have no problem being left on all the time. In fact many recommend it. Tubes in many will last years depending on how much voltage the manufacturer runs them at. Some also have a standby mode. We never turn any of our tube pre's off. This is not the case with all of them and you should check with the selling dealer as to his experience.
jwaugh
103 posts
 
A number of preamp tubes do well if left on (last and can perform well depending on time constants in design & warm up time). Without knowing yours I can't comment further, but your dealer and manufacturer can give some advice.

Even with mute activated, I have found (through a well-meaning visitor who decided to "help" me) that some preamps do give a pretty significant pop when turned off. As others have commented, I would worry about damage to the speakers. Bob_bundus' suggestion seems excellent to me...

Good luck,
Jacob
sugarbrie
3,854 posts
 
If I am in a situation where I want to leave the SS amp on and turn off the Tube preamp, I shut the amp off first; then turn the amp back on after I turn off the preamp.

Then reverse the process turning the preamp back on; ie, shut the amp off first before turning on the preamp.

sean
6,231 posts
 
Leaving low level tubes turned on in standby mode is typically okay and recommended by several different manufacturers. My Father has been doing this for appr 15 years and only had to change tubes one time. Then again, if one uses "low grade" tubes or the component is not properly designed, you can expect significantly shorter lifespan than what he was been able to obtain with his. Sean
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bwhite
807 posts
 
Guess I'll through this in for thought... I believe it puts more shock on the tube component (lowering tube life) to power off and on frequently vs. just leaving it on.

Depending on the history of your tubes (new or NOS or USED), one can expect upwards of 10,000 hours in a preamp sometimes more. Of course as JC Audio mentioned above - this is not the case with ALL preamps and you should ask the manufacturer what he/she considers to be the average tube life in their product.
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