Tube view.....

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bruce egnater

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Here are a few of my views about tubes. Often people get hung up on very specific bias currents for certain tubes. Really this is not something that needs to be that accurate. There is a reasonable range that tubes can safely idle at. 70% is not necessarily the "magic" number that makes everything great. It is just like the idle speed on a car engine. If you idle your tubes (engine) very high for a long time, you will tend to wear things out faster and shorten your tube life, but your amp may feel more responsive. If the idle current is on the lower end, the tubes will last longer but the tone/feel may be affected. This doesn't mean in a bad way, just different. You can experiment to try to find your "magic" setting. It is not like running the idle current (bias) a little high will instantly destroy your tubes. When you play, especially at high volumes, your tubes draw way more current than at idle anyway. Your tubes don't know the difference between idle current and sound. They just respond to some incoming voltage. Point is, if you play often (and loud and distorted) this causes more wear on your tubes than the idle (bias) current. If you play really loud and distorted most of the time, it's sort of like holding the gas pedal to the floor for a long time. Something will eventually give. This even goes for small, low power amps. Same situation exists, just with a smaller engine (power tubes). But........a serious killer of tubes is physical damage. When you move your amp around, you inevitably jar the tubes which can fatigue or break the delicate internal metal parts. When this happens, one part may touch another that is not supposed to touch creating a short. Ah, a shorted tube!! You can help this situation a bit by at least not moving your amp around while the tubes are still hot. If possible, wait a few minutes for the metal parts to cool before you move the amp. Of course, these are generalizations, but you get the idea....I hope.
 
Thanks Bruce. I think you are mostly referring to power tubes, but what about pre-amp tubes. If I have my MV low but push the pre-amp gain into distortion is this putting accelerated wear on the 12AX7s?
 
Yes, I am referring to primarily power tubes.....except for the part about the delicate/physical damage comments. In fact, when a preamp tube gets microphonic, that is the symptom of the rigid metal parts inside the tube being "loose" and actually vibrating. Preamp tubes do not really wear out like power tubes as they are not under the same stress, even with a lot of gain/distortion. Of course, they do age and get fatigued over time and performance/noise/microphonics suffers so replacing them periodically can keep your tone happening. Keep in mind the consistency of today's production tubes can be "iffy". I suggest keeping a couple of known good spare 12AX7 tubes in case of trouble. If you suspect a tube is starting to age/wear/sound bad, try replacing it with your known good one to verify. I have, on more than one occassion, suspected a bad tube and replaced it with a new one...only to find the brand new one was bad out of the box. When I say "known good", I suggest you check it against the ones in your amp that are working properly now and then save it for emergency.
 
Thanks Bruce, I'm in the habit of keeping known good tubes on hand. I'm not that worried about premature tube wear, just curious. Thanks again.
 
Thanks to Bruce, it's easy to find your bias sweet spot. USE YOUR EARS IMHO
 
Hi Bruce and thanks for the tips!

I own 2 or your great amps... (Renegade 212 and Rebel 30 head with 112 cab).

I love the great sounds achievable out of both of these amps, but also know that tubes will eventually need to be replaced.

What is your current replacement recommendations (preamp and power amp tubes) for both of these amps to ensure great sound and reliability?? Currently, both of my amps are sounding great, and have been very reliable. I'd like to purchase some spare tubes that will equal or even better my great experiences with your amps so far.

Please provide me with your current tube suggestions for my Renegade and Rebel 30. It would be most appreciated! :thumbsup:
 
OK...I realize my question in my previous post regarding tube choices is very subjective.

And yes, I also realize that this topic has been discussed to death. However, people's preferred tubes for any amp seem to change quite rapidly this day and age.

Let me rephrase my question....

What type of tubes work well for all of you Renegade and Rebel 30 users, and where do you purchase your spare tubes? Please let me know what is working great for you, and where you purchase them from.

I am most interested in your opinions toward power amp tubes, but would also like to hear your take on preamp tubes as well for either / both amps mentioned.
 
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