When to change tubes.

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When to change tubes.

Postby Winterland » Wed Jun 27, 2007 1:42 pm

may sound stupid... but.....I have a Fender Twin do you change the tubes when they do not seem to glow? I have not changed then in two+ years of playin the crap out of the amp.

Will diffrent tubes change the tone of the amp?
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Postby strumminsix » Wed Jun 27, 2007 4:47 pm

I change mine when they sound bad or I have my tech guy test them. I don't personally buy into changing tubes like changing your oil like some people do.

From what I can gather:
poweramp 2 years with moderate usage
preamp 4-5 years with moderate usage

I have a few tube amps so I think mine will last much much longer. But the road really beats the shit outta tubes. Do yourself a favor and transport your amp on a seat instead of a trunk.
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Postby deadted » Mon Aug 13, 2007 1:06 am

No, you can NOT tell the condition of a tube visually. Well, I guess if the bottle is dark then you know it's not working! Anyway, not a bad rule of thumb, a few years on power tubes depending on how many hours are on the amp and how hard you push the amp. The preamp tubes tend to last much longer than power tubes. Most importantly these days is that preamp tubes tend to be microphonic (noisy) so it can be a pain to find decent tubes... Do have a tech replace the tubes to check for bias and other issues. Great idea to have a tech check out a tube amp even for safety reasons every once in a while... Hope this helps..
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Postby jackr » Mon Aug 13, 2007 7:06 am

What kind of money is involved in changing tubes? ( i have a fender twin 100watt)
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Postby strumminsix » Mon Aug 13, 2007 7:37 am

jackr wrote:What kind of money is involved in changing tubes? ( i have a fender twin 100watt)


What year? Do you know how to bias?

A full compliment of tubes is about ~ $120 shipped.
https://ssl.eurotubes.com/cart/index.ph ... gory_id=38

Okay some don't like Eurotubes but they are, IMO, solid tubes. I've worked with those guys in the past and they care about their customers. I had an amp changing tone after heating up and Bob walked me through tons of ways to work around the issue even though he said it's mostly likely that it caused by the amp's design and not tubes.
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Postby jackr » Mon Aug 13, 2007 10:27 am

it is only a year old. I have no idea how to bias.

This is the one I have

http://www.guitarcenter.com/shop/produc ... sku=480649

For now the amp sounds great, i just wanted to know what I would be looking at.
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Postby strumminsix » Mon Aug 13, 2007 12:27 pm

jackr wrote:it is only a year old. I have no idea how to bias.

This is the one I have

http://www.guitarcenter.com/shop/produc ... sku=480649

For now the amp sounds great, i just wanted to know what I would be looking at.


Jackr, did ya read the manual? I just downloaded it and it give clear instructions on when to bias, how to bias, hot to test, how to balance, etc...

Your amp has all the indicators and controls on the back!
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Postby tigerstrat » Mon Aug 13, 2007 4:39 pm

strumminsix wrote:I change mine when they sound bad or I have my tech guy test them. I don't personally buy into changing tubes like changing your oil like some people do.

Agreed, if it sounds good to me, I don't change a thing.
strumminsix wrote:From what I can gather:
poweramp 2 years with moderate usage

Probably so, also depends on how hot they are biased.
strumminsix wrote:preamp 4-5 years with moderate usage
On that I do not agree, unless perhaps we are talking about some pretty low quality 12a#7's! I am a preamp tube tinkerer- I like to try out all kinds of different tubes in the different sockets... and try those out in combination with different guitars and speakers! I have slowly amassed a small hoard of old 70's or early 80's RCA, GE, Sylvania and Philips preamp tubes, "JAN" or military spec if possible, NOS if cheap, sometimes out of salvage grab bins... some might not be much good but some turn out to be GEMS. The tubes of this era were built to last at LEAST 30 years (possibly up to double that imho). It can be kind of tedious "work" to keep switching out tubes and playtesting in a (pre)amp to find the right combination, but when you starting getting close, it becomes hard to give up the quest!
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Postby jackr » Tue Aug 14, 2007 3:36 am

Yes I read it but that was when I first got it. I dont remember it really but thanks I will review it again.
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Postby strumminsix » Tue Aug 14, 2007 7:30 am

Agreed, TS, I was talking about currently made 12a_7s.

Jackr, I wasn't being condescending but you amp has all these bells and whistles on the back to help you manage your tubes I was surprised you came across as if you had no direction.
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Postby jackr » Tue Aug 14, 2007 12:44 pm

I know you weren't. Believe me, I didnt take it that way at all.
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Postby betteroffdeadnc » Fri Nov 09, 2007 8:08 am

Hey Guys,
I might have missed it, but you all know that only the output tubes need to be biased right? Any of the other tubes can be replaced simply by pulling them out and plugging in the new ones. On the issue of microphonic tubes, tap them with a pencil while the amp in on and running. Microphonics will show up quickly. Tip for making tubes last a little longer include, never start playing until the tubes have warmed up for a couple of minutes ( use your standby switch if you have one), and try not to shake the amp too much until the tubes have a chance to cool down for a couple of minutes after shutting the amp off. They're like light bulbs. If you think a tube isn't glowing feel it (carefully) if its hot its glowing whether you can see it or not.

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Postby Revv23 » Thu Dec 06, 2007 9:30 am

never tap a tube while it's running! Or ever!

if a tube sounds microponic you will hear it in your playing. Or if you are really suspicious switch your tubes out with fresh ones one at a time to see if it improves.

Not all amps need to be baised - i have three all tube amps and only one of them requires biasing.

If the amp still sounds good - there is only one reason to change tubes - and that is to try out different sounds. You will know a tube is bad when either it is microponic (which you will hear) or it red plates (plates on the tubes glow red - this is very dangerous and tubes need to be changed immediatly when it happens.) You will hear it red plate as well.

If an amp is biased properly and not played too hard the tubes might last forever - depending on thier quality. I have seen some 5E3's straight from the fender tweed era that have been gigged with for 30+ years with thier complete original tube set. The mantra - if it ain't broke - don't fix it comes to mind.

If you want to change your tubes to try and tweak your sound - have fun! but learn how to bias your amp (if it requires biasing) and prepare to go on a seeminly never ending quest for very small differences in tone. (trust me it is quite addictive....each one sounds just a little different - and you can't resist trying to improve.)

Oh - and just FYI if you do get new power tubes my favorite new production tubes are the TAD 6L6GC-STR
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Postby Laytonco » Thu Dec 06, 2007 10:27 am

Hey Rev, How do you hear that a tube is microphonic or red plated? Can you decribe the sound. I've had my Heritage Patriot for just over 2 years and have about 100 shows played on these tubes. It still sounds great, but that amp is in my main rig and I would rather be proactive on the retubing than to have a blowout in an upcoming show. Right now, my tubes glow a beautiful blueish purple with a slight rose color at the plate. I am told they are in tip top shape right now.

Peace,
Gil
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Postby tigerstrat » Thu Dec 06, 2007 11:02 am

To me a microphonic tube sounds like a jagged tin can softly scratching a chalkboard with every note, or perhaps just the hardest-picked notes.
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