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Old 01-28-2013, 06:28 PM   #1
YYMMalmsteen
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Amp Tube Replacement

I've owned a Peavy Valveking 112 for a couple of months now, about 8 or so. I've never used the volume up high, mainly 1-2 in my bedroom.

I've recently noticed that when I use distortion, there's a crisping sound in the background coming from the amp (it eventually fades after an hour or so). However, it's there. And I've just played a song on clean, and on each note I struck it sounded as if the amp was cra*ing the note. As if it my playing on 2-3 volume were distorting and bursting the speaker.

I guess the tubes may be dying. If so, how much would the replacements be?

Another option I considered was that the speaker wasn't properly connected. Is that possible? After sounding good some weeks ago? How could I check and fix that?

OHHH. MOST IMPORTANT! Am I safe to keep on playing my amp with the weird noises going on? Or should I stop to avoid any possible further dreadful damage? I need to record a song... that's why I'm asking

THANKYOU
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Old 01-28-2013, 06:48 PM   #2
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I also own a VK112. Nice amp, once you retube it.

Some tubes will make a crackling, or arcing noise. If this is what you're hearing, it means that particular tube is bad. I've had the problem with a couple of my tube amps and it's usually the preamp tubes that do it - usually, but not always.

How much would it cost? All depends on what you replace them with. If you go with JJ and something like a Winged C for the output tubes, you can replace all of them for around $100, give or take.

It really shouldn't hurt anything to use the tubes that are arcing. If you're using the amp for recording, you will have some noises present in the recording.
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Old 01-28-2013, 07:11 PM   #3
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$69 for the cheapest set for your VK
JJ are one of the best tubes you can get without spending alot of money
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Old 01-29-2013, 04:39 AM   #4
YYMMalmsteen
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Quote:
Originally Posted by KG6_Steven
I also own a VK112. Nice amp, once you retube it.

Some tubes will make a crackling, or arcing noise. If this is what you're hearing, it means that particular tube is bad. I've had the problem with a couple of my tube amps and it's usually the preamp tubes that do it - usually, but not always.

How much would it cost? All depends on what you replace them with. If you go with JJ and something like a Winged C for the output tubes, you can replace all of them for around $100, give or take.

It really shouldn't hurt anything to use the tubes that are arcing. If you're using the amp for recording, you will have some noises present in the recording.


cheers

though i must say I was planning on retubing it with the originals because I've heard that switching tubes can somrtimes be a mistake.

The tube can't BE bad. They were ok before but have gone bad with time (that is my guess), as the noise was never always there
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Old 01-29-2013, 08:16 PM   #5
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Well, tubes don't go bad with time. They're not like hot dogs in your refrigerator.

Keep in mind that I have tubes that date back to the 50s and 60s and they still perform as well today as they did then - tubes do not go bad over time.

Ok... so, having said that, let's set up the exception to that rule. Tubes can go bad over time, IF, and only if, they have a slight leak. If they have a leak, this allows air to enter the envelope and the getter (that silvery stuff inside the glass) turns grayish white and the tube no longer functions. I've had tubes do this and it usually occurs relatively fast- over the period of a month or two.

Switching tubes is not a mistake. What happens when the tubes are exhausted and no longer producing proper output? At that point, you're faced with tube replacement. I partially retubed my Vk112 to get rid of a horrible hum that it used to have. I replaced the output tubes with Winged =C= tubes, then replaced a couple of the preamp tubes to quiet it down. The amp is so quiet now, that I occasionally use it for recording. I've also partially retubed my Mesa and Rivera amps to replace noisy preamp tubes and make them better for recording and performing.

When you retube the amp, just make sure you have a goal of what you want to accomplish. Do I want more gain? Less gain? A quieter preamp section? Then, research your choices and ask the guys here for advice. Finally, buy the tubes and install them.

Do remember that the VK112 is fixed bias, so you'll need to buy power tubes specifically for that amp. If you buy power tubes that draw too much or too little current, it can effect the tone and/or cause premature tube failure. Some fixed bias amps have a wide tolerance for power tubes, so it make little difference what you install. I'm not sure if the VK112 is one of these, or not. Cathbard would be a good dude to ask this question.
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Old 01-29-2013, 08:28 PM   #6
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Quote:
Originally Posted by KG6_Steven
Well, tubes don't go bad with time. They're not like hot dogs in your refrigerator.

Keep in mind that I have tubes that date back to the 50s and 60s and they still perform as well today as they did then - tubes do not go bad over time.

Ok... so, having said that, let's set up the exception to that rule. Tubes can go bad over time, IF, and only if, they have a slight leak. If they have a leak, this allows air to enter the envelope and the getter (that silvery stuff inside the glass) turns grayish white and the tube no longer functions. I've had tubes do this and it usually occurs relatively fast- over the period of a month or two.

Switching tubes is not a mistake. What happens when the tubes are exhausted and no longer producing proper output? At that point, you're faced with tube replacement. I partially retubed my Vk112 to get rid of a horrible hum that it used to have. I replaced the output tubes with Winged =C= tubes, then replaced a couple of the preamp tubes to quiet it down. The amp is so quiet now, that I occasionally use it for recording. I've also partially retubed my Mesa and Rivera amps to replace noisy preamp tubes and make them better for recording and performing.

When you retube the amp, just make sure you have a goal of what you want to accomplish. Do I want more gain? Less gain? A quieter preamp section? Then, research your choices and ask the guys here for advice. Finally, buy the tubes and install them.

Do remember that the VK112 is fixed bias, so you'll need to buy power tubes specifically for that amp. If you buy power tubes that draw too much or too little current, it can effect the tone and/or cause premature tube failure. Some fixed bias amps have a wide tolerance for power tubes, so it make little difference what you install. I'm not sure if the VK112 is one of these, or not. Cathbard would be a good dude to ask this question.

Tubes do go bad after years of use. The plates will start to fatigue in side the tubes over the years of use. Some tubes are better than others. Yes tubes from the 40's-50's last a long time, but most were made with superior materials and craftsmanship.

Hell there is a lightbulb in NYC that is over 100yrs old and it still works
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Old 01-29-2013, 09:56 PM   #7
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But I'm not talking about tubes in-use.

Yes, after years of use, tubes will go bad. The electron emission decreases, due to the cathode, which causes a decrease in the output, among other problems. A tube that sits unused will not degrade, unless it develops a leak. Even tubes made today will last well into the future, provided they're properly stored.

The light bulb you're referring to is actually in Livermore, California. It's estimated to be around 110 years old and only consumes 4 watts. Not sure what the Centennial Light has to do with the shelf life of vacuum tubes, but at 4 watts, it's merely idling along. And, it's not's amplifying sound.

Bottom line, don't be afraid to experiment with different tubes to improve the tone of your amp. Again, just have a little knowledge as you go into the project.
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Old 01-29-2013, 10:44 PM   #8
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Quote:
Originally Posted by KG6_Steven

Do remember that the VK112 is fixed bias, so you'll need to buy power tubes specifically for that amp. If you buy power tubes that draw too much or too little current, it can effect the tone and/or cause premature tube failure. Some fixed bias amps have a wide tolerance for power tubes, so it make little difference what you install. I'm not sure if the VK112 is one of these, or not. Cathbard would be a good dude to ask this question.
If he just buys a set of JJ's and throws them in he'll be fine. Peavey are good like that, they may not be biased for optimum performance (which is why people do the bias mod on VK's) but they're always safe.
And btw, don't confuse him. Fixed biased doesn't mean that they are not adjustable, fixed biased amps are the only ones that can be adjusted. The term you are looking for is "non-adjustable fixed biased"
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Old 01-30-2013, 06:43 AM   #9
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^ Oooh, burn.

Just kidding. It's a VK, just chuck some JJs in there. Don't bother getting "the original valves", as Peavey just puts whatever is in the bin in there.

Replacing the speaker is a popular mod, though it might get a bit expensive. There are some other mods which include changing a few resistors. You shouldn't do this yourself though, unless you know your way around valve amps.
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Old 01-30-2013, 07:21 AM   #10
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perhaps it is easy to get confused between a fixed biased which is set in one place manually, or an amp that can take many types of tubes without needing a bias or any adjustments.
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Old 01-30-2013, 06:19 PM   #11
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I'm an electronics tech and that's how I've always referred to it. To me, fixed means I can't change it and adjustable means I have to access a potentiometer and get a meter in there to get the right setting. Why complicate it?
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Old 01-30-2013, 09:00 PM   #12
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Because that's not what it means. Fixed means that a fixed dc voltage is applied to the grid, whether there is a pot to set that voltage or not.
Mesa are to blame to a large degree because their marketing dept like to say things like "Fixed biased so there is no need to rebias the amp." That has led to people using the term incorrectly. They should have called it "non-adjustable" instead but I guess the marketing douches thought that would have made it sound like it was in some way lacking.
It's not I that have complicated it, it's marketing arseholes.

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