My Fender Hot Rod Deluxe III recently developed a glassy rattle. It was only evident at certain frequencies – prevalent when I strummed low chords or struck low notes. At first the rattle was faint and only occurred occasionally. But over a number of weeks the rattle grew in prominence and occurred almost every time I played a low chord or note.
I spent a few hours sitting at the back of the amplifier, strumming chords trying to identify where the rattle was coming from. It seemed to centre around the power valves (also known as tubes) that hang behind the steel cage at the back of the amp. My Hot Rod is 18 months old and only gets an outing a few times a month, but if they were the culprit I wasn’t that surprised. Valves are mercurial beasts. You have no way of knowing how long they’ll survive. They can last a couple of weeks or a couple of years. Power valves are more prone to failure than those in the pre-amp stage. The more you play and the louder you play, the greater likelihood your valves will wear out sooner rather than later. Combo amps, like my Hot Rod, are particularly cruel to valves. Unlike a head and cabinet partnership, the valves in a combo live in a highly violent, reverberating environment directly behind the speaker. Ouch!
Unless they stop working altogether, power valves begin to fail in a number of ways. Tell tale signs are:
- your bottom end becomes loose and flabby
- fluctations in power or power loss
- loss of some top end
- inconsistent sound
- loss of punch
- humming
- rattling
- miscrophonic noises.
Pre-amp tubes exhibit the following symptoms when they are on their way out:
- hissing
- humming
- loss of gain in the gain channel
- loss of dynamics and sensitivity.
If valves do rattle, the rattle will normally only be heard at low volumes. A cranked amp will drown the sound of filament rattle.
I used a quick test for tube rattle. I let the amp cool down and unplugged it. I unscrewed and removed the back panel to expose the power tubes. I gave the one on the right a few gentle taps with my fingernail, nothing. Then I tapped the left power valve. Ahh…it rattled like a broken light bulb. Bingo! I’d found the cause: valve filament rattle.
I was a bit lucky with this test method. Often, tapping very gently on a cold tube won’t tell you anything. Tube internals expand when they are hot and contract when they are cold. So a tube may rattle when it’s hot and not when it’s cold, and vice versa. We are really only concerned if the tube rattles when the amp is on and the tubes are hot. To test for rattle when the amp is on you could very gently tap the power valves with something non-conductive, like a tooth pick. But be careful. Valves break easily. And never attempt to poke around inside an amp with the back cover removed and the power on. You are likely to kill yourself or at least blow up your amp.
As standard, Fender fit the Hot Rod Deluxe III with a pair of Groove Tubes GT-6L6 C(HP) valves for the power stage and three Groove Tubes GT-12AX7-R valves for the pre-amp stage. The GT-6L6 C(HP) tubes produce a tone and response that is warm in the mids with good harmonics, has a decent top and bottom end, and has some natural compression. I love the tone I get from my Hot Rod, but I fancied experimenting with a bit of a valve upgrade. So I did a bit of research and spoke to my local amp dealer. After much consideration I purchased a matched pair of Ruby Tubes 6L6GCM-STR valves. It’s important to get a pair that are matched for the amount of current they draw.
The Ruby 6L6s were packaged in a Peavey branded box and sold as Peavey Super 6 Power tubes. It is more than likely that they are available under a number of brand names. They can also be purchased as straight Ruby Tubes 6L6GCM-STR valves from a wide range of online suppliers.
The pair of Ruby valves cost less than £40 – outstanding value for money. After fitting the Ruby tubes – a delicate operation – my Hot Rod has the same clarity, shimmer and chime it always had, but now has a bit more punch overall with a slight boost in the upper mids and a clean, tight bass response. Some Hot Rod owners argue that the Ruby tubes out perform the factory-installed Groove Tubes. They certainly offer maximum clean power and headroom. If you want to upgrade and stick with Fender’s stock variety, Groove Tubes sell a number of premium 6L6 valves. Many valve enthusiasts argue that the Ruby tubes closely match the tone and response of the much loved classic Philips-style STR tube. I can’t fault them.
When sapping out power tubes, remember to bias your amp or have a professional do it for you:
Fat Sound 
Reblogged this on Theory of Shredability.
Cool that you found a pair of power tubes that work..
For me, Ruby tube, pre and power, haven’t worked for. I’ve tried them in a number of amps, not Fender, and they are my least favorite.
My favorite power tubes are SED Winged C 6L6’s. Fantastic tube in every amp I’ve tried them in, with one caveat. I have 4 Winged C’s 6L6’s, they are not a matched quad, but a matched pair.
I tried one set in my new Hot Rod DLX3 and they didn’t sound as good as they have in other amps I’ve had and have. Running the C’s in my Egnater Vengeance they are sweet, harmonic, warm, punchy, and tight. That pair in my HR DLX3 were ok but not fantastic.
So I tried the 2nd set and THERE is that sweet tone. For whatever reason the first set didn’t sound so good, but the 2nd set are fantastic.
Leaving the bias setting at around 64mV, where the stock GT tubes were, the 1st set of C’s registered around 80mV! But, the 2nd set registered at 45mV, big difference in between those pairs, and that seems to make a difference.
I also have a set of Sovtek 5881’s and those sound excellent in the HR DLX3. So, if you want to try a great low cost power tube I recommend the Sovtek 5881’s.
Winged C 6L6’s are pricey now as they are no longer being made, so what’s left is now NOS.
Matched pairs typically run around $90-$100 and more.
But if you shop you may find a great deal as I did. The recent pair I purchased for only $60 new!
I jumped on those because it’s unheard of to get those at that price now, 8/2014.
I did bias setting experiments and have run the power tubes in the HR DLX3 from around 40mV to 85mV. Interestingly, this amp sounds good anywhere in that range. Of course it depends on the tone one wants, but that range works. On the colder side the tone is “looser” and grittier, which could suit a bluesy tone. On the hotter side the headroom is higher and tone remains very clean with a tighter sound. But, at 85mV the tubes likely won’t last very long.
Like most I find that between 60mV to 70mV sounds the best.
The great thing about this amp is how well it responds to different pre and power tubes.
Of all the tube amps I’ve owned the HR DLX3 responds amazingly with different valves.
Tung Sol 12ax7’s in V1 sound fantastic, much better than the stock GT’s, which are JJ’s rebranded in my amp. Sovtek LPS are creaming and harmonic in both V1 and PI position.
But, they are a long plate design and in loud combo amps they can become microphonic.
If you want a very harmonically rich and warm pre tube the Jan Phillips 5751 are amazing.
They are a bit lower in gain compared to a 12ax7, but they offer great clean headroom and the tone is awesome. They have become a bit pricey though at around $35-$40 each, yet a great pre tube to have in your bag.
I don’t use the high gain channel much in my HR DLX3, but a Tung Sol 12ax7 in V2 does wonders for a light crunch distortion. When I do use the high gain channel I prefer to keep the gain around 5, cause for me, above that the distortion is too loose, and grainy.
For distortion and high gain saturation I have 2 distortion pedals that work fantastically with the
HR DLX3, a Bogner Ecstasy Red pedal and a Wampler Triple Wreck pedal.
With those 2 pedals I can get anywhere from a light distortion ala Hendrix to 80’s metal to all out saturated goodness of modern metal with the Triple Wreck.
Every since I got the HR DLX3 I use those 2 pedals and I have barely played my Egnater Vengeance, even though that is one fantastic amp in it’s own right.
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Hi, great post! I just finished a recording session and my guitar player’s tubes were rattling. They stopped rattling if I held a cloth against them… main question is if they’re rattling then is the best solution to get new tubes? I’m guessing he could use new tubes as he plays loud often and hasnt changed them in over 6 months. Thanks!
If tubes are rattling and they are driving you crazy, there is not much else to do than replace them.
I have a small ibanez tsa5 combo, and there was some noticable high-frequency rattle when playing some lower notes. After reading this article I went and got a new power tube, and swapped it in. The noise is still there. Could it be the preamp tube then? Or is it the rattle normal considering it’s a combo amp?
Rattles can drive you crazy. I recently bought a Marshall Offset which buzzed at certain frequencies. Took it back to the shop and it turned out to be the L-shaped speaker cab cable jack that came with the amp rattling against the back of the cab. Fitted a straight jack and it has been fine since. Who would have guessed? It can be hard to find the cause of rattles and buzzes. See this post for examples of the causes http://www.thegearpage.net/board/showthread.php?t=665687 If it proves difficult to trace I would take it back to the shop you bought it from, if under warranty. Or take it to a tech. In the past, tracing rattles has driven men bonkers.
Thanks for the prompt reply! Ya, it’s been driving me a bit nutty. It’s definitely related to the chassis. I took the chassis out of the cab, and the rattle disappeared. But it seems to be tube rattle, because the sound seems to be coming through the speaker, in the signal. I turn up the signal, and the rattle is amplified accordingly. I’ll look into buying a separate cab to avoid the problem during recording.
Hmmmm well i have a question…
Dors changing tubes fix the problem? You didnt get the same noise after some days or months of playing?
I didn’t get the same problem. And I’ve had the same valves in ever since I made the change. You never can tell how long valves will last. Sometimes they fail pretty quickly, sometimes they last for years.
Ooh, so its just bad tube,
Well thats helpfull🙄
Hmmm one last thing,
From a new tube, you install it, but when its dying you get the rattle again? Microphonic? Or just volume lacks?
Its because i just bought a vox ac30 like 2 weeks ago and i have tube rattle, i wanna make a good desition From contacting them and telling the problen will continue, or just changing the tube and problem wont happen again
Broken or dying tubes can cause a variety of problems. You mentioned the most common. If you bought your amp new I would recommend contacting the retailer you bought it from just to be certain your problem is the tubes.
Oh so it can be anything? I didnt noticed this problem till i got 1 and halg week with the amp, tho im still in contact with them, tomorrow they are going to contact the brand hehe, thanks for fast answer😁,
Its mu first tube amp, i was worried
I have had persistent tube rattle in my Fender Hot Rod DeVille 212. I have tried all the recommended remedies, including the tube vibration damper rings, changing the tubes, and changing the brand of tubes, but I still get tube rattle associated with the two power tubes. My amp technician frequently does business directly with the Fender amplifier staff. I asked him to contact them for any tips on what to do. The Fender people denied that the amps have any problem with tube rattle and said I must have a microphonic tube. This is after I’ve changed the tubes about 4 times and still have the problem. Fender is in denial. I recount this story just to let all of you know that you’re not crazy and other people have this same problem.
The problem is that I really like the tone of the amp and I don’t want to have to buy a new amp. I’m considering giving the amp major surgery. You can buy a couple of the tube sockets for the 6L6 tubes for about $30. I’m considering creating a different mount for the 2 power tubes, mounted to the inside of the cabinet with vibration damping isolators and with a shield between the backs of the speakers and the power tubes. Then, just run point-to-point wires from the amplifier chassis to my new power tube sockets. This ought to prevent vibrations from the amplifier chassis or the cabinet from shaking the tubes, and prevent the air that is being moved by the speakers from shaking the tubes. It’ll be a medium complexity home workshop project, but I’ve lost faith in other solutions.