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SurfGuitar101 Forums » Gear »

Permalink Wow, tubes make a huge difference in a reverb tank

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I’m having an intermittent problem with my amp or reverb unit. After they’ve been on a while (maybe 45 minutes), I get a fizzy sound only when notes are played. Sometimes it seems like I might also be loosing the high frequencies. (Any help on a diagnosis would be appreciated.) I’m not much of an amp tech so I figured that maybe it’s the tubes.

I’m running a bunch of NOS tubes in the reverb unit. An RCA 6K6, a Mullard 12AT7, and a GE JAN 12AX7, based on recommendations here. I put them in the reverb unit as soon as I bought it new, 4 years ago. There was a problem when it arrived and I had to open it up anyways, so I changed the tubes right away. It sounds magnificent. Smile

To see if changing the tubes would eliminates the fizzies, I just put in the barely used Groove Tubes that came with the tank. Holy cow, does it sound different! I had no idea how much difference the tubes would really make. With the Groove Tubes, it’s shriller and much more focused on the highs. Sounds distant. With the NOS tubes it’s a full, rich, warm sound that has a beautiful balance of highs, mids, and lows. When I read about all the differences people attribute to tubes, I thought that it might be something, but mostly hyperbole. I was wrong.

I still have not figured out what the fizzy problem is that I’m having. But I thought that I’d post about how much difference the tubes make in the sound. In case anyone was wondering. I’m quite amazed.

JonW wrote:

I’m having an intermittent problem with my amp or reverb unit. After they’ve been on a while (maybe 45 minutes), I get a fizzy sound only when notes are played. Sometimes it seems like I might also be loosing the high frequencies. (Any help on a diagnosis would be appreciated.) I’m not much of an amp tech so I figured that maybe it’s the tubes.

I had a similar problem with a Silverface Bandmaster Reverb. It turned out to be 5 resistors had gone out of spec. Kevin Silva, of Uncle Albert's Amp Repairs here in Indy fixed it and it sounds great now.

Cats 'n' Strats, 'cause that's how I roll - I eat reverb for breakfast!

Fenderus Collecticus
Strat Blender Pot Modification HERE

Thanks, Doctor. When I bought my amp (blackface Bandmaster) I brought it to Kevin for a complete freshening up. That was about 4 years ago but I don’t play that much. So far, I changed the reverb unit tubes and the fizzies have not returned. But the problem comes and goes. Hard to tell if it’s fixed or not.

Have you eliminated the either the tank or the amp by trying a different amp?

Thanks, vintagesurfdude.

Nope, I have not been able to locate it to either the tank or amp. The intermittent nature of the problem is making it a little hard to diagnose. When I play I always have the tank on. If the fizzies start and I put the amp on standby, disconnect the tank, then hook up the guitar to only the amp, and turn the amp back on, the fizzies are gone. But then when I put the tank back in, the fizzies are also gone.

Do you think that it could just be the tubes? Since changing tubes in the tank there have been no fizzies. But as soon as I type that, we'll see if they come back the next time I play.

If I can make a suggestion, if you get the chance next time the "fizzies" start, don't flip any switches, just pull the cord between the reverb and the amp out At the amp side to prevent the buzz, and see if the noise stops. if it does, immediately plug the reverb cable back into the amp and see if it returns. This should help you isolate the problem to one or the other. If it comes and goes with the plug, it's in the reverb unit, if it doesn't change , it's in the amp. It could very easily be a tube. If you can get the noise going in a non gig situation, gently tap on each tube with a wood stick, I use a small paint brush handle and see if the noise changes with any particular tube. Those intermittent bugs can be a real pain to figure out. Sometimes you just have to get lucky. Hope this is helpful.

Hi vintagesurfdude,

Yes, that's exactly what I need to do next- replug everything without flipping any switches. The intermittent nature of this means that I don't have many chances to trouble shoot.

Good idea on tapping the tubes. Never done that but I'll try. Actually, I think that the next thing to do is put the old tubes bank into the tank, see if the fizzies come back, and try the unplugging as well as they tube tapping.

OK, I’m learning a little bit now. I turned on everything and there was no fizzy sounds but I tapped on all the tubes. Nothing from the reverb tank. Looking at the back of the amp, the right most tube (7025/12AX7) got scratchy every time I tapped on it. The second one in from the right (7025/12AX7) also was scratchy but not on every tap.

So I took the barely used 12AX7 that came from the tank and put it in the amp in the right most position and tapped on it. Silence. Smile Then I moved that newish tube to the next spot in (and put the old tube back) and tapped it. Tapping this newish tube played a sound as if the pencil tap was amplified by a microphone but not really any fizziness. Tapping on the old tube back in the right-most spot and there was not any fizziness any more. Then putting back in both old tubes and tapping both and there was no sound at all.

Hmmm. It’s progress. Maybe it’s time to replace all the small tubes in the amp? Or maybe the tubes were just loose? Or there could be a solder joint problem?

Oh, and the reverb tank sounds much better with the NOS tubes back in there.

Sounds like it could be dirty or loose tube sockets. Have your amp tech clean and re-tighten the sockets if you've never done it before. If it were mine, I'd clean/tighten all of the tube sockets, clean the pots and input jacks. Sound like you're getting closer ! Cool

Thanks again. You've been very helpful! It sounds like a job for a tech. He's an hour away so it may be a while before I get to it. When I got the amp, about 4 years ago, I brought it to the tech for a detailed once over. Since then it's just been in my house, no gigging.

You mention the input jacks. I've been having a problem there, too. Basically, after the amp warms up and I flip on the standby switch, nothing happens. The amp hums a little but no sound from the guitar. So I turn off the standby switch, unplug the cable from the amp, plug it back in, turn on the standby switch and it works fine. Details in this thread:
http://surfguitar101.com/forums/topic/17552/?page=1#p230421

I wonder if it's an input jack issue. This one has also been driving me a little nuts, trying to figure out what's going on.

JonW wrote:

Thanks again. You've been very helpful! It sounds like a job for a tech. He's an hour away so it may be a while before I get to it. When I got the amp, about 4 years ago, I brought it to the tech for a detailed once over. Since then it's just been in my house, no gigging.

You mention the input jacks. I've been having a problem there, too. Basically, after the amp warms up and I flip on the standby switch, nothing happens. The amp hums a little but no sound from the guitar. So I turn off the standby switch, unplug the cable from the amp, plug it back in, turn on the standby switch and it works fine. Details in this thread:
http://surfguitar101.com/forums/topic/17552/?page=1#p230421

I wonder if it's an input jack issue. This one has also been driving me a little nuts, trying to figure out what's going on.

Could be an input jack issue. I see tubeswell had some suggestions. He's really knowledgeable. At this point you may want your tech to give it a once over with the problem in mind. A good tech is worth his weight in gold.

Sounds like a good plan. I think that the amp has placed itself out of my league. Time to see a professional. Smile

Before I do that I want to do a little more diagnosis on the plugging in/out thing. And maybe I’ll order up a set of NOS tubes. When the amp is in for service, that’s an easy time to have him bias it with the new tubes.

I live in a small town and the amp pro is an hour away. So it may be a while before I can get down there. Thanks again for all of the help.

Each tube has a little mojo all of its own and no two of the same 'type' are exactly alike. Mass-production of these 'electro-mechanical' devices leaves a lot of 'room' for electrons to behave differently in the space between the electrodes and is dependent on the plate-cathode voltage (which can vary in different tubes depending upon such things as; the minute variations in distance between the plate and cathode in different tubes, the perfection of the vacuum etc), as well as a whole lot of other stuff like the reluctance of the cathode material to free-up electrons and the random aspect of the way in which electrons migrate the gap to the plate etc.

So much different to transistors

He who dies with the most tubes... wins

Surf Daddies

Last edited: Jun 02, 2012 17:12:20

Thanks, tubeswell. I'm just young enough to have grown up in an almost all solid state world. The only tube things that I've ever owned are my amp and reverb tank. So tubes are not something that I have a good feel for. I guess they can vary quite a lot, as I'm now learning. Still, I wasn't expecting the tubes to make such an obvious anyone-could-hear-the-difference change in the reverb tank. I was expecting something subtle. Pretty interesting.

Now that I've got tubes in the reverb tank that I like, I wonder if I should get some backups of the same tubes. I have no idea if such NOS tubes will still be available ages from now or if we're running out.

Yes you should buy more tubes. Definitely. The more peeps that buy tubes the better. Get out there and hoard tubes. No question about it.

He who dies with the most tubes... wins

Surf Daddies

Last edited: Jun 04, 2012 22:13:49

But then there are fewer tubes for you. Big Razz

Factories will make more tubes

He who dies with the most tubes... wins

Surf Daddies

I just replaced the Russian/Chinese tubes in my newly acquired Peavey Valverb with NOS GE 12ax7's and a NOS JAN 12at7, and it made a big difference. I need to start stocking up on the good stuff.

Thunderbolt wrote:

I just replaced the Russian/Chinese tubes in my newly acquired Peavey Valverb with NOS GE 12ax7's and a NOS JAN 12at7, and it made a big difference. I need to start stocking up on the good stuff.

oooooo....... Valveverb. I'm still kicking myself for selling mine almost 15 years ago.... Good decision BTW going with NOS tubes.

vintagesurfdude wrote:

Thunderbolt wrote:

I just replaced the Russian/Chinese tubes in my newly acquired Peavey Valverb with NOS GE 12ax7's and a NOS JAN 12at7, and it made a big difference. I need to start stocking up on the good stuff.

oooooo....... Valveverb. I'm still kicking myself for selling mine almost 15 years ago.... Good decision BTW going with NOS tubes.

I'm kicking myself for not buying the one I saw in a pawnshop around 10+ years ago for $150, and had to fork out twice that amount for the one I just got. But, at least I can park my digital 'verb pedals!

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