Amp reverb noise - tube problem?

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dainbramage

dainbramage

Well-known member
I'm just going to cut straight to the chase.

The amp is a Heritage Victory. They are no longer made and the documentation is scarce to say the least. A manual exists but it contains no technical information at all.

The more I turn up the reverb on my amp, the more it hisses (well, it's not a consistent hiss, a little scratchy, and sometimes it starts to "whistle" as described by someone else in another thread, but that is only occasionally.)

The noise does not become louder the more I turn up the volume of the amp itself.

Now, the amp has 4 preamp valves:

1. 12ax7
2. 12at7
3. 12ax7
4. 12ax7

After a lot of searching around on the web I figure the 12at7 tube is the one related to reverb. (Or is it?)

My questions are these:

1. Would it be safe to replace the 12at7 with a 12au7 in order to find out whether or not a tube swap would fix the problem? I have a couple of those lying around. According to some people, a 12ax7 tube would not be safe on a Fender Deluxe, which is kind of like my amp in that it also uses 12at7 tubes.

2. If a tube swap does not work, what else could it be? Do some reverbs just naturally hiss?
 
Do not go swapping valve types in an old amp of which you know nothing (nor I!) .

There is a risk, small I grant you, of burning out anode (plate) load resistors and causing yourself more grief.

The 12at7 (aka ECC81) is almost certainly the reverb driver and likely has both triode sections strapped together to get higher power handling. You can easily prove which valve does what.

Pull out the 12AT7. Does the reverb stop working in the "play thru" sense?
If so the T7 is the driver. Has the hiss gone? No? Din't think it would!

Advance the reverb level pot and kick the cab. Does it "KLANG"! If yes then the hiss is in the reverb "recovery" circuitry. Probably a valve, 12AX7 but could be a resistor gone noisy especially in an old amp which uses carbon composition (ugh!) resistors.

ALL circuits hiss! Reverbs are a "lossy and thus noisy system but you should be able to emulate "Wonderful Land" without TOO much noise!

Where in the world are you?

Dave.
 
ecc83 said:
Do not go swapping valve types in an old amp of which you know nothing (nor I!) .

There is a risk, small I grant you, of burning out anode (plate) load resistors and causing yourself more grief.

The 12at7 (aka ECC81) is almost certainly the reverb driver and likely has both triode sections strapped together to get higher power handling. You can easily prove which valve does what.

Pull out the 12AT7. Does the reverb stop working in the "play thru" sense?
If so the T7 is the driver. Has the hiss gone? No? Din't think it would!

Advance the reverb level pot and kick the cab. Does it "KLANG"! If yes then the hiss is in the reverb "recovery" circuitry. Probably a valve, 12AX7 but could be a resistor gone noisy especially in an old amp which uses carbon composition (ugh!) resistors.

ALL circuits hiss! Reverbs are a "lossy and thus noisy system but you should be able to emulate "Wonderful Land" without TOO much noise!

Where in the world are you?

Dave.
Click to expand...

Hey Dave, thanks a lot.

I tried pulling out the 12at7 and yes, the reverb is gone. The "hiss" (kind of) is still there and the more I turn up the reverb, the more it hisses, just like you thought.

It does "KLANG" when I kick the cab, even without the 12at7 in it.

The amp isn't really that old. Probably around 2005-2006.

I'm in southern Norway.

So, what do I do next? Order a new set of 12ax7's and a 12at7 and replace them all?
 
Paul Cochrane designed that amp. Not sure if this number is still good, but I imagine it is: 615-896-8555 Pretty sure he is also a member of the Gear Page forum as well.
 
"So, what do I do next? Order a new set of 12ax7's and a 12at7 and replace them all?"

No! Put the 12At7back where it was and number the other valves so you know whence they came then swap the 12AX7s about to see if one is less hissy in the reverb recovery amp position. If you can identify the hisser, just buy a new one of those.

If none of the X7s improve the hiss you have a problem only an amp tech can sort out.

Dave.
 
SHEPPARDB. said:
Paul Cochrane designed that amp. Not sure if this number is still good, but I imagine it is: 615-896-8555 Pretty sure he is also a member of the Gear Page forum as well.
Click to expand...

Thanks. I'll see if I can find him at that forum.

ecc83 said:
Put the 12At7back where it was and number the other valves so you know whence they came then swap the 12AX7s about to see if one is less hissy in the reverb recovery amp position. If you can identify the hisser, just buy a new one of those.

If none of the X7s improve the hiss you have a problem only an amp tech can sort out.

Dave.
Click to expand...

I tried swapping the valves but the hiss is still there. I'm not sure if it is normal though as I usually play the amp at about 0,5/10 volume or even less due to living in an apartment. The reverb hiss is really noticable when the reverb knob is about halfway up. I don't think I'd really notice the hiss if I had the amp at, say 3/10. My AC30 reverb does not act this way though.

I guess I'll take the amp to a tech some day then. Thanks again Dave.
 
dainbramage said:
Thanks. I'll see if I can find him at that forum.



I tried swapping the valves but the hiss is still there. I'm not sure if it is normal though as I usually play the amp at about 0,5/10 volume or even less due to living in an apartment. The reverb hiss is really noticable when the reverb knob is about halfway up. I don't think I'd really notice the hiss if I had the amp at, say 3/10. My AC30 reverb does not act this way though.

I guess I'll take the amp to a tech some day then. Thanks again Dave.
Click to expand...

Ok. There is always a balance with reverbs between drive level and recovery gain. Naturally, lower drive and higher recovery gain makes for a noisier system but this might be to the designers taste! As you say, if the "dry" sound was higher, reverb noise would not be so noticeable.

This is in much the same way that some amps just do not sound good unless belting it out!

Dave.
 
I noticed something else about this today. When I have my pedal power supply close to the amp, the more I turn the reverb up, the more it buzzes (or hums) like crazy. With the reverb knob on zero, there is no buzz/hum at all, even with the pedal power supply right next to the amp. I tried disconnecting the pedal supply and the noise was less noticable than ever. It still hisses a little bit the more I turn the reverb up, but not a whole lot.

FWIW, the power supply is a T-Rex Fuel Tank Chameleon.

I'm starting to think this may be a problem related to shielding of the reverb tank or something like that? Might be some other power stuff creating hiss with the reverb?

:confused:
 
dainbramage said:
The more I turn up the reverb on my amp, the more it hisses (well, it's not a consistent hiss, a little scratchy, and sometimes it starts to "whistle" as described by someone else in another thread, but that is only occasionally.)

The noise does not become louder the more I turn up the volume of the amp itself.
Click to expand...

Is the tank original or, at least, the same spec as the original.
I blindly bought a reverb tank for a fender amp and was disappointed to find it squealed and buzzed, although it did function.

I later discovered that this particular tank didn't need/want the rca shield connected at the input (or output...I can't remember).
Lifting that yielded perfect operation.

I'm not suggesting going around lifting earths or anything of the sort, but maybe tank model no. something to research?
 
Steenamaroo said:
Is the tank original or, at least, the same spec as the original.
I blindly bought a reverb tank for a fender amp and was disappointed to find it squealed and buzzed, although it did function.

I later discovered that this particular tank didn't need/want the rca shield connected at the input (or output...I can't remember).
Lifting that yielded perfect operation.

I'm not suggesting going around lifting earths or anything of the sort, but maybe tank model no. something to research?
Click to expand...

I just got a reply from the dude that sold me this amp. The tank should be the original one.
 
This is my thread so I feel free to bring it back up.

After advice from people at the Gear Page, I finally tried getting new RCA-cables for the reverb tank, but the problem is still the same. Also I'm not sure why I said it doesn't get worse the more I turn the amp volume up, because it certainly does now. For now I'm using a (digital) pedal for my reverb, but using the amp reverb would be much nicer.

So now I'm thinking I might go ahead and get a new reverb tank, so my question is this: Are all tanks compatible with any amp as long as I connect them with RCA cables? Or is there something I should know about that? Do you guys think it would solve the problem (as I've tried the other suggested solutions).

Also, ecc83/Dave, I just saw that you've posted about this on another forum back in 2014. Thanks a lot for that effort, I really appreciate it.
 
No! Not all reverb tanks are the same by any means!

As this is a valve amp I would guess the tank is driven from a small transformer? The impedance of the tank's drive coil (input) will need to match the transformer ratio, probably 8 Ohms but could be 16 or even 3Ohms. The output coil is not so critical but a lower impedance than fitted will give even less signal and even more noise.

You could measure the DC resistance of the coils and assume the impedance is about 1.5X that but I have no tank to hand to check this ratio. You could be lucky and find the impedance stamped on the top of the transformer (think Fender did that?) might even be on the tank, is there a model number?

But in the limit, tank reverb CAN be noisy and in the live mash with B&D no one noticed or cared!

Dave.
 
Thanks Dave. I wish I had more knowledge of this stuff, but I don't have a clue whether it's driven by a small transformer or not. Honestly I'm not even sure what that means..

What I do know though is that the tank that's in it is from Belton Engineering and the model number is BL2AB3C1B. It does not say anything about impedance.

I found a local ad for a guy selling a pretty cheap MOD reverb tank with the model number 8EB2C1B.

Having done a little research, I see people are swapping their original tanks for this in their AC30's and Fender Blues Juniors at least.
 
22921 Fender Reverb Driver Transformer MADE IN USA

^There's a picky, you can't miss it! There will be 3 transformers in the amp, this will be the wee'est.

You COULD try any ad hoc tank you came across, a valve driver is unlikely to be damaged by the wrong type but it won't be optimum for noise and sound quality.

THE top name for tanks is Accutronics but it seems they suffer from the drive coil going open circuit these days. Mind you, there are some pretty badly designed solid state driver circuits about now!

Dave.
 
Hi again. I tried something today that I should have tried long ago.

I moved the reverb tank out of the amp and lifted it up as far as the cables allowed. The noise got less and less prominent the more I moved it away.

I'm sure that means something?

As a side question, can I touch the reverb safely while the amp is on? I used rubber gloves as I was not sure :P
 
Seems like turning the tank around while on top of the amp helps even more.
 
You can touch the tank...you won't get shocked.

I've moved tanks out of the amp head space....not so much because of noise, but because I wanted to go with bigger tanks and different values to change the flavor.

Anyway...on one of my amps, I switched to longer cables ran them out of the amp, and then I got a heavy padded reverb tank bag, and put the tank in that, and then I mount the tank to the inside of my cab, but so I could flip it and have it hang on the outside, so the speaker volume/movement has less effect.
It worked out great like that.

Not sure the brand of tank you have...but it is possible that some of the amps electronics in such close proximity to be interfering with the tank and causing the noise. I mean...if simply moving it away and rotating it around has an effect...then it does seem to be electronic interference.
 
miroslav said:
You can touch the tank...you won't get shocked.
Click to expand...

Thanks, that's good to know.

miroslav said:
Anyway...on one of my amps, I switched to longer cables ran them out of the amp, and then I got a heavy padded reverb tank bag, and put the tank in that, and then I mount the tank to the inside of my cab, but so I could flip it and have it hang on the outside, so the speaker volume/movement has less effect.
It worked out great like that.
Click to expand...

That's a great idea. I might try something like that. Either that or build something around the tank and have it separate from the amp like one of those traditional tube reverbs. Kind of a hassle to carry for gigs, but then again I only play the occasional gig. I already bought longer cables to see if the cables were the problem.

I have mananged to contact the designer of the amp (Paul Cochrane) and I'm awaiting his take on it.

Thanks Miro!
 
Dain, surprised no one mentioned the possibility of having a highly microphonic tube in the Reverb position.
I recently looked up this issue and where I found you because I am having the exact same problem with my
AMPEG J-12R II. FYI - I found that the highly popular JJ 12AX7 (83S) tube is NOT a good tube for vintage amps.
It is HIGHLY MICROPHONIC and that's what is in my Ampeg right now and also has a hiss, and makes annoying
echo - reverb noises when you jarr the amp or even slap the top of the amp firmly BUT only when the reverb is turned up -
I am going to try my theory about using a LOW microphonic tube (12AT7) to test. Will let you know.
 
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