Vibrosonic Reverb 77-79 era, breaks up too much, noisey

Luke Goetz · From: Saskatchewan, Canada

I have a 77-79 era Vibrosonic Reverb (with master volume). I like the tone i get from it for pedal steel, but if i dial the gain volume past 3 it starts to break up quite a bit. So I have been leaving it at 3 and turning up the Master volume. The problem with that is it creates a lot of hiss and buzz.

I had the tubes checked and they're all good. Someone suggested I change the preamp tubes from 12ax7's to 12au7's or 12ay7's for more clean headroom.

Can anyone attest to this? Is there something else I'm missing? Or is this a downside to the master volume era vibrosonics?

Ken Pippus · From: Langford, BC, Canada

That thing should have enough clean headroom to shake the paint off the walls. Capacitors shot?

David Nugent · From: Gum Spring, Va.

For maximum clean headroom, the master volume setting should always be much higher than the pre-gain setting..A thought; Have you tried plugging the amp into an outlet on a different circuit? I own an earlier Fender Twin (basically the same unit as a Vibrosonic)as well as other tube amps and all are a bit noisy in my music room. In fact, the Twin exhibited so much hiss that I took it to a tech and when plugged in at his shop, it was almost dead quiet. Had him check it thoroughly just to be certain and he pronounced it to be perfectly sound (no pun intended)...FYI: If your guitar is equipped with single coil pickups that could be a contributing factor as well.

Luke Goetz · From: Saskatchewan, Canada

David, I've played the amp for a couple years now. Numerous venues and practice spaces as well as at home. It's noisey pretty much everywhere. I've got the gain at 3 and the master at 8 to get a decent clean volume in a medium volume venue. My guitar does have a single coil pickup, but the buzz isn't nearly as bad when i plug into my twin as when I plug into the vibrosonic.

Might need to be recapped.

Anyone have any thoughts on my tube question?

Lane Gray · From: Topeka, KS

Have you tried using the input 2, which is attenuated?
That will give an approximation of using a lower gain tube in V1 (or 2) with less effort.
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Luke Goetz · From: Saskatchewan, Canada

Not sure if I have, I'll give it a shot.

Aaron Jennings · From: Montana, USA

Luke,

Others with way more knowledge and experience may chime in, but here are my thoughts.

Any tube amp with that many years on it needs a full service from a reputable technician. There is probably a pretty good chance someone has already been 'under the hood' and you never know what you will find...

Often screen resistors on fender tube sockets can need replacing, this can be a big source of noise/hiss.

A microphonic tube could be contributing.

Tubes can often 'test' fine (depending on how they were tested) and perform poorly. One of the best tests is always to swap it with a tube of the same type, in the same circuit.

Is it the original speaker? This also factors in to the volume/breakup relationship.

If you don't feel comfortable monkeying around in these things, I am sure the forum can recommend a good tech in your area!

Just sharing from my personal experience tinkering with tubes. Good luck!

Luke Goetz · From: Saskatchewan, Canada

Thanks Aaron!

I've had bad luck with techs in my city, but they are out there, I just haven't found the right one. You're probably right in saying that it probably needs some TLC. I contacted the previous owner, and it sounds like he didn't do much besides replacing the tubes.

I'll try switching out tubes too and see if that works. It came with the original fender speaker, but I just bought a JBL D130F that I'm going to replace it with, so maybe that will have an effect.

Jon Light · From: Saugerties, NY

Luke, these amps are not fire breathing 'gain monsters' and you should be able to open the master up without any noise (minor background hiss can be accepted). I don't believe that the master circuit adds any gain---it only attenuates---so the problem is not in the MV. It is just that turning down the MV reduces overall output including noise.
There is no doubt that the amp needs service. The good news is that if you can find a good tech in whom you can trust, you will have a great amp when you are done.

Abe Levy · From: California, USA

Having had a vibrosonic reverb for a few years now, here are my two cents: keep master volume at 10. Just forget it exists. Mine was an absolute turd of an amp until I put an altec Lansing 418b in it. I tried tons of speakers including 2 different jbls - a D130f and an E 130 - nothing made this amp sing until I put the altec in. Now it is my favourite amp. It just suddenly came to life. I also had a new pine cabinet made for it with a plywood baffle. This helped as well (I did it a couple years after the altec) made it much lighter too. The particle board baffles in these amps are horrible. It's not a super loud amp though. Not nearly as loud as my silver face twin. Weird since it's basically a twin with a 15. I like this though, since my twin is really too loud for most applications...
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Pete Burak · From: Portland, OR USA

I have also noted that my Dual Showman Reverb is way louder than my Vibrosonic Reverb (and I don't think there is anything wrong with the Vibrosonic).
Does the hiss go away when you turn the reverb knob to 0?
Have you swapped V1 and V2?... You can also re-seat all the tubes by wiggling them in and out a few times to break up any Oxide buildup on the contacts (this happens a lot in the Pacific Northwest).
I once fixed a friends non-functioning reverb by just re-seating the tube.

Buell Wisner · From: Georgia, USA

Stephen Cowell · From: Round Rock, Texas, USA

The pre tubes can test good and still be hissy... replace V2, leave V1 out unless you use the normal channel. Leave the master at 10.

Try this experiment... Swap every 12ax7 in for V2 that you own... Notice the difference in noise and gain? V2 is the most important tube in your signal chain, problems there get amplified down the chain. Money there is well spent.
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Luke Goetz · From: Saskatchewan, Canada

Thanks for all these suggestions! I'll do some toying around this weekend and see if one of these things does the trick. And I definitely need to find someone experienced to take a look at it and do some maintenance.

Buell: I've had the amp for about two years, and I've used it for rehearsals/performances at least once or twice a week since. I usually have the eq set at T= 3, M = 4, B= 8 approx.

Pete: The onboard spring reverb needs some work, so I always have the reverb at 0, and have been using a pedal instead.

Lefty · From: Grayson, Ga.

Luke,
I own one of these and do not get noise and hiss, even with a Stratocaster.
I suggest replacing all the preamp tubes as marked on the chart inside. These are cheap, and a good place to start. Tube Depot now has a sale on their JJ tubes. I just did this on my Mesa mark IIb that was noisy, and it now sounds wonderful.
Check the ground wire to make sure it is grounded to the chassis. I was getting a lot of noise from my 64 super reverb and cured this with a grounded power cord. If you decide to replace the power tubes, the amp should be re-biased properly.
Also if you replace the speaker with a JBL remember they have opposite polarity. Check your speaker harness also. You may try turning the reverb of with a footswitch. As you replace tubes a little Deoxit spray to the tube socket helps.
regards,
Lefty

Carl Mesrobian · From: Salem, Massachusetts, USA

Tony Prior · From: Charlotte NC

as stated, it's a late 70's amp and needs some help..meaning work.

Of course MV on 10 and if there is noise as you stated, stop... theres a problem. Fix the noise and you will be good to go. You can't hide the noise or the issue.

Tubes, tube sockets, screen resistors, power supply caps, don't be afraid to spend a few bucks. It's a fine amp...
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Lefty · From: Grayson, Ga.

Like Carl I always look at the simplest and cheapest fix 1st.
Once I replaced all the preamp tubes in my boogie I was good to go. This is cheap and you can do it yourself. If you need new power tubes or electronic work hopefully you can find a decent tech. I have used the same one for twenty years, and know what you are saying about trust. Try cleaning and wiggling your reverb cables also.
Lefty

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