most popular brand replacement 12AX7, 12AT7, 6V6, 6L6, KT66, KT88

[mikepukmel]

They really have a ton of NOS stuff. First time I ever saw a tube company sell tubes that test weak/low. Why would we buy one of those rather than a new tube?

[Leo_Gnardo]

Wow, they are close, thanks for the link. Will give them a shot.

Keep in mind, unlike Euro and Antique/CE/AmplifiedParts, Viva has no known reputation, good or bad. You will be exploring new territory. I hope your transactions with them work out well, because it's good to have another commendable vendor especially within short shipping distance to save time AND money, right? Keep us informed.

[mikepukmel]

Will do, thanks Leo.

[mikepukmel]

Well, to be fair, that last problem sounds like tank microphony. Further, I can't come up with any reason changing the PI should affect a noise with the reverb up UNLESS it was tank microphony. The tube swap could have lowered gain, changed PI balance and a phase relationship or even the overall EQ slightly. I don't think we should fault the original PI tube for this one. But I can't blame you for wanting to get rid of problematic tubes in general. And, FWIW, I like the Shuguang 12ax7's. But you do need to get selected examples like the Ruby brand. I also like the Sovtek 12ax7lps, though they're always too microphonic to use as an input tube in an amp with much gain. Which is really too bad because to my ears they sound a lot like my old RCA gray plates in the same circuits. And my experience with JJ 12ax7's goes back to a previous epoch, but it wasn't good and I haven't tried them since. Maybe it's time to let bygones be bygones.?.

Chuck you nailed it. I took the amp chassis out of the cab, put it on the stand on my desktop, and hooked up the reverb tank behind that, on the desktop and in the bag. Usually the tank sits in the bag on top of the cab or inside (like its supposed to be). With the tank on the desktop, not a whine!

The only problem is, what the heck do I do now. Is this something that can be patched up fixed with a little glue or duct tape someplace? Maybe some foam insulation inside the tank bag? Tank was pretty expensive.

[nosaj]

Chuck you nailed it. I took the amp chassis out of the cab, put it on the stand on my desktop, and hooked up the reverb tank behind that, on the desktop and in the bag. Usually the tank sits in the bag on top of the cab or inside (like its supposed to be). With the tank on the desktop, not a whine!

The only problem is, what the heck do I do now. Is this something that can be patched up fixed with a little glue or duct tape someplace? Maybe some foam insulation inside the tank bag? Tank was pretty expensive.

I remember from some of my other repairs that in the reverb bag was also a cardboard piece that goes under the tank in the bag. If you don't have one cut a peice of cardboard and try it out. The worst you could do is fix it.

nosaj

[Chuck H]

What sort of reverb tank are you using? Long two spring?

[g1]

Not sure the exact amp you are talking about, but I assume it is a combo.
Sometimes the proximity of the speaker magnet to the tank is enough to do it. I've seen cases where someone changes a speaker to one with a bigger or deeper magnet and the tank starts ringing.
So find out if it is vibration or orientation. If it's orientation you may be able to move the tank enough to cure it.

[Chuck H]

I've had to wrap reverb tanks in bubble wrap and terry cloth stuffed into the bag. Like a reverb sausage. And it's really important to leave the bag mount screws loose so the reverb tank/bag combo isn't tight against the amp cabinet. Sometimes you can tune the reverb EQ with the coupling cap, recovery stage cathode bypass cap or HF bleeder cap circuit to pinch out the offending frequency. And all this with two, or more often three reverb tanks to choose from. New reverb tanks are very finicky and problematic in my experience. This is one of the reasons many modern amps have anemic sounding reverbs. A mass produced product has to be dumbed down to work with any variable for a given tank model so you end up with a tone that is the lowest common denominator.

I've taken to using the three spring short tanks after too many impossible hours trying to make the modern two spring long tanks work in combo amps.

[Leo_Gnardo]

Maybe some foam insulation inside the tank bag? (

I pitched my solution somewhere a couple years ago. At Home Despot pick yourself up a roll of foam weatherstrip intended for mounting camper caps on the back of pickup trucks. It's under 10 bucks last I bought one. About 1/8 inch thick, 1 1/2 inch wide. Mummify the whole tank, including the ends and piece of corrugated cardboard or thin wood covering the open side. Leave 2 holes where you plug the RCA cables. Slide the whole affair into a tolex tank sock, screw ends of the tank sock to the bottom of your amp cab. That oughta do it, and you'll have plenty of weather strip left for other projects or unruly reverb tanks.

[mikepukmel]

Thanks everyone! Amp is a Fender Deluxe Reverb AB763 clone in a 1 x 12 combo cabinet. Tank is a Accutronics/Belton 9AB2C1B 3 spring long tank (Shoulda shoulda gotten the short tank )

Speaker is a Black Shadow 12" Magnet is HUGE.

As Leo mentioned in quite a few posts, shifting the tank left and right changes the hum a LOT.
So far, not able to get rid of the ringing/feedback without taking the tank out of the cab.

Will first try the weatherstrip foam mummy thing, then try futzing with EQ filters if that doesn't work.

[Leo_Gnardo]

Tank is a Accutronics/Belton 9AB2C1B 3 spring long tank (Shoulda shoulda gotten the short tank)

3-spring long tanks have a habit of ringing on and on. If you want to sound like you're in the middle of Madison Square Garden, they're perfect for that. The echo never ends.

Antique / tubesandmore.com offers 2 spring long tanks in short medium & long decay versions: brilliant! I order the short decay, which is plenty long enough for any guitar amp. https://www.tubesandmore.com/product...nk-mod-9ab1c1b Up until recently only their MOD house brand offered the choice, and it looks like "short" decay remains exclusively a MOD product. In my latest blink at the Antique catalog, now Belton offers many of their tanks in medium and long decay, same for Belton's "Accutronics" models.

Short tanks. Sometimes one does sound better than long. Since I always have a few of each in stock, if I run across an amp that's problematic, try a shortie and if it behaves better, in it goes. I know, that can't be done if you're building a project and buying just one. Oh well.

[Helmholtz]

First make sure if its spring vibration. To find out, stop any spring vibration with some soft cotton batting and test in the assembled combo. If this cures the problem, you may have acoustical feedback caused by
- transfer of cabinet vibrations by mechanical coupling between tank and cabinet
- acoustical coupling via soundwaves from the speaker
In both cases the measures recommended above should help.

If spring vibration is not involved, you may have electromagnetic coupling/feedback between the radiated EM field of the voice coil and the reverb transducer coil. This EM coupling can be minimized by increasing the distance between the speaker and the receiving transducer and/or changing the orientation of the tank.
Also it often helps to ground the speaker frame (always recommended in combos) and/or close the open bottom of the tank with a grounded steel plate.

[Chuck H]

Oh, it's spring vibration alright. I'd bet 6 beer PNW. Three spring long tank!?! In a combo!?! I think those days are history my friends. I tried it once. Then I tried the two spring long tanks and still had too much trouble. I've found the three spring short tanks to be about as good sounding as the two spring long tanks and less trouble to get them to behave.

JM2C

P.S. The material for the little rubber transducer grommets that were used in vintage Accutronics tanks to stop ringing while allowing good transducer transfer was made unavailable due to some official finding that it was too toxic to produce or use. I read some time ago that making tanks without this "stuff" was proving difficult and is at least part of why Accutronics sold. And I think it may part of why all the new overseas tanks are problematic.

[Helmholtz]

Oh, it's spring vibration alright.

Most probably, yes. But I have seen (and cured) speaker EM feedback issues as well.

The material for the little rubber transducer grommets that were used in vintage Accutronics tanks to stop ringing while allowing good transducer transfer was made unavailable due to some official finding that it was too toxic to produce or use.

Hard to believe that there is no modern replacement material providing the same mechanical damping/absorption qualities. Sounds like a cheap marketing excuse to me.

[Chuck H]

Hard to believe that there is no modern replacement material providing the same mechanical damping/absorption qualities. Sounds like a cheap marketing excuse to me.

Agree! But I do know that just before Accutronics moved to an overseas company and ever since that it's increasingly difficult to get a reverb tank that isn't overly microphonic. Hardly definitive proof, but compelling.