# Fender Super Reverb RI question



## GTmaker (Apr 24, 2006)

HI folks

Just read this and was wondering if it works/makes sense/should I try it and hope nothing blows up?

*Replace the 12AT7 reverb driver with 12AU7 – Better reverb control.*
Reverb is an important character with vintage amps, yet so individual and mysterious. We all know that speakers change their tonal character during age. So does the reverb. The reverb function sounds and behaves differently between “identical” vintage amps. Some amps have long, lush and soft reverb while others are mushy and overwhelming. We often find the reverb sweet spot around 2.5 on the reverb pot, varying from 2 to 4. Some amps are sensitive and difficult to control the reverb on. The whole dynamic area can be within a narrow interval, i.e. 2 and 2.5. These amps require a careful touch when dialling in the reverb, which irritates us.
The reverb circuitry consists of two tube sections (reverb driver V3 and reverb recovery V4) and the physical reverb tank. All these components will drift during age and minor differences in component values are noticeable to man’s ear.
If you replace the V3 12AT7 reverb driver with a 12AU7, you will reduce the effect of the reverb and it will be much easier to control with the reverb knob. So simple as that.

thanks
G.


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## keto (May 23, 2006)

Geno - yeah, they're basically the same tube with less gain in the U - there's more to it than that, but not much and nothing that puts you at any risk of blowing up your circuit. If you want to mess around with how the reverb reacts, go ahead!


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## GTmaker (Apr 24, 2006)

OK folks...time for you teck guys to call me crazy...

So I put the 12AU7 in the V3 spot on my Super Reverb RI.

The one thing I did notice is that the reverb control became much more useable. Example...my normal setting was at 2 and after the switch, the same amount of reverb was found at 5. Thats pretty cool and as advertized.

This is where it gets tricky.... I found the amp (after the switch) lost a lot of bottom and I had to push the bass knob to 7 (was at 4) the get close to that same sound I had before. Even with that adjustment I could not help but feel that sound was thinner and NOT what I was used to.

There is probaly no reason at all for that tone change and it could very well be just my immagination but I heard what I heard and you'll have to pretty convincing to insist that Im just crazy.

Bottom line , I went back to the 12AT7 and all is good in the world.
As I still have that other tube, maybe I'll revisit this swap another day just to confirm what I heard.

Open to all comments and insults. 

G.


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## jb welder (Sep 14, 2010)

Please retry the swap, but compare with reverb turned all the way down (or off with the footswitch). Are there any tonal differences or loss of bass without the reverb?


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## Wild Bill (May 3, 2006)

GTmaker said:


> OK folks...time for you teck guys to call me crazy...
> 
> So I put the 12AU7 in the V3 spot on my Super Reverb RI.
> 
> ...


No, you are not crazy! You see, the 12AU7 has a LOT more differences than just less gain!

Just because the pinout is the same as a 12AX7 has meant that guys routinely will plop a 12AU7 into a 12AX7 or in this case a 12AT7 socket and think the only difference is gain. With most of the tubes in this family this is pretty well true but the 12AU7 is quite different.

It's plate load and some other parameters are nowhere near the same. This means that the resistor and capacitor values used with the tube will change things drastically. The distortion goes up and because the output plate load is different the tone response curve will be a lot different, as you have found.

This is just yet another case where some self-appointed gurus on the Net have read only one or two pages of an electronics book and made a generalization about the 12A*7 family that is not true. If they had read a couple of pages more maybe they would have learned that for themselves but they never do. They prefer to just "quote each other" - the blind leading the blind.

If you found the original guy about putting in a 12AU7 for the reverb driver and told him what you found I have no doubt he would tell you that you used the wrong brand of tube and that a different brand (one that HE sells, of course!) would sound heavenly!

You did the experiment and you learned something useful. That's more than most do!

Good for you! Crank that sucker up and have some fun!

Wild Bill/Busen Amps


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## keto (May 23, 2006)

Where did I put my damned white cane......


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## nonreverb (Sep 19, 2006)

Precisely the same question I was wondering jb welder. Since the reverb is not directly part of the dry signal, turning it down or turning off the reverb should leave the signal the same
You can remove the reverb 12AT7 and the amp still works...



jb welder said:


> Please retry the swap, but compare with reverb turned all the way down (or off with the footswitch). Are there any tonal differences or loss of bass without the reverb?


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## GTmaker (Apr 24, 2006)

jb welder said:


> Please retry the swap, but compare with reverb turned all the way down (or off with the footswitch). Are there any tonal differences or loss of bass without the reverb?


sorry for the delay in getting back to you.
Finally had a chance to try the NO reverb with the 12AU7 and it made no difference at all.
The tone was changed when I put that tube in and it stayed consistent with and with out reverb.

This will end my 12AU7 experiment.
I initialy got this tube (L&M store - Electro-harmonics 12AU7 - for the low low price of 16.99 plus tax)
to follow up on the sugestion that in V2 or maybe in the Phase inverter position, it would calm my Super Reverb RI down a bit.
Then came the V3 (reverb) experiment.

EVERY time.... that dammed tube sucked the living life out of my amp.
Enough is enough.

I have a working Volume knob that will be used to calm things down and the Reverb Knob can stay on 2.5 and give me incredible tank reverb.

Amp sounds great and I'm a happy camper. 

keep on rockin

G.


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## jb welder (Sep 14, 2010)

Well that is certainly bizarre. With the reverb turned down, the reverb driver tube should be essentially out of the circuit.
If you care to try one more test, compare with the 12AU7 in and the reverb turned down, then with the 12AU7 removed and nothing in the V3 spot. There really shouldn't be any significant change in the sound.


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