Build Your Own Tube Reverb for Less Than $200!

drbob1

Gold Supporting Member
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What you'll need:
1. A small, single ended tube amp. Just about anything will do, but bonus points for repurposing that Epiphone Jr. you've been meaning to mod. I have to suspect that almost any little solid state amp will work, too, but I haven't tried it. I'm using my Superbaby because it's set up.

2. A reverb tank. You can get these new, but it's more fun to prowl flea markets and thrift stores for old organs no one wants. Rescue the tank from that. You'll read online that tanks have an input impedance that you have to match to make them sound good. While this is true to an extent, your reverb is NOT going to be a pristine studio verb, this is rock and roll. You might consider not cranking your little amp all the way up so as to not abuse it… You can measure the tank resistance, which is supposed to be something like 1/4 of the impedance, or read the code on the side of true Hammond tanks to see what they say. This tank is from an old Allen organ and has no markings on it. Static resistance measures 2 ohms, which according to one table suggests that it's an 8 ohm tank, perfect!

3. Some kind of mixer. I'm using a passive DOD mixer and an ABY box. Guitar signal goes to ABY and splits to the Superbaby and pedalboard. Return from the reverb tank and output from the regular pedalboard go to the mixer, output from that to the bigger amp (London Power Studio). Now you have control over Dwell (or tank drive) with the output from the smaller amp, EQ going into the reverb tank, and mix using the mixing knobs on the small mixer. Voila!

I'll do a Youtube video of this later today!
 

drbob1

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28,890
Here's the video…



I just used the mic in the recorder, so it's not great sounding but it'll give you idea. I used my Superbaby, which is the single ended amp I have set up all the time, but any cheap amp will work. And the complicated "split the signal, run 1/2 thru the reverb then recombine" thing I did above is MUCH easier if you have an effects loop! Guitar > amp > effects out > small amp > reverb tank > buffer or boost for tone recovery > effects return. The loop has to be parallel or you end up with the mixing problems again. Anyway, the video shows both ways…
 

deadlands

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1,692
I hate being a naysayer, but that doesn't sound like a very usable reverb. Sounds like there is a layer of distortion behind the dry signal and not a wash of splashy spring reverb.
 

drbob1

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28,890
That is going to depend a lot on the tank, I suspect. This is a long delay, 2 spring tank. I think that guitar reverb is usually based on medium or short delay tanks, and 2 or 3 springs. It's not up to the standards of the Valverb in the background, but then I just put it together in 1/2 hour and spent the requisite 2 hours futzing with getting the video organized.

The idea came from the fact that the Fender Reverb is basically a Champ driving the tank, and fiddling with gain structure, EQ, tube choices and so on would likely go a long way to improving sound.
 

corn husk bag

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4,242
Cool, keep on messing with it! This was brought up in a thread a couple of weeks ago. I don't remember who or where though.

Kind Regards,
Steve
 

drbob1

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28,890
It was the thread on "Are Fender Tube Reverbs Good", but I'd never heard it put that simply before: Champ into Tank, done. I'm guessing you could package one of those tiny EHX SS pedal style amps in a box with a tank and have a real spring reverb for less than $100 plus work. Of course working out the drive and EQ stuff so you loved the sound would take some work. I'm probably done with this because it's kinda fun but I have outboard reverbs (Valverb, Fender and StudioMaster) so I don't really need one. Hey, if someone wants to continue to experiment with this I'll sell you the tank for shipping and handling...
 

deadlands

Member
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1,692
The Fender reverb unit is like a Champ into a tank, but that's not really accurate. The 6G15 circuit is tuned for reverb, not for driving a speaker and the inverse is true as well. There is also a circuit for the reverb recovery, mixer and tone knob. That recovery circuit is where the tone comes from. Running a tank into a pedal that acts as the recovery circuit is not going to work the same. The impedence is way off by a factor in the thousands (tank outputs are measured in kilohms not ohms). That is going to produce the tone in your video. Really raspy and noisy with no oomph. The decay length has nothing to do with it either, the long decay tanks are used in the Fender units, not the short or medium.

You could build a little recovery box with an appropriate opamp to handle the load, something like this http://roymal.tripod.com/ultimate.htm. But now we're just getting complicated.

Also, anyone can build a 6G15 reverb unit for around $200. The kits are around that price. The expense comes with the chassis and cabinet to put everything in, which is still a problem with "single-ended amp as reverb" idea.
 

WhoJamFan

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2,560
Bitmo sells a mod to turn a Valve Jr head into a standalone tube reverb unit. Did this 3 years ago, very cool sounding.
 

S. F. Sorrow

Member
Messages
8,293
Interesting thread.
I have an old Vox tank from a gutted Churchill PA head.
Was wondering what it needs (watts?) to drive it(?) I have an old tascam 4-track and was thinking of running it thru the fx loop, but I assume you need an amp to drive the springs(?)
 

drbob1

Gold Supporting Member
Messages
28,890
The 6K6 in the original reverb unit was capable of what, 2w in single ended, cathode biased? Anything in that ballpark should be fine. Although a tank designed to be driven by an op-amp might be really high impedance (and hard on a tube amp). You do need more than the Tascam to drive it, though.

If the output impedance is a problem you could use something with a very high input impedance. Like the SHO circuit at 5 megOhms. Or you could run it back into a tube buffered effects loop and just forgo EQ and mix capabilities. Anyway, while it would cost $200 to buy the pieces I've used, they're all useful in other terms (as an amp and boost pedal for example) so you're really not putting any cash into this at all, except the tank. Anyway, it IS a safe and reasonable thing to do, go thou and do likewise and let us know how it turns out!

Oh, and if we're talking the best way to get reverb in a guitar setup, just buy a Valverb. They're still less than $400 and they sound great AND you get a somewhat useful tremolo as well!
 






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