Reverb pedal?

[pedaltastic]

Hi everyone,

I would just like to ask whether anyone can offer me advice or perhaps direct me to some layouts/schematics for a good reverb pedal? I am planning on making a spring reverb at some point, but before that I'd like to try something different, more similar to a Boss RV for example.

Thanks,

pedaltastic

btw - great website and forum, definitely the best on the net for pedal building! 

[Seljer]

Besides a spring reverb, the only other thing you can make for a reverb is a digital reverb, which is slightly more advanced. Go check out "Digital and DSP" section of this forum various threads on the Femtoverb. Though it uses surface mount components which may not be your thing (though its always good to try something new)...

[pedaltastic]

Great thanks! Digital hmm... well it does explain the lack of schematics for reverb pedals. 

[tungngruv]

I owned the Boss RV pedal and was really dissapointed in it. In my opinion it sounded like a bunch of really fast delay repeats, not like reverb at all. Have you seen these projects?

http://generalguitargadgets.com/index.php?option=content&task=view&id=124&Itemid=142

http://generalguitargadgets.com/diagrams/stage_center_reverb_lo2.gif

[petemoore]

http://generalguitargadgets.com/diagrams/stage_center_reverb_lo2.gif
  I'm using this one, *Tank Reverb...much more since I put it on a +/-9vdc supply...a MAX1044 type does split supply, a VS One Spot adapter feeds 9.4vdc to the MAX chip...working great...it *was Chowing too quickly Two batteries at once...loss of headroom because of supply drop doesn't sound good either.
  RV-3....agreed, sounds like a buncha tightly batched clumps of echo, does good echoes though.
 

[alecacca]

it's possible to build a reverber tank? i see on guitargeek a setup where the guitarist modded a big beer contenitor to be a reverber tank...   

[idlechatterbox]

QUOTE:
"it's possible to build a reverber tank? i see on guitargeek a setup where the guitarist modded a big beer contenitor to be a reverber tank.."

Probably others have been more successful, but my attempts to build one from scratch were stalled by the difficulty in finding springs that are "gentle" enough. What I found was that about the only place such sensitive springs are used is in, well, reverb tanks.

It's possible to find old hi-fi gear with reverb tanks on ebay (mostly old Pioneer and Sansui) gear, usually in Amplifiers or Equalizers. I guess there was a time when people thought it would be cool to listen to the stereo with reverb. Either way, the old units are super cheap. My plan is to just tear the reverb tank out of those and try to put it into a pedal. The actual tank is pretty small, so size won't be an issue. 

[Pushtone]

QUOTE:
"it's possible to build a reverber tank? i see on guitargeek a setup where the guitarist modded a big beer contenitor to be a reverber tank.."

I saw that, a "reverb tank" made out of a beer keg.

Part of Ryan's rig from Orange Sunshine in the guitargeek.com database.

I assumed it doesn't have springs as its probably just loaded with a speaker
and a microphone. More of an echo tank.  Springs or not I would expect it
to create a constant ringing given the din on typical rock stages.

Its a good DIY idea but it would have to be loaded into a road case with lots of
damping insulation around the keg to keep the stage noise from vibrating the thin aluminum walls.

[alecacca]

so, to make a rev. tank i can put a microphone and a speakerin a iron box?

[petemoore]

so, to make a rev. tank i can put a microphone and a speakerin a iron box?
  ...YEss, bigger the better.
  I wonder how long a dwell a beer keg would make.
  I read about a large tank, dude went to great lengths.
  Starting with an old oil tank like used for oil heated houses..about the size of 4 stacks or so, and ran channels
      Mic    <----------------------------------------------------l
                l----------------------------------------------------^
                ^---------------------------------------------------l
       Speak>---------------------------------------------------^
  Kind of a 'folded horn', the sound has to go a longer way through successive channelling inside the tank...Inside the tanks so that the sound produced by the speaker goes along a bottom channel >>, then ^ up, then back <<, up ^ across the next level>>...making a longer dwell from any size of tank, because the soundwaves have much farther to travel....alot  of welding and such, each 'channel' is a tray in which water can sit, it's excellent reflective properties with it's added weight and smooth surface...a 'wet' reverb.
  Whatever size tank...adding cross channeling adds 'distance'...
  I don't know about storing speakers and mics near standing, enclosed water...supposedly the water helped the reverbs treble.
  I wouldn't call it a 'pedal'.
  One of my favorite reverb sounds was 2500 sq. feet of halls and chambers, tile and finished wood floors, large glass windows...the old, fancy,empty house we were moving out of.
  I wonder what that beer keg idea sounds like...
  I just use the S.C.Reverb which works great, and IMO is worth the extra size compared to a small pedal version.

[Mark Hammer]

The principle behind mechanical reverberation is that you have something where a burst of energy is somewhat conserved and as a result dissipates slowly.  One case would be a spring where a little wiggle at one end produces ongoing wiggling throughout the spring, and plate reverb where a transducer attached to a large flexible metal plate produces the same effects.  The objective, of course, is to mimic the same thing that happens in a defined space with reflective surfaces: yell "TEST!!" and the sound continues to bounce off the walls and other surfaces for a little while until all the acoustic energy is dissipated.

Of course, that "defined space" could be ANY space, so the range of what gets to be called "reverb sound" is essentially infinite.  ALL "reverb" is valid reverb.  The central question is whether it sounds the way you want it to, and the related question is whether that can be done with a minimum of effort and cost.

"Delay" and echo are certainly cousins of reverb, and there are sonic resemblances in that both create illusions of space.  The key difference, though, is that "echo" consists of very identifiable repeats, where natural reverb consists of reflections from many different surfaces, none of which really stand out from each other in dramatically identifiable ways.  Springs have traditionally been better at mimicking this can't-really-hear-an-echo-but-it-goes-for-a-while sound than BBDs have been.  In the early 80's, Matsushita introduced a BBD chip which had 6 harmonically unrelated taps, called the MN3011 (Small Bear sells them).  The idea was that it would serve as substitute for a spring because it provided lots of overlapping repeats, similar to what reflected sound is like.  A few companies introduced "solid-state reverb" pedals based on it, but I think we hadn't really thought out reverberation very much at the time.  The products were not thrilling and they disappeared from the shelves; fast enough that I have to tell you this story because no one remembers them the way they remember phasers or early chorus pedals.

The chief weakness in these pedals seemed to be too close adherence to the Matsushita datasheets.  Although it is true that real reverb consists of later reflections being lower amplitude than initial ones, there is a whole lot more to simulating reverberant spaces than having 6 taps and mixing them together with higher value resistors for later taps.  Missing, usually, was any attempt at recirculation, and any attempt at differential filtering of outputs so that later reflections were not only softer but duller-sounding.  To my mind, the ideal MN3011-based reverb pedal has yet to be built.

It IS possible to make compact spring reverb, and as has been related here on many occasions, small-scale spring reverb was a feature (stock or add-on) on some car radios for a while in the 60's.  If you poke around for the SWTP/Radio Electronics site (http://www.swtpc.com/mholley/index.html) you'll find old magazine projects for these mini-reverb systems. 

I've been trying to get back to a project I started some 2 years ago, without much success.  I was able to find at Home Depot (or maybe it was a local equivalent) some nice compliant short springs, that would allow for spring reverb in a box the size of a Memory Man.  The principle is fairly simple.  One end of the spring is afixed to a driver made up of a small speaker.  The other end is soldered to a crystal/piezo mic/pickup.  I'm using some crystal phone handset cartridges I picked up surplus, but I imagine one could use piezo disc sensors from radio Shack or wherever.  I deftly remove a lot of the speaker cone surface so that movement of the speaker cone is much less audible.  The cone remains very solidly attached to the speaker frame and voil coil, though (think of it like the speaker version of a "chambered) guitar body).  The spring gets attached to the centre of the voice coil with a dab of epoxy (light and secure), and the centre of the sensor by means of soldering.  The speaker is driven with a standard mini-amp/headphone-amp type circuit and can either drive the speaker directly (e.g., with a 386) or via a common 1.3k:8R matching transformer.  The piezo end can be any sort of high input impedance preamp such as you might use for a piezo pickup on a guitar.  The reverb sounds I've been able to get aren't half bad.  I imagine that, much like "real" spring reverbs, having multi-spring systems allows for more of a reverb "wash" than using a single spring where reflection are more identifiable and hence like bad echoes.

A crucial part of this exercise involves having spring tension just right.  The spring also has to be fairly compliant.  It can't be so saggy that the impulse signal doesn't make it to the other end, and it can't be so rigid and strong that a) it rips the speaker cone apart if you tense it even a little, or b) needs a 100W pumped into the speaker to make it jiggle just a little.  The springs I've found cost me just over $1 each, and when stretched out to about 8" have the right mechanical properties.  The speaker can be any small "full-range" speaker.  Don't worry about having restricted bandwidth on those little 2-1/2" beeper speakers from computers because you don't want either bass or treble from spring reverb.  A speaker than goes from 300hz-5khz is fine.

Can you run a spring reverb off batteries?  Well, insomuch as this would be simply a headphone/mini amp and a simple booster preamp, the answer is yes, but not for a long time.  Basically, the same operating rules as any battery-based mini-amp.  Most folks will tell you that things like the L'il Gem (at ROG) will "work" on a simple 9v battery, but will work better with a little more oomph and mass in the battery pack (e.g., 8 AA cells). 

So, the answer is that you COULD make a DIY spring reverb with acceptable tone and convenient powering in a package that used a box small enough to fit on a pedal-board.  It would need to be about the footprint of a Memory Man or Delay-Modeller, and would have to be as tall as needed for the speaker used.

Now the even bigger question:  Would it be worth it to go to all that trouble when you could buy yourself a small digital reverb unit like a Picoverb (or make a Femtoverb) and get equally pleasing tone for $60?  I'd say that's a crapshoot.  The digital stuff sounds great and is trouble-free.  The analog DY stuff is a royal PITA but you can tweak the tone any way you want.  Your choice of poisons I guess.