"Quirky, popular vintage tremolo with multiple lives"




The Swampodillo tremolo rack effect module compares to the Schaller TR-68 Tremolo, Cesar Diaz Texas Tremadillo, and Monster Effects The Swamp Thang pedals.  These tremolos all share the same simple transistor-based tremolo circuit intended to sound like the tremolo circuit in Fender brown face amps.  They have a few slightly different parts that give them different characters.  



Sometime back in the 60's, maybe 1968, the German company Schaller started making a tremolo pedal designed to sound like the tremolos in Fender brown face amps.  It was the Schaller TR-68 Tremolo.  It has been out of production for many years, probably since sometime in the 80's when Schaller discontinued a number of product lines.

In the 90's, Cesar Diaz began building his own version of that circuit, which he called the Texas Tremadillo.

Around 2001, Monster Effects released The Swamp Thang, which also utilizes the same circuit.  Other boutique builders have released their versions of this vintage circuit, too.  Builders in the DIY effects pedal community have also based designs on the circuit, including one by "MarkM" called Hearthrob.

Tremolo is a very simple effect.  It is little more than changing the volume by some amount at some speed with a controlling waveform.  Most of the components in this circuit are used just to alter the volume.  Few of them are in the audio path and have any impact on the tone, since there isn't really supposed to be any impact on the tone anyway.  So while there are some minor part differences used in the various versions of the circuit, the tone is very similar.  The differences are in the shape of the wave that controls the volume changes.

The GT Swampodillo module comes in four configurations that compare to the original Schaller TR-68, Cesar Diaz Texas Tremadillo, Monster Effects The Swamp Thang, and "MarkM" Hearthrob.  Keeping in mind that the part differences are very small among all of them, the Texas Thang and Swampodillo configurations are very similar, as are the German Thang and Throbodillo configurations.  There is some more information about the configurations below.   Some of the differences are in how the controls work and other minor things that have little impact on the tone.  There are some differences due to the wave shape, though the differences are difficult to quantify and describe.

Some of the original pedals came with a second footswitch to change between Fast and Slow ranges of speed.  In our opinion, this doesn't really seem that useful.  The reason is that the Speed and Depth controls are very interactive in this circuit.  When you change the Speed, the Depth also changes.  That change can be considerable and it really isn't controllable.  So the footswitch changes not only the speed, but also the depth, by a good amount.  That doesn't seem too useful most of the time.  The Monster Effects Swamp Thang dropped that footswitch at some point, perhaps for that reason.  By default, we include a Fast/Slow toggle switch instead of a second footswitch.  That also saves a switch on your footswitch for something else.  Of course, we have the option to put Fast/Slow on a footswitch, too.



  • Swampodillo - Compares to the Monster Effects The Swamp Thang.  This is a very pleasant, warm tremolo that adjusts from very subtle to very choppy.  The speed goes from "pretty slow" to "pretty fast".  On and off volumes are basically the same.  Almost the entire range of speeds and depths are usable.  As noted above, the controls are very interactive.  Nice and quiet.  Tremolo is a simple effect and is implemented nicely in this circuit.  By default we build this version with carbon comp resistors like the original Swamp Thang pedals.



  • Texas Thang - Compares to the Cesar Diaz Texas Tremadillo.  The Texas Thang, just like the original Tremodillo is an odd tremolo, a little difficult to describe.  It's possible that the name of the pedal was taken in part from the shape of the control waveform, which looks a little like an armadillo, which is itself a bit of an odd beast...  Rate controls the speed of the modulation, as you would expect.  But Dwell controls the ratio of the time the signal is on and off.  It doesn't affect the positive and negative sides of the wave in the same manner and the same amount, giving it an odd, non-symmetrical shape.  At low settings, the effect is pretty subtle.  At higher settings it gets more pronounced.  The attack is different.  It feels a little like a delay or ramp up time on the first oscillation.  That's the part that is difficult to describe.  Feels sort of like a vibrato or delay with no dry signal for just that split second of time.  As the oscillations continue, it sort of but not really gets more normal like other tremolos.  But it definitely is NOT like other tremolos.  It is a very pleasant, warm tremolo with virtually no noise, and pretty near unity volume.  But of course, a tremolo is cutting the volume - that's what it is.  Because of its funky wave manipulation the volume drop can become more pronounced when the Dwell is cranked up, particularly when the Speed switch is on Fast.  In that setting it is quite a bit below unity volume.  You have to adjust the Rate and Dwell together, as the useful ranges on one control change with the setting of the other.  If you want a fast, choppy tremolo, then you may want a boost with this one.  But if you don't get into the fast and choppy range, then the volume drop isn't really a problem - if you like the unique wave shape.  Some artists that dig that wave shape include R.E.M., Pearl Jam, and ZZTop.
  • German Thang - Compares to the original vintage Schaller TR-68 Tremolo
  • Throbodillo - Compares to the MarkM Hearthrob version of the circuit.  In addition to updating to more modern and available transistors, there are some changes to the wave shape and Depth control that make it a little less quirky and easier to dial in the classic tremolo sounds many of us have in mind we add a tremolo.

All four configurations come with the same controls by default:  Speed/Rate, Intensity/Dwell, and Speed toggle switch.  All configurations also have a blinking rate LED.  This LED can be dim in this circuit, and at higher speeds it doesn't seem like it is on at all.  At slow to medium speeds it is OK.  Normally we like the rate LEDs on modulation effects, but this one isn't as good as most others.  We have an option to leave it off.






  • Speed Footswitch - Puts the Speed function on a footswitch, like the original Swamp Thang and the Texas Tremadillo.
  • No Impedance Fixes - With this option we will only include the input/output resistors if they were in the original circuit.  We add both resistors to all configurations by default.  They weren't included in the Texas Tremodillo or The Swamp Thang.  The original Schaller had the output one and the Hearthrob had the input one.  These may help a bit with other effects in your chain.
  • No Rate LED - By default, we include a blinking Rate LED.  If you don't want it, we can leave it off.


Front Panel

  • Intensity/Depth - tremolo depth
  • Rate/Speed - tremolo rate
  • Rate LED - blinking Rate LED
  • Speed toggle switch - half speed/full speed switch


Rear Panel

  • Audio In
  • Audio Out
  • On/Off Footswitch
  • On/Off Override
  • (optional) Slow Footswitch
  • (optional) Slow Override
  • DC Power
  • DC Power LED


Module Width

  • 1.5" for most configurations, 2" with second footswitch option
  • Check for availability of wing module configuration.  Wing configurations are not presently available if you choose to have the second footswitch.


Power Consumption (aprox)

10 - 20mA


Base Configurations

Part # Description List Price
MOD-SWAMPODILLO Swampodillo module configuration $189
MOD-TEXASTHANG Texas Thang module configuration  $179
MOD-GERMANTHANG German Thang module configuration  $179
MOD-THROBODILLO Throbodillo module configuration $169



Part # Description List Price
MOPT-SWAMP-SPEEDFSW  Speed Footswitch  $39
MOPT-SWAMP-NOIMP No Impedance Fixes $0



Part # Description List Price
MPT-SWAMP-CA Replacement pot, switch, jack, LED cable assembly $19
MPT-SWAMP-KNB Replacement control knob $2
MPT-SWAMP-PB Replacement power board $29
MPT-SWAMP-SB Replacement switching board $29