Micro Tube Spring Reverb


The Micro Tube Spring Reverb is a transformerless stand-alone unit adding rich and spacious reverberation to guitar and line level signals.
A finely tuned and musically balanced circuitry enhances the reverb springs with maximum lively and natural response from the subminiature Micro Tubes.

It connects to guitar amp inputs or FX loops, studio mixing consoles and PAs.
The input can be switched to accept guitar pickup signals or any kind of processed signals at line level.

The transparent MIX control interacts with the REVERB control sweeping from pure input signal with a subtle reverb shadow to deep and endless resonance.
The REVERB control's unique design creates a rich and detailed reverb sound, even in the lowest settings.
DAMPING regulates the range from brighter reflections with more decay to a softer diffusion with shorter decay.

3-spring/medium decay reverb tank is standard. Vintage style 2-spring/long decay tank is optional.
Both tanks switchable is another option.

Available as stand-alone unit or rackmount with optional balanced XLR input and output, using high quality Jensen transformers.

Micro Tubes (subminiature) - Small size, but sizable warmth, presence, power and transparency.
These special purpose tubes were developed by the military to operate smoothly under extreme conditions with maximum life span.

Tube driven Spring Reverb

Transformerless pure and rich reverberation

Transparent Mix preserving the input signal

Reverb only output for dual amp/stereo setup

3-spring or 2-spring or both tanks switchable

Stand-alone or Rackmount with balanced XLR sockets

Works with any kind of audio signal

Guitar amps - Recording studio - PA

Read the Instructions for detailed info on the controls and possible connections.

High Impedance Input
High Impedance Output
High Impedance Reverb Output
Reverb, Damping, Mix
Guitar or Line input switch
Reverb On/Off footswitch
Transformerless tube driver
Shock-mounted tubes
Tube life: 30.000+ hours!
Paper-oil capacitors
Carbon Composition resistors
Laser engraved aluminum chassis
100/120/220/240VAC (50/60Hz)
Handmade in USA

Stand-alone or rackmount with
balanced XLR sockets

17" x 1-3/4" x 8" with single tank
17" x 1-3/4" x 13" with dual tanks

3 Springs vs. 2 Springs:

3-spring tanks have a more smoothed out flutter with a bigger, fuller sounding reverb effect and more lows.

2-spring tanks have more flutter and grit with a simpler sounding reverb capturing that vintage 1960s vibe and 'surf sound'.

No transformer - no loss:

Standard transformer driven reverbs are limited in signal quality and frequency range.
The Micro Tube Spring Reverb is transformerless without signal loss or noise, giving a purer and richer reverb with a wider and lower frequency range.

Reverb only output:

The Reverb only output connected to another amp or mixing/recording console gives a Stereo 3D-effect.
It sounds like coming from a distance, while the Mix output source can be adjusted to move from a dry up-close signal towards the distant reverb signal.

XLR Input and Output

Dual tank version with rackmount brackets

Custom figured spalted maple cabinet with laser engraved brushed stainless panels

Custom figured cherry cabinet with laser engraved brushed stainless panels


Sound Samples:

The following Sound Samples were created by Ryan Fergon from the band Soulajar.

Signal path: Music Man Albert Lee with Dimarzio 36th Anniversary PAFs -> Spring Reverb 3-spring -> Siegmund Midnight Blues with 2x12 Tone Tubby Red Alnico cabinet.
The recording was done with one large diaphragm condenser mic with no EQ or compression and everything flat through a tube mic preamp.

Finger Picking

Chord Strumming

Funky Riffing

Fast Picking

Psychedelic Feedback

I made these Sound Samples showing the difference between the 2 and 3 spring tanks.
The amp, reverb and guitar settings are the same on both sound clips. Only the tanks are switched.
The amp is the Sound King with 15" Field Coil speaker.
The guitar is the Suspense with P90 pickup and Volume and Tone up.
I upgraded a large diaphragm condenser tube mic with a Micro Tube, Neumann U47 replacement capsule and Jensen transformer plugged into the Simplex Mic Pre

2 Spring Tank

3 Spring Tank

Spring Reverb Tank Referrences

Historical use in Musical Instruments
Morrish, John; The Fender® Amp Book; pp. 25, 26 :

Laurens Hammond of Illinois popularized the use of artificial reverberation devices through his church organs in the 1940s and 1950s. The early (pre-B-3® ) Hammond® organs were sold to churches on the principle that organ music is greatly enhanced by reverberation, but the minister's speech in the church is hampered by reverberation. Therefore, churches were designed to be acoustically dead, and the Hammond® organ had to have its own artificial reverberation.
Reverberation made its debut in the Fender® line as a separate item, using a spring unit bought from Hammond® in 1961. It was first incorporated in a Fender® amplifier with the Vibroverb® of 1963 and then spread widely throughout the amp line, just as vibrato/tremolo had before it.

The Reverberation Effect
Scott, J. L. - Chief Engineer; Accutronics® document 126-00005 (February 1, 1978) :

A listener standing some distance from a sound source will perceive sound that is actually a combination of direct sound and indirect sound that has been reflected from the boundaries of the listening area. The reflections are referred to as reverberation. Reverb can enhance the perceived sound from a source by adding depth, color and liveliness. Reverb can be thought of as being composed of two parts:
1) Early reflections shape the listener's conception of room size
2) Cluttered reflections convey the liveliness of a room

The Significance of Multiple Transmission Springs

Imagine you are inside a large hall and you clap your hands once. The length of time required for the arrival of the very first reflections is called the delay time (usually on the order of tens of milliseconds, e.g. 33 ms) and is related to the volume of the room (or distance of the reflective surfaces from the listener). The number and density of reflections increases rapidly with time and they become cluttered while simultaneously decreasing in level until they are no longer audible. The length of time required for a sound to decrease in level by 60 dB is called the decay time (usually on the order of a few seconds, e.g. 3 s) and is related to the acoustical properties of the reflective surfaces in the listening area. For example, poured concrete walls will reflect more (absorb less) acoustic energy than drywall.

The use of multiple transmission springs helps to improve the reverb characteristics. A listener in a large hall with natural reverberation is not usually standing the same distance from each reflective surface. Naturally, there will be reflections from different surfaces having different delay times. The use of multiple transmission springs with different delay times serves to simulate a more natural ambiance, as well as improving the overall frequency response because one spring's response will fill voids or holes in the other spring's response. Vintage Accutronics® specs list the following delay times per spring:

Short 33 ms
Long 41 ms
Medium 37 ms

Decay time should be selected to suit the application. The same reverberation decay time that enhances and adds liveliness to the sound of the guitar can make speech unintelligible. General decay time suggestions traditionally used for specific instruments:

Guitar - Long (2.75 to 4.0s)
Organ - Medium (1.75 to 3.0s)
Vocals - Short (1.2 to 2.0s)