The Phaser E-stim Reference and Glossary
E-stim, or estim, stands for electrostimulation
and means a technique to pass an electric current from one electrode, through living tissue, to another electrode. Sensory perception depends on various variables such as the size and placement of the electrodes, the applied pulse waveform
of the stimulating current, and the pulse repetition frequency.
E-stim is usually broken down into different categories such as electromedicine, electrotorture, electrosex, and electropleasure, the latter meaning pleasure through the erotic use of electricity.
Besides the electrodes, e-stim requires an electric stimulation power source, a device that delivers a pulsed current to the electrodes. For electromedical applications TENS units are widely spread and are gaining in popularity with physiotherapists, and quite often, these same TENS units are repackaged and sold as electropleasure devices.
But more and more the market for e-stim units gets dominated by devices specifically designed and manufactured for erotic use. Prices vary from $60 for a simple TENS machine to $600 for a more sophisticated multichannel e-stim device
Another approach is to use an electric stimulation software
such as Phaser, an amplifier and a step-up transformer circuit, also referred to as a Phaser Circuit
, to generate the stimulating pulses in a most flexible way, creating stimulation effects that are not achievable with off-the-shelf equipment.
A still growing e-stim DIY community prefers homemade devices, also known as White Boxes
Electrostimulation with a Phaser Step-up Circuit
An e-stim device is a self-contained box that is specifically designed for electrostimulation. Most e-stim units are battery powered, some have built-in rechargeable batteries, and some devices come with a mains adaptor that boosts the maximum available output power when plugged in during operation.
The first electric stimulation device to be sold in large quantities is said to be the RelaxAcizor
Microprocessor controlled E-stim Device
The latest generation of e-stim units are digital devices, controlled by a microprocessor inside the box. A software running on a computer allows to design and upload new routines into the device.
More enhanced devices even process audio signals and audio files
that are fed to the unit via an audio input jack. Our electrostimulation software
Phaser is suitable for driving e-stim units via the audio input, introducing new sensations and allowing secure and encrypted remote control over the Internet.
DIY E-stim White Box
A White Box
, in the context of electric stimulation, denotes a homebrew DIY e-stim box that connects to a computer's sound card or to another interface. It usually consists of electronic parts which form a Phaser Circuit
, and optionally a power amplifier.
There are various reasons why people start building their own electrostimulation equipment. The first thing that comes to one's mind is, of course, saving money. Good e-stim equipment does have its price, but apparently not everyone is willing to pay such price. Another motivation is the ability to produce levels and sensations that are not achievable with off-the-shelf e-stim devices.
The photo shows a DIY Phaser Circuit that makes use of 6 transformers. The box connects to a power amp driven by audio signals from a computer.
Homebrew 6 Channel DIY E-stim White Box
E-stim software usually means a desktop or laptop computer application that generates e-stim audio signals intended for electric stimulation, and outputs these signals in real-time through the computer's sound card.
These e-stim audio signals are either fed through an amplifier to a Phaser Circuit
, or they directly drive an e-stim device
with audio input jack. They can also be written to disk as e-stim sound files
for use with other units.
Recent software allows to choose between different pulse waveforms
, and to modulate the amplitude and frequency of the signals. You may also find level displays, waveform viewers, features to measure frequency and pulse response of step-up circuits, and dynamic pulse enhancers.
Electrostimulation software usually comes with a set of ready-to-run sessions that can be tailored to your needs and saved as shareable session files.
The safe and encrypted PRP
protocol of Phaser even allows secure e-stim remote control and chat.
While most e-stim software targets Windows only, Phaser is a true multi-platform solution, providing a distinctive platform-independent appearance with a standard behavior, running on Windows, OS X, and on most common Linux distributions.
The Windows version of our Phaser e-stim software is high DPI-aware and appropriately scales to your current Desktop DPI setting without any blurring. You may also choose another scaling factor to meet your personal needs.
Scaling is required to take advantage of the higher pixel data that high-density displays offer. These high-PPI displays are now becoming increasingly popular on tablets and notebooks, such as the Macbook Pro with Retina display at 220 PPI.
The Java version of Phaser supports scaling factors of 100%, 150%, and 200%. On the right we have 3 instances of Phaser running simultaneously on OS X, at different scaling factors.
3 x Phaser on Mac OS X @ 100%, 150%, and 200%
It is commonly accepted that the most energy effective e-stim waveform is a low duty cycle pulse train, a LDC pulse
. In contrast, sinusoidal stimulation signals require a linear power amplifier and a low distortion step-up transformer circuit, and the average energy delivered to the tissue by sine waves is much higher than with optimized LDC pulses.
However, sine waves are particularly suitable for exploiting interference effects like the Phaser Effect
, and thus are commonly used with StereoStim setups and devices.
The Phaser bPulse
waveform is a bi-directional, balanced LDC pulse that has its interphase interval maximized. This delay between the charging and discharging pulse lowers the excitation threshold, and thus also lowers the total energy delivered to the tissue, making it our preferred pulse shape for electrostimulation.
The Phaser iPulse
waveform makes use of a fixed interphase interval, which is equal to the pulse width of the signal. This is the recommended e-stim waveform for repetition frequencies below 80 Hz.
Both the bPulse
and the iPulse
pulses are DC compensated, i.e., they do not have a DC offset, which is also true for the Sine
Bi-directional pulses, also referred to as biphasic or bipolar pulses, have less average power than sine waves. The average power depends on the pulse width and the pulse repetition rate of the electric stimulation signals.
Recommended energy-efficient e-stim waveforms are the two optimized LDC pulses that our Phaser software emits.
The bPulse Waveform, maximized interphase interval
The iPulse Waveform, fixed interphase interval
ycle pulse waveforms reduce the tissue power dissipation at the skin-electrode interface, compared to a sinusoidal signal that induces the same sensory perception.
Minimizing the delivered energy to the tissue is of particular importance so as to reduce or eliminate e-stim side effects like tingling, numbness, or skin irritation.
Phaser's unique LDC e-stim waveform optimizes the ratio of stimulus perception to delivered energy through insertion of an interphase interval (short delay) between the charging and the discharging pulse. This interphase interval separates the pulses slightly so that the discharging pulse does not reverse the physiological effect of the charging pulse.
Optimized LDC Pulse with maximized Interphase Interval
Optimal E-stim Waveform
The first step on the road to the perfect pulse is to choose an electrode-skin model that most closely reflects the e-stim specific environment, and to calculate the actual values of the model's circuit elements from measurements in the lab.
After doing the math it becomes obvious that the optimal electrostimulation waveform (LDC
) reduces the tissue power dissipation by more than 90%, compared to a sinusoidal stimulation inducing the same sensory perception. (Article is accessible
The pulse width should be chosen to be within the optimum operating range. Phaser's bi-phasic pulse with maximized interphase interval is our implementation of the optimal e-stim pulse waveform.
Optimal Pulse Waveform: Power vs. Pulse Width
The Phaser Effect is achieved by generating sine waves with slightly different frequencies for the two channels in a Three-Electrode Setup
. This is equal to a continuous and periodic change of the phase relationship between the two e-stim signals. Thus, the combined signal amplitude varies in time with the beat frequency, which is the difference between the two interfering signal frequencies.
Fig. 1 shows two sine waves L and R. R does have a slightly higher frequency than L, thus increasing the phase difference with time. The green line is the combined signal L + R, the electric stimulation current through the corona electrode if using this Phaser Circuit
, slowly varying its amplitude with the differential beat frequency.
Using LDC pulses
presents a new problem when it comes to exploiting the interference beats for e-stim purposes. In Fig. 2 two biphasic pulse trains with slightly different frequencies are shown, the blue pulse train having a slightly higher repetition rate. The thing with low energy pulses is that there is nothing, most of the time. That's why it's low energy. Combining both signals does not result in a nicely modulated signal, but in a more or less randomly looking pulse train with some rare peaks when the pulses L and R overlap (green peaks).
The solution here is to apply AM modulation in combination with 180° phase shifts to one of the emitted pulse trains.
In Fig. 3 modulation and phase switching is applied to the pulse train R (blue), the black arrows marking the points of the 180° phase switches. The result is quite comparable to that of sinusoidal interference beats, but at a greatly reduced energy level.
Phaser can emit these LDC pulse patterns and easily turns your computer into a versatile stimulation source, ready to be used in a three-electrode setup.
Fig. 1 Phaser Effect: Interference Beats
Fig. 2 LDC Pulses and Interference Beats
Fig. 3 Phaser Effect with LDC Pulses
A Phaser Circuit, also Phaser Step-up Transformer Circuit
, essentially is a combination of UL listed low cost mains transformers and a resistor network.
The circuit acts as a high impedance current source in order to maintain a constant stimulation current independent of the load impedance.
The output impedance should be at least ten times the load impedance to achieve current source characteristics, i.e., 10 kΩ or higher, way better than the typical 500 Ω of most off-the-shelf e-stim devices and TENS units.
Encapsulated and vacuum potted low cost mains transformers are usually used to convert the AC mains voltage to a rather lower voltage. Using them in reverse and outside the frequency range they are optimized for requires some extra research, as frequency response plots for the entire audio range are usually not available from the transformer manufacturers.
So we tested different samples from various makers for their usability in a Phaser e-stim step-up circuit.
Most transformers are designed for both the US and European market and hence come with two primary and two secondary windings. Connecting the two primary windings in series and the dual secondary windings in parallel gives the best turns ratio.
Our step-up circuit dissipates more than 90% of the supplied input power as heat in the resistors, the price to pay for such a passive current source. Exactly this high power dissipation is the reason why commercially available, battery-powered, lightweight e-stim devices do have a relatively low output impedance (300 to 500 Ω). Converting most of the power into heat would suck the battery dry pretty quick.
On the other hand, a Phaser Circuit is robust, short-circuit and open-circuit proof, and adds yet another layer of security to the setup if UL listed parts are used.
If power consumption is not a concern, a passive high impedance source is the absolute first choice for any high quality step-up circuit.
The transformer circuit forms a low-pass filter with a roll-off of -6 dB per octave. To improve the frequency response of the step-up circuit, this roll-off must be compensated for by applying a pre-emphasis filter function to the signals that boosts the high frequency components. DynaShape
is our implementation of such a digital filter optimized for e-stim.
Phaser E-stim Step-up Transformer Circuit (Simplified)
Tested Transformers for the Phaser Circuit
Typical Step-up Transformer Frequency Response
The Phaser DynaShape
pulse enhancer is an adjustable digital filter that compensates for the low-pass filtering effect of step-up transformer circuits.
To preserve the original e-stim pulse waveform, the necessary step-up transformer circuit, the Phaser Circuit
, must have a flat frequency response curve. Usually these transformer circuits have a low-pass characteristic. DynaShape
applies a pre-emphasis filter function to the e-stim signals that boosts the high frequency components and thus flattens the frequency response curve, as shown on the right.
DynaShape Frequency Response Boost
The Three-Electrode Setup, also Tri-Phase Setup
, combines two e-stim signals from two independent channels to drive three electrodes. If properly used with stimulation signals that exploit interference beats, a very pleasurable Phaser Effect
It is most important to maintain the correct phase relationship of the two signals by observing the transformer polarity markings of the Phaser Circuit
Most of the Phaser e-stim session files and templates are designed for a three-electrode setup.
Three-Electrode Setup: Wiring of E-stim Electrodes, Simplified
E-stim Audio Files
E-stim audio files are specifically crafted sound files that are played through an amplifier and a step-up transformer circuit, a Phaser Circuit
, and deliver stimulation pulses to appropriate electrodes. Some commercially available e-stim devices
are also equipped with an audio input jack and can process e-stim sound files fed into the audio input.
Electrostimulation audio files are either played from a digital player, a CD player, or from a computer.
E-stim audio files tend to be large and often are digitally compressed to save disk space and hence transmission time over the Internet. Lossy compression methods like the very popular MP3 algorithm alter the digital data in an irreversible way and thus should not be applied to any e-stim audio signals. However, such MP3 e-stim audio files are widely available on the Internet, or sold on CDs through retailers.
To create or edit electrostimulation audio files, audio editor software can be used. Tools like Expression Evaluators
allow sound to be generated from almost any equation. Some clever minds quickly adopted this to e-stim and published a wide variety of formulas to evaluate pleasurable stimulation sounds.
A major drawback of expression evaluation is the tedious process of generating the complete e-stim sound file over and over again for each change made. This is where the Phaser software kicks in, generating stimulation signals in real-time.
A Low Duty Cycle (LDC) E-stim Audio File Example
E-stim Signals generated using math. Expressions