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Utilising a non - inverting Op Amp in conjunction with a pair of hard clipping silicone diodes, The Mindflayer will offer an equally beautiful and destructive wall of distorted flavouring to add serious grit and intensity to your signal. Inspired by a classic in the distortion game, The Mindflayer is Buzztones' offering. Displaying a higher input impedance alongside a slightly alternate crafting in frequency response. The Mind Flayer is here to obey your distortion needs.


The Op-amp utilised within The Mindflayer is configured as a non inverting Op-Amp, this factor signifies the non inverting input being utilised to receiving the incoming AC signal. This will lead to the outputted signal occurring with no inversion. The non inverted input is supplied in parallel with a resistor, supplying a 4.5 volt 'virtual ground' signal allowing for an equally proportional voltage swing on either sides of the AC signal.

The resistor values in series and parallel with the non inverted input contribute to the devices overall input impedance value. A desirable value for this factor is deemed around 1 megaohms. The Mindflayer's input impedance is 1.1 megaohms, this factor will help contribute to the device 'loading' factors in regards to the incoming signal, preventing any frequency loss and maintaining the integrity of the signal.

As Op-Amps have extremely high gain values, this factor needs to be controlled to make the Op-Amp a useable device. This is contributed by the use of a feedback loop. In this circuit there is a utilised feedback loop configured with several components. These components will combine to add both a low pass filter, a high pass filter as-well as setting the gain of the Op-Amp. 

The 'Distortion' knob found on the exterior of the pedal is a potentiometer found within this feedback loop, and allocates the gain value of the OP-amp. As the resistance value of this potentiometer changes, the op amp will send a larger signal through the op amps feedback circuit, in its attempts to keep the signal at both inputs the same. This is how a larger value at the output is achieved and a large level of gain is achieved.

As per the case with many Op-amps utilised within Guitar pedals, the Op-amp's slew rate is considered a lesser 'value' than ideal, which is a limiting factor in the total bandwidth displayed by the Op-amp. The slew rate can be described as the maximum rate of change in voltage per unit of time. This simply alludes to how quickly the Op-amp can change its voltage value in relation to the incoming AC signal. This is problematic at high frequencies as there is more cycles per second, requiring a faster change in voltage. In many cases a deemed 'bad' Slew rate would be considered problematic, however in the case of distortion pedals this works in the pedals favour, as heavily distorted high end frequencies can be regarded as an unpleasing audio presentation of a sound source.


Another feature of the circuit that would impact the sonic perception and interpretation of the pedals performance is the clipping diodes. The diodes are configured ‘shunt to ground’  (hard clipping diodes.) After the incoming AC signal has been amplified by the Op-amp the signal is met by a pair of diodes configured in symmetrical clipping.

The signal from the Op-amp output will subsequently be limited as the signal is met by these pair of clipping diodes. Once the forward bias voltage of the diodes is achieved they will 'turn on', sending any signal reading above this value to ground. This leads to a 'limited' signal with the reading of forward voltage of these diodes incorporated in the signals values.

The waveform at this stage will be heavily clipped (looking like a square wave) thus leading to the required distortion sound. As the gain of the Op-amp increases, the waveform clipping will be proportionate to this factor.

Symmetrical clipping refers to the impact the clipping will have on the incoming signal, with both the negative and positive portion of the incoming AC signal receiving the same amount of clipping. Symmetrical clipping can be known for having a smoother sound.

Another important implication of the diodes is the material they are constructed of, as silicone, germanium, schottky and LED diodes all have different forwards voltages and other characteristics that will impact the clipping characteristics on the signal. The Mindflayer utilises silicone diodes, silicone diodes have a higher forward voltage than their germanium counterparts offering more headroom and a less compressed texture. They have a less 'smoother' knee slop when they turn on, meaning they 'turn on' in perhaps a perceived more aggressive way. This factor is a nice complimentary feature to be utilised within a distortion pedal.


The tone control in The Mindflayer consists of a passive low pass filter control. This filter utilises a capacitor value fixed to ground in conjunction with a potentiometer, altering how much high end frequency content is attenuated. As the value potentiometer value is increased with the tone ’knob’ externally being rotated counter clockwise, frequency from the midrange onwards begin to become attenuated. The filter point will begin to move closer to the midrange as the ’knob’ continues further to be rotated. The Mindflayer is useable at either extremes of this tone control, with one side being a more present and upfront in its frequency response and the alternative being a more mellow, and smooth driven sound.

The output of this stage is met with a JFET output buffer, this stage will amplify the current and most importantly ensure the outputted signal leaving the pedal will maintain a low impedance value. This allows the pedal to display good relationships with other devices in the signal chain . The gain of this stage will be less than unity, however this device isn't incorporated to achieve any levels of gain. 


Throughout the pedals circuit there are several filter stages implemented to attenuate some frequency content undesired in the pedals performance. Besides the noted tone control and the impacts this will have on the frequency response, the next most critical filtering stage is the one utilised in the op-amp feedback loop. Within this feedback loop, there is a low pass filter utilised to attenuate some high end content that can be deemed too harsh for the distorted circuit. There is also a double RC network acting as high pass filters, which have an emphatic result of the frequency state. This RC network places two poles attenuating harmonics below the upper midrange. This is utilised to maintain some of the low end that could become too 'bloomy' 'flubby' as its run through this non linear circuit creating distortion. Overall the pedals frequency response is designed to accentuate and emphasize the upper mid range frequency response, adding presence and clarity alongside a heavily distorted sonic character.


Dimensions: 4.7 in x 3.7 in x 1.34 in. (119 mm x 94 mm x 34 mm)
Input Impedance: 1.1 MΩ
Output Impedance: <10 kΩ
Switching: This device is true bypass.
Power: This device takes a standard 9 volt DC power supply with a 2.1mm negative center barrel.


The Mindflayer Price: £89.99


If The Mindflayer sounds like a flavour crafted for yourself and wish to purchase the device, this can be achieved here

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