alpha dog
Vintage Distortion

Overview

Technical

Demos

Our best-selling pedal, the Alpha Dog combines the warmth and sag of tube saturation with the teeth of a modern distortion pedal. Built on the esteemed LM308N chip, the Alpha Dog expands its tone options by adding our proprietary HCC circuitry. The HARD & SOFT controls provide an infinite continuum of voicings, from bluesy breakup, to aggressive grunge, to stoner rock (or whatever the cool kids are calling it these days) and much much more.

LEVEL:

 

GAIN:

 

FILTER:

 

 

FAT:

 

 

HARD:

 

 

 

SOFT:

Sets the output volume of the Alpha Dog.

 

Sets the gain of the LM308N op amp.

 

Variable treble cut, pull it back for a warm, smooth tone, and crank it for clarity & grit.

 

Add up to 6dB full range boost, and contours the low frequency response of the gain stage.

 

Controls the compression & character in the hard clipping stage. V = vintage Rat diodes, T = twin stacked diodes.

 

Controls the compression & character in the soft clipping stage. G = single germanium diode, M = asymmetrical mosfet.

CHECK AVAILABILITY

DIMENSIONS:

 

 

POWER:

 

CURRENT DRAW:

 

INPUT IMPEDANCE:

Enclosure dimensions: 2.37"W x 4.37"L x 1.16"H  (60 x 111 x 29mm)

With knobs & jacks: 2.6"W x 4.4"L x 2.1"H  (66 x 111 x 53mm)

 

Industry-standard 2.1mm, negative-tip 9V to 18V power supply or 9V battery.

 

<5ma continuous, +30ma surge for 4ms during on/off switching

 

1M-ohm

Input & Gain

Hard & Soft Clipping

Filter, Buffer, Volume

 

The first part of the circuit essentially provides the impedance load on the circuit, as well as filtering out supersonic high-frequencies that could cause the op amp to oscillate at high gain settings. The input impedance of the Alpha Dog is 1M-ohm.

 

The next stage is the gain stage, which has multiple layers to it.

 

1) The gain of this section is set by the DISTORTION control, with a gain range from unity to 66dB.

 

2) The FAT control increases bass response & overall gain as it is turned clockwise. Up to 15dB boost at 100Hz, 6dB max overall boost.

 

3) The treble response of this section is interactive with the GAIN & SOFT control. When the GAIN control is fully counterclockwise, there is no treble cut. As the amount of gain increases, the treble response decrease slightly to smooth out the clipping waveform. The filtering is most present in the M side of the SOFT control.

 

4) Due to the limitations of the LM308N chip, the Alpha Dog may respond poorly to extreme frequency boosts put in front of it, such as a wah pedal...often over-compressing & creating a volume pumping effect. Every signal chain & playing style is different, and this symptom has occurred on very rare occasion, but this is a limitation of the LM308N chip in some settings. Check out the Alpha Dog Glass at VFE Custom for a version that uses the NE5534 op amp instead.

Input Stage

Gain Stage

 

The gain section also includes the different clipping elements in the negative feedback look of the LM308N op amp. The type of clipping, and the amount of treble-cut (as described in the gain stage) is dependent on the setting of the SOFT control.

 

G stands for a single germanium diode. The result is a very asymmetrical clipping that emphasizes even harmonics. Use the SOFT control to go from mild harmonic sweeting to nearly octave-fuzz tones.

 

M stands for mosfet transistor, which is arranged in a way that provides mosfet saturation and diode clipping. These two clipping types are in reverse of each other, and have significantly different clipping thresholds (+2.0V/-0.7V). The result is a sweet & open overdrive that can still really sing at high gain settings.

 

Next up is the HARD clipping stage, which transitions between different clipping elements that are shunted to ground. This configuration yields a more biting, harder-edged distortion tone.

 

The Vintage mode is the same type of clipping used in the original Rat distortion pedal. It uses silicon 1N4148 diodes arranged in a symmetrical one-by-one setup.

 

The Twin mode stacks two pairs of 1N4148 diodes for a more dynamic tone that still has the same raw distortion characteristics as the more compressed V mode.

 

With both of the SOFT & HARD controls, the 12:00 position will yield the least amount of compression & greatest overall volume.

Soft Clipping Stage

Hard Clipping Stage

 

 

 

 

 

 

The next stage is a simple treble cut FILTER. This is a very simple circuit, which uses a variable, single-pole passive low pass filter to cut treble frequencies. In short, turning the FILTER control counterclockwise cuts highs.

 

 

 

 

 

 

 

 

 

 

The final active stage is a JFET buffer that simply strengthens the signal before it leaves the pedal, and does not color the audio signal in any way.

The last part of the circuit is the passive LEVEL control. It is setup like a standard voltage-divider, and simply cuts the volume of the circuit. The volume reduction is necessary because of the large amount of volume boost the rest of the circuit produces.

Filter Stage

Buffer & Volume Stage