The Amtec DST-5A is a 500-style analogue clipper/distortion module
designed to add a controlled amount of distortion to the audio signal.
It is a single channel line-level device that can be used at every stage of
audio work (recording/mixing/mastering) on individual tracks of every kind
as well as on sub-groups or entire mixes. Its versatility is greatly expanded
by four different clipping curves to choose from, a novel mixing stage and
simple, but carefully fine-tuned EQ stages.
Two individually selectable EQ circuits positioned around the clipping circuit
have complementary characteristics and allow for frequency-dependent
saturation with no change in tone for signals below the threshold of clipping.

The DST-5A offers anything from subtle peak limiting (rounding off the
transients and increasing apparent loudness) and tone enhancing that adds
texture and attitude and brings out character of vocals, drums, basses,
guitars, synthesizers etc. to fully distorting the original tone. It can be
used to simulate the saturation aspect of tape recording, to add crunch,
grind and growl with a choice of sonic coloration ranging from warm to
The signal is split into two paths, one is the direct path that goes straight to the mixer circuit. The second path consists of two
EQ stages and the clipping circuit with gain controls at the input (DRIVE control) and the output (LEVEL control). The clipping
circuit is positioned between the two EQ circuits (pre- and post-distortion) which are controlled by one common TONE control
with individual bypass buttons. The frequency responses of "pre" EQ and "post" EQs are completely opposite - if one of them
boosts some part of the frequency spectrum, the other attenuates it. Their function is to provide control of the frequency
sensitivity of the saturation and the frequency spectrum of the distortion products.
Setting the TONE control past the middle position with both EQ stages enabled can be used as a kind of "tape saturation"
simulator, as in that position the high frequencies are boosted before the clipping and then attenuated afterwards, hence the
smoother tone (the soft-clip setting should be used).
Any EQ section can be bypassed thanks to the enable buttons. Using only one-sided EQ allows for more radical tonal shaping of
the distorted signal.

The DST-5A’s clipping characteristic (ie. transfer function) is symmetrical and soft-knee by default, but each half of the input
signal waveform can be individually hard-clipped at the level of approximately one-half of the default soft-clip threshold. If only
one HARD CLIP button is pushed-in then the clipping is asymmetrical, resulting in increased amount of even-order
harmonics produced by the clipping circuit. With both buttons in the same position the transfer funcion is almost symmetrical
what gives predominantly odd-order harmonics. Using the hard-clip settings reduce the level coming out of the distortion
section and increase the order of harmonics.

Amtec DST-5A User Manual

Amtec DST-5A - Drums:
Amtec DST-5A on guitar:
Amtec DST-5A - Softsynth - Arpeggio:

Can be used to:

- overcome sterile sound of digital recording medium
- add character, thickness and warmth
- increase apparent loudness
- smoothly tame high frequency transients   
- add edge and brightness to any source
The default soft-clip setting is perfect as a peak level controller, as it allows to smoothly round the peaks of the signal processed
by the module. It works as a "invisible" peak limiter at lower settings of the DRIVE control, but gets more distorted and audible
in higher settings.  

The mixer circuit is unique in that it allows to suppress the dry signal from the distorted signal, leaving only harmonic
components produced by the clipping circuit.
The operation of the MIX control starts at the counter-clockwise position (DRY) with only the direct, non-processed signal
routed to the output, it reaches the WET position at the middle of the range, where only the distortion path is heard, and then
goes to the SUPER WET mode which removes input signal from the clipped signal. The LEVEL control should be precisely
adjusted in that mode for maximum cancellation.