Classic Recording Studio Equipment

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Aphex Model 250

Aphex Model 250 Aural Exciter Type III

The slimmer and more powerful Aphex Model 250 Aural Exciter is the latest successor to the premium product in the field of Aural Excitement.


The of 1989 marked the of the latest generation Aphex Model 250 Aural Exciter III. The slimmer and more powerful Aphex Model 250 Aural Exciter is the latest successor to the premium product in the field of Aural Excitement.

The Aphex Model 250 Aural Exciter was the latest generation, fully professional Aural Exciter, loaded with powerful new processing features and improved circuitry. The dual-channel Type III adds thrilling new dimensions to Aural Excitement. Noise and distortion are virtually eliminated in the Type Ill circuitry, with new special features that make enhancement possible and actually erase noise from noisy sources. The Aphex Model 250 Aural Exciter is the third successor to the original Aphex Aural Exciter that started an audio revolution back in 1975.

The Aphex Model 250 Aural Exciter Type III utilizes a patented audio process that will recreate and restore missing harmonics. These harmonics are musically and dynamically related to the original When added, they restore natural brightness, clarity and presence, and can actually extend audio bandwidth. The harmonics are low in level, however, they add little to the signal. Unlike an equalizer or other “brightness enhancers,” which can only boost high frequencies, the Type III Aural Exciter extends the high frequencies. It is a single-ended process that can be applied at any point in an audio chain, and needs no decoding.

The Type III Aural Exciter consists of two audio paths, the main path and the process side-chain path. The main path transparently conveys the audio signal directly from the input Stage to the output stage, maintaining unity gain with wide dynamic range. The side-chain path contains all of the Aural Exciter processing circuits and receives audio from the input stage. A mixing circuit in the main path allows the sidechain output signal to be mixed with the main signal. You adjust the amount of MIX to set the strength of the effect.

Additional new design features include two modes of noise reduction, Mode A and Mode B, for sound enhancement without adding to the noise of reasonably noise free sources. It can a19 enhance the brightness, detail and clarity of seriously noisy audio while, at the same time, erasing much of the original noise.

Mode A operates as a linear sidechain expander with variable threshold. The expansion ratio of 2.5-to-l the sidechain MIX to follow the signal level below threshold. When the higher frequencies of the input signal drop below threshold, the MIX will drop at a proportional 2.5 to-I ratio. In this way, the original signal-to-noise is not affected even with a great deal of enhancement.

Mode B is a revolutionary new noise reduction technique which operates to actually “erase” audio noise while the III enhances the signal. This feature allows you to restore brightness and intelligibility to noisy recorded tracks or other noisy and improve the signal-to-noise ratio! Both modes are fast and easy to use, and in any application from live sound to broadcasting and recording.

The SPR, or Phase Refractor, function of the Type Ill is a totally new concept in psychoacoustic enhancement which can produce some amazing results. Through the many steps of duplicating, distributing and reproducing the phase of the low frequency audio spectrum becomes delayed compared to mid and high frequencies. This is a natural and unavoidable effect which worse with each generation. When the bass frequencies delayed in time compared to other sounds, the bass loses fullness and definition and *ems to become less powerful, even though there may no actual loss of bass frequency response. The high end also loses definition, seeming to get duller.

Amplitude equalization at this point will not fully restore the clarity and bass In fact, it may worsen the condition causing clipping or overload distortion. SPR corrects the bass delay anomaly to restore clarity and openness and significantly increases the apparent bass energy level without adding any amplitude equalization or “bass ” The SPR function works harmoniously with the new Aural Exciter circuitry to give the Type Ill Aural Exciter amazing new capabilities.

The DRIVE Control of previous Aural Exciters has been eliminated. In its place are two new controls that provide adjustable mixing of the exact amount of desired harmonics level and timbre. These features nuke the Type III more flexible and even easier to use.

Although more costly than conventional designs, servo-balancing offers many Servo-balanced input circuits absorb high common-mode voltages found in long cable runs without headroom. balanced outputs are not only short-circuit proof, but can be used single-ended at any time without the usual 6 dB loss of conventional circuits. To input or output in a (unbalanced) mode, you need only to ground the unused pin. In addition, inputs and outputs are fully RF protected. The unity gain 1/0 structure is normalized for both + 4 dBu. (professional) and -10 dBv (IHF) (Fating levels by switch selection from the rear panel.

NULL FILL is a new and useful tuning adjustment introduced for the first time with the Aural Exciter Type Ill. The addition of NULL FILL to the PEAKING and TUNE controls gives the Ill more power and flexibility to enhance all types of audio sources. To understand how it works, it is necessary to understand a physical phenomenon called “Phase Nulling” which occurs with all Aural Exciters when the MIX control is adjusted to obtain high enhancement.

There is a time delay associated with the sidechain signal which is an important part Of the (Fating theory Of the Aural Exciter. This time delay causes transient waveforms to slightly stretched as the sidechain signal is added to the main audio path. The stretched transients are then perceived by the ear as more pronounced or louder. The side effect of the time delay is a dip or null in the output equalization curve.

The null can a desirable characteristic it compensates for the slight additional power added to the signal by the high frequency shelving boost. The null de-emphasizes the frequency range around the TUNE control setting, thus giving even greater emphasis to the higher frequencies. There are times, however, when the Phase Null is unwanted. The NULL FILL control allows them to fill-in the phase null to any desired amount, thus further improving



  • Frequency Response: 1Hz – 190kHz
  • THD: 0.01% Max at +27dB
  • IMD: 0.01% Max at +27dB
  • Maximum input/output level: +27dB
  • Nominal Gain: 0dB
  • Output Noise: -86dB
  • Unweighted Signal to Noise: -90dB
  • Dynamic Range: 114dB
  • Crosstalk: Better than 85dB up to 20kHz
  • Dimensions: 482.6mm x 44.5mm 228.6mm
  • Weight: 6.3kg


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Aphex Model 250 Aural Exciter Type III

by Jamie Apresto Jr

Sound Quality 90%
Build Quality 85%
Usefullness 95%
Mojo/Funk 85%
Reliability 90%

Nice effects ever most in bands

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