Aphex 661 Expressor Limiter

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Aphex 661 Expressor Limiter
The Aphex Model 661 is a totally new type of compressor incorporating vacuum tube technology with the latest innovations in audio compression. This single-channel compressor/limiter is loaded with features, consolidating for the first time in one rack space, three patented Aphex circuits: Tubessence®, Easyrider®, and High Frequency Expander®.

The UNIQUE 661 CIRCUITRY Tubessence is a true tube circuitwhich provides that "vintage" tube sound without high the heat, bulk, short life, fragility, and sonic variability found in traditional tube designs.

Easyrider is an Automatic mode that actually works, consisting of the Wave dependent Compressor™ (WDC) circuit which takes the guesswork out of compressing individual instruments and vocals especially in live mixes. WDC automatically adjusts attack and release times according to the complexity of the program material. Its No-Knee™ compression curve makes the transition into compression virtually invisible.

In the Manual mode, the Model 661 provides the full complement of compressor adjustments such as Ratio, Attack, and Release, for maximum flexibility. Express yourself and get those "punch", "slap", "fat", "pump", and "squeeze" sounds fast and clean.

The 661 includes the patented High Frequency Expander® (HFX) which decompresses high frequencies, with user-adjustable ratio and corner frequency. Add "life" and "air" to your compressed signals without fear of background noise pumping.

The Spectral Phase Refractor™ restores clarity and punch to your tracks. Bass frequencies are more defined with more apparent power. Higher frequencies also seem to gain more detail and presence.

Use the Model 661 to control dynamics for mixdowns, protect your sound system's loudspeakers from transients and distortion or shape the sound of individual instruments and vocals. Compress dynamic levels without fear of reducing frequency response. Whatever type of dynamics control you're looking for, it can be done with the Model 661 Tube Compressor / Limiter Expressor®.

APPLICATIONS Music Production - Improve the sound on individual instruments, vocals and mixes Sound Reinforcement - A roadable tube compressor/limiter in only one rack space Broadcast & Post Production - A great vocal processor and a powerful studio tool Project Studios - Improve the sound of digital recorders and workstations Musicians - The ultimate compressor for the professional guitar, bass, keyboard instrument rig

Features Auto or full Manual operation. In Auto mode, compression parameters constantly change for best sound A true tube circuit (Tubessence) in the output stage for a "warm", "live" and "full" sound HFX allows the use of high compression ratios without the loss of high frequencies SPR increases the apparent bass energy level, without amplitude equalization or bass boost Use Sidechain Access sends jacks for creative processing (de-essing and ducking) Stereo, dual mono or master/ slave operation for total flexibility



1. The PROCESS IN / BYPASS Switch operates a bypass relay (indicated by a yellow LED) that connects the Main Audio input directly to the Output, completely bypassing the 661. PROCESS IN (indicated by a red LED) engages the 661 circuitry.

2. The SPR Switch controls the Spectral Phase Refractor circuit. SPR can reverse the effect of accumulated low frequency time delays caused by audio passing through too many electronic stages.

3. The INPUT Control sets the amount of gain in the 661's input stage.

4. The THRESHOLD Control sets the level above which input signals will be processed by the 661's gain control circuitry in a manner defined by the settings of the various AUTO or MANUAL controls

5. The OUTPUT Control sets the amount of gain in the 661's output stage, restoring level lost by compression (make-up gain).

6. The LOW CUT Switch inserts a 6dB per octave low cut filter with an 80Hz corner frequency into the sidechain. This is most useful when using the 661 (two in stereo link mode) to process a stereo mix-down of bass predominant material.

7. HIGH FREQUENCY EXPANDER (HFX) is a form of dynamic equalization that boosts high frequencies when gain reduction occurs. The HFX RATIO Control sets the amount of equalization (6 dB per octave shelving) for the amount of Gain Reduction. At 1:1 there is 1 dB of High Frequency Expansion (or boost) for every 1dB of Gain Reduction.

8. The FREQUENCY Control lets you set the (HFX) corner frequency of the shelving EQ anywhere between 2 kHz to 20 kHz.

9. The AUDIO LEVEL Meter monitors the Input and Output level depending on the position of the switch below the meters. A red CLIP LED at the right of the meter indicates clipping.

10. The GAIN REDUCTION meter shows the amount of compression in 2dB steps with a maximum of 30dB.

11. UNLINK must be engaged for normal operation of one 661. Depressing LINK or SLAVE when using only one 661 will cause the unit to malfunction.

12. LINK is engaged when two 661's are used in stereo. Both 661's must have the LINK switch engaged.

13. SLAVE is used when two 661's are being configured for a master/slave operation. Only the unit acting as a SLAVE should have the SLAVE switch engaged. The master unit needs to be in LINK.

14. The LED at the top of the POWER SWITCH illuminates when the unit is powered.

A/M The AUTO / MANUAL Mode Switch determines if the 661's primary control parameters will be manually adjusted by the user or automatically adjusted by the 661. In the AUTO (Easyrider) Mode the Fast / Slow switch is active while Soft Knee, Ratio, Attack and Release are defeated. In the MANUAL Mode, Soft Knee, Ratio, Attack and Release are active, while the Fast / Slow switch is defeated.

A1 AUTO MODE: When in the AUTO Mode the attack and release characteristics of the Easyrider circuit are automatically adjusted based upon the waveform of the input. The SLOW/ FAST Switch selects between two ranges of the automatic release circuit.

M1 MANUAL MODE: The SOFT KNEE Switch in the OFF position results in a transition at threshold that is of the abrupt Hard Knee type. In the ON position (indicated by red LED), signals are processed more gradually and the transition is less noticeable.

M2 The RATIO Control determines the amount of change in output level for a given change in input level above threshold. This is expressed as a ratio: relative input vs. output. The range of this control is 1:1 to 30:1.

M3 The ATTACK Control adjusts the time in which the 661 will reduce the gain after an increase in input over threshold. The range of the control is .05 to 100 ms.

M4 The RELEASE CONTROL adjusts how long it takes the 661 to release gain reduction after a decrease in input level. The range of this control is .04 to 4 seconds

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