Aphex Systems 661 Stereo Amplifier User Manual

11068 Randall Street • Sun Valley, CA 91352 • (818) 767-2929 • (818) 767-2641
Aphex is proudly American... 100% owned, engineered and manufactured in the U.S.A. Aphex is a registered trademark of Aphex Systems Ltd.
Aphex is constantly striving to maintain the highest professional standards. As a result of these efforts, modification may be made from time to time to existing
products without prior notice. Specifications and apperance may differ from those listed or shown. This product is protected by U.S. patents 5115471,
5450034, 5483600.
Model 661
(user selectable on back) +4dBu -10dBV
Connector: 3-pin XLR female and
TRS 1/4” phone jack same
Type: Transformerless, servo-
balanced, RFI filtered same
Impedance: Balanced 20K 20K
Unbalanced 10K 10K
Nominal Level: +4dBu -10dBV (-7.8dBu)
Maximum Level: +25dBu +13dBV (+15.2dBu)
CMRR (typical): >90dB/100Hz; >70dB/1kHz;
>50dB/20kHz same
Connector: 3-pin XLR male and
TRS 1/4” phone jack same
Type: Transformerless, differential
servo- balanced
(may be used unbalanced) same
Impedance: Balanced 65 same
Unbalanced 65 same
Nominal Level: +4dBu -10dBV (-7.8dBu)
Maximum Level: Balanced +22dBu +8dBV (+10.2dBu)
Unbalanced +20dBu +8dBV (+10.2dBu)
Frequency Response: ± 0.5dB 2Hz- 110kHz same
Dynamic Range 94dB same
Hum and Noise (No G.R.): -83dBu -95dBV
(unweighted 10Hz-22kHz)
Crosstalk (10Hz-22kHz @ max output) -80dB same
THD @ maximum output .6% same
THD @ nominal output +6dB .15% same
IMD @ maximum output .5% same
IMD @ nominal output +6dB .25% same
Threshold: Auto Variable: -30dB to +20dB
Manual same
Ratio: Auto The Easyrider No-Knee™ Compression Curve
starts at 1.1:1 and ends at 6:1
Manual Starts at 1:1 and ends at 30:1
Attack Time: Auto Program (Waveform) Dependent
Manual .05 to 100ms
Release Time: Auto Program (Waveform) Dependent
Manual .04 to 4s
Input Control Range: 40dB
Output Control Range: 30dB
Controls: Input; Threshold, Output, Ratio, Attack, Release, HFX Ratio, Frequency (HFX)
Switches: Process In/Bypass; SPR; Slow/Fast; Auto/Manual, Soft Knee,
Low Cut, Input/Output (meter select), Unlink, Link, Slave, Power
Meters: Audio Level (Input and Output), Gain Reduction
AC Input: IEC standard receptacle with voltage selector, fuse and filter.
Power Requirements: 100-120-220-240 VAC, 50-60 Hz
Power Input (maximum): 20 watts
Dimensions: 19” W x 1.75“ H x 10.125” overall depth, depth behind front panel: 9.25”
Unit mounts in standard 19” rack, using 1 RU of vertical space.
Net Weights: 5.5 lbs.
Shipping Weight: 9 lbs.
Tube Compressor/Limiter
Model 661
The 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 Aphex patented circuits; Tubessence
, Easyrider
and High Frequency Expander
Tubessence is a true tube circuit which provides that “vintage” tube sound without, high heat, bulk, short life, fragility
and sonic variability found in traditional tube designs.
Easyrider is an Auto mode that actually works, consisting of the Wave Dependent Compressor™ (WDC) circuit
which takes the guess work 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. It’s No-Knee™
compression curve makes the transition into compression virtually invisible.
In the Manual mode, the Model 661 provides the full compliment 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™ (SPR) 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. What ever type of dynamics control you’re looking for, it can be done with the Model
661 Tube Compressor/Limiter Expressor
• 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 apparent bass energy level, without amplitude equalization or bass boost.
• Use Sidechain Access jacks for creative processing (de-essing and ducking).
• Stereo, dual mono or master/slave operation for total flexiblity.
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.