Sequential Circuits - Pro FX - Ambient Package delay, reverb, flanger

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"Up for auction is a VERY rare Sequential Circuits Inc - ProFX Programmable Modular Effects System produced in the early 1980's.

This particular ProFX is even stranger as it is a preconfigured system dubbed the "Ambient Package" it includes the 524 Digital Delay, 522 Flanger/Chorus and 518 Spring Reverb modules and is housed in the Model 500 Chassis with System Controller.

there is alot of info online : google - sequential circuits ProFX

This instrument has been recently fully cleaned and checked out by a qualified professional audio service technician.. the pro-fx is very clean and fully working.

details on the particular effects in this rack:

500 System Controller:

The Pro FX Model 500 System Controller is the brain behind the Pro-FX Audio Processing System. Although the System Controller has no Audio Processing functions, this piece is required to supply power and programmable memory to the various effects modules. There is room for 64 patch memories within the onboard memory (ROM). Random Access memory (RAM) is required for extra modules to work with an expanded system. Two Operating Systems are known to exist 1.5 and 2.0 .


Other features of the Model 500 are Tape Sync for stepping through patches, memory back up via Tape Interface, Data Interface for daisy chaining 500 controllers, as well as
Footswitch INs and a CV in for routing control pedals to the functions of various modules.

OS: 2.0 is included, the internal backup battery was recently replaced durning testing (Oct 2012)

518 Reverb (module and tank)

The Model 518 Reverb includes a compact, rackmount six spring delay line, and a three-band equalizer which filters the input to and output from the reverb unit. The LP (lowpass) filter limits frequencies above its setting from 200Hz to 20 kHz. The HP (highpass) filter limits frequencies below its setting from 20Hz to 2 kHz. The MID (midrange) band filter has separate frequency (50 Hz to 5 kHz) and EQ boost/cut controls. For example a typical use would be to use the HP filter to prevent a bass drum from dominating the reverb. The module also features automatic limiting which reduces undesirable spring colorations. It contains a PEAK LED indicator for optimizing signal levels.


522 Flanger / Chorus

The Model 522 Flanger / Chorus contains three bucket-brigade device (BBD) analog delay lines which are configured to always provide two true stereo outputs. For basic flanging, the main output (a) is adjusted from 0.5 millisecond (ms.) to 12.8 ms., while the auxiliary output (b) will be simultaneously delayed by twice the time. Because the two delay times "track", the stereo image is preserved. Used by itself, the auxiliary output can provide the extra (X2) range needed to flange low pitched instruments. For full stereo chorusing, the X3 switch is enabled, which triples the output A delay (1.5ms. to 38.4 ms.). Output B still operates X2, producing a rich effect. The module is also capable of vibrato, trill effects and modulation by an internal envelope follower, LFO, or variety of external sources.

The front panel controls are organized into three groups: DELAY, MODULATION, and OUTPUT LEVEL. The delay controls select short or long (X3) delay time for output A and set a basic range over which the delay time can be modulated. Adjustable regeneration varies the feedback which intensifies the flange effect.

The Delay time is normally modulated (varied) by the internal LFO triangle wave to produce effects from a long, deep flange, to a fast vibrato. Modulation depth and speed are indicated by a pulsing LED. A sine modulating wave is also available. Or the internal envelope follower can be used to make the flange respond to specific attacks. Modulation by external sources can be enabled by the Controller CV IN jack.

The actual effect is created in the output section, where the delayed (EFFECT) and the non-delayed (DRY) signals are combined. The output level controls allow independent
adjustment of either signal. Positive or negative flanging can be selected with the INVERT switch.

NOTE: this uses the legendary SAD1024 bucket brigade delay chips used in the Mutron Flanger, electric mistress and other classic 70s/80s flangers

524 Digital Delay

The main benefit of digital as compared to analog audio delays is of course significantly reduced noise and distortion, and increased dynamic range and delay time. The Pro-FX Model 524 Digital Delay Line (DDL) offers a very wide delay range of from 0 to 1 second with a 15 kHz bandwidth, or from 666 milliseconds to 2 seconds with a 7-kHz bandwidth. With integral regeneration and modulation controls, this DDL is capable of the full spectrum of delay effects.

The front panel controls are organized into five sections: indicators, LEVEL, DELAY, REGEN, and MOD. In the indicator section delay time in seconds (and the effect of time modulation) is clearly shown on a large four-digit LED display. Two five-segment LED bar-graph displays monitor input and output levels. (the user can internally adjust the sensitivity of the output bar-graph display) Separate LEDs also indicate a 7 kHz bandwidth, or that the REPEAT function--which endlessly recirculates the contents of the delay line--is on.

The LEVEL section contains an IN switch for activating or bypassing the module (all switching to noiseless), independent input and output controls for optimizing signal-to-noise ratio, and a mixer for the dry (source) and delayed signals.

The DELAY controls adjust the delay length from the shorter times used for flanging, chorusing or doubling, to the longer times used for echo. Delay polarity can be selected and external voltage control of fine delay time can be enabled.

The REGEN section provides the feedback which creates resonant flange/chorus or decaying echo effects, depending on the delay time. External voltage control of regeneration level can be enabled and positive or negative flanging can be selected. External processors can be inserted into the the regeneration loop through back-panel connectors.

The MOD section makes a sine or square-wave LFO, or an internal envelope follower available for modulating delay time. Sine-wave modulation can produce a long, deep flange or a fast vibrato. By alternating the delay time, Square-wave modulation creates complex effects, or "arpeggiated" pitches when regeneration level is high. Flanging and related effects are usually enhanced by using the envelope follower to make the effect respond to specific instrumental attacks. External modulation can also be applied. An LED indicates the speed of modulation."