ACV-NOS Edition Chorus/Vibrato Time Warping Device

At the heart of every chorus is a short delay whose time is modulated by a low frequency oscillator (LFO).

The ACV-NOS uses a New Old Stock Matsushita (Panasonic) BBD, hand tested and selected by our team. The NOS edition features subtle, but noticeable, differences from our standard edition. During audio testing of the BBDs, we observed differences in the headroom, harmonics, distortion, and noise vs. frequency profiles which were consistently different from reissue BBDs. Listening tests clarified the significance of these measurements. The NOS BBD sound is more cohesive, with less smearing. It has a smoother presence with an almost dithered high end, and it possesses a distinct clarity in the fundamentals. To compliment these differences, we moved the center range of the filter down about 130Hz and increased the bass response. This revoicing emphasizes the midrange and the clarity of the bass setting while providing a richer, “meatier” high setting with less sparkle. Lastly, we removed the calibration restriction on the longest delay time, leaving it up to the whims of analog variance. The exact amount will vary from unit to unit, but more than 80ms is typical. This also increases the range of the LFO Amount. Note that, due to these expanded ranges, the Time and Amount positions in our suggested settings may need to be adjusted.

Many choruses keep the delay time fixed, but our Time knob lets you warp through the decades of chorus. Start in the middle for a tight ‘70s-style chorus. Go longer for a drippy ‘80s chorus and a warm slap delay, or go shorter for flanging tones.

Another uncommon addition is our Feedback knob with phase options. This lets you deepen the chorus effect and explore more exotic metallic or vocal sounds. At high feedback settings you can use the Time knob to dial in peaks and notches for resonant sounds, like a pipe or a bell. The Tone control changes the frequency response of the feedback loop to make your chorus more shimmery, or more dark and haunting. Utilizing the phase switch you can produce hollow, deep vocal sounds akin to a talk box.

Our LFO includes multiple waveforms: triangle for classic chorus sounds, sine for gooey vibrato, and square wave for rhythmic glitches and pitch jumps. The Rate and Amount controls have a huge range from subtle dimension to complete time warping madness. Or you can zero out the LFO to explore double-tracking effects, static comb filtering, and short delay.

The Mix control has a range from fully off to 100% wet, which lets you dial in subtle sounds or go all-in for true analog pitch vibrato. These settings are great for Leslie organ sounds or tape-like warble. The Tone control is even more useful here, as a way to sculpt the overall tone of your wet signal.

Finally, the CV jack rewards more intrepid sonic explorers with an even wider range of control. Increase the feedback into self-oscillation, push the LFO beyond its limit to audio rates, or drop the delay time into a lo-fi, ring-modulated soundscape. With its thoroughly engineered set of features, the ACV-NOS synthesizes decades of time warping modulation effects to inspire a whole new dimension of sounds.

The ACV-NOS Edition is 100% analog and utilizes over 350 carefully selected components including premium audio-grade op amps and high-tolerance, non-microphonic capacitors to guarantee high performance, temperature & voltage stability, low noise, and maximum headroom.

We began with a classic chorus architecture using a 1024 stage New Old Stock Matsushita (Panasonic) BBD and a step-up boost power supply for maximum headroom. We then implemented a vintage-style compander with emphasis/de-emphasis coupled with discrete transistor, 5th-order, anti-aliasing and reconstruction filters to maximize the range of delay times without undesirable artifacts. The feedback circuit uses a synthesizer-style VCA to provide a classic, warm regeneration tone while offering an accurate method of dialing in the perfect amount of musical peaks and notches.

The input preamplifier includes a discrete, high impedance, JFET stage that can also be used as an always-on buffer. We also included some soft limiting to provide character with hot signals and prevent transients from overloading the delay section.

The clock, modulation, oscillator, and even the switch logic are all fully analog. Our clock VCO includes a temperature-compensated exponential converter for a wide, even range modulation. The clock drives the BBD at extremely high current to eliminate artifacts and provide a clear, tight sound with consistent gain. An assignable expression input increases the flexibility and control available to the user.

Power and grounding deserve special attention. The ACV-NOS is designed using a multi-layer PCB with dedicated split power and ground planes for low noise and crosstalk. The power input is fully protected from reverse polarity, over-voltage conditions, and ESD spikes. Our custom-designed 9V to 15V power supply works conveniently with standard 9V pedal power supplies, and eliminates sources of noise and radio frequency interference (RFI/EMI). Its boost technology runs at MHz frequencies to eliminate artifacts usually associated with simpler charge pump or older style converters.

Altogether, our thorough approach to engineering ensures carefree operation in any studio or performance environment!

Type: 100% Analog signal and control path

Delay Time: 3.1ms - ~80ms (uncalibrated so varies). Longer with LFO and external Control Voltages

Feedback: 0 to near infinite. Capable of self-oscillation using tone or EXP input coupled with knob position.

Rate: LFO RATE, from 0.1Hz to 14Hz (28Hz with CV control)

Amount: LFO depth control from OFF to 60% of TIME sweep

Mix: Center 50%. Adjust from full wet to full dry

Tone: ~613Hz center tilt filter. Center = Flat to 0.3dB

High +5dB to -10dB, Low +4dB to -7dB.

Phase Switch: 180° phase shift of wet signal and feedback signal.

LFO: Selectable Triangle, Sine or slewed Square wave

Expression Switch: 4 position rotary selects Time, Feedback, Rate or Amount external control. All controls are additive to the front panel knob adding extended range. TRS jack usable with CV or Expression pedal, (CV range is 0-5V). Ring supplied current limited 5V output. Control input on Tip.

Electrical Specifications:

• Bypass Footswitch: Effect on/off user selectable True Bypass or JFET Buffered (Accessible by removing ACV-1 Cover)

• Power: 9VDC @ <150mA. 70-90mA typical. Up to 250mA start up. Standard pedal center negative 2.1mm x 5.5mm barrel.

• Input impedance: >1MΩ

• Output impedance: 1KΩ Max (5k max for buffered bypass)

• Max input level: +14.25dBµ (4.0V RMS)

• Max output level: +14dBµ (3.9V RMS)

• Noise Reduction: 2:1 broadband with 10dB HF emphasis

ACV-1 NOS Differences (see manual for complete specifications):

• Delay Time: 3.1ms - ~80ms (uncalibrated so varies). Longer with LFO and external Control Voltages

• Tone: ~613Hz center tilt filter. Center = Flat to 0.3dB

  High +5dB to -10dB, Low +4dB to -7dB.

Physical Specifications

• Genuine Hammond™ die-cast aluminum enclosure

• Dimensions: D=4.95” (12.5 cm), W=3.75” (9.4 cm), H=2.25” (5.8 cm)

• Weight: 15oz (425g)

Note: All specifications subject to change at the whim of our overlords.