Asheville Music Tools ADG-1 Analog Delay

From AMT:

The ADG-1 includes over 400 carefully selected components. The entire signal chain utilizes premium audio-grade op amps and high-tolerance, non-microphonic capacitors to guarantee high performance, temperature stability, and low noise.

We began with a classic delay architecture using a pair of studio grade Xvive™ MN3005 reissue Bucket Brigade Devices (BBDs) and a high voltage step-up power supply for maximum headroom. We implemented a tightly calibrated vintage-style compander and incredibly deep, discrete transistor, 5th-order anti-aliasing and reconstruction filters to provide a familiar character with superior clarity, noise reduction and dynamic feel. Our feedback circuit uses a voltage-controlled transconductance amplifier, which provides Hawker’s classic feedback tone while offering the most accurate method for dialing in infinite repeats without runaway or for achieving total feedback overload.

The input preamplifier is critical to the sound of any analog effect. A discrete, high impedance, JFET input stage provides consistent operation across all sound sources and can be used as an always-on buffer. The preamplifier and drive circuit can be used to overdrive the delay line and mixer section for unique artifacts and character that only an analog delay can provide.

We spared no opportunity for flexible control while maintaining a completely analog circuit. The clock generation, modulation oscillator, and even the switching logic are all fully analog in nature. Our clock VCO, with temperature compensated exponentiator, drives the BBDs at extremely high current to eliminate artifacts and provide for a clearer sound. An assignable Expression/CV input expands the flexibility to the limits of user creativity: use an expression pedal to warp the delay time, swell in self-oscillating feedback, or add a modulated vibrato flourish in real time.

An effect of this complexity depends entirely on its power supply and input protection. We took every measure possible to eliminate sources of noise and radio frequency interference (RFI/EMI), as well as protect from electrostatic discharge (ESD) spikes to ensure carefree operation in any studio or performance environment. Our step-up high voltage power supply operates in the MHz range, well beyond the audio band and most other pedals. All voltage sources are highly filtered to eliminate noise and crosstalk between the BBD clock, LFO, and other sections with a multi layer PCB utilizing dedicated split power and ground planes. The power input is fully protected from reverse polarity and over-voltage conditions.

Electrical Specifications:

• 100% Analog signal path

• Switchable true bypass or JFET-buffered bypass with switchable trails

• Power: 9VDC @ <150mA (85mA Nominal, up to 250mA start up.)

• Expression / CV input assignable to Time, Feedback, Mod Amount, or Mod Rate (CV range is 0-5V). Ring supplied current limited 5V.

• Delay time:

  • 35-700ms in dual BBD mode

  • 16-350ms in single BBD mode

  • 27-900ms (or 13-450ms) with external CV control

• Input impedance: >1MΩ

• Output impedance: 1KΩ Max

• Max input level: +15dBu (4.3V RMS)

• Max output level: +14dBu (3.9V RMS)

• Maximum drive: >22dB (covers attenuation to gain)

• Noise Reduction: 2:1 broadband with 12dB HF emphasis

Physical Specifications:

• Genuine Hammond™ die-cast aluminum enclosure

• Dimensions: D=4.90” (12.5 cm), W=3.70” (9.4 cm), H=2.25” (5.8 cm)

• Weight: 15oz (0.425kg)