AM8399 Module - Voltage Controlled Delay

Overview This module uses the PT2399 delay chip which is an echo audio processor IC equipped with an ADC, DAC, high frequency sampling and an internal memory of 44KB (which cannot be expanded). Digital processing is used to generate the delayed signals, and the chips has low noise (-90dBV) and low distortion (0.5% THD). Delays of up to 200ms can be achived within these parameters.

AM8399 Design I have used the voltage controlled design idea of Ryan Williams and the basic design in the PT2399 datasheet. The delay time is usually set by a resistor connected to pin 6 (VCO pin). The voltage at pin 6 stays at 2.5V and an NPN current sink attached adjusts the delay time with a current between 0mA and 3mA.

The AM design does not make use of companding or extra anti-alisaing filters as used in some PT2399 guitar effects pedals. These techniques are usually used in BBD devices and contribute to an "airy" sound where the repeated delays are softened. Thje AM2399 maintains the digital sharpness of the delays.

The AM8399 VC Delay has the following front panel controls:

• Feedback
• Feedback CV
• Delay
• Delay CV
• 2x Signal Input Levels
• Signal Mix
• Delay Range
• 3x 3mm LED's to diaply delay range (SHORT, MEDIUM, LONG)

There are six 3.5mm jack sockets mounted on the left hand side of the panel, these are:

• x2 Signal Inputs
• Feedback CV Input
• Delay CV Input
• Delay Output
• Mix Output

PTM2399