AdrenaLinn I, II and III Circuit Description


This description is not necessary for simple repairs, but provided for those who want to know more about the circuit operation in order to attempt a more complex repair. It references the AdrenaLinn circuit board schematics, which can be download from the AdrenaLinn Repair Needs page. Note that AdrenaLinn I, II and III all use one of two circuit boards as described here.




The AdrenaLinn processes audio entirely digitally. The only analog circuitry is the mono input preamp and stereo output amplifier. Here is a general description of the schematic.


The instrument signal comes in through the INPUT jack and is amplified by op amp U1 (page 1). The gain of the input op amp is set by potentiometer VR1. Circuit boards with no headphone jack contain high-frequency pre-emphasis in the feedback of U1; boards with headphones do not. The output of U1 goes to the CODEC U2 (page 1), a Crystal CS4224-KS. This CODEC uses 24-bit conversion and runs internally at 40 kHz, set by the 15.36 mHz crystal Y1.


The digital output of the codec’s A/D converter is passed serially to the DSP processor U8 (page 2), an Analog Devices ADSP-2186 running internally at 77.8 mHz from ½ speed clock supplied by U5, a 38.868 mHz clock generator. All sound processing and sound generation is done in the DSP processor.


The microcontroller U14 (page 2), a Microchip PIC16F877 in AdrenaLinn or PIC18F452 in AdrenaLinn II and III, performs all functions except sound processing, including scanning of the 4 rotary encoders (ENC1-4 on page 3), updating LED displays (page 3), sequencer timing, general system functions, user data saving and loading, MIDI processing (page 3), etc. The microcontroller runs at 15.36 mHz, set by the same crystal that clocks the codec. The microcontroller communicates bi-directionally with the DSP processor, primarily sending commands and data about when and how to process the sound. The software for this processor is stored in the chip’s on-board flash memory. Updating this software in all AdrenaLinn models requires changing the chip or updating over MIDI.


Except for 6 of the discrete LEDs, all other LEDs are driven by the Micrel MM5450BV (U4 on page 3), an LED driver chip with serial input (from the microcontroller) and 37 latched LED driver outputs.


The flash memory chip in U11, a Solid State Technology SST39VF020-90 4C-NH (AdrenaLinn) or SST39VF040-70 (AdrenaLinn II and III), is connected to the DSP and holds all drum samples, factory and user preset and drumbeat data, and the DSP operating software. On power-up, the DSP processor automatically loads the DSP operating system from this flash memory chip into its onboard program RAM.


The DSP processor sends its stereo output serially to the codec U2 (page 1), where it is converted to analog signals and buffered by the op amp U3 (page 1).


If no plug is inserted into the right output jack, both left and right output signals are mixed in the left output. The sensing of whether the right jack is inserted is performed differently in “no headphone” than “With headphones” circuit boards:


For “no headphones” circuit boards:

Mounted on the RIGHT OUTPUT jack are an infrared LED, D24, and infrared sensor, Q1 (both on page 2). If the jack is not inserted, the light from the LED is passed to the receiver, sending a digital ‘low’ signal to the input pin 27 of the DSP, causing the DSP to mix both stereo outputs to mono in the left output. However, if a jack is inserted the infrared light is not received, sending a digital high signal to the DSP pin and causing the DSP to send normal stereo output signals.


For “with headphones” circuit boards:

If no plug is inserted in the right output jack, the jack’s tip connects to its ring, mixing the right output signal (buffered by U3C) with the left in U3B.


Additionally, the revision B board has a headphone amplifier, U16.


The AdrenaLinn receives its power from a wall-mounted unregulated DC power supply of either 7.5 or 9 volts DC. Internally, three DC voltages are derived from the external power as shown on page 1 of the schematic:

+5v: Used for all logic and analog audio, except as follows:

+3.3v: Used by DSP, CODEC and flash memory chip, and LEDs

+2.5v: Used by DSP



Roger Linn Design

Los Altos, CA