Boss Heavy metal HM-2

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Overview

Function Description
Important Technical Specifications
Usage Features
Maintenance Features

The BOSS HM-2 Heavy Metal is a distortion effect pedal specifically designed for heavy metal music. Despite its compact size, it offers a wide dynamic range, allowing for rich and dynamic distortion sounds. It can be effectively used even with single-pickup guitars of low output level due to its high gain. The pedal allows for a wide variety of tone color creation through its two Color Mix Controls.

Function Description:

The HM-2 features several controls and jacks for operation:

AC Adaptor Jack: Used to connect an AC Adaptor for power.
Color Mix L: This knob boosts or cuts low frequencies around 100 Hz. Rotating it clockwise boosts, and counter-clockwise cuts. In its center position, there is no effect on the sound.
Level Knob: Adjusts the volume difference between the direct (bypassed) and effect (processed) sounds. Rotating it clockwise increases the volume of the effect sounds.
Output Jack: Connects the pedal to an amplifier.
Pedal Switch: Toggles the effect on or off. The HM-2 utilizes a FET Switching system, which significantly reduces click noise, making it suitable for studio recording.
Indicator: Serves as an effect ON/OFF indicator and a battery check. It lights up when the pedal is in effect mode and turns off in normal mode. If the indicator becomes dim or doesn't light up, battery replacement is needed.
Color Mix H: This knob boosts or cuts high frequencies around 1 kHz. Rotating it clockwise boosts, and counter-clockwise cuts.
Distortion: Controls the depth of the distortion and the sustain time. Rotating it clockwise increases the distortion depth and sustain time.
Input Jack: Connects an electric guitar or other electronic musical instrument. Plugging a cord into this jack turns on the HM-2's power, so it should be disconnected when the pedal is not in use to conserve battery.
Thumb Screw: Loosens the pedal cover for battery replacement. It should not be removed from the pedal cover.

Important Technical Specifications:

Power: 9V Battery or AC Adaptor (optional BOSS ACA-120, 220, or 240).
Power Consumption: 10mA at 9V.
Controls: LEVEL, COLOR MIX L, COLOR MIX H, Distortion, Normal/Effect Selector Switch, Battery Check Indicator (also serves as a Normal/Effect Indicator).
Jacks: Input, Output, AC Adaptor.
Input Impedance: 1 MΩ.
Dimensions: 70(W) x 55(H) x 125(D) mm (2-3/4(W) x 2-3/16(H) x 4-15/16(D) in).
Weight: 400 g / 14 oz.
Specifications are subject to change without notice.

Usage Features:

To operate the HM-2:

Connections: Ensure all connections are made. When operating from an AC line, use a BOSS AC Adaptor. Avoid using the HM-2 in extreme heat, humidity, or dusty environments.
Initial Setup: Set the panel controls to the suggested initial positions (e.g., LEVEL, COLOR MIX H, DIST. as shown in the manual's diagram).
Engaging the Effect: Press the Pedal Switch. The indicator will light up if the effect is on, and turn off if it's off.
Tone Shaping: Use the COLOR MIX H and L controls to adjust the tone. COLOR MIX H boosts/cuts high frequencies around 1 kHz, and COLOR MIX L boosts/cuts low frequencies around 100 Hz.
Distortion Depth: Adjust the depth of the distortion using the Distortion Control. Rotating it clockwise increases distortion depth and sustain.
Volume Matching: Use the LEVEL Control knob to adjust the volume of the effect sound to minimize volume differences when switching between normal and effect modes.
Power Management: The unit powers on when a plug is inserted into the input jack. Always unplug the cord from the input jack when not in use to prevent battery drain.

Maintenance Features:

Battery Replacement:
1. Loosen the thumb screw on the pedal cover.
2. Open the pedal cover and remove the old 9-volt battery from its housing.
3. Replace with a new 9-volt battery.
4. Ensure the coil spring is properly seated on the spring base on the back of the pedal.
5. Close the cover (pedal) and insert the screw into the pedal guide, tightening it. Be careful not to catch the battery strap or coil spring.
Battery Check: The indicator light also functions as a battery check. If it becomes dim or does not light up, the battery needs replacement.
Battery Longevity:
- Remove the battery if the HM-2 will not be used for a long period to prevent leakage.
- If the battery voltage drops, the effect quality will degrade, or no sound will be produced. Replace the battery in such cases.
- Keep the battery securely connected even when using an AC Adaptor. This ensures the HM-2 continues to operate if the AC Adaptor cord accidentally disconnects.
- Unplug the cord from the INPUT jack when the HM-2 is not in use to avoid wasting battery power.
AC Adaptor Usage: Use only BOSS AC adaptors (ACA-120 for 117V AC, ACA-240 for 240V AC, ACA-220 for 220V AC). Using different adaptors may cause improper operation or no sound.