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HSR Sound Trigger

for Boss DE-200 Delay

A simple but effective circuit for improving the triggering facility on the Boss DE200.

As a creative tool, the Boss DE-200 offers both excellent value and flexibility, but its method of storing sounds can make life very awkward.

The HSR Sound Trigger, however, enables the loading process to be triggered by the sound source itself, which then ensures that the sampled sound will start immediately when retriggered. This is particularly important when the sampled sound is synchronised to a rhythm track as any small timing discrepancy will completely ruin the effect.

To Use

The trigger unit will accept line or mic level signals and a threshold control allows the gain to be optimised such that the panel LED glows brightly when an input is present.

There are two input sockets joined in parallel so that a feed may be taken from one of them to the Boss DE-200 to avoid the need for an additional splitter box, and the trigger output feeds directly to the 'trigger input' of the DE-200.

It is important to remove the footswitch from the DE-200 at this time as it normally overrides the unit's trigger input.

Figure 1. Sound Trigger circuit diagram.


IC1a and IC1b form an instrumentation amplifier, the gain of which may be varied from 0 to around 60dB. IC2 supplies extra gain and positive half cycles are rectified by D1, the peak value being held on C5 for around 100 milliseconds.

TR1 performs the dual purpose of buffering the output voltage and illuminating the LED. The circuit is designed to run from a +/-12V power supply such as the E&MM RackPack or Twin-pack but two PP3, 9V batteries should serve just as well.

Figure 2. Veroboard layout.
(Click image for higher resolution version)


Parts List

(All resistors ¼ or ⅓W metal oxide)
R1 100K
R2,R3,R4 680R
VR5 22K linpot
R6, R7 22K
R8, R9 4K7
R10 10K

C1, C2, C3 33pF
C4, C5 10μF/25V
C6 0.VF
TR1 BC107
IC1 TL072
IC2 741

LED standard red 1 off
¼" jack sockets 3 off
Plastic or metal case 1 off
Veroboard 1 off

The circuit may be easily built on a small piece of Veroboard, a suitable layout being shown in Figure 2. IC sockets are not necessary unless you're paranoid about such things, but do check that all components are the right way around before you switch on.


Pull the welding mask over your face and hold the cushion firmly in front of you.

Switch on!

If the circuit is OK nothing will happen. If the circuit is faulty, nothing will happen. Connect a suitable input and adjust the sensitivity until the LED comes on when a sound is present. If it does this, you're in business; if it doesn't, look for reversed components or shorts on the Veroboard.

When everything is OK, try out the system by sampling something percussive like a drum, a coal bucket lid or the cat, that way you can check out the electronics and write a hit single at the same time!

Also featuring gear in this article

Previous Article in this issue

Boss DE200 Delay

Next article in this issue

Revox PR99 Stereo Recorder

Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.


Home & Studio Recording - Nov 1984

Donated & scanned by: Mike Gorman


Electronics / Build

Gear in this article:

Studio FX > Boss > DE200 Delay

Gear Tags:


Feature by Paul White

Previous article in this issue:

> Boss DE200 Delay

Next article in this issue:

> Revox PR99 Stereo Recorder

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