Shure SCM262 Internal Modifications, Disassembly, Low-CutFilter, Ducking Depth, Ducking Threshold

INTERNAL MODIFICATIONS

WARNING! Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing and modifications to qualified service personnel.

DISASSEMBLY

To access the printed circuit board (pc board) for internal modifica- tions, use the following steps:

1.Unplug the power cord.

2.Remove the knobs and retainer nuts from the front panel.

To remove MIC 2/LINE 2 from the left outputs, remove R910. To re- move MIC 2/LINE 2 from the right outputs, remove R911.

Low-Cut Filter

To eliminate the 80 Hz, low-cut filter, remove resistor R501 (mic 1), or resistor R519 (mic 2). Place a 10 to 33 μF capacitor in X501 (mic 1) or R502 (mic 2). The polarity of the capacitor does not matter.To change the frequency of the low cut filter, remove resistor R501 (mic 1) or R519 (mic 2), and place the proper capacitor into X501 (mic 1) or X502 (mic 2) to get the desired corner frequency.

The following tables list the low-cut frequency corners for some of the most common capacitor values:

3.Remove the two screws at each bottom corner of the front panel.

4.Remove the four screws at each corner of the back panel.

5.Slide the back panel and pc board out from the rear of the chas- sis.

CAUTION: When reassembling the SCM262, DO NOT OVERTIGHTEN the knob retainer nuts. Use a minimal amount of force to secure the nut (0.6-0.8 N⋅m (5-7 in⋅lb)). Damage to the internal components will result if too much force is used.

Capacitor	Corner
Value	Frequency
.033 μF	803 Hz
.047 μF	564 Hz
.068 μF	390 Hz
.1 μF	265 Hz
.22 μF	120 Hz

Ducking Depth

Capacitor	Corner
Value	Frequency
.33 μF	80 Hz
.47 μF	56 Hz
.68 μF	39 Hz
1.0 μF	26.5 Hz
2.2 μF	12 Hz

Mono Mixer Modification

This modification allows all the inputs to be mixed to a single mono sig- nal sent over both the left and right outputs.

Short jumper X203.

This modification adjusts the level of ducking depth attenuation of the input channels when ducking is activated.

The aux ducking depth may be changed by removing resistor R213 and inserting a resistor into jumper X202. Use the following tables to de- termine the proper resistor value for the desired ducking depth.

Phantom Power Disable

This modification disables the phantom power per channel.

To disable the phantom power from mic 1, remove resistor R121. To disable the phantom power from mic 2, remove resistor R122.

15 dB Mic Preamplifier Pad

When a microphone has an extremely high signal, getting the desired gain might be difficult -- a small turn of the gain control might change the sound from a whisper to deafeningly loud. This modification adds a 15 dB Mic preamplifier pad to allow more accurate gain adjustment with ex-

Ducking	Resistor
Depth	Value
6 dB	4,000 Ω
9 dB	5,000 Ω
15 dB	7,500 Ω
20 dB	10,000 Ω
24 dB	12,000 Ω
29 dB	15,000 Ω

Ducking Threshold

Ducking	Resistor
Depth	Value
36 dB	20,000 Ω
42 dB	25,000 Ω
47 dB	30,000 Ω
50 dB	33,000 Ω
55 dB	40,000 Ω

tremely high microphone signals. Remove R160 (mic 1) or R183 (mic 2).

Hard Panning MIC Channels

To remove MIC 1 from the left outputs, remove R912. To remove MIC 1 from the right outputs, remove R913.

This modification adjusts the threshold for activating the ducking cir- cuit.

The ducking threshold can be raised or lowered by first removing re- sistor R333, and then placing a resistor (R) at jumper X303. To lower the ducking threshold, use a resistor value (R) less than 2k ohms. To raise the ducking threshold, use a resistor value (R) greater then 2k ohms.

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