Ramsey Electronics MX10 manual Im E

circuits. The earphone amplifiers LM386s have quite a bit of kick to them, which should be more than enough to out power most DJ systems.

The peak hold meters serve the function of displaying peak amplitudes in your audio so your eye can see them. Normally a short duration pulse such as a drum beat or strum of a guitar has a very short time duration for the initial higher power sound. If we didn’t use a peak hold circuit, your eye would be hard pressed to see the LEDs blink on the bargraph, or in the case of an analog meter, the mechanical weight holds back the needle from going to the actual peak.

The peak hold circuit consisting U4:A and U4:B combined with D6, R43, C14, D19, R60, and C17 takes an instantaneous peak and stores it in the two 10uF capacitors. The resistors then discharge the capacitors at a slow rate. These capacitors and resistors extend the peak long enough in duration so that your eye can see it. The function of the diode is to DC rectify the incoming audio signals since we only are interested in the positive going signals. If we did not DC rectify the signal, we would constantly positively charge the capacitor on a positive pulse, then negatively charge it on a negative pulse. The net result would be a meter that just barely twinkled at you. Here is an example of what a peak hold circuit does for you. The dark gray is the original signal, and the light gray is the peak hold signal. As you can see the light gray stays at a higher amplitude for a longer period of time.

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The power supply for the MX10 is a little different than you may have expected. 12VAC is plugged into J8, the power jack. The 12VAC is then rectified to DC using diodes D29, 31, 34, and 35. This is then “smoothed” out using C30, which averages out most of the bumps and lumps out of the power supply noises. VR1, a voltage regulator takes out the rest of the bumps and lumps, and gives us a clean smooth +12 VDC power source with very little noise. U8:C is then set up to give us a buffered, regulated split supply voltage. The output of this opamp is now used to generate a ground, while the supply voltages are now +5 and -5 volts (closer to +6 and -6) in reference to this “ground”. This method is an easy way to get a split supply from a single supply such as ours.

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