Euraudio MID2 and MID2A specifications
Welcome to the Euraudio MID2 and MID2A specifications, in which you can read about the system requirements (application criteria), operation and technical data of the MID2(A).
The MID2(A) is a Mains/line voltage input/distribution board with two auxiliary, separately grounded positive DC power supplies. It can configured for dual auxiliary supply (dual mono) or single auxiliary supply (stereo or mono) systems. Please find the MID2(A) assembly instructions here.
MID2(A) system requirements
What kind of amplifiers can the MID2(A) be used for?
The MID2(A) is part of the stereo CTA MID and LDA MID, the dual mono Euraudio LDA DMx, and the mono LDA MON DiY kits. The MID2(A) PCB can be used for other audio amplifiers that need one or two auxiliary power supplies.
For the dual mono systems, two on/off power switches may be required for the two channels. For amplifiers with two transformers up to about 200 VA each, the two switches can be within a single double pole switch (DPST or DPDT). For amplifiers with bigger transformers, two separate switches are recommended that should be operated one after the other. This is to limit the rush-in current to levels that will not trip your household circuit breaker.
Up to what amplifier power can it be used?
See Technical data.
Operation
The MID2(A) has a mains/line voltage input connector, the mains input then goes two ways to two channels. The following holds for each channel. The mains/line goes through a fuse, then there is connection for an on/off power switch, and there is an X2 capacitor that filters out the EMI. A small transformer, rectifier bridge and voltage regulator provides an auxiliary supply voltage (e.g. +12 VDC or +9 VDC) with separate ground on each channel.
In addition, the MID2A PCB has place for ON/OFF switch class X2 debounce capacitors, while the MID2 PCB does not. The following figure is the schematic of the MID2A with component values for the LDA DMx.
Caution! The operation of the protection circuits in the Euraudio CTA and LDA DiY kits relies on how fast and how predictably the auxiliary power supply collapses when power is switched off. Please do not change the values of the filter capacitors significantly. Use the L7812 or L7809 linear regulator(s) as specified in the BOM list. Do not use switch mode power supplies or switch mode regulators to generate the auxiliary supply voltage(s) for the Euraudio CTA and LDA kits.
Although the simple X2 capacitor in the MID2(A) board is deemed sufficient in most cases, you may also equip your amplifier with a more sophisticated EMI line filter. There are many IEC sockets with built-in, effective power line EMI filters in the market.
Technical data
At 25°C ambient temperature unless otherwise noted.
Mains/line input: max. 250 VAC, max. 5 A
Recommended maximum audio amplifier power (class B or AB amplifiers): 2x250 W / 4 ohms or 8 ohms
Aux. supply voltage output
for CTA MID and LDA MID: +9 VDC, max. 80mA
Aux. supply voltage output for LDA DMx: 2x +12 VDC, max. 40mA each
Aux. supply voltage output
for LDA MON: +12 VDC, max. 40mA