A Designs Audio introduces the 503HR horizontal, three space, 1RU rack for the 500 Series (Lunch Box) crowd.The 503HR is replacing the A-Designs 500HR two-slot, horizontal rack to accommodate the increasing need for Channel Strips in both recording and live application fields.We have been asked by our customers to develop a 3-slot version in a horizontal 1RU rack. Well, the end result is the 503HR. We feel this meets the need for a full-blown Channel Strip, a requirement for Pro Audio Recording and live applications for performing artists that wish to adapt their sound for changing venues. This can be accomplished by using a simple insert of a different module (or two, or even three). The 503HR has a robust external power supply with an LED display. This displays the amount of power being consumed or if the units in the 503HR are drawing too much power. But, the robust power supply can handle the demand. There is a 3-LED array on the face plate which displays the +16V, -16V and +48V. Some 503HR features include: All metal construction, XLR in and out, as well as a "FEED" switch on the front. This allows you to come into slot 1 and out slot 3. It also allows you to just feed 1 and 2 or none. The "Feed" switch is a 3-position switch used for: Slots 1 and 2 or "Off" or "All". This reduces the need to use six (6) XLR cables for a channel strip. But, if you are inclined to do so, you still have that option. When using the 503 with the "Feed" switch, all that is needed are two (2) XLR cables - Male and Female. The input, as an example, would go to Slot 1 and the output to Slot 3, when the "Feed" switch is in the "ALL" position. This is very useful for live applications. For example, you may only require the 503HR (with a 500 series Pre, Compressor, EQ), a power amp and a cabinet. Place the "Feed" switch to position "All." The connections would be as follows: Assign the output of Slot 2 for FOH (Front of House) and the output of Slot 3 for your amp. Used as a Channel Strip for Bass or Guitar [Preamp, Compressor and EQ], your 500 series Pre-amp would go into the 500 series Compressor, Compressor out to the FOH and your 500 series EQ to your power amp then to your cabinet. This works extremely well.