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Elma Jumbo A47 Assembling

22.12.2014 16:00

The Elma A47 Jumbo is a quality audio switch which comes from the A47 product range. More space for big sized resistors and a shunt switching function makes the A47 Jumbo a high-end switch. Shunt function is similar to ladder switches but less space with the same high fidelity audio qualities. Shunt uses one input impedance resistor and one loading-resitor for each single step. So the signal always passes only two resistors, the shunt resistor and the loading resistor. The Jumbo PCB is labeled userfriendly from R1 which is the shunt resistor to loading risistors R2 up to R46. The position 47 is the direct trough position which only passes the shunt-resistor to get maximum loudness - smallest attenuation value.

Calculation of the loading resistors and single steps

Use the Excel Elma Switch Calculator, choose the Calculation Tab for the Jumbo in the bottom and configure your own switch with custom dB steps. The calculator helps a lot, it calculates automatically the correct resistor values.

Calculator instruction

Type the required shunt impedance into the R1 field of the resistor calculator.
Now type in the dB fields the steps in decibel (dB) you like to achieve with each step into the dB field. The calculator shows up the correct target Resistor values you can go for. If you order the resistors for the A47 Jumbo, make sure no resistor has the same values. ... small tolerances from the calculator are ok because it won´t be possible to find the exact calculated values - try to select the nearest values you can get.

Assembling

Assembling and soldering takes time - I recommend to place the switch high on the desk, maybe just a few cm under your head by placing a box onto the desktop as higher working-base. Use a solder-iron with a spiky end to work precise. Use High-End solder Mundorf Gold/Silver which has a nice welding point and does not splash as much. If you want to save time, we offer Assembling Service for all switches or already Assembled Elma Jumbo with PRP Resistors or whatever you like to have one it, just give us a mail.