09 March 2009

Friend-Chip DMX16 Modification

Recently I bought an additional Friend-Chip unit for my studio. It is a DMX16 that I plan to use to convert ADAT into SPDIF back and forth. I needed these extra ports to be able to hook up the digital FX processors that I have that all have SPDIF connections on them and I need to connect those to my RME MADI interface which only has ADAT ports. The unit takes Word Clock from my Big Ben and there something strange occurred. When I correctly terminated the unit it didn't synchronize to the Word Clock, but when I removed one of the 75 ohm terminators it started synchronizing. But then the Big Ben showed a red error led indicating that the impedance on that particular Word Clock bus was not correct. Very strange and I was sure that I had everything connected like it should be.

At first I E-mailed the dealer where I bought it about this and they had no idea and asked me to send them an E-mail in English to explain what happened. I got an E-mail back suggesting that the input voltage on the Word Clock bus was too low and they asked me to measure the Peak-Peak voltage on the Word Clock bus when the unit was connected. I connected my oscilloscope and measured 2 Volts on that. I decided to E-mail the answer to Friend-Chip directly to save some time. I immediately got an answer back saying that the Friend-Chip needed at least 2,5 Volts and that they were going to investigate. Then I got an E-mail that they found a solution with two options. Either to send the modules to them for modification or modify them myself. So I opened the unit and investigated what had to be done.

It turned out that the modification was actually quite simple. On the two MQA modules that have the Word Clock input I had to remove a resistor. They send me this neat picture that clearly showed which resistor had to be removed. Removing it was a bit tricky since it are SMD components that are very very small. But I maned to do this quite quickly actually. After wards I carefully inspected the PCB to make sure I didn't make any short circuits and put the unit back together. I hooked it up with both the terminators attached to the unit and it synchronized perfectly and also the Big Ben found everything to be in perfect working condition :) So the modification was successful. I'm very surprised by the level of support I got from Friend-Chip in Germany and it is great that they came up which such a great solution even trusting me to do this modification myself. Big thumbs up for Friend-Chip!!

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