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Super Stereo DN78 Phantom Valve Rotary DJ Mixer

This one came across my bench after the owner had it sent over from the UK. Function issues not unusual for devices that have been in transit, with vibration a given and poor handling not uncommon. When opening the device up, something more was amiss. This is an case study of why an engineer is not necessarily a technician.




First off, the one across my bench was the first release of the Super Stereo DN78, which has since been bought out by the reputable Formula Sound company, who design and manufacture all products in house, to a high industry standard. The DN78 II is world class, most notably it has been re-engineered with a 30% improvement in sound.


First test revealed the issues the owner had mentioned, but of course still shinning through was the sound quality. The tube stage is on the output of these mixers, providing a warm, clear sound. Weighty, solid knobs and dials with a smooth action only achieved from the best possible potentiometers. Sleek design with wooden side panels - everything you'd expect from a boutique rotary mixer.


Upon opening it was obvious that whoever had designed this, was not an experienced design engineer. Incorrect male/female connectors mating, far too tight component placement, making replacement possible by having to remove surrounding components also, incorrect cable gauge for some connectors used. Further disassembly revealed PCB design not favourable to soldering (unisolated ground planes for instance) and loose solder balls among the internals (!) All quite elementary errors not to be expected in any electronic device.


This is where the owner was fortunate to be referred to JZ Services. "Discover the unparalleled level of service an industry trained technician can deliver." is not just an empty line for marketing. Having worked in every facet of electronics - from design, prototyping, production and assembly, installation and repair/service - the production weaknesses/mistakes were easily identified and resolved. Just some minor but timely reverse engineering was involved, as no schematics were available.





There are some excellent engineers out there, who can design, test and assemble a solution/product in-house from beginning to end, and there are those who only design, with no hands on experience on the tools. I've worked in numerous workshops with both. No disrespect to the later, as both smaller and larger companies will have engineers who design, produce a protoype pcb, then a production technician will assemble, making note of all areas that need improvement (such as tight placement of components) In this case, the design engineer did not posses the skill set to complete this on his own.


What the reader can take away from this is that you can be an engineer your whole career and never use a soldering iron for more than 10 hours of your life. You can also call yourself a "technician" all your career and never use a soldering iron without damaging the pcb around components replaced..Ive seen it first hand numerous times..actually I need more than 3 hands to count the number of times.

Industry training is crucial for technicians and engineers who want to deliver to a customer at an industry standard. You are not taught these skills at TAFE or University level, nor from watching Youtube or reading AV forums. After study of the theory and basics, you then begin to learn how to be an engineer or technician by working in a workshop...the quality of your skillset developed being directly aligned with the quality the workshop and its employees deliver.


After all in said and done, an interesting, timely, delicate and of course rewarding job, that ended with the device leaving the workshop in a state far better than the original owner would've purchased it in.



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