I was at one time a technical salesman - is that in your background as well?
My Southern California territory back in 1978-1981 included aerospace companies and many subcontractors serving that sector. They called us "Sales Engineers," and although most of us were not engineers, it was our job to coordinate our engineers with those of our customers, and get specced on drawings - and then get the orders, which might take years. We received a good bit of technical training at our factores and labs in New Hampshire, and knew more about the practical aspects of bearings and rotating systems than most mechanical engineerswho did not work in that sub-field.
My employer designed and manufactured some of the highest precision and most exotic "super-precision ball-bearings" on the planet, and one of my customers was involved in the design of a mechanical subsystem for the Hubble Space telescope. The Hubble was launched in 1990 - and is still functioning, thanks to some later repairs and upgrades by a Space Shuttle crew.
Am I a ball-bearing expert? No - but I know more about them than most people. Did I help to design the Hubble Telescope? No, but I did work with people who were involved in Hubble sub-system design, and it feels good to be even a tiny part of the huge team behind that project.
None of this helps me with audio since for me, all" rotating components except a volume control are now obsolete - no more rotating LPs, CD's tape spindles...but wait - my NAS still uses an enterprise class Hitachi mechanical hard drive, although that may change in a couple of years.
You may not technically be an expert in RF pollution, but you know enough about the technology to be very informative and helpful. I for one, very much respect and appreciate your input regarding Class-D amplifier design and dealing with potential RF emissions, noise and filter issues.
Thank you for the kind words.
OK this is going to be a totally off topic departure and should probably be moved to the "member introduction" section
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@amirm @Thomas savage
To answer your question, well my professional background is pretty varied, I have managed to have a career that spanned many technical disciplines.
Spent many years at Rolls Royce aero engines (Mainly military but Civil engines too) in electrical/electronics and instrumentation/data acquisition roles. As part of component and whole engine test and development, we would have to measure and analyse all types of physical parameters - pressure, temperature, vibration, stress/strain, displacement, rotational speed etc etc. On face value you might ask what has that got to do with audio, but it was doing very similar things to a studio recording engineer. For example, small audio frequency signals from vibration transducer or strain guages would need to be taken from the engines (think cabling in harsh conditions) amplified (without adding noise and distortion) , signal conditioned, often buffered to multiple data acquisition systems whilst maintaining absolute accuracy and integrity. We would then monitor and analyse these signals on scopes and spectrum analysers. I have been staring at FFTs for more years than I care to mention and installing, maintaining the associated electronic systems.
Dynamics (read anything changing at say audio frequencies) such as vibration / stress/strain guages and pressures was formerly analogue recorded to reel to reel FM tape in mobile recording vans similar TV outside broadcast vans. These recorders were excellent and could go up to 80kHz bandwidth IIRC at 60 IPS the tape would last about 7 minutes, but we rarely did that. 10kHz might be more normal. I was very heavily involved with progressing the systems to digital recording before I moved on from Rolls.
28 track Recording Van with se7000 reel to reel tape deck. This is going back quite a few years now.
Scopes, RTA, signal conditioning amplifiers (In house design switchable 6dB gain steps + strain guage supply), signal generators, signal patch panel.
Gone digital
Oh and we even used a massively powerful xray machine to look inside running engines to see how components moved through thermal and rotational forces. Should have seen the massive concrete blocks on the far side of the test bed to stop the rays!
Whilst similar to audio recording engineer in many respects there is one difference in this "measurement engineer" role. Signal integrity and accuracy is absolutely paramount. The data collected would be used to validate and modify engine design. As you can imagine, the worst case scenerio is if you collected poor quality or inaccurate data an engine could fail and people could die.
Sort of testing I used to be involved with:
Dave Hogan in this video was head of vibration when I was at RR Bristol. Very nice chap
Trent (A380) fan blade containment test
Spent many years testing EJ200 Eurofighter Typhoon Engines. Shown here being used in the Bloodhound land speed record project (exciting bit at about 3:45)
and as its meant to be use in the Typhoon - possibly the best display I have seen of its capabilities
Unrestricted climb
Possibly my favourite/proudest memory is of working on Concorde on its return to flight project (sadly after the accident)
Final landing at Bristol next to the Rolls Royce and Bristish Aerospace factories where it was built. We all lined the runway.
https://youtu.be/K4UHTiMJqpM
Worked on many other projects such as Joint Strike Fighter engines at GE in Cincinatti and supporting the US jet trainer aircraft at multiple Naval Air Stations. I think this was either Nas Kingsville in Texas or Meridian in Mississipi.
After Rolls Royce I spent time at HGL Dynamics developing high channel count high bandwidth digital recording and analysis systems (for primarily aerospace applications). Think systems that can record 256 or more channels at 80kHz bandwidth with real time Ffts of each channel.
After moving to Australia I worked in an engineering firm that provided a range of services related to sound and vibration. I worked on acoustic modelling of noise in complex engineering environments, as a noise officer for health and safety hearing protection, and vibration analysis of rotating machinery and acoustically induced vibration in things like piping. Lots of bearing anylsis as you mentioned it above.
After that I worked for a measurement systems supplier. They are the Agilent WA rep. We did a lot of work with RF kit, spec ans, VNAs etc.
Now I am putting more effort into doing my own thing with March Audio and thoroughly enjoying it
