Honestly, I can’t think of anything that technically qualifies as a frequently asked question, but it might be I just don’t notice them as such.
Here are potential idiosyncrasies that come to mind:
Power supply: I’ve grown fond of SMPS that switch at a high (measured in hundreds of kHz) frequency. The main issue I face is that most of my designs are largely (if not entirely) discrete transistors operating on a single voltage rail. This means RMA stuff does not benefit from common mode noise cancellation that most integrated operational amplifier based circuits enjoy. Furthermore, I’m not shy about cascading gain to the point at which what would be largely unnoticeable noise in a single transistor circuit has been amplified to very noticeable levels, especially with cheaper linear supplies that never quite shake the 120 Hz chopped wave coming out of the rectifier.
Crustaceans in particular are picky about supplies, and will happily amplify or sing along with dirty power supplies. Early Crustaceans (through version 1.3) required 12 volts for correct operation. Around version 1.2 I started supplying these with the units, so I have a first hand experience regarding how many supplies *don’t* work well. If you have a Crustacean that cannot seem to settle on a supply (through either loss or failure), feel free to contact me and we’ll get something sorted. Version 1.4 support 9 volt operation.
All RMA builds are supplied with a polarity protection diode to prevent disaster when randomly plugging PSUs in, enjoy life.
Warranty: Extends to the lifetime of the unit, or the lifetime of the builder – whichever is longer. Early failures (in under a year) are repaired free of charge and I carry the cost of return shipping. Anything past a year is a bit more open to interpretation (case by case basis) but typically my bench investigation & repair time will be free of charge as I consider it study from destructive tests for the betterment of future work.
In the event shipping is a logistical nightmare (hello rest of world!) I will gladly work with either you or the tech of your choice in terms of supplying knowledge base (schematics, experience, etc.), but cannot carry financial costs of work performed outside the RMA factory.