I cannot really say anything about "Vietnam being worse than japan/china". I really don't have any knowledge regarding this. However, I have ordered individual electronic parts (capacitors, op amps, etc.) from digikey/mauser and they always come with a packing slip that indicates the origin of that batch. I have had parts that came from Japan, Malaysia and even Mexico. So even though it's "manufactured in Vietnam", the individual parts could come from anywhere. The electronics industry is now a world market.
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I can really only tell you how I believe a particular piece of equipment is going to sound based on the circuit design, personal experience, and youtube videos. So if you feel nervous about buying something made in Vietnam, by all means go buy something you feel comfortable with!
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I don't think there is really a firm "rule" when choosing fuses. It is a tool to tune sound, just like power cords, interconnect, speaker cable. They all affect the end result in some fashion or another. If you want a good cable brand, my usual recommendation are Audioquest and Wire World. Audio quest is mostly solid core (except for the cheap stuff). Wire World is not quite solid-core, but it's close. Then pay attention to the types of terminations and wire (copper, silver-palted, silver, etc.) and choose based on how you want your equipment to sound.
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Parasound is an excellent amp, but it is voiced warm with softer highs. The fuse combinations all depend on what kind of speakers you have - as I said, with my B&W D3, I had to use all silver fuses in the amps. However, with Focal, which is a much faster responding speaker, I could not use a single silver fuse and had to use all Furutech rhodium fuses.
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In my listening and opinion, Anthem amps have a weird sort of compressed sound to them. It's hard to explain, but they don't seem to have very good high resolution "air" and seem to compress or create a messy like signature in the mids. Other people may have different opinions, but this is what I hear with the Anthem amps. The Anthem MRX receivers do not seem to have this sonic signature.
The Rotel would probably be the best fit among the brands we have mentioned. I heard Rotel amps at RMAF and they are very refined and actually sounded very good. They are not as "warm" sounding as Parasound or NAD and have more resolution than Parasound/NAD/Anthem.
