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In Reply to: silver-plated copper posted by Lew on February 1, 2005 at 07:54:51:
I agree with Lew's general observations & particularly wrt silver plated copper - it sounds far worse than either type alone.Actually, polyurethane has comparable or worse AC properties than PVC does, fwiw. It's advantage with magnet wire is that it's physically tough and available in high temperature versions. Teflon insulated magnet wire is made - might be a good way to cover your sonic bets.
Follow Ups:
The advantage of magnet wire is the tiny mass of dielectric. Worse than PVC doesn't matter nearly so much when you have such a small fraction of the amount. Polyurethane and enamels and magnet coatings come in various forms, the problem with teflon is that it is so soft it's prone to cold flow, meaning that pressure can push it out of the way and give you some shorts. Not a good thing by any account. Urethane and polyurethane are much tougher.
Makes me wonder about the use of Zero autotransformers -lots and lots of coated magnet wire, especially in comparison with the minimal lengths inside the amps. If a Zero is used, does it matter what's in the amp?
Hi -The lower stepdown ratio, plus the autoformer configuration does help minimize some of the capacitive effect, but, IMO, it still reintroduces several of the traditional weaknesses of a conventional transformer coupled output to a reduced degree. The question is then whether the reduction in distortion, increase in damping factor and increase in power is worth it for the application at hand.
I've always run my DC coupled OTL direct into the load, but when I was pushing it hard into the nominal 4-5 ohm load of the Basement Blasters a while back, I realized eventually that its distortion was audibly somewhat higher than into an easier load, but in this case, I was able to compensate here by biasing the OTL somewhat farther into Class A operation and accepted the slight loss of power. Of course, unlike some OTLs, mine has a high damping factor, so that frequency response dependencies on the load were not an issue here.
You may be right about polyurethane, but I may be wrong in saying that polyurethane is the coating on magnet wire. It's something made from petroleum, however. By all accounts, the magnet wire sounds excellent, but I have no experience with it.
You don't need to depend merely on my word - look up the electrical properties of polyurethane for yourself - they're mediocre on an audio quality scale and polyurethane is one of the more popular resins used for magnet wire.
I guess I did not make myself clear. I don't disagree with you at all. In fact, when I first heard that the wire is coated with a petroleum derivative, I was skeptical re its use. I am only saying that several DIYers have reported that magnet wire sounds excellent when used as chassis wire and so constitutes a very inexpensive and good choice. I speculate that the reason it may sound good IN SPITE of the polyurethane is that the coating is very thin.
My impression is also that the deleterious effect of mediocre insulation materials is minimized when buffered by a relatively large air gap. Probably the reason that round magnet wire air core inductors don't sound worse than they do are the unavoidable air gaps between turns.
Several years ago, I built a small 2-way speaker system using, in the xover, Solo foil wound inductors having polyester insulating tape (which is a better dielectric than polyurethane or nylon, but not nearly as good as, say polypropylene) and I was disappointed in the relatively strong negative effect the insulating tape had on the SQ (lacking air gaps - it hardly sounded better in this regard than round wire air core inductors). So, as soon as I could, I replaced them all with Goertz foil wound inductors which used polypropylene insulating tape, which sounded substantially smoother and more neutral than the Solos.
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