Litz wire (alternatives and hype) - Page 1
Forum section: electronics / beginners

author: 13hm13
author_rank: Frequent Contributor
timestamp: November 23, 2022, 07:06:49 pm
content: In the audiophile world, one often encounters the term "Litz wire".https://en.wikipedia.org/wiki/Litz_wirehttp://www.cardas.com/litz.phpI think the term is being used incorrectly ... maybe because its sounds German and fancy! But also because Litz is usually referring to enamel-coated wire strands, and the strands are wound together (coiling).Maybe this can be called "Litz" in some context:In any case ...How much is hype?For example, certain projects use this in their BOM:soft Litz OCC silver plated cable 20 core*0.08mm OD:1.25mm 24awg 110metershttps://www.aliexpress.us/item/2255801044933932.htmlor:Silver Plated FEP Wire High Purity OFC Copper Cablehttps://www.aliexpress.us/item/2255800303788403.htmlor:https://www.aliexpress.us/item/2251832748319440.htmlInexpensive stuff from Ali in China.But how does it compare to, say, stuff I have in my parts bin. Such as this USA-made hookup wire (9609):UL Style 1213 and MIL-W-16878/4 Hook-up Wire[9606 24 (7x32) SP PTFE .010 .044 200 600 1213, MIL-W-16878/4]https://www.conwire.com/product-category/wire-cable/hook-up-lead-wire/high-temperature/1213-high-temperature/Thanks!

author: james_s
author_rank: Super Contributor
timestamp: November 23, 2022, 07:11:03 pm
content: Litz wire means wire made of individually insulated strands. There is no way to tell from that photo whether that is Litz wire because it's covered by an outer jacket that hides the strands. There's nothing sketchy about Litz wire, it has substantial benefits in high frequency, high power transformers. It is pointless to use it as speaker wire but there's no point in trying to use logic to analyzer anything audiophile related.

author: 13hm13
author_rank: Frequent Contributor
timestamp: November 23, 2022, 08:20:09 pm
content: Quote from: james_s on November 23, 2022, 07:11:03 pmYes, going by the PURE sense of the orig term, it does connote something like:I have several high-end IEM earphone cables that use coated conductors, in a twisted spiral, single-insulated cable. However, those enameled stands arethemselvespainted different hues. One-color group of strands carries L, another R, and the third is Ground. And there is glass fiber that is meshed in each group:Quote

author: TimFox
author_rank: Super Contributor
timestamp: November 23, 2022, 10:00:55 pm
content: I believe the literal meaning of the German "Litzendraht" is "stranded wire" in English, but in English technical usage "Litz wire" means that each strand is individually insulated. Good Litz wire will assemble the strands in a better configuration than merely twisted together as are the strands of normal "stranded" wire.Inhttps://context.reverso.net/%C3%BCbersetzung/deutsch-englisch/Litzendraht#litz+wirethe translation examples include both "stranded wire" and the usual meaning "Litz wire".

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 24, 2022, 02:41:01 am
content: It's exquisite for high frequencies. I wound an inductor of apparently Q > 400 @ 200kHz the other day, using some on a gapped ferrite core. Which is to say, if I dump 400 VAR through such an inductor -- as might happen in a not-very-sharp signal filter (say 2nd order Butterworth), at the cutoff frequency, transmitting about as many watts; or say in a SMPS operating at ~100% ripple fraction, and doing a few times more watts DC output -- it dissipates merely 1 watt in the process. Which for something its size, is nothing at all; it could dissipate probably 4W or so (size of ~30mm cube).As for claims in audiophile circles -- as usual -- it is meaningless masturbation at audio frequencies.Tim

author: MrAl
author_rank: Super Contributor
timestamp: November 24, 2022, 06:26:55 am
content: Quote from: 13hm13 on November 23, 2022, 07:06:49 pmHello there,Litz wire is associated mostly with skin effect which causes higher loss in wires when the frequency goes up. To lower the loss in the wire, multiple insulated strands are used. Silver plating on the surface of each wire would help due to the lower resistance of silver compared to copper, but how much difference that makes depends on the skin depth.The idea is that since skin effect causes the current in a wire to flow closer to the surface of the wire than the center, the center of the wire has higher resistance than near the surface. If you use thinner wire however this is not as bad so you see a wire of a certain gauge have an AC resistance that is very close to the DC resistance when the AC frequency is lower than some limit value.If i remember right, #26 gauge wire is the largest size wire to be used at 100kHz to avoid too much loss from the skin effect, and if you need a heavier gauge wire then you can use several strands of #26 that add up to the gauge you really need. That way even the new heavier gauge wire has AC resistance close to the DC resistance, where if you just used one solid wire it would have a much higher AC resistance than DC resistance.You can also think about harmonics when dealing with rectangular waves. They have mostly odd harmonics but you dont want to increase resistance for them either or you start to loose efficiency there too.There is another use for litz wire too. That is when the wire has to bend a lot. Since litz wire can bend back and forth without breaking as easy as a regular stranded wire you can use it to help avoid internal wire breakage. This could be found sometimes in computer mice. It's not that they never break though, it just takes longer. They also use coiled wire though where each wire is a very small tightly wound coil of wire that runs the entire length of the wire.Unfortunately there are other effects that can hamper the ability of the wire to conduct AC current at higher frequencies. One is called the proximity effect. Just as it sounds, it means the current flow is also affected by the proximity of one wire to the other. That makes the litz wire less effective because although the strands are insulated from each other unlike regular stranded wire, they are still usually bundled fairly close to one another.You can look that effect up on the web to find out more about it too if you like along with skin effect and litz wire.

author: TimFox
author_rank: Super Contributor
timestamp: November 24, 2022, 05:30:01 pm
content: There is a good treatment of practical details of Litz wire at high frequencies in the classic first edition of F E Terman: "Radio Engineers' Handbook", McGraw-Hill 1943,See pp 37, 74,and 80. On p 37, he summarizes: "Practical litz conductors are very effective at frequencies below 500 kc, but ... , seldom is useful at frequencies greater than about 2 mc."

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 24, 2022, 05:48:22 pm
content: Heh, worth minding that Terman quite predates modern SMPS applications. Not that there's many applications yet at such high frequencies, but interesting to think about how the contents would be adapted to modern needs, if it were written today, that is.The main difference is, everything was toob back then, stupid high impedances aside from transmission lines. More need for high-Q resonators, to get impedance matching in relatively few steps. SMPS however are sometimes terminally low impedances, like, fractional ohms, intractable beyond some margin of power level and speed per stage. Let alone when transformers are involved (having to handle such wideband square pulses).Tim

author: TimFox
author_rank: Super Contributor
timestamp: November 24, 2022, 06:31:54 pm
content: The discussion about AC resistance of litz wire in Terman is still the best that I have seen.Experimentally (in non-tube circuits), I found that even an extreme litz wire (1200 strands of AWG 50) had hit diminishing returns by roughly 2 MHz.Litz wire is very useful in high-frequency switching power supply transformers, but few of them operate at > 2 MHz.Those chapters of Terman come well before any discussion of tube circuits in the book.

author: MrAl
author_rank: Super Contributor
timestamp: November 24, 2022, 09:35:47 pm
content: Quote from: TimFox on November 24, 2022, 05:30:01 pmYes i have to wonder if that limitation is due to the proximity effect. The wires are after all very very close to each other.

author: MrAl
author_rank: Super Contributor
timestamp: November 24, 2022, 09:40:28 pm
content: Quote from: T3sl4co1l on November 24, 2022, 05:48:22 pmWell it depends what causes the limitation. If it is the proximity effect then that would have to be addressed by separating the wires more or maybe orienting them in a different pattern.I dont think they used resonant converters back then either which today are becoming a big thing because of the higher efficiencies attainable when transistors do not have to turn on and off with concurrent large collector current levels. That would lower the higher harmonics which would mean the litz wire would mainly see the fundamental frequency and few higher ones.

author: jonpaul
author_rank: Super Contributor
timestamp: November 24, 2022, 09:51:10 pm
content: production transformer designs avoid litz, costly and hard to terminate properlyOur designs used solid or bunched wire, or Cu foil.Jon

author: TimFox
author_rank: Super Contributor
timestamp: November 24, 2022, 09:53:11 pm
content: Quote from: MrAl on November 24, 2022, 09:35:47 pmYes, he discusses the proximity effect. In litz wire at high frequencies, the capacitance between strands (through the enamel) reduces the effective insulation.In coils wound with solid wire, the proximity of neighboring turns is also important.Terman’s 1943 edition is a good reference for the Q of practical inductors.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 25, 2022, 04:13:18 am
content: As I recall, there are builds in theNEWTcatalog where twists are assembled around an inert core (insulating rope), presumably because proximity would be just too bad in the middle of that build, so why not keep current to the outside in the first place. They don't give any explanation of the various builds, but I assume these are for high frequencies relative to the diameter.Indeed, skin effect doesn't stop just because of insulation; eventually the loss tangent of the insulation itself will dominate. Or on a related topic, ferrite cores are self-shielding in the same way (hysteresis makes up part of the large-signal loss tangent) and therefore up to a certain cross section / diameter is useful for a given frequency. (IIRC, typically some inches at 100kHz, so it's not a big deal, but still, part of the reason very large industrial transformers are made of bricks glued together.)In modern context, the biggest thing is probably that, because Litz is transparent to magnetic fields (which is an equivalent description of what it does / how it works), the whole volume of the wire participates in leakage inductance. So it's rather ponderous to use at very low impedances, and foil/sheet may be preferable (despite the increased losses from eddy currents and such).Conversely, because foil blocks fields, it's essentially useless for more than a single turn per section. So... application is a bit limited. Not to mention how hard it is to get connections in and out of a build.Tim

author: 13hm13
author_rank: Frequent Contributor
timestamp: December 03, 2022, 05:39:38 pm
content: Here is a DIY way to do it:https://youtu.be/5-ShuLHnB7k

author: tooki
author_rank: Super Contributor
timestamp: December 04, 2022, 01:02:58 pm
content: Basically, “Litze” in German means “stranded wire”, and the English term “litz wire” is what is called “HF-Litze”* in German.*Hochfrequenz-Litze, “high frequency stranded wire”

author: tooki
author_rank: Super Contributor
timestamp: December 04, 2022, 01:12:55 pm
content: Quote from: 13hm13 on November 23, 2022, 07:06:49 pmThat aliexpress wire is not litz wire by any accepted English definition. The first one is just stranded wire, for making multi conductor headphone cables by braiding a few of them together into a fake “litz”.Just a reminder that AliExpress terminology cannot be taken as an indication of proper terminology in English, or German, or any language other than Chinese (maybe?). They a) keyword-stuff listings with tons of irrelevant words (that they think are relevant but aren’t) to try to appear in more searches, b) use tons of poor machine translation, and c) copy keywords and descriptions from one another, without knowing (or caring?) that they’re wrong. The end result is that everyone there uses the same sets of lousy keywords which often bear little resemblance to the correct terminology. (For example, how the original Mini-PV connector became known in China as DuPont, presumably because it was coined there during the couple of years that DuPont owned that product. So then the clone products got that name, and because hobbyists have enjoyed buying cheap stuff from China, hobbyists now call them “DuPont”. And now the Chinese vendors put “DuPont” on every kind of crimp connector, regardless of whether it’s even distantly compatible. I suspect they’re now thinking it just means “open barrel crimp”.)As for Cardas: While theirs is at least individually enameled wire, it’s still not what litz wire is normally understood to be. And the audiophile world also loves to abuse/repurpose real words and concepts into perverted ones to sell overpriced crap to gullible rich people. So don’t take them as any kind of authority, either.

author: mawyatt
author_rank: Super Contributor
timestamp: December 04, 2022, 02:42:49 pm
content: Quote from: tooki on December 04, 2022, 01:12:55 pmExactly!!One must be extremely careful when using AliExpress, from descriptions, specifications, terminology, images and so on. We've found that after careful review, then ordering, on average about 30% of the things we've received from them are useless, 30% barely usable, 30% OK and 10% good quality, and then try and remember who, when, where the 10% came fromAlso, we never consider any sort of semiconductors (diodes, transistors, MOS, chips, etc) from them, as the very high probability of counterfeit devices which you usually don't find out until they've been soldered in (Murphy's Law)Best,

author: TimFox
author_rank: Super Contributor
timestamp: December 04, 2022, 03:08:45 pm
content: Another interesting type of wire, for special purposes requiring flexibility, is "tinsel wire"https://en.wikipedia.org/wiki/Tinsel_wireI first encountered it in old-fashioned headphones and for patch cords on switchboards.It's impossible to solder, and one must use crimp terminations.

author: tooki
author_rank: Super Contributor
timestamp: December 04, 2022, 03:14:14 pm
content: Quote from: TimFox on December 04, 2022, 03:08:45 pmIs it actually still made and used? I have never found a source for it, nor have I ever encountered it in any headphones. Instead, what’s everywhere is the close relative of it, with enameled (round) strands coiled around synthetic fibers. Heck, even that stuff is almost impossible to buy on its own — even though it’s used in essentially all earphone cables, I’ve never found a source for it outside of aliexpress.

author: TimFox
author_rank: Super Contributor
timestamp: December 04, 2022, 06:35:48 pm
content: Seehttps://www.ganpatiengineering.com/braided-tinsel-lead-silver-copper-wire.htmlhttps://www.midwestspeakerrepair.com/shop/speaker-repair-kits/tinsel-lead-wire/tinsel-lead-wire/