Concerning wires, in general...
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  1. #1
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    Default Concerning wires, in general...

    http://www.roger-russell.com/wire/wire.htm

    "Speaker Wire: A History" by Roger Russell, former Director of Acoustic Research at McIntosh Laboratory, Inc.

    i thought i'd share an interesting article on speaker wires that i'd recently read. although not directly related, i've also been contemplating the DJTT usb cable: not as a potential buyer, but from the theory aspect. food for thought. discuss?

  2. #2

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    it's true, copper is copper. there was post here a little while back with rca cables that were over a grand each. wtf you say? yes, wtf indeed. however, some people like thinking that by spending that amount of money, you're in fact getting a better quality cable. in reality, however, i could probably make a cable that is as good as that (i took a soldering course, and have made a couple 1/4'' and XLRs - it's not that hard).

    now regarding the djtt usb cable - i think this is kind of different than the argument in the article. the djtt cable's main advantage over other cables is the ferrite, plain and simple. it's purpose was to help controller users battle interference they were experiencing, if the stock cable that came with their controller/device was of a shoddy build.

    if there's one potential difference in audio/data cables that *does* weigh in on the price, it's durability. as far as audio quality/signal clarity goes..there's only so much you can do..and most everyone already does it anyway.
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    Tech Guru jakeintox's Avatar
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    I know a guy who makes some of the sturdiest speaker cable I've ever seen out of extension cords. Green or orange cable is damn ugly, but they'll stand up to almost anything.

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    Dr. Bento BentoSan's Avatar
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    Quote Originally Posted by djhipnotikk View Post
    now regarding the djtt usb cable - i think this is kind of different than the argument in the article. the djtt cable's main advantage over other cables is the ferrite, plain and simple. it's purpose was to help controller users battle interference they were experiencing, if the stock cable that came with their controller/device was of a shoddy build.
    That pretty much sums it up, the cable we put out wasnt meant to compete against the monster cable market of marketing wank. Its just a no nonsense cable thats built to the usb 2.0 specification, it does exactly what its meant to without all the extra jargon that just misleads people into thinking the cable does something that it doesn't.

    If you believe all the monster cable marketing jargon (which i hope by now people realize is just just that... jargon) go blow an extra $40 on a monster USB cable and put some ferrites on either end (Monster USB Cables do not come with ferrites) for exactly the same performance.

    The DJTT cable is essentially a usb 2.0 cable with ferrites on either end - nothing more nothing less. Thats all you need for good connectivity, if your still getting drop outs after that its not the cable and will be something wrong with the software or hardware on your computer.

  5. #5
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    Default !

    for the sake of discourse, i beg to differ on certain points.

    in response to djhipnotikk:

    however, some people like thinking that by spending that amount of money, you're in fact getting a better quality cable.

    an unfortunate observation, but nevertheless most agreeable.

    now regarding the djtt usb cable - i think this is kind of different than the argument in the article. the djtt cable's main advantage over other cables is the ferrite, plain and simple.

    technically, it's really not as "plain and simple" as one might presume. hence why i had explicitly noted that the article was not directly related technically, but i'm rather convinced that the idea of these not-so-frivolous marketing claims w/ respect to this particular item is very similar to the argument that mr. russell of mcintosh labs was kind enough to share with us. this is my train of thought; WARNING: this might get a bit technical.

    first off, per usb 2.0 specifications, "use of ferrite beads on the D+ and D- lines of full-speed (USB 1.1) devices is discouraged" and "the use of ferrites on high-speed data lines is strongly discouraged" (ref. usb 2.0 specification, section 7.1.6.1 low-speed and full-speed input characteristics, and section 7.1.6.2 high-speed input characteristics, respectfully). although this does not mean that the usb cable is not 2.0 compliant, there's a reason why this practice is frowned upon.

    we can think of the usb cable as a transmission line (more on this later) with the ferrite core acting as an inductor in series w/ the conductor's inherent resistance. with the host port modeled as a thevenin-equivalent circuit connected to a peripheral device w/ some load impedence via our usb transmission line, it can be shown using frequency analysis in the complex domain that our ferrite bead will cause the circuit to act as a low-pass filter, attenuating high frequencies to perhaps unacceptable levels.

    here's a worst case scenario thought experiment: usb 2.0 signal transmitted at the theoretical max of 480 Mbits/sec, every 2 bits being 01, i.e. 01010101010101..., such that bit stuffing does not occur. this means that the signal is being sent at a frequency of 240 MHz (every 01 half-nibble is a cycle), and after the NRZI xmission encoding (just wiki it), frequency is further reduced to ~120 MHz while in transit. if the signal is traveling at the speed of light, then

    c = frequency * wavelength

    therefore, wavelength = c / freq ~= 2.5 meters. usb 2.0 spec calls for the cable to be no longer than 5 meters, and electromagnetic field theory states that if the phase factor = ratio cable-length / wavelength is >= 0.01 (in this case it's 5 / 2.5 = 2), then it becomes necessary to treat the cable as a lumped-element model and use telegrapher's equations for analysis. this implies that parallel capacitance and conductance, and series inductance caused by data xmission em radiation become significant. granted, this is a theoretical limit that really isn't achieved in practice, the question still remains why would you purposely incorporate not just 1 but 2 ferrite beads that would invariably alter the cable's characteristic impedance and could potentially attenuate the very same high-frequency signal that you intend to preserve??

    another thought experiment, this time looking at full-speed (usb 1.1): 12 Mbits/sec theoretical max. using the same worst-case scenario, that's an NRZI encoded xmission frequency of ~3 MHz, signal wavelength of 100 meters, and assuming the same 5 meter cable, a phase factor of 0.05. although not as drastic as usb 2.0, at the theoretical limit, our ferrite contributes significantly to overall signal attenuation. (this would explain why, according to spec, ferrites are "strongly discouraged" with high-speed and simply "discouraged" for full-speed; quite honestly, i don't think they intended this limit to be reached).

    lastly, low-speed (usb 1.0): 1.5 Mbits/sec theoretical max, NRZI encoded xmission freq of ~375 KHz, wavelength of 799 meters, and phase factor of 0.00625, being below threshold at theoretical but non-practical limits.

    i was too lazy to calculate the cutoff freq of the low-pass filter, which would be rather difficult w/o knowing what kind of inductive forces the ferrite was contributing to the xmission line and which would invariably change as the cable was moved from one device to another. i can confidently say that it'll be inversely proportional to the inductance of the ferrite; you can crunch the numbers.

    it's purpose was to help controller users battle interference they were experiencing, if the stock cable that came with their controller/device was of a shoddy build.

    2.0 spec requires the cable to be wrapped in a >= 65% tinned copper shielding (ref. ibid. section 6.4.1 standard detachable cable assemblies, fig. 6-2 usb standard detachable cable assembly). the shielding deters external em field interference; the ferrites do not. the ferrites may possibly aid in dissipating reflected xmission line signals, but that's another story and hardly worth its undesirable low-pass filtering characteristic.

    furthermore, if the manufacturer of the controller was delinquent enough to supply an inappropriate or sub-par cable with the midi controller, one would more intuitively question the build of the controller foremost as it is more complex with respect to the cable, thus rendering it more susceptible to malfunction, viz. if the manufacturer can't get something as simple as an interfacing cable right, how can one be so confident about the quality of the device in which the cable was intended to interface with?? that would be the moral equivalence of a car randomly stalling in the middle of the interstate and its driver immediately placing the blame on "malfunctioning gas" rather than a miscalibrated fuel gauge or empty fuel tank.


    in response to BentoSan:

    That pretty much sums it up, the cable we put out wasnt meant to compete against the monster cable market of marketing wank.

    never said it was, although i'm quite convinced that it's not too far from marketing wank.

    The DJTT cable is essentially a usb 2.0 cable with ferrites on either end - nothing more nothing less.

    on the contrary, and i quote directly from http://techtools.myshopify.com/colle...ity-usb-cables, this cable is equipped with the following features:

    3.5 ft long: Shorter cables picks up less interference

    in general, true (i'm not well versed in antenna theory) but really inapplicable. in our case, shorter cables are really more desirable to reduce propagation delay between xmissions. also, less cord means less spaghetti to mess with.

    High-speed 2.0 certified cable: The best data transfer rate available

    3.0 is actually the new standard now, which blows 2.0 out the water 24-fold. unfortunately, commercial development hasn't been as progressive as standard development and it won't be for a while 'til this technology hits mainstream en masse.

    Fully shielded: Protects against interference from club lights and other electrical sources

    not sure how photons can cause interference, but all 2.0-compliant cables require full shielding, so thumbs up.

    Gold connectors: Connection points last longer

    not really. gold has a young's modulus of 79 whereas copper is 130, a sizable 65% greater (ref. tensile strength wiki). from a strength of materials perspective, copper is hands-down superior (incidentally, from the conductivity perspective, copper is also superior to gold; silver is better too). gold is nice for its ability to resist corrosion, but it's a relatively weak and malleable material unalloyed. nevertheless, if the usb receptacle is truly gold-plated, then it is not in compliance w/ 2.0 specification (ref. http://www.usb.org/developers/docs/usb_20_122909-2.zip section 6.5.3.2 receptacle shell materials, and the associated materials engineering change notice). regardless, the receptacle itself does not xmit data; it exists for structural support and is electrically connected to the virtual ground at the host end. in fact, the ECN specifies that "the shell material may simply be unplated steel" (ref. ibid. engineering change notice to section 6.5.3.2 receptacle shell materials). in other words, gold receptacles neither affect structural integrity nor data xmission performance.

    if we assume that majority of customers are not completely ignorant of technology and we look beyond the visually misleading and understand that by "connection points" you really meant contacts, then this really isn't anything to bolster considering how all 2.0-compliant cables are required to have a minimum of 2 microinches of plating over each pin mating surface (ref. ibid. 6.5.3.3 receptacle contact materials).

    Two ferrite chokes: Eliminates any noise interference in both directions

    see lengthy argument above.

    this bit of constructive criticism has gotten to be a bit lengthier than i had anticipated. as a side note, i do applaud djtt for being more honest than most other businesses. i'm brand spankin' new to this controllerism thing, but ean's blog and youtube videos have really helped me to understand and appreciate the art more than i had anticipated. i must admit that i'm definitely more interested in the technical aspects of midi controllers and interfacing than i am with actually making music. it'll only be a matter of time before i completely reverse-engineer a vci-100; i just need to get my hands on one first. food for thought.
    Last edited by slateraptor; 04-20-2010 at 02:56 AM. Reason: grammatical corrections for the sake of clarity; fat-fingered 75 instead of 65

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    p.s. in hind site of the above discourse, i can think of just one reason in which a single ferrite bead located closer to the peripheral end (controller side) may in fact be advantageous (hint: it's not as a noise attenuator), however, a ferrite bead at each end completely eludes me and just doesn't make any intuitive sense from an electrical engineering standpoint. perhaps more on this tomorrow; sleep beckons at this time.

  7. #7

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    not trying to discredit your insight on this matter, as you have obviously done your homework (we need more people like you), but dude:

    it's a usb cable. cmon. if it doesn't work, get another one.
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    My solution: Pay some one to whack them so you don't have any competition

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    it's a usb cable. cmon. if it doesn't work, get another one.

    alas, it's quite evident that many within this relatively small community have been in that it doesn't work, get another one situation (according to the djtt storefront, their usb cable has been on backorder for the past 2 weeks) and the question that naturally arises to the unbiased customer is should one spend $0.69 for this, $14.99 for that, or $19.95 for the other? although this may be pocket change to some of you, it's still the principle that matters. in fact, a slight rewording of the proposition shows its true colors. let's call our $.069 cable item X, djtt cable item Y, and monster cable item Z, then the question can be asymptotically rewritten as, "if i spend $0.69 for item X, will spending 2172% more for item Y yield a proportional gain in performance? how about spending 2891% more? granted, it's a general rule of thumb in the retail industry that a 300% markup is practically a loss, let me remind you that americas get pretty livid about a 1.7% increase in gas price. according to mr. russell of mcintosh labs, an entire industry of fraudulent swindlers has been created based on deceit, unethical marketing tactics, and millions of ignorant sheep to "prove" that the product they were conned into purchasing really work. it is only through proper discourse and reason that we can ever hope to deter this scandal.

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    Tech Guru Fatlimey's Avatar
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    Slateraptor, thank you for your insightful analysis of the DJTT USB cable. Here are some comments on why and how we designed the cable.

    Your analysis is looking at the cable as a point-to-point transmission medium and, yes, you're right there is no need for a ferrite to aid transmission in that case under ideal conditions. Our cable was designed to fix three problems that we had heard from many first-hand reports of USB dropouts:

    1. USB cables that are not built to USB2.0 spec.
    2. Using the cables in an RF noisy environment.
    3. Length for normal DJ use cases.


    Firstly, we wanted to offer a cable that absolutely followed the USB2.0 specs with the shield grounding correctly connected at the Host end, had the correct resistance, had gilded connectors for long term durability (ever seen a 10 year old USB cable? They get corroded due to finger oils and moist environments like clubs) and most importantly had the correct twisted pairs internally. By getting our own cables made we could lock down the issue of "using a bad cable" and start to look at other sources of connectivity problems.

    Secondly, after we had made sure we had correct shielding and twisted pairs we could start trying to make a cable that corrected some of the dropout issues people had reported using the stock cables with the VCI100. The stories we were hearing were about mysterious dropouts in club environments, places where people had no control over the magnetic and RF environment. LF interference from the soundsystem would be handled by the twisted pairs. By adding ferrites we hoped to remove the problem of HF and UHF interference from GSM chatter, from PWM LED lights and other sources. (Why both ends? I forget the reasoning, I'll punt to Midifidler for that answer).

    The third reason was to make a USB cable that was just the right length for controllerism use. Standard USB cables are made to be used with a desktop computer, to reach across a table and down the back to the motherboard back pane so 6ft is the standard length - way too long for our default "tabletop" use case. Having all this extra cable coiled up and secured somewhere close to cellphones or lighting cables is just asking for more interference. I had had a lot of success in replacing my all my 6ft USB cables with shorter 3ft ones so that was one of our design features - just the right length.

    So there you go. We have ferrites to counter cellphone noise and we make the cable ourselves so we can guarantee you have at least one "good quality" cable. These are not rebadged cheap bulk cables, we get these made from scratch only for DJTT. The anecdotal results we have heard from our customers is that these cables have solved persistent mysterious dropout problems for a number of users. We think they're worth it - if you can specify a better product or have any ideas for items that will solve real world issues for our users, please tell us!

    Hope that answers some questions.
    Last edited by Fatlimey; 04-20-2010 at 12:32 PM.

  10. #10
    Dr. Bento BentoSan's Avatar
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    Quote Originally Posted by Fatlimey View Post
    Why both ends? I forget the reasoning, I'll punt to Midifidler for that answer)
    I thought it was to cancel the antenna affect on both ends of the transmition, putting one on one end only stops the antenna affect from from the incoming(or outgoing) signal and not both - though to be honest i don't know in the end why you guys ended up choosing going for ferrites on both ends.

    I remember arguing that we should have them on both ends, then you guys said they are only needed on one side, then we ended up putting them on both ends Im sure in the end though they were put on both ends for a good reason.

    Quote Originally Posted by slateraptor View Post
    i'm not well versed in antenna theory
    you should research it more, thats pretty much at the heart of the fact why we use ferrites.

    Quote Originally Posted by slateraptor View Post
    Fully shielded: Protects against interference from club lights and other electrical sources

    not sure how photons can cause interference, but all 2.0-compliant cables require full shielding, so thumbs up.
    I think we deserve a bit more credit than that, we never said photons cause interference - plain and simple they don't ! Its the power supplied to those lights that causes the problem, when you got a lot of power running around the place you have a lot of electro magnetic interference which we argue plays a part (but not is solely responsible) in drop outs.

    MF and Fatlimey are really the brains behind those cables though, i brought up the idea of selling them and did a bit of research to help throw ideas around about what the cable specifications should be, but they know waaaay more about electronics than i probably ever will.
    Last edited by BentoSan; 04-20-2010 at 01:32 PM.

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