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Amithlon

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  1. One needs to look at what a USB cable is actually doing. Firstly, what are we asking it to do A. Transfer a differential pulsed signal of high frequency and containing many harmonics B. Transfer a zero reference and a 5V (nominal) reference, technically these may not be required C. Transfer 5V power Easy peasy, no not in the real world. Firstly we look at what a radio tech would regard as normal As we are dealing with a high frequency signal, they are sensitive to RF noise (and we swim in an RF sea) , impedance is rarely mentioned, but this allows the signal to transfer correctly, also termination of signals is very important, these eliminate unwanted reflections that can produce erroneous data on the lines. On a similar note USB power is DIRTY and transfers of noise from power to signal lines IS going to occur - NOT maybe. And then shielding, no such thing as perfect shielding- anyway i have used solid copper Triax (yup better than coax) at many GHz for satellite receivers - should work great for USB - doesn't exactly bend well though ! Sort of reminds me of the building of the Apple I , jobs didn't realise all those digital signals were really analog anyway.... (out with the bypass caps etc) To sum up it is a tranmission line, affested by it's own design and external factors. Any failures in the sysem will result in necessary retransmissions, affecting the data flow. (sort of reminds me of a Quasi realtime data system used to transfer cardiac information over a 10baseT system, at a data rate of 15% of maximum we start to see data drop outs and other weird anomolies, basically under 10% to keep data "real time", i believe similar effects are to be seen in USB) As the Geekout needs a modicum of power to run, this is the power side, I use AB systems split signal/data cables, i then disconnect the power at the computer end and insert my power , supplied by a miniature 240V multistage filter, then a low noise 12V reg into a specialist ultra low noise ultra stable 5.2V power supply giving upto 1.0 amp (noise figures under 2uV pk-pk broadband), just need the next gen of silicon to tame the phonon noise/heat problem. Just awaiting my geek desktop unit now....
  2. I live in Brisbane Australia, in fact i have lived in most of the major cities of this country. I am 52, I am a rank mad Mni driver, owned a supercharged 1312cc SS show special (1976) pumped 165hp, 147mph 14.8s quarter.(all my custom design end to end) now own a 2005 ligh tblue MINI cooper, and son is building an 73 Mini - in aston martin pearl orange. As to technical history, 3 years in Army engineers (sapper), 6 years in Avionics with RAAF, Hydro electric electrical standards laboratory,Automotive engine analysis systems, everything from DC to 200GHz, 1fW to 200Kw, TV transmitters, translators, Amiga computers, (my first 12 bit DAC !), Degree in electronic engineering, Associate diploma in electrical engineering (sorry masters not worth it in $ here). Modified audio since my dad's days, Teac reel to reel, home built amps , home built speakers, custom wound transformers, Sound system ? Polk model 5's, Technics SB-10 with strathearn mofidied leaf tweeters, Hafler 100W/side amp (totally rebuilt) with 150W/side, Sansui AUD-11, sansui AM/FM tuner, teac and akai tape decks, Sony PSX-800 linear tracker with shure V15-V MR cartridge, local JH audiolab turntable with micro acoustics 630e cartridge, just about everything i own is hacked modified or tweaked, currently building an Arduino based 8 digit voltmeter - thus the need for ultra quiet power supplies, heavy duty computing (4.8GHz water cooled i7 2600K with 40TB of HDD, just put in a 250GB Samsung 840EVO drive) rechipped the cooper, Building ultra quiet supplies with HARD voltage regulation - to split off computer power supply and give the best i can into it. Also building a custom headphone amp, similar (but modified topology to the RSA XP-7 ), sennheiser and other headphones. Also looking at a newer power amp, (maybe build, maybe modify). Also getting a Highface2 DAC- but using a split cable and custom psu... Brought up in the age of monster cable, quads, Nakamichi, Infinity, pre digital, quadraphonic popped around, many have top end english gear, B&W, Quad, Linn..... I love Magneplanar, no preference in amps at the moment, would like the Stax headphones (one day). intending to build a specific PC just for music (possibly with a linear supply and modified cases, anyone know where i can get mumetal ?) hope that helps a bit....
  3. Hi peoples, I previously wrote abut an ultra clean power supply for USB DAC use. Having located only a very few (affordable) and a couple more (expensive) cables, i wondered if it were possible to design a voltage breakout of some sort. (primarily i wanted to disconnect the 5V computer supply from ever getting to the DAC, or even the cable) so i settle upon some basic design criteria (others exist and i may need to add them later) 1. remove dodgy 5V supply ASAP 2. maintain signal integrity through the adaptor phase to this end the USB standard of 90 ohms must be maintained, ideally the port to be used and the device to be used should be allowed for and set up (and that is a problem for most users) and probably accounts for much of the problems involved (having worked with RF in the upto 200GHz range upto 200Kw, and optical fibres, VSWR and signal propagation are of utmost importance. - phase velocity, signal velocity etc) I remember working on a BOTWT (backward oscillating travelling wave tube), where the output was there before the signal went in ! as well as phase velocities well above the speed of light. (Quacky sorry Quantum mechanics) The design uses 2 spaced standard 1oz GRP PCB boards, one is the ground plane, the other carries the signal on 2 tuned impedance lines. the gap between the 2 allows me to tune the impedance, both in and out, from around 70 to 110 ohms (maybe a bit more). One could use a screw (nylon) to independently adjust the in and out impedances - could be used on its own to match any DAC to a cable. A switch will allow the ground from the computer to be isolated or not (through a PI low pass filter). Banana sockets on the case would allow injection of the clean 5V supply. It had also come to me that both supply, switching and signal path etc could be placed in a single box. or offered separately. Aluminium shielding with a perspex case would be fine, but the use of Mumetal would be the ideal situation (no magnetic field = no induced voltages), the former would look much speccier. What do you guys think ? Is there anyone keen to trial the device and/or the power supply ? You would need a good assortment of cables from bottom to top. Off to do some more design implementation then.....
  4. I am building a 2 stage power supply for USB use, the first will supply 7.5Vdc with low ripple (<1mV) for upto 1A, RF control will be a priority, as well as propogation of noise from mains to output. The second box supplies 5.000V upto 1.0A, fully protected, noise figure under 5uV rms, controlled turn on (reduce in-rush), high stability with regard to temp, load etc. I am also modifying a 24bit ADC with a 4.096V reference (SOIC) to be trimmed to 4.09600V and +/-1ppm/oC and noise figure around 2uV rms . for my DAC i am obtaining a Hiface2. System Sansui AUD11, Modded hafler DH100 (150Wrms), JH audiolab turntable, Sony PSX-800 turntable, Sansui FM tuner, TEAC and ROTEL cassette units, Technics SB-10 and Polk Audio model 3 speakers. Computer custom water cooled i7 2600K @4.8GHz 16GB of 2133 @ 2400MHz, 10x4TB HDD, 2x250GB SSD, 2 x Bluray burners, 1.5Kw power supply, 2 x24" monitors, Fatality pro soundcard , dual tuner digital TV card etc etc , Blackberry playbook, looking for an HP white tablet (touchpad ?) . I am getting an A&B systems 6N MkII cut to allow the psu to be used (power lines only). Love a pair of magneplanars..... I i get the overall consensus, copper can be a bit dull, silver a bit bright, has anyone used silver plated copper, litz wound, platinum, palladium or rhodium coated/solid wires ?? The 90ohm transmission doesn't need to be maintained on separate power supply lines in the USB cable.
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