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JohnSwenson

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  1. I agree with mansr on this. Unless something is really done wrong the reflections on USB are quite small. This all started for S/PDIF interfaces using RCA plugs and jacks which DO have significant relections (RCA plugs are nowhere near 75 ohms). The 1.5 meters was based on the round trip time of a cable relative to the cycle time of the 44.1 S/PDIF stream. Even if there ARE reflections on USB this is only going to be appropriate when using full speed NOT high speed. Using this logic the minimum would be an inch or so for high speed USB. I don't see this as a criteria at all. John S.
  2. The issue there is the SBT, IT doesn't have a standby mode either. When it is "off" everything is still powered up, there is just no audio data flowing through it. So the power draw when "off" is almost the same as running. Thus whatever is powering it is still supplying almost the same amount of power. John S.
  3. JohnSwenson

    Article: SOtM sNH-10G Network Switch Review

    I was listening to headphones, how could that happen? John S.
  4. JohnSwenson

    Article: SOtM sNH-10G Network Switch Review

    It's been over two years now. I actually had everything all built, FPGA code written and started trying it out about two months ago and found out the system as a whole did not work. The system consisted of 7 boards tied together with a forest of coax and board to board connectors. I deliberately made the system highly modular so many different tests could be performed. Well that was a BAD idea! All those connectors proved very problematic, I could never get the whole system to be working together at the same time. Some connector or other was always working poorly, I just could not get it all working together. So back to the drawing board. I replaced 5 of the boards into one board, getting rid of almost all the connections, did the highest quality connections I could come up with on the board etc. I just finished the layout of this board a few minutes ago, so now its get the board fabricated and solder all these parts on. Then I try again. John S.
  5. JohnSwenson

    Article: SOtM sNH-10G Network Switch Review

    The pulling the plug thing is what actually got me looking into this. A while back I had a prototype of one the streamers on the bench feeding a little inexpensive DAC ($110) feeding some inexpensive Senheiser headphones($69) when I accidentally unplugged the Ethernet cable and the increase in sound quality blew me away. There was about 1 minute of music stored in the streamer so I got 1 minute of REALLY good sounding music. So yep, pulling the plug DID make a big difference, but it wasn't a "test", there was no expectation involved. John S.
  6. There is no "standby" mode. There is off and running. Do you mean running with no load? What is going to happen is the current from the feed supply is going to be small most of the time, then every so often it will switch and pull a fair amount for a small period of time, then go back to a small amount etc. I don't have the numbers right now on what this is. It will probably vary depending on the output voltage. There is no particular advantage for leaving it on all the time, although you can if you wish. John S.
  7. You shouldn't actually need a crossover cable. Almost all modern equipment uses auto-MDIX which figures the pairs out automatically. The ultraRendu Definitely has auto-MDIX, so if your PC does then you don't need a crossover. Essentially anything that supports gigabit will support auto-MDIX. So you only have to worry about this if you have a very old computer that doesn't have gigbit. John S.
  8. JohnSwenson

    CLOCKS, what should we look for in next generation

    I've been looking into this issue for some time now, unfortunately it is not simple, there are no "it's always this way" rules in this game. First off previous posters are correct, the common external clocks on the market (most of which are 10MHz) have different frequencies than those used in audio DACs. Thus they HAVE to go through frequency synthesizers to generate the frequencies used in the DACs. So the big question is how good is an extraordinarily good external clock going through a synthesizer compared to a good oscillator without the synthesizer. Of course this depends on the synthesizer! Until recently they were not particularly good, but recently there are some really good clock synthesizers on the market. The hard part about choosing them is that none of them are perfect, they do very well at some things and not so good at others. So it comes down to choosing one that does well at what is important for audio. For audio what seems to be the most important part is close in phase noise (1Hz, 10Hz etc), the higher frequency "noise floor" seems to be less important. So the task is to choose a synthesizer that adds very small amounts of close in phase noise but may not have the lowest noise floor. Fortunately such devices exist! The best ones do have a limit, as the close in phase noise of the reference goes down the phase noise of synthesizer output goes down, to a point. Then lower phase noise of the reference doesn't improve the output. This limit is really good, better than what is in almost all DACs. Thus with this synthesizer and a REALLY REALLY good external clock you probably CAN get an improvement over what probably comes with the DAC. Note the above is not a universal statement, the DAC has to properly implement that particular clock synthesizer, note the properly, it's not easy to get the best out of the synthesizer, so it takes a designer that knows what they are doing. As a side note, the cabling method these external clock boxes use is far from optimal. Single ended coax and BNC is far from ideal. When you are dealing with phase noise at these extremely low levels properly done differential cabling is much better at preserving this extremely low phase noise, but nobody uses this. Probably because there are no standards for this. Belden makes some differential cable assemblies that are fantastic, but expensive. But until DAC makers all use this and clock box makers use this, its not going to get used. Oh well. John S.
  9. I'm not upset at all, I just have only checked the spec sheets for Belden cable, most others don't have the spaces and I not going to spend time measuring others. SOoo all I can really say is that the Belden ones are the same and many others are PROBABLY similar except for the expensive ones that do all kinds of weird things, they will probably not be the same as the Beldens. John S.
  10. For the EtherRegen there is no requirement for minimum length. You can run down to a couple inches on any of the RJ45 ports. OTHER devices (not connected to the EtherRegen) may or may not have this minimum length issue. I checked a bunch of spec sheets for Belden cables a while back and they all had similar capacitance figures. If those are representative of other cables then it probably doesn't matter much what type of cable it is. I can't tell you if some $1000 per foot cable has the same capacitance as Belden cable, the $1000 per foot guys usually don't give hardly any specs and I'm not about to spend my life measuring them. John S.
  11. It turns out that "normally" there is a minimum length of Ethernet cable of 1 meter. The PHYs don't work if there is less capacitance than you get from one meter of cable. BUT since I found out about this I have been adding that amount of capacitance on the boards so it doesn't matter. The EtherRegen will definitely have the caps so there will be no minimum cable length. As to maximum cable length the spec is 100 meters. The longer the cable length the worse the signal integrity. For the EtherRegen the only place that matters is the connection from the EtherRegen to your renderer. On the other side it does not matter. So you want to keep the EtherRegen near the renderer and use a short cable between them. On the other side you can have a long cable. I'm not sure I would go for exactly 100M. I would probably give it a little margin to make sure things work. John S.
  12. The problem with doing it yourself is that "spade", I have not seen it anywhere. It is very special, it is designed to exactly fit the barrel and has little protrusions at the end that "click" into place when you place it around the barrel, this holds the spade tightly to the barrel and makes a decent contact. I'll bet that iFi had these spades custom made. John S.
  13. The JS-2 has both its outputs isolated from ground. To use one as the supply for the EtherRegen, you need an external safety ground connection, there are a couple ways to do this: buy a "ground plug" and connect the wire to the ground connector on the EtherRegen. The ground plug looks like a normal mains plug except only the ground pin is metal, the others are plastic. There is just one wire coming out of this special plug (usually green). You plug this into an outlet on the same power strip you plug the JS-2 into. You do need to get a ground plug that works with your country's AC sockets. The other option is the GroundHog from iFi, it is a kit that starts with an IEC SOCKET, into which you plug your own power cord (whatever works in your country), the output has various different adapters, one of which is a little spade lug that fits around the barrel of a standard DC barrel plug. Just clip this on to the plug going into the EtherRegen and it is grounded, simple to use, but fairly expensive. John S.
  14. JohnSwenson

    micro/ultraRendu - support thread

    What is happening to the LEDs on both the ultraRendu and the LPS-1? John S.
  15. JohnSwenson

    cheap/chinese LPSU's - minefield?

    Here is some (maybe unwelcome) details on switching supplies etc. First off there are two very different types of "switching things": The ones that plug into a wall (ie the input is AC mains, 120/230V AC, 50/60Hz), and ones you find on a board which take DC in (say 12V) and output DC (usually lower voltage). These behave quite differently and I think it is important to not ascribe the same properties to both. The AC line input ones I'm going to call "SMPS", the other I'm going to call "switching DC/DC converter", you can also call this a switching regulator. An SMPS takes the raw AC line and switches it, breaks it up into tiny time slices, since this is slicing the AC line, it the amplitude of these slices is still going up and down at line frequency. The frequency of the slices is somewhere between 30KHz and 100KHz. A lot of old ones worked at 30KHz but modern ones seem to like 60KHz. On the other side of the transformer there is a diode bridge, and caps and some circuit that measures the voltage.The output of the voltage sensor is fed back to the circuit that slices the line voltage which modulates the slices so that on the other side you get pretty flat DC. So you don't need the giant capacitor banks to smooth out the line AC, as the line voltage goes up, less power is sent to the transformer, and as the line goes lower more power goes to the transformer. So why even bother doing all this? Primarily is the reduction in size, weight and cost of the transformer, and also the vast reduction in capacitors after the diode bridge. Line transformers have to be large heavy and expensive to work at 50/60 Hz. The transformers that work at the high switching frequencies are much smaller, cheaper and lighter weight. The switching DC/DC converter takes DC in, slices it up and feeds an inductor with the pulses (note: NOT a transformer). These frequently run in the 400KHz to 1MHz range. Again a sensor looks at the output voltage and adjusts the slices to get the output voltage required. Again why do this? Primarily because switching DC/DC converters conserve POWER and linear regulators conserve CURRENT. So waht does this mean? Lets look at a linear regulator, lets say the load is pulling 1 amp, this means the input current is also 1A. If you have a large voltage across the regulator you have to dissipate a lot of power. If your input is 12V and your output is 1V at 1A, the input is 12V at 1A, so 12W in and 1W out, that means the regulator has to burn up 11W!! The switching regulator is constant POWER, the input power is the same as the output power, thus for above the input is only 1W instead of 12W, the current is 1/12 W. Non of these circuits are perfect so there is SOME power lost in the switching regulator, usually not very much. The "noise" that comes out of an LPS and an SMPS are very different. An LPS with a decent regulator has broadband noise usually measured in micro-volts (uV), the best ones are around 1uV, the worst can get up to 60uV. If you look at this on a scope you usually see a flat line, you have to increase the gain dramatically to see this noise. An SMPS (and DC/DC converter) have ripple at the switching frequency, usually measured in milli-volts (mV), this is much easier to see on a scope, but is very hard to see using normal settings. Say you have a scope set to measure 12V, you will see a flat line, 20mV won't even show up on that line. You have to go to AC coupling and turn the gain up. Not as much as with a LPS, but still a lot more than a normal setting. In most circumstances either of these noise levels is not going to make any difference, since almost everything you are powering with an external box, will have their own regulators, THOSE are what really matter. Now there are two other aspects of a power supply that DO seem to have an affect on what is powered, they are a lot harder to understand than noise, and nobody ever puts measurements for these in a spec sheet so there is no way to compare. These two things are output impedance and leakage current. The output impedance is what the voltage does when a change in load current happens. This is particularly important for quick changes in load current. Slow gradual changes can easily be handled by the PS, but quick changes cause the output voltage to change, frequently it will then slowly recover to the original value. This is most important for devices like computers which have large, quick changes in current draw. In many cases the regulators in the device can't handle this voltage change either and it winds up getting to the circuitry. There is no generalization about this with LPS VS SMPS. Both types have some that have very low output impedance (this is good) and some have high output impedance. Since nobody measures this or puts it in spec sheets there is no way to know. The only correlation seems to be that the specialty, expensive LPS tend to have very low output impedance. I have done a bunch of measuring of PS and have found some SMPS that beat a lot of the less expensive LPS. But you can't tell which they are, they don't look any different, they don't cost more, they just are better. BTW some of the SMPS that are touted as being low noise have horrible output impedance. The other property is leakage current. I'm not going to go into details on this, I have written tons of posts on this. For this there is a BIG difference between SMPS and LPS. The both have leakage, but the type that comes from an SMPS seems to be much more damaging to digital audio than what you get out of an LPS. The SMPS DO vary a fair amount, again hard to tell which are the lower ones. The largest amount of leakage I have ever measured is from an SMPS that talks about how low its noise is. A switching DC/DC converter does not generate leakage, it does not STOP leakage, but it does not generate its own. If a switching DC/DC converter is fed from an SMPS, whatever that SMPS produces is what will be on the output of the converter. One thing about SMPS that is talked about a lot is noise from the SMPS being "backwashed" into the AC mains. This used to happen many years ago, but modern SMPS don't seem to have this issue at all. Because this is something people can understand I think this gets the credit when I think in most cases the real culprit is the leakage current. So what does all this mean for a computer? The primary effect from powering a computer from an LPS seems to be the reduction in leakage current, NOT ripple on the output of the supply. There are fairly inexpensive ways to deal with leakage current, so in most cases using LPS ATX supply is mostly wasting money. If you have a computer directly driving a USB DAC there are some waysto prevent most of the leakage from getting through. But in my opinion a better way is to use a renderer powered from an LPS. In this case all you have to do is prevent the leakage coming over the Ethernet connection from getting onto the USB connection. Fortunately this is very easy to achieve and quite inexpensive. So the upshot is that you can achieve most of what advantage there is in using an ATX LPS in other ways for a LOT less money. John S.
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