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JohnSwenson

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  1. 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.
  2. You said ALL the RJ45 ports and the SFP port will be equal. What I am saying is they are NOT ALL equal. How can they ALL be equal if sending a signal from RJ45 jack 1 to RJ45 jack 2 is different from sending a signal from RJ45 jack 1 to RJ45 jack 5? IF the behavior fo the two paths is different how can they ALL be the same? Now maybe you are thinking what you are saying is that all the jacks in the 4plex RJ45 jack are the same, THAT is true. But saying "ALL the RJ45 jacks" includes those 4 plus the 5th jack on the other side of the isolation. It IS different than the other 4. Thus saying ALL the RJ45 jacks are the same is not true. I think there is some weird misunderstanding what the term ALL means here. So I'll just stop here, I've said what I can say about this. John S.
  3. Your statement said that ALL the RJ45 jacks and the SFP cage are the same, this is not true. Going from J1 to J2 does not block clock noise, but going from J1 to J5 does. To me at least this does not agree with "All the RJ45 jacks are the same". Now going from J1 to J5 and going from J2 to J5 is the same , but going from J1 to J2 is different. Think of it this way, there are 4 RJ45 jacks and the SFP cage all connected to a very high quality switch, another port on the switch is connected to the special isolation circuitry which blocks leakage and clock noise, the other side of that circuitry connects to another RJ45. This isolation circuitry (both leakage and clock) is effective in both directions. That's it. If that doesn't make sense I don't know any other way to explain it. John S.
  4. As far as the clock noise attenuation goes there are two domains: one has the 4 RJ45 jacks and the SFP cage. The other side has the 5th RJ45 jack. So going from any of the 4 jacks or SFP cage to the 5th jack blocks the clock noise. Going from the 5th jack to any of the 4 jacks or the SFP cage blocks the clock noise. Going from a 4 jack to another 4 jack does NOT block the clock noise and going from a 4 jack to the SFP cage does NOT block the clock noise. So as long as the 5th jack is involved in the path then clock noise is blocked. John S.
  5. JohnSwenson

    Sonore systemOptique

    What makes you think the price to make an opticalRendu is the same as an ultraRendu? There is no way I'm going to use the same cheap circuits used in inexpensive FMCs. I spent MANY MANY months working out the best possible circuit to provide the highest signal integrity, lowest noise and lowest jitter signal to the processor as I could get. This is NOT about using the cheapest possible circuit that works, it is about finding the best possible circuit without using extraordinarily expensive parts. Yes there are some expensive parts in this, by that I mean $15, $12, $7 parts, but no $1000 parts thrown in just for bragging rights.There are several times more parts on this board than for an ultrRendu. I spend a huge amount of time trying to optimize the performance versus cost equation for these products. That's my passion, producing circuits that sound really good without costing many thousands of dollars. You are of course free to put whatever value you wish on any product out there, but my guess is you are going to have a very hard time finding anything that outperforms this at anywhere near the price. John S.
  6. Here is what is actually going on inside: the ultracaps are charged at two rates, the high current mode is roughly twice the current of the low current mode. The change between modes is determined by the output current, with a threshold of 0.5A. Above 0.5A the high current mode is used, below,, the low current mode. There is also a fixed current overhead that powers all the control systems, sensors, ADCs, opto isolators etc. The overhead is constant, so "low current mode" is a bit more than half of what high current mode takes. For a particular charging mode the current to the ultracaps is constant, BUT the voltage it charges to is higher for the higher output voltages. The caps are charged to 5V higher than the output voltage. Thus the power required to charge the caps increases as you go to higher output voltages. Thus the highest input POWER happens when in high current charge mode, and 12V, output. At lower output voltages the maximum input power is lower but it is NOT in strict relationship of output voltages. Remember the charging is 5V above the output voltage, the fixed overhead and the fact that the charging current actually increases at lower output voltages. There are fixed voltage drops in the charge circuit, at the lower voltages these become a larger percentage of the whole voltage budget, thus the current has to be increased to cover these fixed losses. Its all quite complicated, but we take care of all that. THEN once you have the input POWER requirement you get to compute the input current needed for a particular input voltage. But the conversion is not perfectly efficient, there ARE some losses there. The result is that yes the input current requirement decreases for lower output voltage, and for output current below 0.5A, but there is no easy way to calculate exactly what it is. Its not even easy to measure, the input current is not constant, charging happens for a period of time, then turns off while the other bank is discharging. In addition the current changes during a charge time. When charging is happening the charge current is constant, but the voltage increases, thus the power during a particular charge time is increasing. If you look at the input current on a scope you will see a saw tooth because of this. The peak of that saw tooth is the important part, that is the peak current required by the input supply. To actually measure it you need a peak hold current meter or a scope. So yes, the input current requirement IS lower for lower output voltage, but don't even try and figure out what that might be. The 36W covers everything so we recommend using that. A 27W or 25W supply MAY work for a particular load and output voltage, but there is no way to calculate that in advance. You can certainly try something lower if you want to, but it may not work, there is no way we can guarantee anything below the 36W. We know 36W works for the maximum the LPS-1.2 can output, for anything else it's up to you to test it out. On a note to Alex's post above, the LPS-1.2 has a much higher maximum input voltage than the LPS-1, it is rated for 24V input. John S.
  7. JohnSwenson

    Sonore opticalRendu

    The opticalRendu runs at gigabit, period. It will not run at 100Mbit or 10G. The technical details are that the protocol used by most of the optical SFP modules runs at gigabit without auto-negotiation. Theoretically it could run at 100Mbit, but without auto-negotiation there would have to be a switch to select which speed. I considered that to be way too confusing for most situations. There is a different protocol that runs over SFP that DOES implement auto-negotiation so it can automatically deal with different speeds, but the number of modules that use this protocol is very small. The problem is that it is very difficult if not impossible to tell which type of module you have. So it was decided to make it work with just the vast majority of modules which will be what most users will be using. John S.
  8. JohnSwenson

    Sonore opticalRendu

    Correct, first off it is still in development, it is very expensive, it takes a lot of room. The upshot is that to put it in an opticalRendu would mean a bigger case, Two power supplies, and cost a LOT more. This did not seem like a good way to go for something that may or may not make a difference depending on the users system. John S.
  9. JohnSwenson

    Sonore opticalRendu

    This is not necessarily true. Phase noise from upstream clocks DOES pass through optical cables as well as copper cables. The prime reason for the EtherRegen is that it blocks this upstream phase noise. So it may still provide some improvement with an opticalRendu. You may hear the difference, you may not depending your system. So I would not say there is guaranteed to be no advantage of the EtherREGEN if you have an opticalRendu. It's going to have to be a try it and see. John S.
  10. JohnSwenson

    Sonore opticalRendu

    The SFP cage side of the SFP module is standardized, same physical, same electrical and same protocol. The part where you plug in the fiber can be different. There are two common wavelengths, usually referenced as SX and LX. There are two different types of fiber: single mode and multi mode. So any optical SFP module will work with any SFP cage designed for optical use (which is pretty much all of them). You DO have to match the fiber side. Use an SX to SX, LX to LX, single mode to single mode and multimode to multi mode. If you have an SFP cage on both sides, its easy just use the same model SFP module on both sides and use a cable that matches. If one side is an FMC with a built in optical interface (ie NO SFP cage), you need to find out what it is and get an SFP module that matches. As to which of these combinations sound better, who knows. But be careful, LX is designed for much longer range, but that doesn't mean it is going to sound better between two boxes in the same rack. There are some people that think LX is actually bad for very short lenghts, the electronics are designed assuming a lot of attenuation due to the long fiber length, with a short cable that does not exist and are probably putting the receivers in a state they were not designed for. It may or may not make any difference, I have not spent any time comparing different combinations, other than do they WORK. John S.
  11. JohnSwenson

    Sonore systemOptique

    I did a lot of measuring of the signals from SFP optical modules and came to the conclusion that I could not do much if any better than what was already out there, the difference is in what is around the SFP module. I would much rather spend my time working on things where I can make a significant difference. John S.
  12. JohnSwenson

    Sonore opticalRendu

    The SFP module is off the shelf. John S.
  13. The Sonore opticalModule is a small box with SFP cage and RJ45 jack (and power connector of course). It is NOT an SFP module itself, you plug an SFP module into it. It is an extremely well done FMC. John S.
  14. JohnSwenson

    Sonore opticalRendu

    A RJ45 SFP module WILL work, as long as it is NOT a 10/100/1000 one, it HAS to be JUST a gigabit module. These modules do not block leakage currents from the network. The optical does. How much this is going to effect the sound is of course dependent on the network setup. Another issue is the difference between an optical and Ethernet SFP module. The optical module is very simple, the incoming light from the fiber goes to a high speed photo diode, then to a simple amplifier. The output from the amplifier goes to my circuit. All the signal conditioning and clocking, protocol conversion etc is done in my circuit which uses very low phase noise clocks, extremely clean power etc. With a RJ45 SFP the clocking and conversion circuits are all done with whatever is in the SFP module, I can guarantee it is not as good as what is in my circuit! The signal from the RJ45 SFP still goes through my circuit which can clean it up some, but it's not as good as what I can do with the optical signal. So an opticalRendu with an RJ45 SFP WILL be better than an ultraRendu fed by the same Ethernet cable, the opticalRendu fed by an optical signal is significantly better. John S.
  15. JohnSwenson

    Sonore opticalRendu

    Let me try and address some of these questions without giving away too much. In the ultraRendu the Ethernet port from the iMX6 is connected to an Ethernet PHY, which talks to a very high quality Ethernet jack with built in magnetics. The PHY is directly connected to the "outside world" which leaves it somewhat susceptible to the signal integrity of whatever is connected to it. In the opticalRendu I re-designed the Ethernet circuit. I'm not at liberty to discuss the details of this circuit. What I can say is that this circuit uses a ton of very high quality voltage regulation and very low phase noise clocking. The result is that the processor is fed a signal that is cleaner than any external Ethernet connection you can buy today. This circuit is the primary new addition to the opticalRendu and is where the additional oscillator is used. Using an optical network connection provides a remarkable synergy with this circuit allowing it to produce such a clean output to the CPU. As has been mentioned other parts of the opticalRendu have been significantly improved as well. That's as much as I can say right now. John S.
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