Re: [SlimDevices: Audiophiles] Hi-Fi critric reveals their limited vision
This is why I built a PC for my parrents. It sits in their basement next to the wifi router on the cable modem. It's quiet, and low power (used old compaq biz desktop I salvaged) It runs linux so I can update it remotely for them, has a Xvnc server running grip that auto-rips the CD, tags it, and has a post-run script that activates a look for new music slimserver scan. Then it ejects the CD when the disc is ripped. This sounds neat, if you don't fancy making a product out of it would you care to share a bit more detail about the setup? This sort of simple 'insert a disc to rip' process is exactly what Slimserver needs in my view to make it accessible to the masses who 'don't do computers'. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=39438 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: The modifying crowd and the Transporter
I guess that depends on the guy. A lot of great things started in sheds I think you'll find. Like Hewlett-Packard to name one high profile example. Naim audio started similarly, Ivor Tiefenbrun's LP12 turntable started life in his father's engineering company, as a one-off project. In fact many engineering companies start in very humble and low-profile ways, whether they survive and grow is a good way top tell whether the output from the 'shed' had any value. Andy (inveterate shed-dweller ;) ) -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=28080 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: The modifying crowd and the Transporter
I guess that depends on the guy. A lot of great things started in sheds I think you'll find. Like Hewlett-Packard to name one high profile example. In fact many engineering companies start in very humble and low-profile ways, whether they survive and grow is a good way top tell whether the output from the 'shed' had any value. Sean can tell us the story of those first Slim Devices products, I bet they started similarly. Andy (inveterate shed-dweller ;) ) -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=28080 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Power Supply Downgrade
Maybe one of Andrew Weeks' Super Regulators feeding a series-pass power transistor might be the answer? No need for an additional series pass transistor - a standard super-reg can provide 1.5A continuous if built to current spec. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=26937 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Is max volume really max?
Yet when I grab the bits going to the DAC chip itself in the SB3 the volume is lower than when I send the same file through a normal player to my external DAC. Are the analogue gains in both systems the same? Exactly the same digital data, with a different DAC o/p spec and analogue gain post-DAC, will result in different levels. Is your I2S design such that the combined DAC o/p voltage + subsequent analogue stage gains are identical to the SB3's internal gains? This sems to point to something in the volume control processing that just goes to the analog outs and not the digital out. Whatever this is also seems to be effecting softsqueeze in the same way as the actual hardware. The volume control for both is done at exactly the same place as far as I understand it. It's not done within the DAC, but in the data before the DAC, so the both the digital out and the data to the DAC are the same, hence the question above. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=26002 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Raise Your Hand If You've Ordered a Transporter
0. A way to purchase individual songs online in lossless format. I'm certain this will come if demand is there. I bought my first electronic download in lossless format a while back, interestingly from some old hippies, rather than a modern 'with it' band ;) http://gdstore.com/ A 'five CD' set of songs cost way less than the individual discs, the quality is superb and I'm hooked, it's a great way to get music, the only downside being you lose the tactile element of the packaging. The record companies are just so far up their own backsides they really are missing a trick here, instead of constantly whinging about their sales, trying to make it illegal for us to use the music we own through copy protection etc. they should be opening up and generating a whole new generation of customers. The problem for them is it effectively kills the current distribution models, the ability to trial tracks in your own home and only buy the stuff that's actually any good, instead of paying over the odds for what often turns out as a dissapointment scares them rigid! Andy -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=25835 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Is SB2 (or 3) a source of RF interference?
Hum is a low frequency phenomena. It is more likely to be caused by improper grounding than by a squeezebox radiating at 2.4 GHz. Make sure that your preamp and turntable are grounded together. Whilst hum is a low frequency phenomena, RF interference -can- manifest itself as an audible hum. It depends on the nature of the signal and quite how the device that's being affected demodulates it. Naim equipment, due to the nature of it's design, is particularly sensistive to RF problems, especially high-gain phono stages. That said I use a Naim prefix and have no problems with the SB and it's only a shelf or two away. Try disconnecting the audio leads from the SB to preamp first, to confirm it's not an earthing problem. There are Rf kits available for the Naim bits, but they progressively worsen sound quality as the manuals clearly state. Distance is the best cure if it is RF! Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=22274 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SPDIF question - error correction and interconnect quality
Actually, I know there will always be some reflections, as nothing is perfect, but I plan to do what I can to minimize the reflections. You want one of these then :- http://tinyurl.com/o4cbl Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=21415 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SPDIF question - error correction and interconnect quality
John, Do you mean 75 Ohm? Yes. It seems that there are several manufacturers of 75 Ohm RCA connectors (Canare, et al) who would be highly vulnerable to false advertising suits if their product did not meet their published specifications. I don't know what they've published, but it is physically impossible, given teh physical dimensions of the connector, for an RCA Phono to be 75ohms and be able to plug into an RCA phono socket, period. Ask them for verified measurements as to the wideband impedance of the connector, and see what they come back with ;) The closer an impedance anomaly is to the sender or receiver, the less effect it will have. Why do you say that? It represents an impedance discontinuty that will give rise to reflections that are serious enough to impact the performance of SPDIF. It's specific location is largely irrelevant here - a mismatch is a mismatch is a mismatch. I would expect at least the high-end units to use something else if the RCAs didn't work. Well engineered units do, but the Sony/ Philips spec calls for RCA - for a manufacturer to use something else makes it not compliant with the SPDIF standard. Most manufacturers don't even realise it's important and the mismatch introduced by their SPDIF circuitry is so bad the RCA is just a factor in the equation. Dorkus, yes, i know they claim their UltraLock is completely immunte to input jitter, but that's what it is - a claim. if they showed spectral analysis of the jitter with varying input sources, that would lend it some credibility. [image: http://www.benchmarkmedia.com/dac1/D-A%20JITTER%20TOL.gif] The thing is this is just one spec the BM measures well on, who knows what the audible effect of the ASRC circuit is? Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=21415 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SPDIF question - error correction and interconnect quality
'certainly not to my ears! :) but in this age of compressed music and ipods, i think people are not aiming very high anymore. i also feel that mp3s and headphones are the death of music and a bane to society, but that's another rant. :p' Well I still enjoy dragging a rock around a lump of plastic, which I guess gives my view on the state of 'modern' audio ;) Andy. P.S. I think you'll find the DAC1 is insensitive to jitter on the SPDIF, it's a function of ASRC, but I don't think that will tell you a lot about how it sounds overall! -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=21415 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SPDIF question - error correction and interconnect quality
Fortunately, high-bandwidth cable with the proper impedance isn't expensive or difficult to find. That's true, but similarly accurately engineered SPDIF inputs and outputs aren't so readily available ;) If they use an RCA phono (as the Philips standard specifies), you're immediately stuffed and can't do much about it. That's where most of the problem lies - there's no such thing as a 75R phono anywhere in the universe, no matter what any salesman might try and tell you :) Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=21415 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Q on the internal SB2/3 switcher
http://tinyurl.com/do5ne Producing 1.2V and 3.3V. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=20884 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SB1 digital out compared to SB2 and SB3
Interesting. What is the equations that describe this? If it is too long to post, got an URL? SNR (DBC)=#8211;20 LOG10(2#960;.FIN.TJITTER), WHERE FIN IS THE ANALOG-INPUT FREQUENCY, TJITTER IS THE TOTAL SYSTEM JITTER IN SECONDS. Immediately it should be clear that the fIN factor gives result dependant upon the sampled frequency, using the figures mentioned, 20,000ps gives, assuming no other system errors, 98dB dynamic range (non-dithered CD spec) at 20Hz, but only 51dB at 20kHz. 100pS would meet the 20kHz non-dithered spec, but what about dithered input signals? Factor in a 15dB additional dynamic range from a properly dithered input signal, or a 24bit system (or worse still, a wide-bandwidth system) and you can see things rapidly becoming much harder. It's one reason why the newer, hi-res formats fail to live up to my expectations, they make the engineering, which is already bloody difficult, MUCH harder. It really isn't as easy as many so called 'experts' make out, jitter isn't that easy to measure (to the man in the street) and even when one can, it's not as simple as a headline figure. The recent volume rounding error problem of the Squeezebox gave rise to an error at the 16bit of the audio data - so many experts would tell you this is inaudible, yet people here (without knowledge of any change) found it wasn't. The human ear / brain interface is a really astonishingly complex thing, that can at one and the same time be both amazingly sensitive, yet easily fooled. What it isn't is measurable, in any quantitative manner. No-one, anywhere, with any experiment or test, can 'prove' the absolute audibility or inaudibility of anything when it comes to music. Realising that is crucial to avoiding the often prolonged debates that happen around these subject areas. Whilst the maths above, for example, explains a mechanism for audibility, it tells you nothing at all about an individual's ability to hear the effects, there are few absolutes of 'audiblity'. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=18116 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: The Aberdeen Components HACKsaw Mod
Digital out. the other picture shows a Scientific Conversions Shielded pulse transformer for the rca digital out. So not only do you use a shielded transformer, which worsens the mismatch to a purely 75R transmission line, you also use a non-75R RCA plug. This is supposed to be an improvement in what way exactly? A transformer is the best way to do a good SPDIF, but I guarantee your implementation cannot be remotely optimal. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=15574 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Volume bug - can you really hear it?
That means that -35dB corresponds to a volume setting of 12 in the SB 0-40 volume range. I believe you'll find the changeover is at 16 on the 0-40 range. That's what the measurements indicate - below this value the old and patched code measure identically. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=18439 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Volume bug - can you really hear it?
Can you tell me what FFT software you used to read in through the SPDIF of your sound card? Was it shareware or did you roll your own? It's Spectralab. Also, can you tell me what type of windowing you used on the input data stream when you measured THD? Windowing for those measurements was Hanning which is generally good for distortion and noise measurements. Blackman being the other common choice for distortion only. Andy. P.S. I'll install the 6.5 nightly on the test PC later, but may not be able to make any measurements 'til Friday, as I'm busy tonight and tomorrow. P.P.S. Sean / Dean, does this show on the D-Scope - it should? -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=18439 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Squeezebox 2 - Subtle noise and distortion.
I'm not sure if this will provide any help, but I've just looked at the sample files and performed an FFT (fast fourier transform) anlaysis on them - the one that exhibits the noise has a 20dB increase in high frequency noise over the good file, right out to 20kHz. It's also varying with musical content - the music causes a rise in HF content, which decays as the music quietens, which gives rise to the 'pumping' effect you can hear between musical phrases. It strikes me very strongly as a processing / transcoding / file type error of some description. Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=18219 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SB-3 and external DAC
Patrick, Yes, but in order to upsample it, it will still need to synchronise it's upsampling clock(s) to the incoming signal - so it still must require a PLL. The Benchmark uses an AD1896 and upsamples asynchronously, the incoming clock is not used at all beyond the AD1896, there's a local clock that totally determines the jitter performance at the DAC. Everything is upsampled to 110kHz then fed to an AD1853 DAC, the ASRC acting as the de-jitter process. Of course the internal clock has to be low jitter (which it appears to be, from the measurements I've seen). Andy. -- Andrew L. Weekes Andrew L. Weekes's Profile: http://forums.slimdevices.com/member.php?userid=573 View this thread: http://forums.slimdevices.com/showthread.php?t=17948 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: DAC technical question
Early CDs sound bad not because of the 16 bit samples, but lack of dither, bad recording and mixing techniques, etc. Good RedBook can sound very good, and average SACD and DVD-A is not inherently better. I mainly agree with that, in fact some early AAD CD's sound fantastic as the analogue noise inherent in the recording acts as highly effective dither to the A-D transfer process. That said I don't feel that 16 bits is adequate and in my view it's CD's greatest limitation. The pursuit of greater bandwidth is folly in my view and makes the bulk of the engineering much harder (although there are potential engineering benefits that have been highlighted to me that make the A-D process that bit easier). I'll always claim though that you cannot hear above 20k, but note I'm not saying that things above 20k don't matter, as I feel they do, but only in as much as they affect the performance =20k. It's obvious to me that effects at the LSB of 16 bit audio are easily heard and that engineering changes at levels around here or below have audible effects. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: DAC technical question
However, the performance of the DAC will be compromised because you are not using the full output range - so AFAIK your interpretation is correct. Especially bearing in mind no 24 bit DAC I'm aware of achieves 24 bits of actual performance at the analogue output. You're lucky in most cases to get 18 bits of actual analogue resolution, so the likelihood is you'll get losses creeping in way before the full 8 bits of shifting. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Looking for advice on sound quality
Honestly, how much can you really dress that up? Well, the 16bit part is the only real limiting factor (unless you are a bat ;) ) and since surprisingly few systems actually to manage the full 16 bits in actual reality, you may be surprised! Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: RCA Digital Output Stage Impedance
Another reason for using transformers, is they are just about the only way to acheive any significant high frequency common mode rejection. Trying to do this actively, is virtually impossible. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Purpose of the BigASS cap?
Purpose of the BigASS cap? I thought it improved your bottom end :) Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Re-boxing SB2
What do you mean by lower bandwidth for batteries? I understand your other two points, but I am not grasping this one. D.C. power supplies are often considered as simply DC, i.e. thay have no AC content, but of course the reality is this is never the case. For a PSU that experiences a dynamically changing load, as most do, it's response to this is important. In an active regulator, it is attempting to keep it's output constant, based upon the changes it measures through it's (internal or external) feedback connections. The load placed upon any power supply will have an inherent bandwidth, i.e. it will be making current demands upon that power supply, in relation to it's own internal activity. In the case of something like an audio amp, the demands placed upon the PSU will be related to the audio frequencies it's dealing with, primarily, in the case of digital they will be related to clock speeds and edge transitions, which can generate very high frequency demands on a PSU. The reality is one can never deal with very high frequency demands actively, only through passive means, like decoupling etc. The bandwidth of a PSU therefore needs carefully defining, in order to ensure it is capable of meeting the demands of the loads placed upon it, and keeping the supply within the design criteria. For feedback based regulators one needs to define these bandwidths very precisely to ensure that the system is stable and performs as expected. The regulator can affect the system being powered, but equally the system can affect the performance of the regulator, in a critical manner - it's for this reason it's much harder to do stuff actively. For batteries, the ability of the system to respond to transient (and by definition higher-frequency) demands, is related to the ability of the battery to maintain a constant DC potential, which is related to the internal impedance of the cells and the chemical reaction that goes on internally. A chemical reaction is, by it's inherent nature, slow in comparison to the demands of either an audio, or particularly, a digital system. It also tends to be ill-defined in terms of response to a transient demand, which from my perspective makes batteries a poor choice unless care is taken to limit the demands placed upon them, which ususally requires active circuitry after them, to acheive this. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Re-boxing SB2
I'm not a big fan of batteries, under most real-world loads they are always worse (noisier, lower bandwidth, poorer transient performance) than a *well-designed* linear regulator BUT they are possibly easier for the average DIY'er to get reasonable results from, hence the appeal, I guess. Added to the inconvenience of charging and maintenance, they'll never be my first choice, I've certainly never acheived state-of-the-art performance with them. I've never tried NiMH, but have no reason to suppose their chemistry makes them any better than NiCD for audio. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Re-boxing SB2
I think the SB2 would be worth your attentions, mine is sounding bloody marvellous at present, to the point I now feel it's little different, and possibly slightly better, than my main CD player (which cost a 4-figure sum)! Having heard Patrick's last week, with super-reg's installed it sounded amazingly good. This is all still without actually using any of my super-reg's (yet) in mine as I need to do a re-box to allow this, I do have one used as an external linear supply replacing the standard wall-wart though. The things I've done to mine, in some approximation of sonic importance are: - 1) Added a linear regulator (3-terminal at present) to the 'HCU04 (currently fed from the internal 14V) 2) Disabled the 12MHz clock and the SPDIF from the 'HCU04 3) Routed the clock directly to the DAC 4) Added an external linear supply (5V) 5) Changed the analogue decoupling electrolytics for polyester film caps (with 0.5R in series) 6) Changed the output op-amp for an AD8066 7) Re-jigged the o/p stage to be a 2-pole Bessel filter and using polystyrene caps in place of the ceramics 8) Changed the coupling electrolytics between DAC and op-amp and op-amp o/p for Elna Silmics 9) Changed the op-amp bias voltage decoupling for a film cap 1-4 are by far the biggest winners in my view, and I'm certain there are large gains to be had from much better reg's all around, my intention being to replace all the analogue supplies with super-reg's (14V, 5V, 3.3V) once I get the box drilled and ready to receive the SB2! I'll then examine whether the internal switchers cause any problems, now they are isolated from the critical analogue /clock functions. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Actual jitter measurements!
These were in fact taken at the DAC input, except the last one which was taken at the hcu04. I was tired when I read your post - now it's obvious, sorry! Interesting then, it seems there's around 10ps or so added by the circuitry / traces between the clock and the DAC, which is pretty good, but explains the audible benefit of the direct feed I've now implemented, which has made this little unassuming box sound rather marvellous and very engaging! It might be interesting too to try a linear reg dedicated to the 'U04, in order to see the benefits of that, which I would expect to be clearly resolvable, although one does need to implement it with care to optimise results*. Great stuff, thanks for sharing it! Andy. * re-reading it looks as if you may have tried this - the pk-pk change is probably simply down to the spectra of the PSU noise, with the skirts being affected more than the main distribution of jitter? -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Actual jitter measurements!
Interesting measurements Sean, if you still have access to the measurement apparatus, I'd be interested to see those jitter measurements replicated at the DAC clock input. I wouldn't be surprised if the CPU / internal digital activity had a greater effect at that point, since you then have the cumulative effects of the additional circuitry and the PSU interactions (some of which is related to CPU activity, I suspect) on that same clock signal. I'd tend to agree with MarcBernard's observations too, that you can generally assume a 120dB dynamic range + reserve margin when choosing acceptable jitter specs whether the system actually acheives this in measurement or not. Certainly my experience is that anything to reduce jitter is audible, even in the best engineered of devices, even when at very low levels already. I'm not convinced of the evidence cited by the late Julian Dunn, or the other figures quoted. The reality is jitter is one of the most critical issues to deal with, in my view, from a sound quality perspective, certainly my onw mods on an SB2 confirm that improvement on those already good figures, is clearly audible. One thing that is important though is the jitter spectrum - it's one of the things Guido has openly talked about, he openly admits the clock's he sources are not specially designed, but they have been chosen from a range of candidates, most of which sounded far worse, as much due to the different jitter spectra ans any absolute jitter number. As mentioned, Guido is very approachable and open, if a little busy, so it may be worth talking to him, or reading some of his output in places like diyudio.com. Andy. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SB2 mods by The Bolder Cable Co. - First impressions
Jitter doesn't have as much effect on the sound of the complete unit as does the power supply, coupling capacitors, op-amps, etc. The PSU stuff is inextricably related to jitter, as Patrick has pointed out. Replacing the internal switcher with a linear supply will have had a big impact on this aspect. Certainly in my experience the analog circuitry is of far less importance than the jitter performance, I've changed a few things in mine, including the op-amp and the coupling caps, but attempts to reduce jitter have had by far the greatest effect on my SB2. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Trichord Research
-Just to update anyone who is interested, Trichord are investigating the Squeezebox after I contacted them with a view to clock and PSU upgrades. I'll let you know what they say as they also believe there are other upgrade possibilties. They work wonders with CD transports, so I'm looking forward to their response.- Make sure they get one in their hands before offering solutions, since without actually doing that first it's impossible for Trichord to know what improvements you can gain from their advice. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Wired vs. Wireless audio differences
In the interests of science, would you do another test comparing your CD player (assuming you have one) to the SB2 in a blind test. The results may be interesting! Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Wired vs. Wireless audio differences
-From my understanding jitter is a time based issue that occurs when the timing on the transmission side is unstable and the DAC uses this unstable timing as a basis for conversion.- That is true. -I would presume the Squeezebox or XBMC in my case would read the FLAC file into a buffer and then send it via the digital output to the receiver where the DA conversion would take place. If this were the case as long as the buffer was never empty the wireless-ness of the transmission should not contribute to jitter in my opinion.- What you may have overlooked here is there will be jitter on the transmission interface to the DAC and it is this jitter (and this jitter only) that can cause audible degradation, depending on the DAC's jitter transfer function (i.e. how much jitter on the interface gets to the DAC clock). In the case of a Benchmark DAC1, it's none, for other DAC's it varies a lot, depending upon how well engineered they are in terms of the SPDIF interface, the receiver circuitry, the clock regeneration etc. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Wired vs. Wireless audio differences
These links make good reading: - http://www.benchmarkmedia.com/appnotes-d/jittercu.html lots more here: - http://www.pinkfishmedia.net/forum/showthread.php?s=threadid=10480 Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Wired vs. Wireless audio differences
-It is very easy to verify bit-perfect output from SB2 either by playing non-PCM material or by recording with a PC.- The only problem with this (from the perspective of audible differences) is that the bit perfect test is in the digital domain, where jitter is almost irrelevant unless gross enough to exceed the SPDIF receiver's jitter limits. The conversion to analogue is where the problem arises. If for any reason the jitter spectra changes on the SPDIF, between wireless and wired operation, even if 'bit perfect', there will most likely be audible differences. I'm not saying either party is right here, since I've not yet tried it, but it's easy to think that just because it's bit perfect in the digital domain, it remains so when converted to analogue, which isn't true. Jitter only matters at the point of domain conversion, from A-D, or D-A, whereupon its effects are totally dominated by the digital receiver's jitter transfer function. Most SPDIF receivers use a single PLL, with a corner 5k, so any jiter below that remains unattenuated. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Wired vs. Wireless audio differences
-It is very easy to verify bit-perfect output from SB2 either by playing non-PCM material or by recording with a PC.- The only problem with this (from the perspective of audible differences) is that the bit perfect test is in the digital domain, where jitter is almost irrelevant unless gross enough to exceed the SPDIF receiver's jitter limits. The conversion to analogue is where the problem arises. If for any reason the jitter spectra changes on the SPDIF, between wireless and wired operation, even if 'bit perfect', there will most likely be audible differences. I'm not saying either party is right here, since I've not yet tried it, but it's easy to think that just because it's bit perfect in the digital domain, it remains so when converted to analogue, which isn't true. Jitter only matters at the point of domain conversion, from A-D, or D-A, whereupon its effects are totally dominated by the digital receiver's jitter transfer function. Most SPDIF receivers use a single PLL, with a corner 5k, so any jitter below that remains unattenuated. To measure the effects of jitter (on the analogue output) is quite hard to do, yet the effects are clearly audible. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Off The Shelf Power Supply
-Just curious: how low in frequency do you see these components and how far down (magnitude) from the fundamental (if you have that handy)?- I'll re-run the test when I get a moment, but from memory the products I was seeing were around -65dB just above 20k. You can tell they are aliasing products (produced by the analyser, not the SB2 directly) since in response to a rising sweep, the resultant signals drop in frequency, which is classic aliasing behaviour. This is just with an audio band (20Hz to 20kHz) sweep too, I'll produce some wider band test files when I get a moment. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SB Audiophile Wish List
-I've seen these on some equipment, is there consensus (audiophiles, consensus? HA!) on BNC vs. RCA for S/PDIF?- The simple fact is that compliance with the consumer spec. mandates RCA, but this will *always* sound worse, unless the external DAC is completely insensitive to incoming jitter (e.g. Benchmark DAC1) since the RCA can never be a true 75R. AES / EBU allows XLR's, which are nominally 110R, but discontinuous impedance characteristics, which makes them pretty poor too (but not as bad as RCA). The reflections introduced will add significant jitter, for most consumer grade units the jitter on SPDIF with an RCA is likely to be in the order of 500-1000ns, with a really good one being maybe 10ns. You wan't picoseconds here...the sonic results usually largely depend on how well engineered the DAC is. Even with a BNC it's hard to get it right, but at least it's not intentionally handicapped from the outset. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Digital Radio audio quality
You'd have to check the bitrates used on the various online BBC stations, and compare it to DAB to try and get an idea of a comparison. But bearing in mind the different compression systems (Real Audio vs. Mpeg L2) it will be hard to do. As a country we have the worst DAB quality of anywhere in the world and I predict it will get worse still, as time goes on, since the economics of the service almost guarantee it, so I suspect it's a bit of 6 of one, half a dozen of the other! Neither come remotely close to the FM broadcasts, in terms of quality, I wonder if a way could be found to stream a feed from an FM tuner to the SB for best quality? That all said, the convenience and access of either DAB or the Internet-based stations are a huge bonus to me, and the 'Listen Again' stuff really adds the icing on a great cake! Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Upgrading my power supply
-I'm amazed by the 40+ dB delta between the light blue and dark blue. Is this attributable solely to cable length and connectors?- It's not so surprising when you work out the maths: - Those plots are calibrated, so if you take the worst case scenario of a change from around -145dBV to -80dBV, from light blue (as you say, measured at the regulator) to the top magenta trace, that represents only around 1mV of noise, give or take a few nV. For ease of maths, make the current consumption 1A (it's actually lower than this) and using good old Ohms law, we can see than the impedance that represents is: - R=V/I = 1e-3 / 1 = 1mOhm, not a lot, really! Remember these are sensitive measurements, that reveal tiny voltages and as alluded to before, they don't necessarily correlate directly with sound, that depends more upon the nature of the noise and what it's correlated with and what the noisly supply feeds. They also exclude all the stuff above 90kHz or so, that I can't measure ;) Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Upgrading my power supply
-Andrew, do you hear differences with an external DAC or with the internal DAC?- Internal DAC - I don't have an external one at present. -What i would say though is that a price has been paid - I'm finding the treble a bit overbearing now and will need to tame it by recorrecting on the Tact RCS though ill probably wait a while and let it settle down.- Thanks for the report - I found that the most obvious change from SMPS to linear supply was a removal of a treble harshness and lack of clarity that actually bothers me when using the supplied PSU. The linear one really helped here, I wonder if the RA unit is suffering a similar problem? Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: Upgrading my power supply
-Do you think (theoretically even) that the sound on the SB2 could be improved by changing the power supply?- In my experience (having done it) there's no doubt at all. I do have some reservations over the RA Powerpak's though - they are SMPS, which is part of the 'problem' in my view, with the supplied PSU. I've had a bit of a prod around inside and outside my SB2 (wireless version) and discovered some intersting stuff (like Sean did a good job on the design ;) ). For starters the supplied SMPS supply is pretty noisy, compared to what is possible from a well-designed linear PSU: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/Noise%20Comparison.gif] BUT, as Sean has pointed out, this external supply has a long way to go before it reaches the circuits inside. Even though, the linear supply has a quite marked effect on some of the internals, for example: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/14V_internal_supply.gif] The above shows the effect of the noise out of the 14V internal supply (derived from the display) when fed from the SMPS and the linear supply (red trace is the noise floor of the measurement system). The 14V supply is a lot noisier, especialy at HF, when the SMPS is used. Interestingly it also changes with the brightness level of the display: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/14V_vs_display_brightness.gif] Both of these plots are worse again with the SMPS supply (not shown). Having said all that, the most critical supplies, the 5V and 9V linear internally regualted supplies are commendably quiet and show good engineering, design and layout around the audio sections: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/5V_internal_supply.gif] and [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/9V_internal_supply.gif] These don't tell all in my view or experience though - whilst there's little evidence in most cases of the 14V supply (that feeds the 5V / 9V regs) breaking through to the audio circuits, the reg's will be affected by this noise, and in my view (and actual experience) the effect of a better external supply is clearly audible in my experience. Measurement in this relatively simplistic manner doesn't tell the whole story. Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
[SlimDevices: Audiophiles] Re: SB2 and Audiophile go together?
-However, the thing about an opto/mechanical (CD) transport is that you have to deal with how well the, uh, transport itself is working - and that's a real-world error-prone process involving light, motors, and quite fragile media. I have several real-life, perfectly reproducible cases where a slightly scratched CD plays fine in one player, and with skips/clicks in another. On a CD with even the most utterly microsocopic imperfections (even a brand new one), you'll find one transport plays it with more errors than another. Impercipble to the ear, maybe, (a single bad sample just gets interpolated) but it's not digital perfection.- It's often salient to remember that the signal from the CD player pickup (mechanism) isn't digital at all, it's a high-frequency RF signal, with plenty of opportunity for it to get messed up before we even get to processing it! Anyway, to try and understand and visualise jitter better, this little FAQ may help: - http://www.pinkfishmedia.net/forum/showthread.php?s=threadid=10480 Andy. -- Andrew L. Weekes ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
