Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
Jeff Flowerday wrote: > I'd be interested in John's opinion on these transformer based > converters. These transformers can be quite decent. This is how I would do an AES/EBU output. On anything I do with an S/PDIF output I provide a 75ohm BNC, if the user wants to go to an AES/EBU input they can use one of these transformers. Whether it's going to be the best way to get into a DAC is going to be DAC specific. John S. JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
^ You can still stream up to 96/24 PCM using the current (non-beta) LMS and it works fine with EDO, that's what I do. S/PDIF & coax. Agree streaming PCM is preferable than decoding e.g. FLAC on the SBT, at least here. cfraser's Profile: http://forums.slimdevices.com/member.php?userid=48869 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
Yes, the MX model has an XLR male plug at one end. Nice all metal build quality by the way. cfraser wrote: > An issue is it won't be any good for better than 96/24 You are probably right about this. I have not tried the EDO plugin yet. I stream PCM to the Touch and I'd need LMS 7.8.x for EDO and PCM to work so I'll wait until 7.8 is released OGS's Profile: http://forums.slimdevices.com/member.php?userid=32981 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
^ Do you use that Neutrik adapter to plug directly into your DAC? What I'm getting at is I want to avoid having to use 2 cables, and was hoping the adapter has XLR male pins in such a manner it plugs directly into the DAC (pics I've seen don't show the XLR end clearly). Oh yeah: big Neutrik fan, usually good value for money, no marketing hype. Thanks. [I have tried to find stand-alone 75-110 transformers, but not good luck yet at a price that makes even moderate sense.] cfraser's Profile: http://forums.slimdevices.com/member.php?userid=48869 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
I am using a 5 foot length of this cable: http://www.l-com.com/item.aspx?id=7436 from SB Touch to my Devialet D-Premier. I replaced the BNC at one end with a RCA to fit the Touch. I then use a Neutrik NADITBNC-MX 75/110ohm converter: http://www2.neutrik.com/uk/en/audio/210_1923043515/NADITBNC-MX_detail.aspx for the AES/EBU input of the D-Premier. The Canare unit HumanMedia mentions above may be even better than the Neutrik although both are spec'ed at 6MHz bandwith. To prevent noise from ground plane of the Touch reaching the amp I removed the direct ground connection (desoldered XLR pin 1 inside the Neutrik). This clearly sounds better than a connection to one of the RCA digital inputs of the D-Premier. OGS's Profile: http://forums.slimdevices.com/member.php?userid=32981 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
HumanMedia wrote: > Here is the exact one I use. I have a hardwired standard Blue Jeans coax > with bnc from the SBT connecting into the BNC at one end of this. The > other xlr end plugs into the AES/EBU Dac input. > > http://www.ebay.co.uk/itm/Canare-BCJ-XP-TRB-Digital-Audio-Format-Converter-Balun-XLR-Male-BNC-Female-/280892208028 I'd be interested in John's opinion on these transformer based converters. Jeff Flowerday's Profile: http://forums.slimdevices.com/member.php?userid=15883 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
cfraser wrote: > ^ Tell me more!! Please. I have never heard of such an xfmr before, but > I should have known they existed... > > The AES/EBU sounds better here too. Has an open-ness and a sense of the > music coming out of "infinite" blackness; very noticeable when other > DACs/inputs *don't* have it. I have not opened this DAC (years of > warranty left) to see if I can tell why the AES/EBU sounds that extra > notch better. > > Thanks. Here is the exact one I use. I have a hardwired standard Blue Jeans coax with bnc from the SBT connects straight into this and this plugs into the AES/EBU Dac input. http://www.ebay.co.uk/itm/Canare-BCJ-XP-TRB-Digital-Audio-Format-Converter-Balun-XLR-Male-BNC-Female-/280892208028 HumanMedia's Profile: http://forums.slimdevices.com/member.php?userid=44865 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
konut wrote: > The prevailing wisdom asserts that no RCA termination will give a true > 75 ohm result. Then again if the source and DAC were designed to be > impedance optimized with the RCA jacks then this wouldn't really matter. Unfortunately impedance was not a design characteristic of the RCA plug, in actuality they vary all over the place, from something like 25 to 45 ohms or so. They were designed as cheap audio plugs with no thought that they needed tight impedance characteristics for RF frequencies. BNCs OTOH WERE designed as RF connectors so do include impedance as a design spec. Speaking of impedance and BNCs, they come in two flavors, 50 ohm and 75 ohm. They are interchangable from a mechanical perspective. The 50 was the original version and existed for a long time in the marketplace. Then someone realized that you could take off some of the solid insullation and make it air insullated and presto, its 75 ohms, perfect for 75 ohm systems such as S/PDIF. Unfortunately MANY companies that sell 75 ohm cables with BNC connectors use 75 ohm cable but use 50 ohm connectors! I did a very unscientific sampling of cables available on the internet and found that only 30% used real 75 ohm connectors. So even if you get equipment with BNCs make SURE it uses a 75 ohm jack and that you get cables with 75 ohm plugs. And it's not just "audiofile" companies that get this wrong, I bought some cables from several cable places that specialize in selling cables to pro broadcast customers and their 75 ohm cables had 50 ohm connectors on them! I'm completely at a loss to understand how this happens, that a cable company doesn't know the difference and the "professional" customers don't either. It's interesting that Blue Jeans gets it right, they are inexpensive yet extremely high quality cables done right. John S. JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
^ Tell me more!! Please. I have never heard of such an xfmr before, but I should have known they existed... The AES/EBU sounds better here too. Has an open-ness and a sense of the music coming out of "infinite" blackness; very noticeable when other DACs/inputs *don't* have it. I have not opened this DAC (years of warranty left) to see if I can tell why the AES/EBU sounds that extra notch better. Thanks. cfraser's Profile: http://forums.slimdevices.com/member.php?userid=48869 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
I actually use a BNC to AES/EBU 75ohm To 110ohm impedance transformer to connect the hardwired 75ohm cable from my Touch to the AES/EBU input of my DAC. It sounds better than going from the 75ohm cable to the 50ohm RCA input. Maybe it's because of the impendance transformer instead of the abrupt change at the RCA, maybe it's because the AES/EBU input is a higher quality signal path than the RCA path. HumanMedia's Profile: http://forums.slimdevices.com/member.php?userid=44865 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
Thanks for your detailed and thorough explanation. I always look forward to reading your posts. I suspected that the difficulty in measuring and optimizing this spec was the reason that this aspect of S/PDIF behavior is ignored by manufacturers. One would have thought that by now a few of the better designers would have addressed this issue. OTOH, I'm sure that most assumed that all S/PDIF ins and outs adhered to the 75 ohm spec. I know I did. Does anyone know of any sources or DACs that actually address this? It seems that the only importance that is given to this is with regard to the cable and its terminations. The prevailing wisdom asserts that no RCA termination will give a true 75 ohm result. Then again if the source and DAC were designed to be impedance optimized with the RCA jacks then this wouldn't really matter. konut's Profile: http://forums.slimdevices.com/member.php?userid=1596 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
I knew someone was going to ask this! The above post was actually an oversimplification, in actuality the impedance can vary with frequency. Its similar to saying a speaker is 8 ohms, very rarely is it 8 ohms at all frequencies in the audio range. Some reviews will publish the full graph of speaker impedance VS frequency, but how does a consumer use this? How can a consumer figure out whether this speaker is going to sound better than another using a graph for each? The same sort of thing applies to S/PDIF systems. IF you want full information you need a impedance VS frequency chart (covering at least 1MHz to 200MHz). So you have one of those for the source and one for the connecting cable and one for the receiver. What do you DO with this information? A human can probably do some gross interpretaions with these, particularly if the spread for each one is not too large, but if each one has a large spread, how do you make meaningfull interpretations of how the system as whole is going to behave? There ARE ways to take this information into a computer and simulate what the total SYSTEM behavior is going to be, but then you have to know how the particular DAC product is sensitive to this, different ones are sensitive in different ways. Once a group of people have discovered the sensitivities of a particular DAC then this information might be useful. (note that very few manufacturers even think about any of this stuff, so information on this is NOT going to come from a manufacturer) There certainly are test equipment that can measure this, the telecom industry uses this stuff all the time, but they are not cheap, $20,000 to $100,000. It should be possible to design a piece of fairly inexpensive test equipment that has a USB interface to a computer so the computer can do all the heavy lifting and have it just do this one function over just the frequency range we are interested in. Unfortunately the market will be small, so even if technically it is not too difficult, it will still be fairly expensive. Somebody could probably market such a device for $4k-$5k. If a bunch of DIY types get together to do the circuit design and programming it could be a DIY project for a lot less. Note that DIY, open source, cooperative projects for test equipment are quite rare! It would be interesting to see what would happen in the industry if reviwers started publishing this information. My guess is that LONG term it might be usefull, manufacturers might actually start measuring their products and put some effort into getting things closer to spec. But short term it might be a major problem because most consumers would have no clue what it all meant, the market (audiophiles and reviewers) would wind up fixating on some aspect to make comparisons on, which may or may not have any relationship to something important. The important thing would be to get the market to focus on what is primarily important, low spread, and averaging around 75 ohms. This is something that is very obvious by looking at the impedance VS frequency charts, as long as all the charts are done the same way, have the same units etc. For a particular peice of equipment built using surface mount parts on PC boards the impedance is going to be quite uniform from box to box as long as the board design is not changed and the components stay the same. Changing a chip from one manufacturer toanother CAN have a significant change impedance, since that is usually not a parameter that is "tied" to the part number. Yes it IS possible in many cases to build a device that you can insert between boxes to improve the match, but they would have to be engineered for a specific combination, there is no such thing as one box that you can use that does everything. I suppose it's possible to build a device that measures the system and configures a network to optimize it, but such a device would be exceedingly expensive. It would be way cheaper to just build the sources and recivers in such a way that they don't care. John S. JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
[SlimDevices: Audiophiles] Impedance Matching Squeezeboxen to DACs
John Swenson wrote in the "Upgrading the clocks in the SBT - is it necessary?" thread. "For example the impedance of the output is just as important as the jitter of the signal, the official spec says outputs and inputs should be 75 ohms, but in reality the impedance of outputs, inputs and cables varies all over the place from 25 ohms to 120 or so. What matters is that they match as closely as possible. So if your DAC has an input of 90 ohms, it doesn't matter if the source has precisely 75 ohms, you will get better results if the source is closer to 90. I have actually seen a case where a reclocker sounded better, even though the jitter on the output was worse than on the input, BUT the output impedance more closely matched that of the input on the DAC." This raises several questions not really specific to Squeezeboxen, but hey, thats where we all are. 1. When reading technical reviews of various digital sources, how come no one measures the actual output impedance? Its always "assumed" to be 75 ohms. 2. How difficult is it to measure this spec? 3. Will the actual output impedance vary from unit to unit, or will it be the same for a given circuit? 4. Is it difficult to measure the actual impedance of a digital cable (including the plugs, RCA, BNC, etc)? 5. When reading technical reviews of various DACs, how come no one measures the actual input impedance? 6. Would it be possible to construct a device to insert between sources and DACs for optimum results? Ideally this would have a facility to monitor and adjust impedance for an ideal match. konut's Profile: http://forums.slimdevices.com/member.php?userid=1596 View this thread: http://forums.slimdevices.com/showthread.php?t=95614 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
