WaveIO usb in input !!! good.. just waveio its ok or other xmos board ?
you can configure i2s in slave with this board ?
I'm making more of my system digital after ripping my CDs to a MacBook Pro laptop (using FileMaker DB).
So I'm thinking of driving my wonderful DCX2496 using the XLR SPDIF Input A. Can someone link me to guidance about that, please.
(There seems to be some competition for who can make the priciest bestest USB-SPDIF versus priciest USB-DAC converter, hard to know whether it is wisest to employ the DCX internal AD converter or skip it by using DCX internal SPDIF converter, which may have its flaws. Sometimes shakes my belief that all digital boxes are perfect, including stuff inside the DCX. After all, in a computer world, all file transfers from storage and between machines even from beat up old disks are perfect.)
Thanks.
Ben
So I'm thinking of driving my wonderful DCX2496 using the XLR SPDIF Input A. Can someone link me to guidance about that, please.
(There seems to be some competition for who can make the priciest bestest USB-SPDIF versus priciest USB-DAC converter, hard to know whether it is wisest to employ the DCX internal AD converter or skip it by using DCX internal SPDIF converter, which may have its flaws. Sometimes shakes my belief that all digital boxes are perfect, including stuff inside the DCX. After all, in a computer world, all file transfers from storage and between machines even from beat up old disks are perfect.)
Thanks.
Ben
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No experience with others, a friend who owns it recomended the WaveIO and I also have good opinion about it.
I just use SPDIF, WaveIO has such an output. I soldered the coax directly to the (replaced) transformer on the DSP board and cut the traces to the original input. I also replaced the 110R resistor.
Unfortunately it is rather complicated to get the I2S signal in to the DCX, WaveIO outputs the same sample rate it receives and the DSP expects 24/96. The asynchronous sample rate converter in the DCX is flawed in that it has a bug, documented in it's datasheet, that causes clicks, pops, 'frying egg' and dull sound. Ocasionally... So it needs replacing.
If you try to replace it beware of the fragility of the DCX PCB, it is really easy to destroy traces.
If I find akompatible ASRC kit with I2S input that would make my day.
ah, good point; if you are trying to bypass the onboard spdif receiver, its also a SRC chip and so you DO have to dump 24/96 i2s onto the bus if you remove that chip and put your own front-end there, instead.
you can do that via a pc, though. my source is always a pc (in fact, I have an spdif switch (external box) in front of the dcx and I pick one pc for movies and another for music) and if you enable an always-on sample rate converter (foobar2000 comes to mind) then you could feed a 24/96 signal into the dcx and truly get rid of its existing SRC chip and use a simpler spdif rx chip.
given a decent i5 or i7 pc these days, its quite conceivable that a pure host-based sw solution is going to exceed the chip-based SRC solution.
you can do that via a pc, though. my source is always a pc (in fact, I have an spdif switch (external box) in front of the dcx and I pick one pc for movies and another for music) and if you enable an always-on sample rate converter (foobar2000 comes to mind) then you could feed a 24/96 signal into the dcx and truly get rid of its existing SRC chip and use a simpler spdif rx chip.
given a decent i5 or i7 pc these days, its quite conceivable that a pure host-based sw solution is going to exceed the chip-based SRC solution.
I can see you are sophisticated in this matter. But can you (or someone) please provide me a noobie-suitable link to running the DCX with an Input A supplied by a SPDIF signal.
(Then later I can get into the riddle of controlling the volume with a MacBook feeding the DCX from a variety of apps.)
Thanks,
Ben
I'm not sure I understand the problem, ben. where are you having trouble?
as for vol control, my approach is to not have a digital box do vol control. I prefer to do it in analog domain. I've spent a lot of time studying and implementing vol controls and its not that hard to do it after the dcx and before any final amps.
my setup is to use the dcx to split a full spectrum spdif signal into 2 spdif-out signals, HP'd and LP'd. then each spdif stream goes to a DAC box (whatever dac-of-the-month you like; spdif is spdif so you are free to pick any dac you want as long as it can do 24/96). each dac output is analog and THAT is what you vol-control. you leave levels in the dcx alone and, for me, you leave levels in the dac boxes alone.
if you like vol control digitally, then it may be worth looking at vol-controlling the final dac boxes. there are ways to do this but its not very mainstream and will probably require lots of customization to get it working well. but its technically possible.
the easiest and best, I think, is to just ignore all the digital stages in between and vol-control things just before the final amps.
I and others have had good luck with cs3318 cirrus 8-ch chips. some like the PGA style chips. some like LDR solutions. some even like r2r relays 😉 and I suppose there is always the multi-gang analog pots and stepped-attenuators.
if you keep the dcx as an analog-out box, then you still can do the external analog vol-control thing and treat that as a separate box, having nothing to do with the dcx.
(not sure if that cleared anything up or just muddied things even more) 😉
as for vol control, my approach is to not have a digital box do vol control. I prefer to do it in analog domain. I've spent a lot of time studying and implementing vol controls and its not that hard to do it after the dcx and before any final amps.
my setup is to use the dcx to split a full spectrum spdif signal into 2 spdif-out signals, HP'd and LP'd. then each spdif stream goes to a DAC box (whatever dac-of-the-month you like; spdif is spdif so you are free to pick any dac you want as long as it can do 24/96). each dac output is analog and THAT is what you vol-control. you leave levels in the dcx alone and, for me, you leave levels in the dac boxes alone.
if you like vol control digitally, then it may be worth looking at vol-controlling the final dac boxes. there are ways to do this but its not very mainstream and will probably require lots of customization to get it working well. but its technically possible.
the easiest and best, I think, is to just ignore all the digital stages in between and vol-control things just before the final amps.
I and others have had good luck with cs3318 cirrus 8-ch chips. some like the PGA style chips. some like LDR solutions. some even like r2r relays 😉 and I suppose there is always the multi-gang analog pots and stepped-attenuators.
if you keep the dcx as an analog-out box, then you still can do the external analog vol-control thing and treat that as a separate box, having nothing to do with the dcx.
(not sure if that cleared anything up or just muddied things even more) 😉
Many thanks for your detailed reply. I guess I was wondering if there's general wisdom about bits and pieces with this approach.... starting with the hard topic of VC and losing bits.
Am I correct to think that a path from lossless computer file to USB to converter/SPDIF to Behringer Input A is naturally bit-perfect? And that it is better than the usual way peole do it with a computer lossless file to USB to DAC to Behringer because no DAC can be perfect (not to mention TWO conversions take place in the DAC and at the analog Behringer input too)?
First, where can I buy one of those ganged 4 or 6 pot analog volume controls (to work between the Behringer and the amps)? With a remote? Kidding?
The pot matching has to be reasonably good but not perfect. Simple as it seems, makes the best sense.
(All of us already have VCs on our amps if we care anything about gain management with the DCX!)
I'm not yet ready to modify the DCX (maybe if I study this thread much longer and see some solid evidence of stock DCX deficiencies I'll get out the soldering iron).
Ben
You plug your S/PDIF signal into the input A jack and switch the mode to AES/EBU on the "sum/setup" tab of the software...or via front panel. When you hear the relay click inside you'll know you've made the input selection successfully.
Dave.
its a bit fuzzy when you think of what goes on AFTER you receive the bitstream, though. first, there is a SRC chip that is always-on even if you send in 96k to begin with (digitally). you can argue that if you send in 44.1k to the dcx, its not 'bit perfect' once it gets converted to i2s after SRC phase.
but as for the computer side of things, these days its hard to NOT have bit-perfect usb audio out if the device is digital (coax or opto). it used to be that windows (at least) would force a resample to 48k and audio guys had to go to special pains to ensure that if the file was 44.1 that the output stream would stay 44.1. but now (and since the last 10 years or so) its not been a 'fight' and its easy to support bit-perfect audio, even up to 192k with low-powered consumer pc's. I don't speak mac (sorry) but I am sure its also not hard to get spdif out of your system.
one device that works for me and can directly talk to the dcx is this thing: m2tech hiface2 (search on it). if your mac supports it, its an easy way to get very clean spdif out that is high enough voltage (more than the spec says) and can directly drive your dcx's xlr input, if you just physically adapt the xlr and bnc or rca's. you can find things like this that do that:
http://www.amazon.com/Neutrik-NADITBNC-F-Female-Adapter---Neutrik/dp/B005TE710Y
canare also makes 'barrels' that can easily convert unbal to bal and 75 to 110. if your spdif is already 'high voltage' (more than half a volt) then you are all set.
I would not use physical pots, but I do like the electronic pots, so to speak. ganged PGA chips or cs3318 chips (single 3318 does 8ch of unbal analog i/o) work well but there are not a lot of ready-made solutions for this. I have one that works for me but it has no pcb and is all hand wired perf, so its not exactly an easy or fun build. if you look around you may be able to find other multichannel vol controls that are remote controlled. I plan to complete my design and release it, but I don't have a time table that I can commit to.
I can point you to a multichannel relay atten solution (that does run my own code and is remotely controllable) but the chatter of that many relays is not all that appealing to me and once I get beyond 2ch, I start to dislike the relay approach for vol control and start to prefer the all-electronic methods.
you should also consider a multichannel ldr solution, just for completeness. some folks love those ldr's and I'm sure you could gang a few stereo ldr 'preamps' and control them as a unit, if you like that kind of thing.
it takes a bit of work to make an ldr set do a linear volume transform across a wide range, more work to keep each channel matched and still more work to keep it all in calibration. to me, its more work than its worth but I mentioned it since some really like the ldr idea and its just an attentuator engine, to me. one of many technologies you could choose from.
I had a triple relay attenuator going, once. 'it made the devils own noise' is, I believe, the correct phrase in describing the mechanical switch noise 😉
I used 3 ebay 128- step attenuators and controll it with Arduino. Programing is realy simple quasi-C and over USB. So I added a 0.3 s delay between switching the relays to a new state. It is responsive enough and it makes the noise acceptable. 🙂
if all 3 of those relay attens are operating at the same db level, then you could do an optimization and send out one 'global' command and have 3 slaves get that one i2c command. it breaks the spec but it works (I tried it).
where it gets really ugly is if you want different vol levels for hp/mp/lp sections and each time you vary the knob, you send 3 diff values to the relay banks.
devil's own noise. fact. LOL 😉
I could not live with that. I built it to try out, but it was never practical and I now use the cs3318 which is silent and does the same job as the relays, functionally, at least.
where it gets really ugly is if you want different vol levels for hp/mp/lp sections and each time you vary the knob, you send 3 diff values to the relay banks.
devil's own noise. fact. LOL 😉
I could not live with that. I built it to try out, but it was never practical and I now use the cs3318 which is silent and does the same job as the relays, functionally, at least.
... and here's Rod Elliott's voltage controlled resistance multi-gang VC using THAT2180B devices:
Project 141
Ben
Project 141
Ben
I'm not a big fan of voltage controlled amps or attenuators. for me, they are more work and given how easy it is to speak 'direct digital' to the various vol control chips, these days, having to go back to using a literal analog control voltage to control the resultant atten or gain - that just seems like using older tech that doesn't offer any advantage over modern tech.
the one place that I use a control voltage is to sense a linear analog pot and take its value from an analog-in pin on a controller and quantize that to a discrete db step that gets sent to a digitally controlled attenuator. the pot is just a 'hint' to the controller and it can even wiggle and vary a bit; it would have to vary a lot to cause a -95.5db reading to jump to the next step up or down from there. the result is that the quality of that line essentially does not matter.
but if the atten stage is directly tied to the stability of the control voltage, then you really have to keep that line clean and quiet. I just feel that extra work that does not justify itself anymore. of course, if the current digital vol control chips did not exist, I'd feel differently about this; but they do exist, and are easy to use. they are easy to buy and lots of sample code already exists for them.
if I want to do a remote control front-end for that pure analog solution, I'd have to have a dac, more or less, just to create the analog control signal. again, too much fuss and work and hassle if there is going to be a cpu around.
the one place that I use a control voltage is to sense a linear analog pot and take its value from an analog-in pin on a controller and quantize that to a discrete db step that gets sent to a digitally controlled attenuator. the pot is just a 'hint' to the controller and it can even wiggle and vary a bit; it would have to vary a lot to cause a -95.5db reading to jump to the next step up or down from there. the result is that the quality of that line essentially does not matter.
but if the atten stage is directly tied to the stability of the control voltage, then you really have to keep that line clean and quiet. I just feel that extra work that does not justify itself anymore. of course, if the current digital vol control chips did not exist, I'd feel differently about this; but they do exist, and are easy to use. they are easy to buy and lots of sample code already exists for them.
if I want to do a remote control front-end for that pure analog solution, I'd have to have a dac, more or less, just to create the analog control signal. again, too much fuss and work and hassle if there is going to be a cpu around.
I need some help comparing my before/after results.
I replaced the output OP-amp stage with a simple unbalanced capacitor coupled one.
Now i get ~20 dBV smaller signal out of the DCX with the same setting on the FastTrack and ARTA.
If I toggle the 20dB pad on the FastTrack everything goes up eg. the 1k sine but also some worrying signals which were buried in the noise of the measurement and possibly burried in the noise of the unmodified unit measurements.
I'm not sure if my results are any worth...
I replaced the output OP-amp stage with a simple unbalanced capacitor coupled one.
Now i get ~20 dBV smaller signal out of the DCX with the same setting on the FastTrack and ARTA.
If I toggle the 20dB pad on the FastTrack everything goes up eg. the 1k sine but also some worrying signals which were buried in the noise of the measurement and possibly burried in the noise of the unmodified unit measurements.
I'm not sure if my results are any worth...
Spent the last few weeks working on a MacBookPro laptop music server, ripping my CDs (some with content going back 60 years or more). Being a classical music fan, iTunes and metatags aren't helpful but FileMaker database is great and it can link to the music files and even play them within FileMaker (esp since my library is already documented and satisfactorily cross-key-worded there on 900 records).
I've been seeking the "straightest pipe" (fewest converters) along the playback path. What seems to work very well is using a USB output from the Mac (avoiding USB hubs, if possible) into a DAC-like box (Creative Sound Blaster, $4 from Salvation Army store... very old, I don't know if it is asynchronous) with SPDIF/coax output (not optical SPDIF, which some find flawed, even though the MacBook can output that itself).
The SPDIF/coax plugs right into the DCX2496, input A... without needing to say a word about it to the DCX first. Since some web critics of the DCX focus on the analog stages, this leap-frogs the input analog stage and the ADC stage and keeps the signal digital from Mac to inside the DCX. Sure more sanitary than doing surgery on your DCX.
The one special piece of gear needed is a 4 or 6-gang analog volume control, downstream from the DCX. I haven't built this yet.
No place for a pre-amp. Other sources, like an FM tuner (love my Sony iBiquity tuner) are treated like recording sources inside the Mac (QuickTime player handles this with minimum mouse clicks). My tuner has to pass through an ADC into the Mac, but some tuners might have digital outputs.
Seems to work really well and brings down the noise floor by running the DCX "loud". Also, no tricky digital volume control, since things are played loud right into the 4-gang VC (once I build it).
Might be possible to do some EQ inside the music server and thus save the DCX brain some effort. But time and phase adjustments have to remain within the crossover box.
BTW, tested a $15 Shure A95U mic transformer with the DCX output (this device hasn't changed in decades since I bought my pair). It is a mic-to-high-impedance transformer. Near perfect curves in REW (incl distortion and phase). It is XLR but some gender-bending needed (which should be recognized to those who know the XLR convention). DCX output signal gets 10-20dB boosted; pity few of us want any boosting. But this could be useful for long leads out of the DCX, ending in the balanced/transformer A95U near an amp (and might provide isolation between boxes too).
Ben
I've been seeking the "straightest pipe" (fewest converters) along the playback path. What seems to work very well is using a USB output from the Mac (avoiding USB hubs, if possible) into a DAC-like box (Creative Sound Blaster, $4 from Salvation Army store... very old, I don't know if it is asynchronous) with SPDIF/coax output (not optical SPDIF, which some find flawed, even though the MacBook can output that itself).
The SPDIF/coax plugs right into the DCX2496, input A... without needing to say a word about it to the DCX first. Since some web critics of the DCX focus on the analog stages, this leap-frogs the input analog stage and the ADC stage and keeps the signal digital from Mac to inside the DCX. Sure more sanitary than doing surgery on your DCX.
The one special piece of gear needed is a 4 or 6-gang analog volume control, downstream from the DCX. I haven't built this yet.
No place for a pre-amp. Other sources, like an FM tuner (love my Sony iBiquity tuner) are treated like recording sources inside the Mac (QuickTime player handles this with minimum mouse clicks). My tuner has to pass through an ADC into the Mac, but some tuners might have digital outputs.
Seems to work really well and brings down the noise floor by running the DCX "loud". Also, no tricky digital volume control, since things are played loud right into the 4-gang VC (once I build it).
Might be possible to do some EQ inside the music server and thus save the DCX brain some effort. But time and phase adjustments have to remain within the crossover box.
BTW, tested a $15 Shure A95U mic transformer with the DCX output (this device hasn't changed in decades since I bought my pair). It is a mic-to-high-impedance transformer. Near perfect curves in REW (incl distortion and phase). It is XLR but some gender-bending needed (which should be recognized to those who know the XLR convention). DCX output signal gets 10-20dB boosted; pity few of us want any boosting. But this could be useful for long leads out of the DCX, ending in the balanced/transformer A95U near an amp (and might provide isolation between boxes too).
Ben
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What is your reason to avoid USB hubs? Wouldn't they actually be beneficial in isolating the DAC from the Mac?
Digital volume control would not provide sufficient SNR?