Opii fed, arduinii controlled . . .
I should at least take a look at the glt code rather than write from scratch, hochopeper. I prefer the ease of wireless provided by WiFly->Xbee->Arduino. My final vision includes resolution independent bitz from a NAS and control by a windoze app rather than the separate UI hardware components. At least initially CPUstick would just be used to load registers for exploring filter selection. I already wrote code to read that ancient Audio Alchemy remote (the one that resembles a Hummer accessory).
How soon do you anticipate having powsupps working?
I should at least take a look at the glt code rather than write from scratch, hochopeper. I prefer the ease of wireless provided by WiFly->Xbee->Arduino. My final vision includes resolution independent bitz from a NAS and control by a windoze app rather than the separate UI hardware components. At least initially CPUstick would just be used to load registers for exploring filter selection. I already wrote code to read that ancient Audio Alchemy remote (the one that resembles a Hummer accessory).
How soon do you anticipate having powsupps working?
power supplies hey? glad you asked!
At the moment I have no PCBs, no components and no firm decision on how I'll power any of this. I grabbed the 2 x Opus 2nd hand from a local guy without any psu. I have some ideas and options in mind, though I am now trying to decide how it (PSUs, DAC, USB to i2s, The Wire will all fit in a box (or 2) in the end before I decide on a final power supply designs and physical arrangment ...
Suffice to say: I'll be a while yet! Will hopefully start ordering most of the parts for The Wire(s) and some power supply gear in 2nd or 3rd week of Jan, maybe a month after that I'll have something to show. Lets call it mid Feb before I expect to have anything like a prototype running.
My arduino plans are quite simple compared to yours, primarily volume control/mute with a touch of filter selection mainly for while I am testing.
At the moment I have no PCBs, no components and no firm decision on how I'll power any of this. I grabbed the 2 x Opus 2nd hand from a local guy without any psu. I have some ideas and options in mind, though I am now trying to decide how it (PSUs, DAC, USB to i2s, The Wire will all fit in a box (or 2) in the end before I decide on a final power supply designs and physical arrangment ...
Suffice to say: I'll be a while yet! Will hopefully start ordering most of the parts for The Wire(s) and some power supply gear in 2nd or 3rd week of Jan, maybe a month after that I'll have something to show. Lets call it mid Feb before I expect to have anything like a prototype running.
My arduino plans are quite simple compared to yours, primarily volume control/mute with a touch of filter selection mainly for while I am testing.
I just finished building the BAL-BAL wire. I am connecting the wire directly to the balanced output of a Twisted Pear Buffalo II DAC, or single-ended output from Metric Halo LIO-8. The sound is very impressive. It is extremely transparent, like it is not there. The bass has noticeably more power comparing to driving my LCD-2 singled-ended. It also made the LCD-2 sound more open, and removed some of the signature darkness associated with this headphone. I am not sure how much the headphone wire mattered in this case, as I handmade the balanced headphone cable using silver-plated teflon wire. Some pictures below. Big thank you to Owen for putting together this awesome kit and the wonderful wikis.
https://plus.google.com/u/0/photos/...lbums/5691975215218591265/5691975218560753442
https://plus.google.com/u/0/photos/...lbums/5691975215218591265/5691975218560753442
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BTW, the amp is completely silent at 100% volume, and the DC off set is immeasurable with a digital multimeter. I did not use the heatsinks that came with the kit. Instead, I sandwiched the board using two pieces of aluminum board and ArcticSilver thermal paste. The whole thing stays very cool under the the heaviest load.
I've been thinking about this as well, and in particular about the DC levels. Say the WM874X is running off a 4.5V (or 3.3 or 5 or whatever) analog supply and so the DC level at the output is halfway between there and its ground --- i.e. +2.25 V above the DAC ground. If that DAC ground is then tied to the ground of the Wire amp, then the DAC outputs sit at 2.25 VDC above Wire ground. This seems to be the scenario discussed above.
But what if we don't tie the grounds? The DAC's 4--5V power supply and the Wire's dual +/- 12 V supplies would normally be independent units anyway, so couldn't the DAC supply just be left to float relative to the Wire? The only connection between the boards would be through the DAC's balanced outputs. Does this seem reasonable?
If letting the DAC float relative to the amp seems too weird, a more active way to align things might be as follows: place a TLE2426 rail-splitter across the DAC's analog rails to produce a level at the midpoint, and then tie that TLE output to the Wire ground. Would this work? Any reason to prefer this to the passive approach of just letting the DAC supply float?
@curlew Thanks for making my confused thinking more explicit. The Opus contains a resistor network including the L-RMIDs that I cannot figure out, but guessed would do what you are thinking. I would like to leave that unpopulated and hook to the 'wire' differential opamp (much as is shown on the application schematic in the datasheet).
Are you sure? If the two power supplies (for DAC and amp) are independent, with no DC connection between them, and with neither one (or at least not both) tied to the chassis, how can we say that "0V" on the DAC is the same as "0V" on the amp? Sure, the DAC output is offset from DAC ground, but what stops me from making the DAC mid-rail (at 2.25 V above DAC ground) equivalent to the amp 0V?
Wolfsin: if you have clarified you thinking based on curlews post, then i'm a little worried about your thinking =)
Curlew, you seem to have a fundamental misunderstanding of what a ground offset at least in this case; means. the ground terminal on the opus and the ground on the wire are at the same potential; connecting the 2 at some point is not 100% necessary, but advised, however it will not cause any conflict/change, as they are at the same potential. the offset in this case is produced by splitting the dacs analogue reference in half; its a DC component of the signal (referenced to ground), not some charge in the signal ground.
there is no problem using the opus and the wire bal-bal directly like this as long as you remember the offset is there, so dont use rails on the wire that are too low, twist the wires evenly and dont add more than X gain that might multiply the offset+signal so as to exceed the rails on the wire.
adding a rail splitter wont make any (well no positive) difference, its not needed and it can only cause problems
Curlew, you seem to have a fundamental misunderstanding of what a ground offset at least in this case; means. the ground terminal on the opus and the ground on the wire are at the same potential; connecting the 2 at some point is not 100% necessary, but advised, however it will not cause any conflict/change, as they are at the same potential. the offset in this case is produced by splitting the dacs analogue reference in half; its a DC component of the signal (referenced to ground), not some charge in the signal ground.
there is no problem using the opus and the wire bal-bal directly like this as long as you remember the offset is there, so dont use rails on the wire that are too low, twist the wires evenly and dont add more than X gain that might multiply the offset+signal so as to exceed the rails on the wire.
adding a rail splitter wont make any (well no positive) difference, its not needed and it can only cause problems
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OK, I'm willing to listen.... FWIW, I understand perfectly well that we're talking about the DC levels. Your fundamental assertion / assumption is that:
Maybe I'm missing something here, but until the DAC and the Wire are connected in some way, it's completely meaningless to claim that the two grounds are "at the same potential." If the supplies are isolated, the circuits themselves are isolated from a common chassis, and the two grounds aren't otherwise tied (e.g through a shield), where is the connection that forces the grounds to be equivalent?
And if the _only_ connection is from the DAC outputs (at +2.25 V with respect to DAC ground) to the Wire input (at 0 V w.r.t Wire ground), it seems to me that the DAC ground now sits at 2.25 volts below Wire ground.
Where have I gone wrong?
sorry yes you are missing something. it is NOT meaningless to say they are at the same potential, because they ARE at the (roughly) the same potential unless you generate a DC offset virtual ground to reference the power supply of one or both of them to.
i take it you dont own this dac correct? experiment, measure from the signal ground pin to earth ground; connected or not they are the same. connecting the 2 will have no impact. the offset is in the signal (which is balanced and not even referenced to ground, thats the point). are you saying that since my speakers and headphones dont know what ground is and in a balanced or single ended connection to them are floating, that if there was say a 10vdc differential offset potential between the wires it wouldnt matter because they dont know what ground is?
i take it you dont own this dac correct? experiment, measure from the signal ground pin to earth ground; connected or not they are the same. connecting the 2 will have no impact. the offset is in the signal (which is balanced and not even referenced to ground, thats the point). are you saying that since my speakers and headphones dont know what ground is and in a balanced or single ended connection to them are floating, that if there was say a 10vdc differential offset potential between the wires it wouldnt matter because they dont know what ground is?
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the offset is only of consequence is its not the same on both phases. if the dac and amp arent connected and you take one of the phases, just the signal phase and measure it against earth ground it will be offset. the only way it wouldnt is if A. you use a cap, B. you have referenced the power supply of the dac to a potential that is equal, but opposite to the offset. then you would have problems connecting i2s or spdif signals without some form of isolation. if the dac is powered by batteries and the grounds still not connected, the signal will still be offset compared to ground
anyway this is off topic for this thread, i suggest you do some actual experiments rather than thought experiments
I just confirmed just in case by pulling out an old beat up opus that its power supply ground and output ground have 100% continuity, they are THE SAME
anyway this is off topic for this thread, i suggest you do some actual experiments rather than thought experiments
I just confirmed just in case by pulling out an old beat up opus that its power supply ground and output ground have 100% continuity, they are THE SAME
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