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Post by ocean2059 on Dec 4, 2010 10:22:55 GMT -5
I have been using the XDA for two days now using Oppo 93 ->XDA -> XPA-2 (balanced) -> B&W 805. The gain control I've used varies from 2 to 15 depending upon different CDs (mostly classic music). I don't really feel the gain control is too high for the system I have.
As for the XDA, I really like it, open, clear, with great resolution. It's a keeper!
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Post by ajani on Dec 4, 2010 11:14:11 GMT -5
The issue is therefore the extra high gain on the Emo amps then... Well actually there might still be an issue with the XDA-1... is 1V = half the volume of 2V or just half the wattage? Remember that half the wattage means just 3db less volume, not half the volume... I think the real issue is how the volume control is implemented. Since half of the volume reading (40 vs. 80) leads to half the voltage (1 volt vs 2 volts), the volume is a linear volume control. In almost all stereo components, the volume control does not use a linear volume control but a logarithmic volume control. For a logarithmic volume pot, the volume control is much more responsive to small turns of the volume pot at high volume and allows for greater control at low volume. Basically the XDA's linear volume control doesn't have enough steps at the low end of the scale to finely control the volume for some systems, i.e. those with sensitive amps and sensitive speakers. See this link about linear vs. log volume www.learnabout-electronics.org/resistors_09a.php"Using a log pot therefore gives the effect that a setting of full volume on the control sounds twice as loud as a setting of half volume. A linear pot used as a volume control would give large apparent changes in loudness at low volume settings, with little apparent change over the rest of the control´s range ." The XDA volume control is basically a linear volume control. But there is nothing wrong with it's gain -- its outputting a standard output voltage. Just compare with cfelliot's other CD player, both output 2 volts. Thanks for the technical explanation... I figured gain wasn't the correct term for the problem, but I didn't know what was... |
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Post by rockguitar on Dec 4, 2010 22:17:21 GMT -5
Hey no problem. I know exactly where you are coming from.  |
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Post by wizardofoz on Dec 5, 2010 0:16:12 GMT -5
OK well the fedex man came at about 9Am sunday morning....gotta love asia was expecting delivery by 6pm tmor...but ill roll with this for now  Yeah its heavy ... first things first lose the 2 end plates...now all black.... thats better...now to plug it in...all good so far...DYI MK hospital grade plug to belden mains and Wattgate320I IEC ... now on it...80 on the Volume as indicated before...OK thats a bit high....do they really test them out of production up to this....are they driving speakers diectly off this? ..... ok down to 0.5 ... and select a source...my NEW ERC-1 using opt and coax so I can A/B output RCA to my DIY GainClone bridged amp and 15" Klipsch sub for some bass and (cringe) Bose cubes laying about. very nice all working.... max vol for this arrangement ERC maybe 10 and for my vortexbox coax out at maybe 20. ...but 1-2 is fine for normal listening...wonder if there is any USBable firmware fix for the attenuation... its a pity the DIM doesnt get to all off, but at least there is no power button glow. now the bigger issue... no USB detection from Linux based vortexbox (fedora 14) - have yet to try another source like my iPad or Mac 80 on the |
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MikeWI
Emo VIPs 
DC-1, ERC-1, USP-1, UPA-2, Sub 10, Emotiva 4S
Posts: 346
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Post by MikeWI on Dec 5, 2010 8:33:44 GMT -5
Yeah its heavy ... first things first lose the 2 end plates...now all black.... thats better... Yep, did that. its a pity the DIM doesn't get to all off, but at least there is no power button glow. If I keep the XDA-1 (right now, it seems only marginally better than the internal DAC in my Rotel RSX-1056 receiver, but further time will tell), and 1. I don't get any love from a firmware update to enable a lights-off policy or 2. There isn't an easy way to disable lights internally I have already spec'd out a 17" X 1-3/4" X 1/4" #2074 Dark Gray Plexiglass w/12% light transmittance front panel overlay that will fasten with 4 allen bolts using spacers just enough to clear the buttons. That will of course disable physically pushing buttons on the front panel, but I will still be able to see what's going on and it will work with the remote. It's tough for me to get past the 10 too-bright blue lights with the mismatched blue-green display, so I have a piece of cardboard in front of the front panel to get me through the sonic evaluation period. Steve Steve - Where's the pic of the cardboard workaround? ;D Mike |
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Post by rockguitar on Dec 5, 2010 23:57:03 GMT -5
I tested the XDA-1 outputs tonight by doing the following: I created a pink noise wav file on my PC normalized to 0 dB. I burned this file to an audio CD. I played the track with my old CD player and observer 2.1V out with my multi-meter. I played the track on my PC to the XDA-1 at a volume level of 80 and also got about 2V. Note - unbalanced! I lowered the volume to 40 and got about 1V. Bottom line: nothing wrong with the XDA-1! I've posted earlier about how I was sure the volume control of the XDA is linear not logarithmic. Just to satisfy my curiousity, I broke out my digital multimeter and test tone CD and have confirmed it. Here are my results vol. rca xlr (volts) set. 80 1.497 1.522 40 0.746 0.759 20 0.372 0.378 10 0.185 5 0.0935 0.5 0.0182 I graphed the results and got the results using the RCA outputs in the attached graph. I didn't bother getting all the XLR results because they are consistently close to the Rca values but a little higher. img97.imageshack.us/img97/6267/xdapic.jpgYou can clearly see the volume attenuator is linear Using another CD player with the same test tone at full volume gives a result of about slightly over 1.5 volts (comparable to the 1.497 volts. The difference between my results and cfelliot's is that my test tone is not recorded at the absolute max possible. In other words, it's like comparing two different CD's, one of which is mastered louder than the other. |
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Post by rockguitar on Dec 6, 2010 0:10:40 GMT -5
does anyone know how to paste a pic directly into the post? I can't seem to do it in my previous post.
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Post by Chuck Elliot on Dec 6, 2010 0:17:41 GMT -5
does anyone know how to paste a pic directly into the post? I can't seem to do it in my previous post. I host my pictures on my web site and link to them with the image html tag. You can open a flicker account, put your picture there and then link to it too. Here's a picture of linear vs log. X is the volume setting, Y is the gain reduction dB.  |
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Post by rockguitar on Dec 6, 2010 9:33:28 GMT -5
 Got it now, thanks for the heads up. Are you sure you got the labels (blue, red) correct for your graph, they look reversed to me? |
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Post by rockguitar on Dec 6, 2010 9:47:54 GMT -5
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Post by Chuck Elliot on Dec 6, 2010 10:38:24 GMT -5
... Are you sure you got the labels (blue, red) correct for your graph, they look reversed to me? Yes, they are correct. The reason it looks reversed is because the Y axis is in dB. You want the change in dB to be linear. The graph shows that you have a huge jump in dB in the lower volume settings between steps with the XDa-1 as is. |
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Post by rockguitar on Dec 6, 2010 10:52:00 GMT -5
I guess I was not clear enough -- which occurs often with me . I understand about the axis, what I meant was that blue - looks linear and red -- looks log, which is the reverse from how they were labeled. |
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Post by Chuck Elliot on Dec 6, 2010 10:59:45 GMT -5
I guess I was not clear enough -- which occurs often with me . I understand about the axis, what I meant was that blue - looks linear and red -- looks log, which is the reverse from how they were labeled. Take the data you have. Instead of plotting the raw output convert it to dB. Do this by normalizing it first so that max output is 1. You can do this by dividing your data by 2. The dB value is then 20*log10(value) in Excel. When the log function is applied to output that has a log step it , it makes it look linear. And, the linear step looks log!!!!! |
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Post by rockguitar on Dec 6, 2010 12:00:06 GMT -5
I get where you're coming from and thought that might be what you are doing graphing logs, but I wasn't sure. The thing that threw me off is I had forgotten that db already includes the log function in there. I'm so used to see log scales on the axes when graphing logs.
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Post by Poodleluvr on Dec 6, 2010 13:14:32 GMT -5
I appreciate all the log and linear stuff, but....
To my understanding on the XDA-1 output voltage:
"Nominal Output Voltage: 1V RMS"
"Peak Output Voltage: > 12VRMS (balanced)"
Basically, it appears to me as not that of a fixed nominal 1 Volt but 1V with peaks of up to 12V which can create dynamic swings in voltage depending upon the source material?
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Post by Chuck Elliot on Dec 6, 2010 14:14:10 GMT -5
I appreciate all the log and linear stuff, but.... To my understanding on the XDA-1 output voltage: "Nominal Output Voltage: 1V RMS" "Peak Output Voltage: > 12VRMS (balanced)" Basically, it appears to me as not that of a fixed nominal 1 Volt but 1V with peaks of up to 12V which can create dynamic swings in voltage depending upon the source material? I can't speak to balanced outputs as I have not used them that much, so the following pertains to unbalanced. Most CDs are mixed with around 6 dB of headroom. That means that the output will be around 50% max, voltage wise. If you create a CD from test tones with no headroom at all, the XDA-1 will put out about 2V as will most CD players. So the "Nominal" output will be around 1V (-6dB from 2V) for an average CD. All output will be someplace between 0V and 1V for the average CD. This does not say that there might not be peeks that go near the 2V level. Example (Iron Man - Black Sabbath):  |
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Post by rockguitar on Dec 6, 2010 20:06:35 GMT -5
I've been looking closely at the Lavry DA-10, the reason being it uses the same AD1955 DAC chip and it also uses the onboard volume capabilities of the chip -- similar to the XDA. The Lavry DA-10 uses a logarithmic taper for the volume control vs. the linear taper for the XDA. The Lavry documentation also confirms that the volume control is analog.  www.lavryengineering.com/productspage_da_10.htmlwww.lavryengineering.com/white_papers/DA10_manual.pdfThe graph is my clumsy exerpt from the Lavry manual. The output voltage at the right hand side of the graph shows the logarithmic volume control. The left hand side is in db and also shows a log taper. You can read the manual for a detailed explanation. If as mentioned earlier, the XDA used a log taper, like the Lavry, we would have much better and fine control at normal and low listening volumes when connected directly to an amp. Everyone connecting to a pre or receiver is unaffected. |
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Post by pdaddy on Dec 6, 2010 20:43:52 GMT -5
"Ah... I was told there would BE no math"
Yes that's the Chevy Chase reference.
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Post by dumdedum on Dec 7, 2010 17:23:55 GMT -5
I've been using the XDA as a DAC connected to several DVD/Cd players and one dedicated CD player.
The first player and XDA combination I tried was an Oppo DV -980H. By itself the Oppo 980 is really not a good CD player. Way TOO laid back for my taste. With the XDA connected there was not much improvement.
The second DVD/CD player I did the same test with was a Pioneer DV-260. Again I heard the same results. Even with the XDA connected I didn't like what I heard.
The third player I did the test with was an Ultech UCD-100. A good CD player by it self. More to my liking. I connected the XDA to it and NOW I'm hearing a very,very nice open sound with very good detail.
Based on these tests I'm thinking that to get the most out of the XDA used as a DAC only it should be connected to a dedicated CD player.
I'm sure the XDA can be used some other way besides a DAC but that's not my bag.
Last but not the least an Oppo BDP-93 beats all these combination's by quite a bit. It is a terrific CD player. And a hell of a good DVD player. Best I've had.
And! And! None of these player combinations can compare to my APLHIFI CD/DAC player. Of course the APLHIFI player costs mucho BUCKS!!!
Cheers to all and a very merry Xmas!
Charlie
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Post by rockguitar on Dec 7, 2010 17:56:37 GMT -5
Based on these tests I'm thinking that to get the most out of the XDA used as a DAC only it should be connected to a dedicated CD player. I'm sure the XDA can be used some other way besides a DAC but that's not my bag. Last but not the least an Oppo BDP-93 beats all these combination's by quite a bit. It is a terrific CD player. And a hell of a good DVD player. Best I've had. And! And! None of these player combinations can compare to my APLHIFI CD/DAC player. Of course the APLHIFI player costs mucho BUCKS!!! Cheers to all and a very merry Xmas! Charlie Very interesting. Did you try the Oppo-93 and APL into the XDA as the DAC? I think you'll find that a great transport really makes a difference when feeding a DAC. Back in the day, I compared about 4-5 different transports into a Benchmark DAC1 and they all sounded different to my ears. BTW can you give the model of the APLHIFI player? I still own an APL modded Pioneer 563a universal player that Alex Peychev started making his reputation on. |
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