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Can someone pls tell me if the 9008's outputs are referenced to Analogue Ground (0 V DC) or if they are referenced to a "reference voltage" (around 2.5 V DC offset on the DAC output pins)?
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they are symmetrical about VA/2 - VA is 3.3V, so silence gives a DC voltage of about 1.65V.
As the outputs are differential, this cancels out.
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Rank: Advanced Member
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I know that there is an offset of 1.65 V DC, but I am not sure if this is the ansewer I need. The fact is that I am using this tube stage http://www.diyhifisupply.com/node/391 instead of the counterpoints and I was trying to find out the correct settings for its jumpers. Using it as SE device I have the options of 1mA full scale current, 0V reference voltage 2mA full scale current, 0V reference voltage 1mA full scale current, 2.50V reference voltage
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It looks like your choises for offset are 0V and 2.5V, neither of which are correct. You also may have an issue with the amount of current put out by the ES9008, which is greater than that of the chips he lists. Perhaps you should be asking the maker of the tube stage as I think you may need to change some of the components on the board. Edited by user Sunday, December 6, 2009 1:48:34 PM(UTC)
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Rank: Advanced Member
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so far I am using it with option 1ma, 0 VDC which seems to work fine, option 2ma rather seems to overload my preamp.
I have not tried the 2.5 VDC yet.
It seems to be sounding better than the counterpoints...
Would you say that any of these settings, since they are not a match, imply some kind of danger for either the 9008 chip or the stage?
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Rank: Advanced Member
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The following is the answer of the stage maker...
In the last line he is talking about Vcom...
Is this the 3.3V AVCC we used on the counterpoints?
The Buffalo is not quite the same as other DAC but...(untested):
Set UTS either to voltage mode, 1V output or to current mode 2mA.
If using current mode AND only one UTS (single ended) load the unused output of the Buffalo with 51R.
ESS show the Sabre DAC chip used Single-ended, so this kind of approach is entierly valid.
Also, if using single ended output in voltage mode leave other output unconnected. And in Voltage Mode offset is 1.7V, so use the version with 2.5V offset.
So, Buffalo DAC with single UTS uses either 3.02 with 51R on the unused outputs from the DAC (current mode, likely to sound better) or 3.12 (voltage mode).
Buffalo DAC with two UTS (balanced operation) uses 3.06 (current mode, likely to sound better) or 3.13 (voltage mode).
Also, if in 3.02 and 3.06 the output is too much, parallel additional 51R resistors on each of the Sabre DAC outputs.
There should be one set of jumpers different between 3.11 and 3.12.
If the ESS9008 does not tolerate the DAC output tied directly to ground (which their material implies it does), then use the configurations for 2.5V offset current out.
The difference between 1.7V and 2.5V is small enough to not upset anything major.
Vcom should be connected to the common mode voltage of the DAC. In most cases there is one, often called Vref or such. As the ESS9008 does not have such, and if I/V to ground is not permissable, a 1/2 Vadd node needs creating with suitable decoupling, in this case voltage mode may be the better choice.
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So, how did this work for you? I'm curious to hear about your impressions...
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Rank: Advanced Member
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It did work, better than ever hoped.
I do not remember the exact settings of the stage, but even if something may not be quite OK, the result is great.
If anyone is interested I can tell you the exact setting.
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Rank: Member
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dhmpan wrote:It did work, better than ever hoped.
I do not remember the exact settings of the stage, but even if something may not be quite OK, the result is great.
If anyone is interested I can tell you the exact setting. Sorry for the late reply, I just saw this thread. Thanks for your impressions, will let you know if I need more information. :)
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