ive never said anything like what i said there, not repeating myself in the slightest other than wishing you luck with the new forum, so sorry for that sentiment, should i take it back?
i got what i wanted and i'm moving on.
I have read the 'exaU2I - Buffalo DAC Integration' sticky but had a question for those using tridents with their Buffalo II. Where tridents are used, L8 is removed, where is the best place to tap to get DVCC. Also did you have to change the current resistor on DVCC trident to allow more current through for the 20ma used by the exau2i?
Hi
is there any instruction how to connect exau2i with wm8741 DAC?
I know that i should connect the: GND, DVCC , DCK and LR, but what about SCK pin? I use WM8741 reference board
http://www.wolfsonmicro.com/documents/uploads/misc/en/WM8741_6060_DS28_EV2_REV1_Schematic_layout.pdf
thanks in advance
is there any instruction how to connect exau2i with wm8741 DAC?
I know that i should connect the: GND, DVCC , DCK and LR, but what about SCK pin? I use WM8741 reference board
http://www.wolfsonmicro.com/documents/uploads/misc/en/WM8741_6060_DS28_EV2_REV1_Schematic_layout.pdf
thanks in advance
You should connect SCK to MLCK - this is H3/pin14 on the WM8741 reference board.
You can find the general instructions here - http://exadevices.com/exaU2I/DIYGuide.aspx.
Last edited:
exaU2I - noise with and without ground isolation
One of the most heated debates on this thread is about the benefits and drawbacks of using GMR isolators. To illustrate the benefits I came up with a simple measurement. Here is the noise spectrum when exaU2I is used with and without ground isolation.
I used TrueRTA, generic sound card and a low-noise amplifier. I used Foobar to play a WAV file: 1kHz signal at -100dB. exaU2I was connected to an ES9018 DAC, the DAC output amplified and fed into the soundcard. The measurements show A-weighted spectrum of the DAC output amplified 70 times. The first one is taken with exaU2I as is - the grounds are isolated. For the second measurement the analogue and digital grounds of the exaU2I were shortcuted.
One of the most heated debates on this thread is about the benefits and drawbacks of using GMR isolators. To illustrate the benefits I came up with a simple measurement. Here is the noise spectrum when exaU2I is used with and without ground isolation.
I used TrueRTA, generic sound card and a low-noise amplifier. I used Foobar to play a WAV file: 1kHz signal at -100dB. exaU2I was connected to an ES9018 DAC, the DAC output amplified and fed into the soundcard. The measurements show A-weighted spectrum of the DAC output amplified 70 times. The first one is taken with exaU2I as is - the grounds are isolated. For the second measurement the analogue and digital grounds of the exaU2I were shortcuted.
Attachments
Last edited:
Details
hi exa, thanks for posting this info. It would be instructive to know the computer hardware involved in providing the USB source: desktop vs laptop, make model, etc.
hi exa, thanks for posting this info. It would be instructive to know the computer hardware involved in providing the USB source: desktop vs laptop, make model, etc.
This does not seem like the most neutral test of the benefits of GMR isolation. Considering the controversy over ESS90xx jitter rejection via SRC, it seems entirely possible that the added noise that you witnessed is due to particular side-effects of the ESS Tech processing.
Do you have a bit-perfect DAC that is wired as the master clock for the exaU2I that you could test in a similar fashion? I'd like to see the noise floor differences, if any, when there is no DSP altering the samples.
I find your hypothesis very artificial
In my opinion the test is clean. The idea behind this experiment is that exaU2I owners can easily repeat it in their own environments. They can evaluate the benefits of ground insulation for their particular combination of computer, DAC, power supplies, and connections topology.
Actually what the isolators are doing is effectively breaking a ground loop between the PC and the DAC and it's the ground current circulating within the analogue connectors shielding that is inducing crap into the signal line. You can easily see this as the spikes and its harmonics at multiples of the mains frequency in the non isolated test.
This isn't showing any benefits of isolation on maintaining the integrity of the digital signal, more it's simply showing what a standard ground loop can look like. If you want to see what effect the isolators have you'd need to use a double insulated piece of test equipment that wouldn't form a loop when plugged into the output of the DAC.
This isn't showing any benefits of isolation on maintaining the integrity of the digital signal, more it's simply showing what a standard ground loop can look like. If you want to see what effect the isolators have you'd need to use a double insulated piece of test equipment that wouldn't form a loop when plugged into the output of the DAC.
Eliminating ground noise
Your observations are absolutely correct. The very purpose of the ground insulation is to break the ground loops.
However I disagree that using double isolated measurement equipment will provide more meaningful results. The purpose of this test is to highlight the difference in noise levels when real-world audio equipment is used.
Measurement taken with double-insulated equipment will show less or no difference between the two tests. When real amplifier is connected instead of the measurement tool, the noise will be there.
Note also that in addition to the harmonics of the mains frequency there is high-frequency noise coming from the computer. It is very important that the ground isolation reduces this high-frequency noise.
I would like to explain that the 1 kHz signal at -100dB is used just for visual reference for the noise level. This is necessary because the "measurement equipment" is far from being calibrated. Once you know the scale of the graph, the 1 kHz signal can be turned off.
Your observations are absolutely correct. The very purpose of the ground insulation is to break the ground loops.
However I disagree that using double isolated measurement equipment will provide more meaningful results. The purpose of this test is to highlight the difference in noise levels when real-world audio equipment is used.
Measurement taken with double-insulated equipment will show less or no difference between the two tests. When real amplifier is connected instead of the measurement tool, the noise will be there.
Note also that in addition to the harmonics of the mains frequency there is high-frequency noise coming from the computer. It is very important that the ground isolation reduces this high-frequency noise.
I would like to explain that the 1 kHz signal at -100dB is used just for visual reference for the noise level. This is necessary because the "measurement equipment" is far from being calibrated. Once you know the scale of the graph, the 1 kHz signal can be turned off.
As my previous response to this wasn't quite what you were happy with I'll try again.
The purpose of the ground isolator isn't to break ground loops but to prevent any high frequency hash from finding its way into the audio circuitry.
High frequency hash wont tend to flow through a ground loop anyway as high frequency currents follow the path of least inductance and you can bet your bottom dollar that down the mains safety earth and through the audio cable shielding isn't that path. It will however help to reduce the effects of any EMI induced currents from flowing.
As you said yourself, the isolator is showing the result of breaking a ground loop, but with it breaking all the traditional crud that can find its way into the loop too. The point of the isolated test equipment would be so that you can show what the isolator does to the performance without the results being impaired by a ground loop.
Preventing a ground loop and isolating the two circuit grounds are completely different things, as you can prevent loops from forming whilst keeping the two circuits coupled. What I'd guess people want to see (at least what I'd be interested in seeing) is the effects of decoupling/breaking the two circuit grounds without anything else happening to join the party, such as a ground loop.
The purpose of the ground isolator isn't to break ground loops but to prevent any high frequency hash from finding its way into the audio circuitry.
High frequency hash wont tend to flow through a ground loop anyway as high frequency currents follow the path of least inductance and you can bet your bottom dollar that down the mains safety earth and through the audio cable shielding isn't that path. It will however help to reduce the effects of any EMI induced currents from flowing.
As you said yourself, the isolator is showing the result of breaking a ground loop, but with it breaking all the traditional crud that can find its way into the loop too. The point of the isolated test equipment would be so that you can show what the isolator does to the performance without the results being impaired by a ground loop.
Preventing a ground loop and isolating the two circuit grounds are completely different things, as you can prevent loops from forming whilst keeping the two circuits coupled. What I'd guess people want to see (at least what I'd be interested in seeing) is the effects of decoupling/breaking the two circuit grounds without anything else happening to join the party, such as a ground loop.
I think the ground isolation is a very good idea and in this case is one of the times where you can easily use an isolator to do away with any 'headache' that designing to avoid loops can create.
Usually loops are easy enough to understand in principle, the hard part is often coming up with a complete system design that will prevent them from forming.
Usually loops are easy enough to understand in principle, the hard part is often coming up with a complete system design that will prevent them from forming.
e18 DAC - 8 channels at 32bit /384 kHz
I am very excited to introduce a new member of the exa family, the e18 DAC. e18 is not a DIY product, but it is a close relative to the exaU2I. It uses a second generation USB to I2S interface and it can handle 8 channels at 384 kHz. Your support for exaU2I made releasing the e18 possible - thank you!
The e18 will help us to further develop our technology and we will make the advancements available to the DIY community.
You can find out more about the e18 DAC here.
I am very excited to introduce a new member of the exa family, the e18 DAC. e18 is not a DIY product, but it is a close relative to the exaU2I. It uses a second generation USB to I2S interface and it can handle 8 channels at 384 kHz. Your support for exaU2I made releasing the e18 possible - thank you!
The e18 will help us to further develop our technology and we will make the advancements available to the DIY community.
You can find out more about the e18 DAC here.
To flemming3520,
I'd like to express my gratitude to the advice above very much.
Your method easily made me create a DSD256 test audio file!
To exa065,
I think both your exaU2I board and your new DAC must have capabilities of playing DSD256 or DSD512 sources.
Bunpei
exaU2I plays DSD128 - DSD512 sources since February 2010. flemming3520 just needed some time to discover it
- DSD Playback with exaU2IIn our test environment the exaSound e18 DAC can play 6 channels DSD. We need some extra time to release this feature.
exaU2I plays DSD128 - DSD512 sources since February 2010. flemming3520 just needed some time to discover it
Oh, that's wonderful!
DCLK for DSD512 is 44.1 x 512 = 22.5792 MHz.
As the exaU2I has 11.2896 MHz oscillator on board, this might mean the FPGA logic includes special 2 x multiplying functionality only for DSD512 sources.
It's really a well-prepared approach!
DSD came as a gift, Bunpei. It came at no extra charge. This is more than we have expected from our original design. It's really a well-prepared approach!
Happy Holidays!