AC Filtering, Grounding Boxes, Linear PSU and Balanced Power.

[Cornan]

 

d) Connected both sides (this seems to be the default configuration on all USB cables although Cornan mentioned some USB cables aren't like that, I think only specialised cables would be built to break that connection though - any default off-the-shelf cable would have the connectors at each side connected to the shield)

 

 

Yes, it is true that off the shelf USB cables usually have the shield connected to ground at both ends...but there are plenty of specialized audio USB cables that offer other ready-made shielding solutions.

 

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[Cornan]

Why self powered? I am just now listening via A) method, my DAC USB port is powered from a small LPS. My external monitor need not be powered on, it is enough that the mains plug in inserted into the socket. Sound quality is very good. How to use an external monitor.

 

The only trouble is that the A) method interrupts playback after some tens of minutes. It seems the ground is not quite stable.

Just missed the LPS part in your reply. Anyway, if you use a LPS for 5v injection it is infact a 3-wire USB cable with clean power. Not a 2-wire USB cable with Data only.

I still recon that you create a ground loop with your monitor on. As soon as you get rid of the ground loop you will most likely loose the connection to your DAC.

 

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[bogi]

As soon as you get rid of the ground loop you will most likely loose the connection to your DAC.

Yes, that's happening as soon as I am unplugging the monitor mains cable. I described it in 1) http://www.computeraudiophile.com/f8-general-forum/ac-filtering-grounding-boxes-linear-power-supply-unit-and-balanced-power-24916/index42.html#post613683

[bogi]

To be able to use 2-wire USB cables you'll need your whole system connected to a perfect star ground which is not an easy task in most systems.

Let's discuss this point. some form of ground connection is always needed for the return current to flow. Without ground connection USB connection cannot function. We are discussing the possibility to lead that return current through other path than the USB cable itself.

 

What's the difference between 'perfect star ground' and my case? In both cases the return current is flowing across mains cables and wall sockets. OK, in my case also via DVI cable and that is one difference. But I could be able to ground my notebook too ... in fact, when I connect the external monitor, it is grounded, but I could ground it with extra cable too.

 

Another idea ... I could directly connect grounds of my notebook and DAC with a separate cable (to avoid interference with USB DATA wires), would that help? I suspect it could. I will try it with an "crocodile" cable. What's the practical difference between such direct ground connection and 'perfect star' grounding via mains cables and wall sockets?

 

Quite generally: What's the main point why sound with lifted ground is reported to be better? Is it because of avoided interference between data and power/ground wires? Or are there any other reasons?

[r_w]

I'm reasonably confident that USB can operate with only data pins 2 and 3 after handshake (without any gnd connection). I'm pretty sure that's happening in my system, as in, there does not appear to be a gnd loop in the mains, otherwise it would handshake without the USB gnd connected... and it doesn't until all three of my USB cable gnd lift switches are set to on.

 

?

... but this stuff is definitely system dependent.

 

 

 

Let's discuss this point. some form of ground connection is always needed for the return current to flow. Without ground connection USB connection cannot function. We are discussing the possibility to lead that return current through other path than the USB cable itself.

 

[Cornan]

Let's discuss this point. some form of ground connection is always needed for the return current to flow. Without ground connection USB connection cannot function. We are discussing the possibility to lead that return current through other path than the USB cable itself.

 

What's the difference between 'perfect star ground' and my case? In both cases the return current is flowing across mains cables and wall sockets. OK, in my case also via DVI cable and that is one difference. But I could be able to ground my notebook too ... in fact, when I connect the external monitor, it is grounded, but I could ground it with extra cable too.

 

Another idea ... I could directly connect grounds of my notebook and DAC with a separate cable (to avoid interference with USB DATA wires), would that help? I suspect it could. I will try it with an "crocodile" cable. What's the practical difference between such direct ground connection and 'perfect star' grounding via mains cables and wall sockets?

 

Quite generally: What's the main point why sound with lifted ground is reported to be better? Is it because of avoided interference between data and power/ground wires? Or are there any other reasons?

 

The star-ground path is something that Karin at Vbooster explained on another thread and is still my personal mind-ghost as I mentioned earlier on this thread. The way I want to try sooner or later is via chassi-to-chassi grounding that tie all audio components together to a single star ground. I have not tried it yet...but this is how I figure it could work. You might can also be able to create a star ground point via mains cables..but since I am using battery supplies I believe it is impossible. I already have just one safety ground connection but I cannot use a 2-wire cable.

 

The SQ is a lot better with lifted GND on all parameters. Think of the ground as a carrier of noise and currents and you understand more why it makes a difference. Also digital ground contains high frequency noises that analogue signals are very sensitive to and the USB data cables are infact analogue.

 

You'll need to have a single ground connection that ties all equipment together. Using unshielded ICs require a chassi-to-chassi grounding AFAIK.

 

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[bogi]

The SQ is a lot better with lifted GND on all parameters. Think of the ground as a carrier of noise and currents and you understand more why it makes a difference. Also digital ground contains high frequency noises that analogue signals are very sensitive to and the USB data cables are infact analogue.

Thanks, that's helpful explanation for me. It sound reasonable.

[Cornan]

Since I own a Entreq Minimus grounding box I am curious if it would work if I connect all my chassies to the Minimus and connect the Minimus to the safety ground pin...creating a star grounding point with the Minimus. However, in lack of true insight I am not 100% sure if I will create a dangerous setup by doing so. I will need to ask Entreq before even trying!

 

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[bogi]

I'm reasonably confident that USB can operate with only data pins 2 and 3 after handshake (without any gnd connection). I'm pretty sure that's happening in my system, as in, there does not appear to be a gnd loop in the mains, otherwise it would handshake without the USB gnd connected... and it doesn't until all three of my USB cable gnd lift switches are set to on.

... but this stuff is definitely system dependent.

 

Thanks! Because of differential nature of DATA+ and DATA- signal during data transfer it sounds to be possible and it confirms with your experience. In my case it doesn't function so, DAC is immediately disconnected when ground connection is broken. But that may be related to concrete implementation (Gustard DAC-X10 with XMOS in my case, Windows ASIO driver).

[Cornan]

How the handshake is performed all comes down to the DAC. First step would always be to ask the manufacturer how the handshake is implemented. I have seen other people using Y-cables to their DAC that requires 5v just for the initial handshake and not for the 5v power...and when they disconnect the power+GND leg it all works fine. However, I have also heard people frying their Regens due to this perticular setup with Y-cable...so it always best to ensure safety first and start the journey by asking the DAC manufactorer or on the specific DAC thread on CA.

 

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[Cornan]

Double post

[Middy]

Hi everyone... This is a regulator question than a recommendation...

LOD batteries.... John mentioned regulation... I use the Phone bank I never thought of its voltage out and attached regulators.....

Any DIY regulators that can help the out DC.....

 

This tied in what I have heard here but I never knew that 3.7v is upped to 5v.....

This seems ok below can't remember if it's off Headfi or Here but the description got me thinking. Especially since we are trying to make the incoming data and power. .GND Clean...

 

http://www.musicalparadise.ca/store/index.php?route=product/product&product_id=76

 

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[Cornan]

Hi everyone... This is a regulator question than a recommendation...

LOD batteries.... John mentioned regulation... I use the Phone bank I never thought of its voltage out and attached regulators.....

Any DIY regulators that can help the out DC.....

 

This tied in what I have heard here but I never knew that 3.7v is upped to 5v.....

This seems ok below can't remember if it's off Headfi or Here but the description got me thinking. Especially since we are trying to make the incoming data and power. .GND Clean...

 

http://www.musicalparadise.ca/store/index.php?route=product/product&product_id=76

 

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Hi Middy!

If you need a stabile 5v battery supply you'll need to look for 7,4v battery packs with linear step-down regulators. An example of that is the Kingrex uPower that I use in my system for powering my Regen (ie. I am not using the 5v linear regulated USB output...but the 7,5v output).

You can also choose to buy a 7,4v battery pack or higher and a separate linear step-down regulator that can handle the needed input/output voltage.

 

 

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[Cornan]

Hi Middy!

If you need a stabile 5v battery supply you'll need to look for 7,4v battery packs with linear step-down regulators. An example of that is the Kingrex uPower that I use in my system for powering my Regen (ie. I am not using the 5v linear regulated USB output...but the 7,5v output).

You can also choose to buy a 7,4v battery pack or higher and a separate linear step-down regulator that can handle the needed input/output voltage.

A step-down regulator is less noisy than a step-up dito. Also a linear regulator close to the powered source is even better for SQ than one built into the battery pack.

 

 

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[Cornan]

BTW @Middy! That battery supply on your link looks very good!

 

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[bogi]

How the handshake is performed all comes down to the DAC.

 

Thanks. I figured it out already about 2 years ago. My DAC required both ground and VBUS connection to be identified in Windows, I see it immediately in XMOS control panel. Music is playing and when I disconnect anyone of (VBUS, ground), playback is immediately interrupted and XMOS control panel doesn't see the DAC anymore.

 

As I already wrote, I have connected my LPS permanently to the DAC USB port through the adaptor cable I showed a page back. Now I tried 2 things - with external monitor unplugged.

 

A) to connect DAC chassis with notebook via crocodile cable ... I succeeded. One crocodile on the Supra type B body (the metal part is long enough) and the second on VGA connector of my notebook.

 

B) to connect mains wall ground (Earth) to VGA connector of my notebook with banana - crocodile cable ... I also succeeded.

 

In both cases DAC was recognized and playback went fine.

[Cornan]

Thanks. I figured it out already about 2 years ago. My DAC required both ground and VBUS connection to be identified in Windows, I see it immediately in XMOS control panel. Music is playing and when I disconnect anyone of (VBUS, ground), playback is immediately interrupted and XMOS control panel doesn't see the DAC anymore.

 

As I already wrote, I have connected my LPS permanently to the DAC USB port through the adaptor cable I showed a page back. Now I tried 2 things - with external monitor unplugged.

 

A) to connect DAC chassis with notebook via crocodile cable ... I succeeded. One crocodile on the Supra type B body (the metal part is long enough) and the second on VGA connector of my notebook.

 

B) to connect mains wall ground (Earth) to VGA connector of my notebook with banana - crocodile cable ... I also succeeded.

 

Thanks for sharing! That surely support that the chassi-to-chassi grounding to safety ground pin (star wired via grounding box) should work in my case as well.

 

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[YashN]

This was just me trying to make it easy to understand the handshake proceedure on any type of source. On many setups it is impossible to know when the handshake exactly occurs...so doing the GND lift after music starts playing make it easier IMO.

 

Hmm, but you thought the DAC was only found after you pressed play, which isn't the case in reality.

[YashN]

but there are plenty of specialized audio USB cables that offer other ready-made shielding solutions.

 

So, most people using a default USB wouldn't be able to benefit from those isolations here.

 

What are the 'plenty of specialised audio USB cables' which offer the different Jack-shield combinations?

[Cornan]

Hmm, but you thought the DAC was only found after you pressed play, which isn't the case in reality.

I still actually do not exactly at what instance that the DAC make handshake. My way of assuring that the handshake is made is when the music starts. After that point I know for sure it is OK to lift the GND.

 

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[YashN]

I was going to test the different combos today, but the connections were a bit fiddly, so I removed my iMac-to-SS amp chassis-to-chassis connection, connected one side of the jack the shiel (computer-side) and also both sides to the shield, and now the DAC isn't recognised.

 

So, it looks like this is one leg of the very circuitous path for a ground loop, especially since I removed my AC Filter experiments.

 

I've disconnected everything again and put the DIY cable back in the workshop to re-work it. I managed to make it quite short, but it becomes difficult to reach those two jacks + shield to make the connection, so switches with some wires will probably be used in the next iteration.

 

Additionally, I'll probably need a 3-way toggle: one with GND connected for handshake, one with an isolated GND, and one with the GND completely disconnected (for post handshake).

 

Getting things to work in a robust way without any fiddling and open wires and no circuitous route looks like a much-needed better way of testing various combinations.

 

I'm taking the circuitous route as similar to the GND just cut off, which iFi says isn't recommended. Actually they said the GND has to be lifted in a safe way and in accordance with the USB standard, so that's what I'll be looking at.

 

I figure once this is made correctly, nothing prevents the chassis-to-chassis grounding to be re-implemented properly.

 

Now, here is why this is quite circuitous as I found today:

 

- My iMac has a 3-prong power cord, but my SS amp doesn't...

 

- Chassis link was from the iMac to the SS amp

 

- However, there was no chassis link between the iMac and the Tube Amp

 

- The Tube amp isn't connected to the SS amp and the Tube amp has a 3-prong power cord

 

So, I am not sure how the SS chassis link to the iMac is actually causing the handshake to occur or not occur when it's removed. Sounds odd to me like that.

[Cornan]

So, most people using a default USB wouldn't be able to benefit from those isolations here.

 

What are the 'plenty of specialised audio USB cables' which offer the different Jack-shield combinations?

It was a long time since I searched for different USB cables...but for example Elijah Audio supplies unshielded USB cables and Entreq have shielded cables with drain wire to external grounding boxes. Sablon Audio also comes in mind. If you want more brands I will need some time to dig them up.

 

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[YashN]

I still actually do not exactly at what instance that the DAC make handshake. My way of assuring that the handshake is made is when the music starts. After that point I know for sure it is OK to lift the GND.

 

It take a tiny amount of time on connection. It's much faster than someone reaching for the Mouse to press play actually, at least that's what I find here.

[YashN]

It was a long time since I searched for different USB cables...but for example Elijah Audio supplies unshielded USB cables and Entreq have shielded cables with drain wire to external grounding boxes. Sablon Audio also comes in mind. If you want more brands I will need some time to dig them up.

 

Yep, heard of those.

 

The Entreq drain wire implementation is intriguing but could be interesting to try.

 

Must check the implementation of drain and shield and their effects on signal or noise if any. I think it could be a paper by Jim Brown showing measurements of those.

[Cornan]

It take a tiny amount of time on connection. It's much faster than someone reaching for the Mouse to press play actually, at least that's what I find here.

Thanks. Sreamer as I use might respond differently. I will check it out when I have got the time.

 

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