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USB Ground Lift


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3 hours ago, beerandmusic said:

i had to look myself...i was thinking how is this even relavent with all the usb toys on the market...then i noticed timestamp.

 

Yeah its an old post. However there is still some truth in it. Battery supplies do improve SQ when a Entreq Minimus grounding box is attached to the -Ve of the battery output. Let me get this straight that this have probably nothing to do about grounds or 0v reference. Probably more about static electricity and/or EMI or even high impedance leakage. I don’t really know. It is just a guess based on other experiments in the field. All I know is that it 100% improve SQ.

 

A grounding box can have a very positive impact on the shield ground on USB cables. At the time of my original post back in 2016 I thought it might be positive to GND of the USB cable, but it is not. It is soley positive to the shield.

 

 

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I made my current USB cable into a dual headed USB cable with the help of my friend

One connector has the Data + and - connections and other Voltage and its ground

 

But the moment i remove the connector carrying voltage my DAC is disconnected from windows.

So does that mean my DAC needs constant voltage even after hand shake?

 

My DAC is a Burson Conductor having a C-Media USB interface

 

Or is it that i just have to disconnect the voltage ground, but even doing that will make the circuit incomplete

I am a little confused so want help from members who have tried this trick

 

Will it be a good idea to connect the second USB connector carrying voltage and its ground to a linear power supply ?

 

Lastly with this modification is a USB regenerator / reclocker like Uptone / W4S recovery advised to be used between PC and DAC?

 

TIA

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26 minutes ago, Cornan said:

Yes, it could mean that your DAC needs to see a 5v feed. You can possibly still do a USB ground lift, but for that to work the 5v lead needs to be attached at all time and the GND lead needs to have its own detatchable connection (for example a DC male plug and a DC female plug). When the DAC have started you can unplug the GND (but keave the 5v connected). This might work IF your DAC does’nt require GND as well. To find out you’ll need to do a little research among other users of your perticular DAC or just make your own experiment to see if it works or not.

If the DAC requires the 5V connection but works with GND disconnected, it means there's some other ground path back to the computer. In this case, disconnecting GND is a bad idea.

 

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I disconnected the 5volt + line and everything worked fine but the moment 5 volt (-) is disconnected the dac is disconnected from windows

 

So does that mean dac needs to see a ground to function?

 

Sorry for asking another dumb question, what happens when the laptop is running by battery and power brick completely disconnected ? Is there no ground to the laptop?

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On 10/9/2018 at 3:08 AM, Cornan said:

 

Yes, it could mean that your DAC needs to see a 5v feed. You can possibly still do a USB ground lift, but for that to work the 5v lead needs to be attached at all time and the GND lead needs to have its own detatchable connection (for example a DC male plug and a DC female plug). When the DAC have started you can unplug the GND (but keave the 5v connected). This might work IF your DAC does’nt require GND as well. To find out you’ll need to do a little research among other users of your perticular DAC or just make your own experiment to see if it works or not.

 

Furthermore some DACs need to have the 5v and GND removed in a certain sequence. Starting with removing GND and then 5v (or the other way around. My memory fails me). I have no idea if your DAC is one of those though.

 

It is always a good idea to provide clean power to the USB so a LPSU is a wise choise as well as using a ISO Regen or similar USB re-generators on top of that (powered with clean power). Mind you that ISO Regen needs to see 5v as well.

Tried connecting voltage + and - to an LPSU but still DAC is not detected

Need to connect the USB header having voltage + and - to PC , then only DAC gets detected 

 

Not sure what to make of this :(

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7 minutes ago, mansr said:

You must have ground connected to the host PC for detection to work, even if +5V is supplied separately. Once the high-speed handshake has completed, the ground can be disconnected. Full-speed devices need ground connected at all times.

First of all thanks for your reply

 

My DAC has cmedia cm6631a USB interface so it's a USB 2 high speed

 

So I will try to experiment connecting ground with DC male and female pins so I can disconnect it later on

 

How can I connect only 5 volt plus to any external PSU?

 

TIA

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1 minute ago, rikhav said:

My DAC has cmedia cm6631a USB interface so it's a USB 2 high speed

 

So I will try to experiment connecting ground with DC male and female pins so I can disconnect it later on

 

How can I connect only 5 volt plus to any external PSU?

Connect ground and +5V to the external supply. Also connect ground to the PC during the handshake.

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48 minutes ago, rikhav said:

Tried connecting voltage + and - to an LPSU but still DAC is not detected

Need to connect the USB header having voltage + and - to PC , then only DAC gets detected 

 

Not sure what to make of this :(

Sounds to me that you have a ground loop since it is working with just 5v but not 5v+GND connected to a LPSU. Draw a simple diagram of your system ground connections (AC/DC/IC) and post it here in order for me (or anyone else) to help you.

 

 

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Quote

Connect ground and +5V to the external supply. Also connect ground to the PC during the handshake.

- mansr

 

 I presume that you mean 0 Volts of the external +5V supply. It doesn't need to be earthed as the +5V supply can even come from a battery with a possible further improvement due to isolation from mains earth.

Also make sure that the incoming shield from the USB port isn't connected through . It may be connected internally to mains earth.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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7 minutes ago, sandyk said:

I presume that you mean 0 Volts of the external +5V supply.

I mean what I said. Connect USB ground and +5V to the corresponding terminals of the power supply. Connecting only one would be rather pointless.

 

7 minutes ago, sandyk said:

It doesn't need to be earthed

Of course not. I mean ground in the usual 0V reference sense.

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7 minutes ago, mansr said:

I mean what I said. Connect USB ground and +5V to the corresponding terminals of the power supply. Connecting only one would be rather pointless. 

 

 

I think we may be talking at cross purposes here.¬¬

Perhaps a simple diagram also showing a USB ground switch may help the less experienced members  ?

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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36 minutes ago, sandyk said:

I think we may be talking at cross purposes here.¬¬

Perhaps a simple diagram also showing a USB ground switch may help the less experienced members  ?

  DAC                    PSU
+------+               +-----+
| +5V  |---------------| +5V |
| GND  |-----+---------| GND |
| D+/- |==#  |         +-----+
+------+  |  |
          |  |
          |  |            PC
          |  |         +------+
          |  +--<SW>---| GND  |
          #============| D+/- |
                       +------+

 

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29 minutes ago, mansr said:

  DAC                    PSU
+------+               +-----+
| +5V  |---------------| +5V |
| GND  |-----+---------| GND |
| D+/- |==#  |         +-----+
+------+  |  |
          |  |
          |  |            PC
          |  |         +------+
          |  +--<SW>---| GND  |
          #============| D+/- |
                       +------+

 

Thanks. That should assist quite a few members.

 

Incidentally, anything further on the USB Widget  ?

 

 Also, a front panel like the attached also has the advantage of the USB shield not being connected through at the front panel, which gives the possibility of a separate earth shield from the device end, as well as shielding of the actual internal cabling in the Computer.

(Click on the photo of the USB Widget for a much larger photo.)

 

USB widget.jpg

USB 2.0 front panel.jpg

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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32 minutes ago, sandyk said:

Incidentally, anything further on the USB Widget  ?

Funny you should mention the USB Troll. It fell by the wayside for a while, but PCBs with a few tweaks are being made as we speak. My plan is to do some testing to find the best settings, then get rid of the switches to reduce component cost and assembly effort. (The switches are actually the most expensive parts.)

 

For those who missed the original discussion, the USB Troll is a device that automatically disconnects the ground when safe while providing an input for separate power.

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