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Ideas for making a USB voltage swing eavesdropper? Please!

post #1 of 22
Thread Starter 

Hello

Some time in the second week of March I should take possession of my first audiophile grade listening kit. Which will include the DAC "Little Dot DAC_I Digital to Analog Converter" this is a DAC with its own power supply which does not draw any power from the USB line, but the input to it can come from USB. I presently listen to my music with a USB headset either right in front of my computer with its little monitor or on the other side of a 82 foot USB cable where I have my big-screen television. Initially I wish to move, my first owned, DAC back and forth between the two locations. The trouble is I do not know if the voltage swing at the end of my 82 foot USB repeater cable will be sufficient to drive my chosen DAC totally optimally. Consequently since I own an oscilloscope I would like to make a way of eavesdropping on this voltage  swing.

 

So could anybody give me some good ideas in how you build an adapter that will let you eavesdrop on USB voltage swings? I mean if you could give me exactly what parts you would use that would be great. I would also want to know would you just use wires or some sort of crossbars or what? Exactly what you think would be the best way to build a USB voltage swing eavesdropper appropriate for an oscilloscope probe?


Edited by bbmiller - 2/19/14 at 8:16pm
post #2 of 22
Thread Starter 

PS

what do you think of this plus, this plus,this plus?

One of many choices at eBay. "USB Female Type B 5-Pin DIP Right Angle Plug Jack Socket Connector"

One of many choices at eBay. "USB male Type B 5-Pin DIP Right Angle Plug Jack Socket Connector"

One of many choices at eBay."5pcs Universal Double Side Board PCB 5x7cm 1 6mm DIY ..."

 

Do you think this would work?

 

 

If you have any experience doing this sort of thing are there any pitfalls? Does it matter which of those parts available at eBay I choose?

post #3 of 22
I would take a USB extender cable, cut off both connectors leaving each with a short (~3 inch) pigtail, strip back the wires (outer ~1 inch, inners ~1/4 inch), and solder them to a bit of perfboard (small, no more than an inch), red-red, white-white etc. You can solder in some solid wire risers with a little loop on the end to attach crocodile clips to for convenience.

w
post #4 of 22
Thread Starter 
Quote:
Originally Posted by wakibaki View Post

I would take a USB extender cable, cut off both connectors leaving each with a short (~3 inch) pigtail, strip back the wires (outer ~1 inch, inners ~1/4 inch), and solder them to a bit of perfboard (small, no more than an inch), red-red, white-white etc. You can solder in some solid wire risers with a little loop on the end to attach crocodile clips to for convenience.

w

How do you know when you have a USB extender cable which has honest to God wiring? I mean significant copper. I know when try this shortened the wires on cheap headphones the wires in cheap headphones are not real. There some sort of mixture between wiring thread. Is that not the case with USB extension cables?

post #5 of 22

I'm not sure that an oscilloscope will tell you anything. Just because you are getting signal at the far end of the cable does not mean it is readable. Stories abound of people having USB devices fail with 20ft cables... 

 

I would do the following:

Find software to monitor that everything is working properly. USB will resend failed packets - you may never know its not working.  

You can probably tell with just the TV at this point. 

 

If it holds up, great.

If not get a USB repeater or figure out how to set the system up using wifi or ethernet. 

post #6 of 22
Thread Starter 
Quote:
Originally Posted by nikongod View Post
 

I'm not sure that an oscilloscope will tell you anything. Just because you are getting signal at the far end of the cable does not mean it is readable. Stories abound of people having USB devices fail with 20ft cables... 

 

I would do the following:

Find software to monitor that everything is working properly. USB will resend failed packets - you may never know its not working.  

You can probably tell with just the TV at this point. 

 

If it holds up, great.

If not get a USB repeater or figure out how to set the system up using wifi or ethernet. 

I don't think you understand a TV single is not being carried by the USB.  The USB is only carrying the sound for the TV or more importantly the music videos. The USB is working successfully with my USB headset and had been working successfully with my USB soundcard.

 

 

My concern now is a good enough for audiophile quality DAC. I know it works, but I don't know if the signal is degraded. I mean I think a true digital signal for USB is very close to 5 V and zero votes. So I wish to take a oscilloscope and with the load of my soon to have DAC see if voltage  swing is where it should be. I figure I do not want my enjoyment to be degraded by slightly degraded sound which is in quick to notice without learning how to listen very critically.

post #7 of 22

I am not quite sure what you are asking for here!

Neither if you do so yourself!

An 82 feet long USB cable will never work!

USB cables are not recommended longer than 5 meters, about 16 feet or thereabout.

Longer cables will give you timing issues and losses.

post #8 of 22

What USB headset is yours?

post #9 of 22

His 82 foot USB cable is not just a cable, it's a repeater designed to carry USB over extended distances.  

 

That said, if it works, it works. I don't want to start a big USB cable thing here, but I imagine if this was failing, it would fail spectacularly... You'd hear glitches, dropouts, etc. Does it sound good to you? That's what really matters, isn't it?

post #10 of 22
Thread Starter 
Quote:
Originally Posted by brhfl View Post
 

His 82 foot USB cable is not just a cable, it's a repeater designed to carry USB over extended distances.  

 

That said, if it works, it works. I don't want to start a big USB cable thing here, but I imagine if this was failing, it would fail spectacularly... You'd hear glitches, dropouts, etc. Does it sound good to you? That's what really matters, isn't it?

I have a Plantronics 780 headset which I equalized twice purdah dictates of these forms. After I equalized it the second time it started sounding so good to me I got the idea I wanted audiophile level kit so that I might take music listening as far as it could go. I will be using the DAC with the USB signal. This DAC along with my new headphones and headphone amplifier will be by far the best audio equipment I have ever owned. So I am worried not that it will not continue to work, but rather it won't supply a totally adequate signal for optimum audio. My DAC does not drawer any power from the USB line it has its own power supply, consequently I am just worried about adequate voltage swing to provide a totally adequate signal for the DAC. Perhaps DAC's of this type have regenerative powers and it should be a problem I just don't know that much about them.

post #11 of 22
Thread Starter 
Quote:
Originally Posted by bbmiller View Post
 

PS

what do you think of this plus, this plus,this plus?

One of many choices at eBay. "USB Female Type B 5-Pin DIP Right Angle Plug Jack Socket Connector"

One of many choices at eBay. "USB male Type B 5-Pin DIP Right Angle Plug Jack Socket Connector"

One of many choices at eBay."5pcs Universal Double Side Board PCB 5x7cm 1 6mm DIY ..."

 

Do you think this would work?

 

 

If you have any experience doing this sort of thing are there any pitfalls? Does it matter which of those parts available at eBay I choose?

So since there isn't anybody further addressing  the way I propose making my access to the five go fault digital lines of USB for purposes of temporarily attaching an oscilloscope I'm assuming it's OK way of doing it. You all just addressed other issues so I my right my way of doing it would work just fine with no pitfalls?

post #12 of 22
No, the kind of wire you are talking about is peculiar to very thin headphone cables.

The sockets you have shown will not fit on 0.1 inch perfboard without issue. The pins are staggered.

w
Edited by wakibaki - 2/20/14 at 3:27pm
post #13 of 22
Thread Starter 
Quote:
Originally Posted by wakibaki View Post
The sockets you have shown will not fit on 0.1 inch perfboard without issue. The pins are staggered.

w

OK  been looking into this would this work? With that 0.1 inch perfboard without issue.?

EBay copy reads (PCB USB Plug Connector Type A Surface Mount (Pack of 3))

 

 

 

 


Also would this work?

 

EBay copy reads (20Pcs USB 4 Pin Type-A Female Socket Connector DIY)

 

 

Does that abbreviation DIY Also mean the pin spacing will be the same as 0.1 inch perfboard?

 

 

Also would a little plastic breadboard like this have to same hole spacing as 0.1 inch perfboard and work?

 

If not what you think of these?

 

EBay copy reads(USB2.0 Type A female socket breakout board)

 

It can be found at ELABGUY site.

post #14 of 22
I think, but I don't know for sure, that the breadboard has 0.1" spacing.

The sockets have 0.1" spacing on the signal pins, the problem is with the thick prongs which are an extension of the shroud. They're not on the 0.1" grid, and anyway they won't fit in the holes. They're normally used (soldered) to the PCB to secure the socket, because otherwise removing and inserting the plug will break the signal pins after a few cycles.

The USB breakout board looks good to me, the pin spacing will definitely be OK.

w
post #15 of 22
Thread Starter 
Quote:
Originally Posted by wakibaki View Post

I think, but I don't know for sure, that the breadboard has 0.1" spacing.

The sockets have 0.1" spacing on the signal pins, the problem is with the thick prongs which are an extension of the shroud. They're not on the 0.1" grid, and anyway they won't fit in the holes. They're normally used (soldered) to the PCB to secure the socket, because otherwise removing and inserting the plug will break the signal pins after a few cycles.

The USB breakout board looks good to me, the pin spacing will definitely be OK.

w

Thanks

 

I'll try that than it's a little pricier but not since considering it sounds like it should last a long time.

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