Amr dp-777

[Her Master's Voice]

ROC,

That "dirty" 5V really screws things up.

That is the only reason why data transfer via USB does not sound too good. And bi-wire USB cable like those from Artesan, iFi or WSS really help to solve this problem. ROC wants to buy a bi-wire cable, so this tweak is not necessary anymore.
BTW when you disconnect the 5V cable, what about the initial 'handshake' between computer and DAC?

 

[kanwar]

That is the only reason why data transfer via USB does not sound too good. And bi-wire USB cable like those from Artesan, iFi or WSS really help to solve this problem. ROC wants to buy a bi-wire cable, so this tweak is not necessary anymore.
BTW when you disconnect the 5V cable, what about the initial 'handshake' between computer and DAC?

A little off-topic,

Another way of keeping the PC noise out of the USB section of DAC is implementing pure Galvanic Isolation front end, which can be found on some nicely implemented USB Dacs.

JDS Labs Blog | Premium Headphone Amplifiers

ADUM3160 datasheet and product info | Full/Low Speed USB Digital Isolator | Digital Isolators | Analog Devices

 

[Nikhil]

And bi-wire USB cable like those from Artesan, iFi or WSS really help to solve this problem. ROC wants to buy a bi-wire cable, so this tweak is not necessary anymore.

The bi wire is just separating the +5V and GND from the data wires.
Snip the red wire and you don't have to deal with the whole thing unless I am missing something
This is well within the scope of a decent technician and costs less than Rs 200 including the cable.

BTW when you disconnect the 5V cable, what about the initial 'handshake' between computer and DAC?

Not really the expert here but I imagine that since most DACs are powered this is not an issue.
I was surprised at how much effect it had despite the extensive care taken to treat the power internally in my DAC.

 

[reignofchaos]

A little off-topic,

Another way of keeping the PC noise out of the USB section of DAC is implementing pure Galvanic Isolation front end, which can be found on some nicely implemented USB Dacs.

JDS Labs Blog | Premium Headphone Amplifiers

ADUM3160 datasheet and product info | Full/Low Speed USB Digital Isolator | Digital Isolators | Analog Devices

Galvanic isolation exists in almost all good DACs including the amr.

As for adum3160 it is useless - I have one isolator. It doesn't work well with usb class 2 async DACs that negotiate at high speed. Yes high speed is higher than full speed.

 

[kanwar]

As for adum3160 it is useless - I have one isolator. It doesn't work well with usb class 2 async DACs that negotiate at high speed. Yes high speed is higher than full speed.

Yes, sadly its only full speed complaint 12Mbps , not the High speed USB which has operating speeds of more than +100Mbps. For USB 2.0 high speed one has to get something like ISO7221C or Silicon Labs SI88XX series which are around 150Mbps. or something like This

 

[gobble]

Not really the expert here but I imagine that since most DACs are powered this is not an issue.
I was surprised at how much effect it had despite the extensive care taken to treat the power internally in my DAC.

Only the ground wire is required for device detection and handshake,

Galvanic isolation exists in almost all good DACs including the amr.

As for adum3160 it is useless - I have one isolator. It doesn't work well with usb class 2 async DACs that negotiate at high speed. Yes high speed is higher than full speed.

I believe many former based isolation devices have a negative impact on SQ.

G0bble

 

[reignofchaos]

Only the ground wire is required for device detection and handshake,



I believe many former based isolation devices have a negative impact on SQ.

G0bble

Yep absolutely. These devices are not meant for audio isolation. My experience was absolutely negative when I used one with an m2tech hiface. It robbed the music off its life.

 

[ravi_d]

Yep absolutely. These devices are not meant for audio isolation. My experience was absolutely negative when I used one with an m2tech hiface. It robbed the music off its life.

For audio, isolation (using hi-speed chips) is followed immediately by re-clocking for best results.

 

[reignofchaos]

For audio, isolation (using hi-speed chips) is followed immediately by re-clocking for best results.

Yes reclocking matters but what matters more is the high end dac arena is the precision of reclocking. AMR claims an accuracy of 0.001Hz (i.e. ~0.04ppm). There are only one or two cost no object designs from MSB and dCS which better this. But those cost multiple times of the AMR and you need to purchase a high precision external clock in addition to just the dac.

 

[square_wave]

Yes, that bi-wire tweak yields nice improvements. Highly recommended tweak if you do usb.

Removing that 5v pin sounds logicalNever tried that out though. Thanks Nikhil for the tip.

 

[reignofchaos]

Yes, that bi-wire tweak yields nice improvements. Highly recommended tweak if you do usb.

Removing that 5v pin sounds logicalNever tried that out though. Thanks Nikhil for the tip.

Actually my plan is to not remove any pins. I plan to buy one of those 5000 mAh usb chargers that supply 5V from a lithium ion battery and plug the power end of the gemini cable into that. The data end obviously goes into the music pc. Even though the DAC doesn't use the 5V input, this would avoid any cable splicing and 5V would be as pure as possible.

 

[Her Master's Voice]

Actually my plan is to not remove any pins. I plan to buy one of those 5000 mAh usb chargers that supply 5V from a lithium ion battery and plug the power end of the gemini cable into that. The data end obviously goes into the music pc. Even though the DAC doesn't use the 5V input, this would avoid any cable splicing and 5V would be as pure as possible.

Why not simply disconnect the 5V power cable from the computer after the handshake, like Artisan recommends: ARTISAN SILVER CABLES - Ultimate Silver Stream "Double-Purity" pure silver USB cable

 

[ravi_d]

Actually my plan is to not remove any pins. I plan to buy one of those 5000 mAh usb chargers that supply 5V from a lithium ion battery and plug the power end of the gemini cable into that. The data end obviously goes into the music pc. Even though the DAC doesn't use the 5V input, this would avoid any cable splicing and 5V would be as pure as possible.

I don't think you need to worry about the battery power or any additional stuff to make it better.

The idea of galvanic isolation is the USB receiver part (which shares the ground with the computer) and the critical re-clocking part are isolated from each other and thus making later free from noisy computer environment.

The USB part (before isolation) may or may not be using the power from the computer USB cable but the re-clocking part will be powered by an ultra low noise regulated power supply which is critical.
Either way AMR would have known and implemented what works better.

 

[reignofchaos]

Why not simply disconnect the 5V power cable from the computer after the handshake, like Artisan recommends: ARTISAN SILVER CABLES - Ultimate Silver Stream "Double-Purity" pure silver USB cable

Not a good idea - removing the cable suddenly might blow something because of a surge.

I don't think you need to worry about the battery power or any additional stuff to make it better.

The idea of galvanic isolation is the USB receiver part (which shares the ground with the computer) and the critical re-clocking part are isolated from each other and thus making later free from noisy computer environment.

The USB part (before isolation) may or may not be using the power from the computer USB cable but the re-clocking part will be powered by an ultra low noise regulated power supply which is critical.
Either way AMR would have known and implemented what works better.

Yep in theory what you say is absolutely right. In any case, I want to try a cheap 5V lithium ion battery backup. Nothing wrong in trying - If there's no gain, I'll use it to charge my phone during travel :lol:.

 

[gobble]

What are these Lithium Ion battery products? Are they available locally?

G0bble

 

[reignofchaos]

What are these Lithium Ion battery products? Are they available locally?

G0bble

Any of those portable mobile chargers - they have a Lithium ion or LiPo battery inside. They cost 2k or less and are available everywhere :lol:.

 

[gobble]

Any of those portable mobile chargers - they have a Lithium ion or LiPo battery inside. They cost 2k or less and are available everywhere :lol:.

Aaha! I didnt know these were LiPo!! Way to go then...

Thanks

 

[reignofchaos]

Aaha! I didnt know these were LiPo!! Way to go then...

Thanks

At least the better ones like sony etc do. Not sure of the uber cheapies. It would be a good way to power small computing devices like Rasberry Pi/BBB etc as well.

 

[gobble]

At least the better ones like sony etc do. Not sure of the uber cheapies. It would be a good way to power small computing devices like Rasberry Pi/BBB etc as well.

I did see the Sony 10000mAH one for 4950/- here: Sony CP-F101

But it can be charged only 1000 times. After that it is EOL.
And I don't believe this unit has a trickle charging circuit that is isolated from battery output and we can keep it plugged in even when using it for playback. Because one of the operating instructions says

Charge the unit away from a TV, radio or tuner as noise may occur.

see operating manual

With both usb ports used and drawing 3.6A of its max capacity it won't last more than 100mins on a single charge.

Assuming you use only one usb port and being conservative, a typical listening session should last about 150 mins max if its a low power drawing DAC that draws about 2A as a rough estimate. If it fails to supply current as needed towards the end of battery, the dynamics of the music will silently suffer for the last 1/4th of its battery life of each playback/usage cycle without the listener realizing its time to recharge until its completely drained. A continuos trickle charged battery circuit is a must for audiophile usage IMHO.

G0bble

 

[ravi_d]

...
see operating manual

With both usb ports used and drawing 3.6A of its max capacity it won't last more than 100mins on a single charge.

Assuming you use only one usb port and being conservative, a typical listening session should last about 150 mins max if its a low power drawing DAC that draws about 2A as a rough estimate. If it fails to supply current as needed towards the end of battery, the dynamics of the music will silently suffer for the last 1/4th of its battery life of each playback/usage cycle without the listener realizing its time to recharge until its completely drained. A continuos trickle charged battery circuit is a must for audiophile usage IMHO.

G0bble

The max current a usb port can supply is 500mA for a USB 2.0 device and 900mA for a USB 3.0. You can safely assume a USB 2.0 device consumes less than 2.5 Watts.

Further more the lipo batteries are available in multiples of 3.2-3.7V. So a cheap switching DC-DC converter is used in such battery packs to bring down voltage to 5V.

Here is a diy solution which I think can be tweaked to to put out 5V with the help of an additional ultra low noise voltage regulator but I'm not sure.