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Shanti Dual LPS 5V/3A , 5V/1.5A

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G

Greg Stewart

Member
Joined 2003
Paid Member
terry22 said:
Hi Greg,
Thank you for your answer.
About grouding, I was more specificaly asking if I have to connect usbbridge ground hole to the chassis or directly to the ground of my AC IEC/plug.
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@terry22,

You are welcome.

On grounding, IMHO that depends more on your system grounding and that of the power supply you will use with a USBBridge Sig.

In my setups, on the Ethernet input side the last connection is from an FMC (fiber media converter) that provides an optical isolation on the incoming network connection. That power supply for that FMC is an off-the-grid Uptone Audio LPS-1.2. So no ground connection there.

On the GPIO I2S & I2C side, all of my setups feed an isolation barrier, either the Allo Katana Isolator or an Ian Canada FiFoPi. So no ground connection there either.

My power for the USBBridge Sig is through either a Shanti or a somewhat modified K&K Audio 12W low voltage supply. The outputs of both are not grounded, that is the negative side of each output is not connected to ground. So no ground connection there either.

When not grounded, I have had noise issues from both static electricity and from SMPS's (which in my setups MIGHT be used on a power amp, but nowhere else). So I always ground.

As Ioan suggested, I always connect the ground connection of the power supply (Shanti or K&K) to ground. BUT since the outputs of these supplies are not grounded, that is not sufficient.

Then I also connect from the RPi / USBBridge Signature to ground. I have cut off the end of an old USB cable and bring out the ground connection, isolating and insulating the rest. I connect this to ground and plug it into the RPi / USBBridge Signature.

YMMV

Greg in Mississippi
 
C

cdsgames

Member
Joined 2015
mdelrossi said:
Regarding grounding the shanti to the raspberry pi, should I use the ground pin 6, or is there a better place to connect it?

Also how long does it take to charge up and discharge the Shanti super caps, while connected to the raspi and digione sig?

Thanks.
Mdr
Click to expand...


I think that pin 6 is sufficient for earthing (not grounding)


The supercaps on Shanti are rather low value (F) so charging is very fast and discharging depends on load (but its rather fast as well)
 
C

chipzahoy

Member
Joined 2009
CallMeMike said:
Quite unusual ... debating 'mods' on a Vendor's thread... plus losing the warranty cover should the need arise.
Click to expand...

I get your point, but there were discussions about modding the Shanti, and people didn't seem to have issues with that. I will remove the comment if cdsgames deems it appropriate.

Plus it's diyaudio.com, I'm sure most of us are familiar with acts that void warranty :cool:
 
T

terry22

Member
Joined 2017
Greg Stewart said:
@terry22,

As Ioan suggested, I always connect the ground connection of the power supply (Shanti or K&K) to ground. BUT since the outputs of these supplies are not grounded, that is not sufficient.

Then I also connect from the RPi / USBBridge Signature to ground. I have cut off the end of an old USB cable and bring out the ground connection, isolating and insulating the rest. I connect this to ground and plug it into the RPi / USBBridge Signature.

YMMV

Greg in Mississippi
Click to expand...

Thank you Greg,
I’ll try the usb cable trick too
 
C

cdsgames

Member
Joined 2015
Hi



USbridge is feed 5V and outputs 5V on the USB port . As such, "cleaning" is mostly done via passive filtering . So if you feed your DAC from USB port of USBridge you need a quiet PSU to feed Usbridge




Some DACs have USB + PSU in the same cable , but better DACs have separated data and power..



The above is differential noise .



Usbridge has common mode noise filtering on all inputs including ethernet ,so your DAC will be feed less CM noise


Data integrity was also important . Please check the USB hub physical location as close to the " USB DAC" output..



Earthing is a big part of USBridge. Gnd and earth are separated and connected together using capacitors and resistors in a few places. This protects against the leakage currents .



At last , USB data path has some good common mode noise choke and the USB hub ic is feed using LDOs decreasing noise on USB bus.


Even the CPU itself (USB host) is feed LDOs so the USB data arrives at USB hub with low noise..




Frankly speaking , all of the above should not matter much in a digital system (and it doesn't in a pure digital system ) but somehow when connected to a DAC( analog output) a change in sound quality is quite obvious .


To answer the question...I don't think you can simplify Usbridge to a single comparator (like diff noise) . Its the whole approach (what I call architecture) that has to be compared .
 
W

weaver4044

Member
Joined 2019
pkdick said:
Hello,

Just to confirm that it will be difficult to assemble the Katana Dac without the isolator on the Usbbridge SIG board as there are capacitors whose metal body can get in touch with other parts of the dac...
I tried it by myself without success.
Click to expand...

Greg Stewart said:
I checked this earlier in the week when planning Katana trials without the Isolator on a USBBridge Sig.

The RPi GPIO header on the USBBSig is about 3mm taller than that on a stock RPi due to it being a surface-mount header instead of through-hole. The pins are about 1.5mm longer. That gives you plenty of leeway to add more spacers to lift the Supercaps on the bottom of the Katana DAC board above the filter caps on the USBBSig.

I suggest first insulating the Supercaps with something like Kapton tape, then selecting additional or longer spacers to provide the needed height. With about 1/2mm of clearance between the Katana DAC board Supercaps and the USBBSig filter caps you'll still have plenty of GPIO pin length in the Katana DAC board sockets.

BUT do be careful on your spacers. There are filter caps very close to the RPi footprint mounting holes on the USBBridge Signature. IF you use metal spacers or washers that are any larger than the mounting hole outline, you risk shorting those and having a bad day for your USBBridge Sig and any attached HAT. When in doubt check for continuity. I use fiber washers here.

Greg in Mississippi
Click to expand...

cdsgames said:
I will check on Monday
Click to expand...


@cdsgames - This question has now been largely answered (thanks Greg) but did you get a chance to check on it and if so is the solution outlined above how you had envisioned the various boards stacking together? Many thanks.
 
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