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In Reply to: RE: Newbie questions, etc. posted by internethandle on March 09, 2011 at 01:09:51
Forgot to mention my questions about the Circuits@Home ADuM4160-based USB isolator board mentioned on the website under "Optimizing USB DACs" - how much soldering know-how would I need to have if I bought the "Populated" board sold at the link provided on the site? (http://www.circuitsathome.com/products-page/usb-interfaces) It seems that it's advisable to bypass the onboard voltage regulator with a 5v battery supply, and I'm assuming I'd have to at least know something about circuit boards and soldering in order to do that, which I really don't, but I suppose I can learn. If I opted to skip providing it with a separate battery supply, would the board work as-is if I bought it populated, or would it need more modifications? Does it need an enclosure, for instance?
Sorry for the plethora of questions, guys - any help is very much appreciated.
Follow Ups:
if I bought the "Populated" board . . .You have setup options but you will need some DIY skills.
1 Basic. Get the right barrel connector, connect the board to a wall wart or similar in the range nine to twelve volts DC (absolute max, 25v). The 5-volt supply for the ADuM4160 is generated from that by an on-board LT1376 switching regulator. You need about 20 mAmps max (i.e. negligible) to drive the circuit; the +ve line must connect to the centre pin of the barrel connector. This is pretty easy to do and a good place to start;
2 Better. As above but use a 5-volt DC wall wart or similar DC supply and by-pass the on-board switching regulator. Provided you can use a soldering iron, this is easy to do as it only involves a couple of links;
3 Best. As #2 but use a good-quality 5-volt supply. This is IMHO well worth the trouble and is in any case recommended by the board’s designer for audio use.
4 Slickest. By-pass the barrel connector and solder the 5-volt supply direct to the board. It makes no sonic difference but it’s neater.
Would the board work as-is if I bought it populated ?
It has to be powered but, otherwise, yes.
I don’t use batteries so I can’t comment on them except that, unless you use one to drive the chip directly and thus by-pass the LT1376 (i.e. it’s a five-volt battery), I strongly suspect you’d be better off using a linear PSU. There's battery gurus galore on this list.
Does it need an enclosure ?
I don’t have one but I don’t have children crawling over my system either. Your shout.
Would it need more modifications ?
I took a shot of my board while testing setup 3 - the red wire by-passes the LT1376 and another, small link connects the ground lines (hard to see it in this pic):-
HTHDave
Edits: 03/10/11 03/10/11
Hi Ryelands,
I have just got the same isolator as shown in your photo. I would also like to use option 3 and have purchased a linear 5V power supply. I would just like to confirm that to bypass the on-board regulator, I need to :
1. Connect pins Vin to Vbus (as shown in the red wire in the photo), and
2. Connect pins AGND to Shdn (as not at all clear in the photo)
Your help is deeply appreciated.
I've arrowed the jumper in the attached pic. Hope that's clearer.
You can also solder the power lines to the underside of the barrel socket - easier than finding the right barrel plug.
HTH
Dave
Thanks for the speedy reply. You do connect AGND to Shdn with a jumper.
However I have another question. According to the USB Isolator web page, the designer only mentioned that the first connection ( Vin to Vbus) and hadn't mentioned the second connection, as in this paragraph here:
"Now, let’s discuss building the circuit. First of all, you need to understand one thing. This circuit is an isolator and consequently has two power rails and two grounds, marked GND and AGND. Don’t connect these two grounds together. Uplink side of ADuM4160 is powered from host USB bus, downlink power has to be provided form separate supply, usually wall wart. If you have 5V wall-wart capable of providing enough power to the USB device connected to the downlink port plus 10ma for isolator itself, you don’t need to build a regulator. Simply connect pad marked “Vin” to a pad marked “Vbus”. If your device is self-powered and have 3.3-5V supply, it can also be used to power downlink side of ADuM4160 by connecting it to “Vbus” pad."
And looking at the wiring diagram, AGND is connected to the input return. Why is it needed to connect to Shdn?
Thanks again for your help.
. . . looking at the wiring diagram, AGND is connected to the input return. Why is it needed to connect to Shdn?
What follows are extracts from the e-mails I exchanged with Oleg Mazurov back in April last year.If possible, use DACs power supply to power B-side of isolator instead of the supply on isolator board. Also, if USB cable on DAC side is of any length, find out if cable shield is grounded on DAC connector and, if not, ground it on the isolator board ( it is not grounded by default ).
By that, do you mean connecting a clean 5-volt supply to the V-bus pad and its Gnd to the AGnd pad? Currently, I'm using a12v supply via the barrel connector but by-passing the switching regulator with 5v makes sense to me.
Yes, that's why Vbus pad is there. Ground to agnd is optional - you'll get ground return via USB ground wire anyway. There is also Vin pad close to barrel connector which can also be used if you want to use your own power supply - wire Vin to Vbus, Shdn to Agnd (this will switch off the power supply ) and supply 5V via barrel connector.
There are also ways to power B-side from 3.3V - you will need to supply it directly to pin 14.
Hope that's clearer,
Dave
Just plugged it in. It works as advertized and no problem of any kind.
Without burning in, the sound is already fuller and more liquid than before. Thanks for your help.
Oh, "wire Vin to Vbus, Shdn to Agnd (this will switch off the power supply )", to switch off the power supply. Got it.
Thanks. Will give it a go.
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