IC: Modular USB Power Supply
Mar 30, 2009 at 1:26 AM Post #61 of 66
I'd have to agree with not having data breakouts. Most things, like the bantam dac, also get powered from USB so it makes more sense to have power breakouts on those devices.
 
Mar 30, 2009 at 2:18 AM Post #62 of 66
The fact that not all devices have "power breakouts" is kinda the point.

Which crappy way would you like to try to connect this to a Bantam DAC (for example)?
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Mar 30, 2009 at 3:15 AM Post #63 of 66
The way I'm taking power from the BantamDAC to the Carrie is by soldering wires to C7 above the board. I was originally thinking of doing it by soldering to the pads underneath the board, but that requires a little bit of room between the boards which makes for a wobbly fit. I rather just have the boards sit flush within the case and not solder C7 flush with the board. It may be a little unsightly that way, but it's actually a pretty convenient way of grabbing power if you don't spec C7 too tall.
 
Mar 30, 2009 at 3:53 AM Post #64 of 66
Quote:

Originally Posted by MisterX /img/forum/go_quote.gif
The fact that not all devices have "power breakouts" is kinda the point.

Which crappy way would you like to try to connect this to a Bantam DAC (for example)?
tongue.gif



I'd snake fine-gauge wire right from the power pins on the USB connector on the BantamDAC to the appropriate spots on this PCB, which is undoubtedly crappy, but seems considerably less crappy than running data lines around unshielded.

The only situation I can fathom where you would realistically need or even want to do that was if, for some reason, you wanted to try to minimize EMI/RFI issues by getting a DAC as physically close to the input of an amp as possible, like if you wanted to use an old SOHA Mk. I board, where the input and output are right on the front edge of the PCB, but wanted a rear-mounted USB connector.

Anyway, it can be done, so however dumb it is, might as well do it:

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So, the latest revision is everything to everyone. Yay, design by committee. (Not.)

Now that this thing's been over-engineered to death:
  1. Does anybody actually want one or more of these?

And, if so:
  1. Do you have a prejudice against ordering, via PayPal, from an established online merchant in China, or do you insist on doing the "group buy" thing from an individual somewhere in North America? (I ask because of the Monofied BUF634 boards, linked to in my signature - a dozen or two people expressed concrete interest over the course of CobaltMute's threads on the boards, for a couple score PCBs; he withdrew from the project, and I stepped in and had the boards fabbed by Seeed; in the months since then, three of you - three - have bought a whopping ten PCBs between you, which makes me wonder...)

Firm price for a domestic "group buy" is $3 USD/board, or $5 USD/pair, plus a buck-fifty for postage/envelopes/instructions/PayPal fees in the U.S or Canada, two-fifty the rest of the world. Prices via Seeed would be a buck or two higher.
 
Apr 6, 2009 at 3:38 AM Post #65 of 66
I would recommend an LED on the load side of the circuit. Unloaded, I get 30.5 volts which might not be a problem in some circuits but the cap I used can't take a no-load voltage that high. Keep that in mind but don't worry about those voltages under load. My cmoy has 660uf of capacitance in the virtual ground and the LED on the usb board noticeably decreases in brightness when it is switched on but recovers very quickly. Under normal use the supply is steady at 16.2v. (Kinda relying on that divider to be working right as my caps are only rated to 10v...)
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I bridged C3 and used a 25v 10uF cap at C2 (Mouser 81-GRM31CF5E106ZA01) and am currently testing the device. I went with the 10uF because the datasheet for these boosters lists it as a point of diminishing returns.

USB is known for being dirty power. If you connect an amplifier's inputs and turn the volume up even a little bit you start to hear system noise, this is especially true of front USB outputs and headphone jacks because they run across the system to feed the front. This power supply makes for an awesome isolator, I can't hear system noise at all with this thing using my front USB ports.

It also gives me more confidence in the Carrie amp as being a good USB powered amp. And I'd definitely take at least 4 of these. They would be great little things to have around. Make a 9V version that better suits my cmoy and retire that poor 9 volt in there.
 
May 1, 2009 at 9:27 PM Post #66 of 66
I know nobody was all that interested in this (surprise, surprise), but a handful of PCBs (2-ounce copper, RoHS-compliant gold plating) for the original incarnation of this design (i.e. full-size B connector only, all SMD capacitors) are available, for the one or two people who might want 'em. PM me if you're one of them.

A few of the turned-into-a-crowded-mess-by-request-of-the-masses version of the board will be available in a month or so, for those who really want the mini-B connector.
 

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