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The Soundwerx Designs DoodleBug
Overview
What is the DoodleBug?
| The Soundwerx Designs DoodleBug is an independently-powered, linear-regulated, and USB-stream isolation device. Specifically, it is intended to improve the operation of many USB-powered audio devices and some that may not be USB-powered. When assembled properly and attached to the computer via a USB port and attached to an independent wall adapter, it intercepts the power rails of a PC's USB connection and also intercepts the USB data stream, providing its own packet-by-packet monitoring and data transfer. This greatly reduces the amount of noise on the USB line and can enhance/improve response and reliability of the USB connection. The performance is provided using the Analog Devices ADuM 3160 with its proprietary iCoupler method of high-speed CMOS and monolithic air-core transformer technology. Fron Head-Fi user "Avro_Arrow," the DoodleBug's designer: The DoodleBug is two products in one case: 1) a USB isolator and 2) a linear-regulated power supply. The USB isolator provides galvanic isolation from the source (usually a PC). An example of simple galvanic isolation might be an isolation transformer. However, due to the complex nature of the USB signal stream, such simple methods will not work. The Analog Devices ADuM3160 was designed specifically for this purpose. The ADuM3160 is able to handle both USB 1.1 and USB 2.0 low-speed and full-speed communication. In USB Audio terms, this means up to 24-bit, 96KHz sample rate. However, in the DoodleBug, the ADuM is set for USB Full Speed only and will not work at USB Low Speed. Continuing from "Avro_Arrow," The linear-regulated power supply replaces the power that would've been provided by the switching power supply inside the PC. While a switching power supply is more efficient that a linear-regulated supply, it is noisier and not as suited to high-quality audio uses. The linear-regulator IC used in the DoodleBug is the familiar and time-tested LM317. However in the DoodleBug implementation, a novel twist is used to improve its performance - the use of LEDs instead of resistors to provide the voltage drop control in the LM317 circuit. LEDs are inherently more linear than resistors in providing a specific voltage drop over a wide range of conditions. Finally, Avro_Arrow says, "The DoodleBug can potentially provide up to 1.5 Amps of current at 5 Volts (limited by the wall adapter). However, the DoodleBug is limited by an auto-reset PTC fuse to 500ma." (Editor's note: Did someone say a "tweak" was available?) |
 (Beezar/Hammond custom DoodleBug case)
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 (Beezar/Hammond custom DoodleBug case) | |
 (DoodleBug production PCB) | |
 (DoodleBug production PCB) | |
What's needed ...
Basic construction and parts selection is covered in detail within these web pages. Other than the parts in the Bill of Materials, you will need a soldering iron and solder, sufficient for SMD PCB work. This is not as intimidating as it sounds - just be sure you have a low-power soldering iron with a small chisel tip and good solder (eutectic recommended) that is thin and easy to use. A Hakko 936 with a T-0.8D tip or equivalent will go a long way in success of building the DoodleBug, but is not strictly necessary. In fact, I built mine using the standard 1.6D tip that comes with the Hakko 936. Solder should be on the order of 0.025" diameter or smaller, although smaller diameters can be difficult to use (lots of breakage). Eutectic solder is best - a blend of 63/37 tin/lead with a rosin flux core (non-corrosive).
Besides the miscellaneous tools used in PCB work such as needle-nose pliers (smooth jaws), flush cutters, DMM, and wiring tools - strippers, wire cutters, heat shrink, etc., there are a couple of specialized tools that can make the difference between success and failure with building SMD projects:Tweezers - These should not be from your mother's, wife's, or girlfriend's makeup kit. Instead, if you invest in only one tool for this project, a quality pair of SMD tweezers is it. There are many to select from and can be found at Mouser, DigiKey, Allied, Newark, and even Fry's. Try to buy one that's specific for SMD and not from a combination kit, unless the kit is specific for SMD work (in which case, it's probably way too expensive for this project). I purchased some #7 stainless-steel, non-magnetic curved tip tweezers:  These were somewhere around $10 for an off-brand copy (GoldTool at Fry's) and have worked fine for me, but be careful that you get good-quality ones with tips that do not flex and are as sharp as a pin, almost. Xcelite makes good ones (shown) and Wiha makes outstanding versions. Others go for the straight tweezers, but I find the curved tip is more natural for me. It is the only tweezer I use. Flux Pen - These are unbelievably helpful with SMD work, and also unbelievably sticky - so be careful. Used liberally, the flux from a flux pen can almost glue the part down. It can get a bit troublesome if you get it on the tip of your tweezers, though. Helping Hands - These are more or less obvious. I use ones that are only $1.99 at Harbor Freight, but you shouldn't have to spend more than about $5 almost anywhere that carries them. The board is way too small to hold with your hands while soldering. (Use some electrical tape to protect the PCB surface from the alligator clips.) How to get help ...
DIYforums.org has more than enough information to help you complete the DoodleBug. Besides these web pages, the forum itself provides ample opportunity
to search for answers or for asking direct questions. Most of the DoodleBug designers and prototypers are all very active forum participants and will do their best to get your problem solved.
In addition, there are many other builders that post and answer questions at:
Head-Fi.
We hope you enjoy building and listening to the Soundwerx Designs DoodleBug!
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