Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Doodlebug - USB Isolator
New Posts  All Forums:Forum Nav:

Doodlebug - USB Isolator

post #1 of 246
Thread Starter 

For awhile now, I became aware in an acute sense of how fickle a USB connection and power supply is from many PC's, especially a laptop - even one with an elaborate docking station, etc. The reason is that the pupDAC, designed by cobaltmute, seems to push the limit of what is possible with a USB-powered DAC. Every voltage source needed on the pupDAC is regulated. However, the power consumption and voltage needed to maintain the regulation and data streams may significantly tax a computer's USB power supply.

 

At work, we've all converted to laptops with docking stations (part of the "teleworking" movement). I regularly have my pupDAC knock off line at work, have to re-start Foobar2000, and unplug and re-plug the DAC numerous times, all depending on what I'm doing at the time I'm listening to music. Besides that, the exquisite detail is lost compared to when I listen to it at home with my ample-power-supplied tower PC. For awhile, I thought perhaps that a powered-USB-hub was an answer. For instance, there are numerous reports of the ODAC performing better with a powered-USB hub compared to a basic USB connection. It didn't seem to work in my case. The sound was still bad on my docking station at work and it didn't prevent it from knocking offline.

 

Enter Avro_Arrow with a design called the Doodlebug - a USB Isolator.* Avro's design is based on some new chips that Analog Devices have developed for isolating a streaming, USB connection.  The Doodlebug is based on the ADuM3160.  Besides isolating the USB data streams, it also isolates the downstream power connection from the upstream USB bus.

 

Accordingly, the Doodlebug also includes an externally-powered, linear-regulated power supply. Further, since the voltage is small with USB, Avro uses several diodes to provide the voltage drop control and reference for the LM317 power supply. The result is a stable, high-quality and low-noise power supply that IMHO, improves the sound quality and reliability of any USB-powered DAC. Even with my [formerly] OK desktop tower at home, the Doodlebug has noticeably improved the sound quality of the pupDAC. More micro-detail is heard, firmer bass, and none of the knock-off-line irritations.  Tests at work have yielded similar results: sound quality is equal to at home and there are no more line knock-offs.

 

Best of all, it's a fairly simple build and inexpensive, to boot. Here is a pic of the first prototype:

 

 

The terminal blocks, heat sink, and switch were pre-pre-prototype configurations for simplicity of testing.  The next set of prototype PCB's (currently in shipment) use USB connectors on both ends and with the selected walwart, no giant heat sink is needed for the LM317.  The switch was also deleted and a trimmer included to account for the variances in USB bus voltages of a source PC.

 

I think it's an easy statement to make that the Doodlebug will improve the sound quality and reliability of any USB-powered DAC.

 

EDIT: Full details on the production prototype here:

Doodlebug Production Prototype website

 

 

 

* Full disclosure, there is a somewhat similar device available on HiFiDIYme called the "USB Isolator," but it does not use a full-blown, linear-regulated power supply.


Edited by tomb - 2/7/14 at 10:12am
post #2 of 246
Thread Starter 

We are asking for a few volunteers to prototype the current version of the Doodlebug.  The new layout is here:

Software: Microsoft Office

 

We (Avro_Arrow and myself) need 5-6 volunteers who will agree to build one fairly quickly, test it out on their USB DAC, and report back in this thread with feedback.  I would really love to get someone who has an ODAC or other non-Beezar DACs to try this, too.  It should improve the performance of almost any USB DAC.

 

PCB's will be free.  I'll supply a web page in a couple of days that will have the Bill Of Materials, schematic, etc.  Please PM me if you are interested.

 

P.S. Avro_Arrow sized the PCB for the Hammond 1455C801 case. ;) 

 

NOTE:  The Analog Devices chip is compatible with USB 2.0 and below.


Edited by tomb - 1/31/14 at 4:55pm
post #3 of 246

Great news. More choice is good :-) 

post #4 of 246

This is cool Tom , I would be up to build one of these  -  I actually recently revisited the usb isolator designed by oleg as I thought it would be interesting to see how this impacts the odac I have at work. 

 

..dB

post #5 of 246
Thread Starter 
Quote:
Originally Posted by dBel84 View Post
 

This is cool Tom , I would be up to build one of these  -  I actually recently revisited the usb isolator designed by oleg as I thought it would be interesting to see how this impacts the odac I have at work. 

 

..dB


Thanks!

 

PM me with your address - the PCB's are going fast!

post #6 of 246
Thread Starter 

5 PCB's are accounted for - 1 left.

 

EDIT: Still need a couple of addresses from the volunteers thus far. ;)


Edited by tomb - 2/1/14 at 7:55am
post #7 of 246

i'm in if still available.

post #8 of 246
Thread Starter 
Quote:
Originally Posted by fishski13 View Post
 

i'm in if still available.


Got you - you're the last one!

 

All PCB's are accounted for ...  I will post and include pics when they arrive.  I thought maybe they'd be here today, but nope ... maybe Monday.

post #9 of 246
Awesome!
post #10 of 246
Quote:
Originally Posted by tomb View Post
 

 

We (Avro_Arrow and myself) need 5-6 volunteers who will agree to build one fairly quickly, test it out on their USB DAC, and report back in this thread with feedback.  I would really love to get someone who has an ODAC or other non-Beezar DACs to try this, too.  It should improve the performance of almost any USB DAC.

 

Tomb, I got no skills to build one but I do have an ODAC and would love to try it out, if you are looking for more guinea pigs. I have been looking for a USB isolator and was rather confused by the options (or lack of). BTW, I'm just up I-85 from you in Greenville, SC. PM me if I can be of assistance. All the best to you in this most worthy project!

post #11 of 246

Nice one, count me in for a PCB. :)

post #12 of 246
Thread Starter 

PCB's are in!  Not enough time tonight, but I'll try posting some pics tomorrow.  Sorry, but I'm still working on the webpage for the BOM, etc.  It's just kind of tough for me Mon-Thurs, but I'll keep trying to get it posted.  Stay tuned ... :)

post #13 of 246

 

Great news Tom!

 

I guess I will have to order my parts as soon as the credit card billing cycle

rolls over...

 

If you stick with the 6 volt wall wort for the other prototypes, I do the 9 volt

one for mine.

post #14 of 246

I also own an ODAC, though it seems I may need to wait for a bit until the next batch is ready.

 

I'm definitely interested to join the next group of "testers", if not for testing then sign me up as an interested patron!


Edited by JacobLee89 - 2/5/14 at 2:22pm
post #15 of 246
Thread Starter 

Yes - sorry to say all the PCB's are spoken for.  I hope to get them shipped out on Friday.  Mon-Thur is very busy for me, this week more than usual.  Beezar will be moving, as a matter of fact, in about a month and a half.  So things are very hectic around here, right now. :eek:

 

Anyway, here are some pics of the PCBs!


They're attached together in threes.  I should be able to break them apart without much trouble.  It's certainly not like the share sides with a scoring mark - those are very tough to separate.;)

New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Doodlebug - USB Isolator