ODAC Output Switcher

ODAC Output Switcher

I wanted to use my ODAC as my central PC audio device so I needed it to be able to output to either 3.5mm (to headphone amplifier) or RCA jacks (to active monitor speakers), but I didn't want it outputting to both at the same time to prevent unnecessary loading. I ended up implementing a tiny little board that simply routes the audio signals through a 3PDT switch to either output jack. You can see what it looks like in the image gallery above. It doesn't exactly look elegant as I more or less just glued the board to the top of the ODAC case, but it gets the job done.

DIY OVC3860 Bluetooth Receiver / PKB-PCBA Evaluation Board

Introduction
Continuing on my quest to get good audio from my phone to my car's aux in I started playing around with bluetooth receiver modules.  The ElectroDragon PKB-PCBA caught my eye as a fairly easy to implement solution that offers potentially good quality for the price.  It uses the OVC3860 IC which I've heard good things about and also features a SGM4917 headphone amplifier IC which appears to be a fairly handy part with both integrated click/pop suppression and charge pump circuitry to generate it's own negative rail for producing a ground referenced output.  Many of the other similar boards I've seen use a basic opamp with a single supply and bulky capacitors at the output to get rid of the resulting DC offset.  I believe this is the main reason for their poor performance.

As with all of these Chinese made modules English documentation is sparse at best for the PKB-PCBA and ElectroDragon support was utterly useless as well when I tried to ask for more specifications.  Fortunately whoever designed the board had easy implementation as a goal and pretty much all you need to do to use this thing is just feed it power and get your audio output from it.  I don't know the exact schematic of the board but it probably looks similar to this application circuit for the BLK-MD-SPK-B which looks fairly solid to me.

If I wanted a more audiophile grade solution I could try to lay my own PCB using a Roving Networks / Microchip RN52 Bluetooth Audio Module with a TPA6138A2 from TI driving the output, but I don't have the equipment or experience needed to take measurements for optimizing the layout/performance of such a design and it's really just too much work for me.  My approach of using a highly integrated module saves a lot of time and still yield respectable performance.

Note that I tried the Griffin Technologies BlueTrip Aux (it is one of few commercial products low profile enough to plug-in inside my car's center compartment) before pursuing a DIY solution and found that the BlueTrip outputs a low volume signal with completely non-existent bass.  My music simply sounded so terrible that I returned the BlueTrip immediately after testing it.  The funny thing is that I was contacted by another BMW owner about my Amazon review who had the same issue with the BlueTrip so I know it isn't just me.

Mediasonic HFR2-SU3S2 RAID Enclosure Review & Fan Replacement

Introduction
The Mediasonic HFR2-SU3S2 is a nice little USB3.0/eSATA HW RAID box that's perfect for various storage applications. Personally I use it in RAID5 mode over USB3.0 with 4x SAMSUNG EcoGreen F4 ST2000DL004 2TB hard drives for backup and media storage.  It has been working for almost two years now without a single hiccup and even when a hard drive died it proceeded to reconstruct my array with a replacement drive without any problems.

The Mediasonic HFR2-SU3S2 has a reasonable MSRP of $199.99 but can often be found on Newegg with a rebate or promo code (or even both) which brings the price down to around $129.99.  This is a great price for a plug and play USB3.0 hardware RAID box.

Manufacturer Page: http://www.mediasonic.ca/product.php?id=1358153144
Newegg Page: http://www.newegg.com/Product/Product.aspx?Item=N82E16816322004

Build Quality, Features, and Service
The enclosure is constructed mainly of metal and feels very heavy and solid with the exception of the front door which doesn't seem to latch too well and feels rather light and flimsy.  The indicator lights on the front of the enclosure provide some useful information and are laid out in an intuitive and logical manner.  Overall it's a pretty nice looking enclosure and the build quality is much better than you'd expect for the price.

One aspect of the design I don't like is the power brick; the cable for it feels of rather low quality and it's a bit on the short side in my opinion as well.  If I put the enclosure on the top of my desk, the power brick will end up hanging off of the ground because of how they've placed it which is rather annoying.  I'm also not a big fan of the power connector coming in from the side rather than from the back, but this is a fairly minor complaint.  It's would've been better if they integrated the power brick into the enclosure and put the plug in the back much like on the Sans Digital TR4UTBPN.

I use my enclosure in RAID5 mode with 4X SAMSUNG EcoGreen F4 HD204UI 2TB HDDs. (no TLER I believe) The auto USB on-off functionality performs as expected and I haven't seen any disconnect issues like some others report except for one time when I was copying data off of it for 10 hours straight. It randomly powered off during the copy but after I rebooted it I never saw the issue again so I have no idea what happened.

I've shipped this thing across the country three times with hard drives installed - twice in the trunk of my car and once on a domestic plane flight in my checked luggage. (in the original box) After my plane flight I opened up my checked luggage to find the metal HDD retention bracket warped with the drives partially hanging out of the enclosure next to a TSA inspection note.  Upon trying to power the enclosure up the red light next to one of my hard drives lit up to indicate it was bad. (needless to say I was not very happy that day)  I immediately replaced the dead hard drive and the enclosure completed the rebuild overnight without any hiccups.  During this time I was able to access all of my data without any issues, albeit at much reduced speeds.

Mediasonic documentation isn't the best, but the setup is really fairly straightforward and you can get whatever additional help you'll need on the forums.  Generally speaking you only need to consult the manual once to set it up at the beginning and you won't need it for anything afterwards.  Mediasonic support is generally very fast to respond to questions on their forum or via email. I asked for a replacement fan when mine was getting rumbly and received one within only a few days with no questions asked - all I had to do was email them.

CrystalDiskMark Results (USB3.0)

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The HFR2-SU3S2 isn't exactly a speed demon but it's respectably fast enough for a budget external USB3.0 RAID array. It's fast enough for me to store and run all my Steam games off of it without load screens feeling particularly long, and loading media files off it is fairly snappy as well.

Final Words
I think this is a great product if you need a 4-bay RAID enclosure; it's not only cheaper than most of its alternatives but offers a good set of features and solid build construction to boot. Mediasonic isn't exactly a well known company, but their support has been more helpful and responsive in my experience than that of many larger companies I've had to deal with.

The Sans Digital TR4UTBPN would probably be the closest competitor to the Mediasonic HFR2-SU3S2 and it's worth looking at as well.  The TR4UTBPN is from a more reputable company and looks to be quite a bit speedier while costing a little bit more.  I am unsure if the Sans enclosure automatically turns on and off with your computer, and this is a feature I use a lot since my RAID array is basically like a secondary drive to the SSD in my desktop.

Car 12V Cigarette Lighter Receptacle Power Isolator Circuit

Introduction
An age-old issue of mine was having to jack the volume on my car stereo (2008 BMW 328xi) way up when playing music from my phone (Galaxy Nexus) over the 3.5mm aux connection.  I actually tried using a bluetooth receiver from Griffin Technologies to solve this problem but only found that I had to jack the volume up even more and that the whole bass-band disappeared when using it as well.

I found, however, that using my Objective2 headphone amplifier to amplify the aux in would both solve my low volume issue as well as make my music sound better in general.  It was clear to me that a basic amplifier typically used for headphones would probably do the job, but I wasn't willing to swap out or recharge batteries every now and then to deal with it. (especially since I'd always accidentally leave the amp on after exiting my car)

The 12V power from a car's cigarette lighter is far from I an ideal power source, and in many vehicles it shares a common ground with everything else in the car.  This leads to a lot of common noise and will also end up blowing up amplifiers using a virtual ground scheme such as the cMoy if you try powering them directly off car power. (as the stereo may also share the same common ground)

Project Overview
I ended up making a fairly basic circuit which consists of only 3 ICs.  It basically takes in the 12V from your cigarette lighter and produces a regulated, isolated 12V output.

This powers a cMoyBB from JDS Labs which is configured with a gain of approximately 5.  Since the cMoyBB board is nice and compact I'm able to cram my circuit in there right next to it.

I'm using pretty much as much heatsinking as possible on the LM2937 as it really does get quite hot.  The cMoyBB only draws about 40mA of current even while playing music into headphones but the LM2937 has to deal with almost 300mA coming into it since it's driving the rest of the circuit.

Purdue Engineering Fountain Model

Back when I was in high school I was asked by my boss to create a nice gift for a Purdue professor....this is what we came up with.  He was generous enough to give me one too!

Objective2 Headphone Amplifier SS Front Panel

All sold as of 2/20/2013!  I could have another batch made if there is enough demand but so far the batch of 20 has not been profitable for me and it doesn't seem like there is much interest.  Be happy if you're one of the few people that managed to get one!

Introduction
When I decided to build a batch of five O2 amps with my friends I, like many others, went to JDSLabs to order their aluminum front panels.  When I got them, however, I was honestly rather disappointed - it looked all shiny and nice in the pictures on their website but the actual parts I received looked fairly lackluster and were rough around the edges.  I wasn't a big fan of their company logo on the front panel of my DIY amp either.  I decided to fire up my CAD program and look into getting some nice stainless steel panels custom machined for me...

DIY Audio Forum Thread

This revision features chemically etched lettering and symbols filled with black oil-enamel paint and uses a #4 (brushed) finish rather than 2B.  The panel material remains 304 stainless steel and it can be either waterjet, laser cut, or CNC milled depending on my supplier's capabilities.

Overall I think it is much nicer than the panels from either JDSLabs or Head 'n' HiFi though admittedly it's a good deal more expensive to manufacture as well.  You can see from the images that my panel is slightly thicker and fits more tightly around everything.

Here are some images of my initial prototype batch of 20 with Kunshan Krell:

Machined Stainless Steel Objective2 O2 Front Panel

For a production batch of 100 I can easily hit a $12 price point.  The main problem is that I never wanted to commit the investment for such a large batch since this isn't my full time job and I don't want to potentially end up sitting on a large pile of these.