Review on Signstek HiFi USB to Coaxial S/PDIF Converter: Transform Digital Signals to Analogue with Mini USB DAC PCM by Bryan Turner

Over the last few years we have acquired several of these impressive DACs from various sources and we felt it was time to write a real review. Spoiler alert: while our first impressions agree with the vast majority of the other positive reviews posted here, we will find that this device performs MUCH better with a few minor tweaks. If this is of potential interest to you then feel free to read on, otherwise rest assured that even in the original 'return on investment' configuration it is exceptional here. Considering the modest cost, we think it's unlikely to disappoint. Please note that this identical DAC can be found elsewhere on the web with different brand names on the case. The original design appears to have been created by Muse Audio and has been widely copied by numerous overseas manufacturers and sold through many channels. In our experience, although the overall circuit design remains the same, the quality of the internal components varies somewhat, and the TI/Burr-Brown 2704 chipset, although an older D/A chipset, is certainly of high quality. With a background in electronics and an innate desire to tinker, we decided to see how much performance we could squeeze out of this little beast. Part of the appeal here is the small overall size and lack of an external power supply for convenience. . Essentially, any device with a typical 5V/1A USB connection should be able to adequately power this DAC. The build quality of the aluminum case is surprisingly high at this price point. After removing the four screws holding the end plate, the entire board can be carefully pulled out. After doing a little digging into the circuits themselves and deciphering the resistor groups, they seem to have pretty tight tolerances. Subsequent check with a multimeter confirmed. The ones we left alone. Having personally reinstalled many old components (amplifiers, receivers, crossovers, etc.) over the years, we know that a few well-chosen capacitors, particularly those located in critical locations, can make a significant difference in the perception of sound quality located (especially in the signal path). This is one area where all the DACs we buy differed from each other - capacitor brands. Externally identical, but internally even the color of the circuit boards has changed. One was blue, the other was white and the third was black! There isn't much consistency. It's most likely a question of which parts supplier was slightly cheaper when ordering in bulk during production. No problem. Ultimately we decided to update ALL the caps on the board. The factory settings of the components have been retained. After many hours of listening to various configurations in full, the final mods (see photos) featured a mix of our favorite silky smooth Elna Silmic II, Nichicon Fine Gold and Nichicon BP (1uF - 50V). As you can see from the photos, the Elnas in particular are absolutely massive compared to the clearly inferior originals that were removed. After some careful measurements it was decided that they would just clean the case and they do. Nowadays, due to strict ROHS standards, almost all electronic devices are made with lead-free solder, which is much more difficult to process. Some also believe it has a detrimental effect on sound quality. We chose to melt the entire PCB at the same time as updating the cover using the Cardas Silver Solder. Crazy overkill for this tiny, inexpensive DAC? Absolutely no questions were asked but it was a fun project and we just wanted to see what additional sonic potential could be unleashed with this little guy. The actual total cost of the parts is very modest and they are readily available. Anyone with basic soldering skills can easily make these modifications (and we hope this will inspire some people to try it - we'd love to hear your thoughts). So what is the bottom line, you naturally ask yourself? Wonderful! Unbelievable! Fabulous! Okay, okay, if we temper our enthusiasm with a touch of reality, it really is better than it should be. Many friends listened to this DAC with amazement. Much dizzying distrust. I even reluctantly sold a few after much begging. Paired with the pristine JRiver Media Center software (an important part of the equation in our opinion) and works with everything from a netbook to our custom laptop, gaming desktop, you name it. this thing delivers the goods. On a whim I even tried hooking it up to a huge, pure Class A power amp and massive infinity tower speakers, and that wouldn't necessarily make a mega-dollar, high-end audiophile DAC in an A/B unnerving Test, it certainly has not been ashamed. Now there's a real, honest soundstage, and it has a palpable breadth and depth, even through regular computer speakers. Never experienced before! There is dead silence in the background. High frequencies do not disturb or tire you even after prolonged listening. It never gets hotter than a little, even when working 12 hours a day. The cinch and headphone outputs sound identical to our ears. Optical and S/PDIF conversion. Well, that's just the icing on the cake. In general, if that sounds like you, we're glad the total investment including the DAC was less than $50. You are right. It would be more correct to say "pleased"! UPDATE: It has been over 3 years since this original review was posted. We had no idea this would generate such interest! Thanks to everyone for the (mostly) positive feedback and congratulations to those who have successfully completed similar mods with great results. For another fun project, we recently (2019) decided to take one of these and give it a "Full-Monty" treatment consisting of the aforementioned capacitor swap. PLUS has now replaced the 100% cheap factory carbon resistors with ultra-low noise metal film versions of the Vishay Dale CMF series, again retaining all of the original characteristics. The only original components remaining on the board are the DAC chip, I/O headers and some diodes. Everything else has been updated. See the last photo of the nearly finished board which still shows one of the bearing resistors. This would have been an easy project if the original lead free solder wasn't such a problem. Here's the real question: is it really worth investing that much time/effort/$$ in an inexpensive DAC? That's a question only you can answer, but as far as we know, this little guy has now got an appropriate new name: The Giant Killer. It's really wonderful! PS For those who want to try, I think the list of starting values is as follows: (5) 22 ohms, (3) 100 ohms, (1) 220 ohms, (1) 300 ohms, (4) 1.5 kΩ, (1) 5 kΩ and (1) 1 MΩ (megohms). There should be 16 total, but please check your specific board with a meter and check for the possibility of manufacturing changes. Feel free to ask any questions. It's great to hear from some people who are feeling brave enough to take the risk and try this additional mod!