Stereo_Electronics 0 Report post Posted March 30, 2013 So, what's in an iDAC? some have asked. Well, on the left-hand side, it is AMR's Asynchronous/Jitterless Lite USB module. One the right-hand side, the dac and headphone amplifier... The DAC directly drives the RCA Sockets without any additional electronics, plus it drives the analogue volume control and headphone Amplifier. Quite a purist approach for this type of product, where others often pass the line out also through the headphone amp and volume control without bypass. The headphone Amp can output > 3.3V and has less than 1 Ohm output impedance and 110dB signal to noise ratio at 2V RMS. Therefore, the DAC's dynamic range is fully-utilised, so the Headphone out can be used as Line out with volume control while retaining the overall superlative sound quality. This is the iUSB Power Circuit board... As it was so well liked, let's show another bit "under yeah olde bonnet". Note how in the iUSB the plug-top ultra low-noise SMPS powers a lot of internal circuitry. The already quite clean DC from the SMPS then goes through a LC noise filter which starts filtering at 150Hz and filters around 90dB at the common SMPS switching frequencies around 50KHz. The filter is effective well past 100MHz. This eliminates any switching noise and RFI dropping it well below -150dBV with our low-noise SMPS. After that filter we have a so-called "super-regulator" with a lot of trickery for very low-noise. Key is the Precision Voltage reference that is driven by a Constant Current Generator for maximum isolation from any supply noise. This is actually how we get "lower than battery" noise levels with the iUSB... Quite complex, for a such a simple looking device. Often we get asked: "What exactly is inside those iFi Units?". It's not like we are shy or want to hide things. But taking really good looking Photos is not so easy and we have other work to do. But we can "lift the skirt" a little and "show some leg". Here is one of our test shots of the PCB for the iCan Headphone Amplifier... The iUSB with some quality brands: Bel Canto uLink USB-S/PDIF Converter | AudioStream Schiit Audio Modi USB DAC | AudioStream NEWS: Meridian Releases The Explorer Pocket-Sized USB DAC Review of the iUSB by EarMass iFi Audio iUSB : Clean Power Clean Sound | Earmass Review of the iCAN by Nirmalanow on HeadFi iCAN Amp Review: A New Amp that Gives You More: More Bass, More Soundstage and More Detail Pictures: Courtesy of iFi Audio Facebook page Share this post Link to post Share on other sites
