Introduction

JDSLabs is known for the quality of their premade CMOY headphone amplifiers, but they have also been a good source for higher end op-amps. Recently, they launched their prebuilt Objective2 (O2) amplifier following the open source design of NwAvGuy. The version we will take a look at today has an integrated Objective DAC (ODAC), which means you can hook it up to any PC or Mac as long as you have a powered USB connector. The ODAC, which, as the name implies, is also designed by NwAvGuy, aims to introduce high-quality digital to analogue conversion to the masses.

NwAvGuy's designs are prime examples of budget components that can, with a lot of knowhow, get you very close to perfect sound. The design process was documented on his blog NwAvGuy's Blogspot. It shows the meticulous process of both selecting and implementing each component in search of perfection. What sets NwAvGuy apart from many is his level of documentation - every little thing is measured and benchmarked against other designs.

The O2 amplifier design is open source and there are circuit boards and kits available from multiple manufacturers. They are all licensed under one term: that no changes will be made. The ODAC is made with SMD components, which is why all of them sell for around $90 as prebuilds.

Specifications

The O2+ODAC features a box standard O2 amplifier and an ODAC integrated into the same package. We have broken the specifications down into the two sections. The specifications list is from JDSLabs. Visit NwAvGuy's blog for a much more comprehensive analysis. One thing that is not mentioned on JDSLabs' site is that the ODAC is wired to the input jack as well, which means you can use the O2+ODAC as a standalone DAC. All you have to do is leave the power off before connecting a cable to the jack that is usually the input jack for the headphone amplifier section and, voilà, you have a true line-out.

Headphone Amplifier Section

• Frequency Response: +0.01, -0.01 dB (20Hz-20kHz)
• Gain: 2.5x and 6.5x
• Output Impedance: 0.5 ohm
• Volume Potentiometer Taper: 15A
• Case Dimensions: 108.50 x 80.00 29.50 x mm (excludes knobs/buttons)
• Weight: 11 oz

DAC Section

• Audio Formats: 16/44, 16/48, 16/96, 24/44, 24/48, 24/96
• Frequency Response: +/- 0.1 dB (10 hz – 19 Khz 24/44)
• THD+N 100 hz 0 dBFS: 0.0029%
• THD+N 20 hz –1 dBFS: 0.003%
• THD+N 10 Khz –1 dBFS: 0.003%
• IMD CCIF 19/20 Khz –3 dBFS: 0.0011%
• IMD SMPTE –1 dBFS: 0.0004% A
• Noise A-Weighted dBu 24/44: --102.8 dBu
• Dynamic Range: > 110 dB A-Weighted
• Linearity Error -90 dBFS 24/44: 0.0 dB
• Crosstalk 0 dBFS Line Out 100K: --93.5 dB
• USB Jitter 11025 hz J-test 24/44: Excellent
• Maximum Output Line Out 100K: 2.0 Vrms
• Distortion: < 0.005%
• PCB Dimensions: 49.0 x 58.0 mm