The Cayin N8ii Reference Grade Master Quality Digital Audio Player Main Features:
- Dual ROHM BD34301EKV, TOTL mono mode current output DAC
- Balanced tube amplification with matched paired KORG Nutube 6P1
- Fully-discrete fully-balanced headphone amplifier with Dual Amplification Mode (Choice of Class A/Class AB)
- Dual Output Mode: P (Standard) and P+ (High Power) mode
- Premium grade resistor ladder electronic volume control from JRC
- High Quality “unamplified” single-ended and balanced Line Out
- Snapdragon 660 CPU, 6G DDR4 RAM, 128G Internal, 1xTF card (upto 1TB)
- Android 9 with Google Player preinstalled, streaming ready
- DTA bypass Android SRC, Hi-Res playback to all applications
Dual ROHM BD34301EKV, TOTL mono mode current output DAC
The new reference grade DAC chipset from ROHM Semiconductor
was announced back in late 2020 (Feb 2021 according to public announcement), a perfect timing to rescue our AK4499 based N8 successor project. The AKM fire was one of the hardest hit to our industry and Cayin started to look for new DAC solution almost immediately. Since Cayin is a long-term customer of ROHM, we received sample, reference board and technical documents of BD34301EKV promptly. This new DAC chipset is part of ROHM’s MUS-IC
lineup of ultra-high-fidelity audio ICs. It incorporates a circuit to verify signal quality while providing class-leading low noise and low distortion decoding that works perfectly for our high-end Digital Audio Player (DAP).
Cayin is the first audio company to adopt ROHM BD34301EKV in portable personal audio applications. Commodification of a new chipset from scratch is a tedious and resource consuming process. Our engineers have spent a lot of resource to learn, experiment and find tune the supporting system for this new DAC chipset. We have developed 6 rounds of engineering PCB to explore the potential and implementation options for BD34301EKV. We grasp massive raw data through I2S and compared to numerous analog output data we have experimented with, and cross compare to the ROM demo board to validate the improvement we have achieved. We see a lot of potential on this chipset because it really excels on both technical measurement and listening impression.
To maxima the performance of the digital audio circuit, our FPGA enhanced and reorganized the incoming digital signal and passed the audio bit-stream to two pieces of BD34301EKV in mono mode. N8ii can decode up to 32Bit/768kHz with PCM, and 1Bit/22.6 MHz (DSD512) with DSD. It offers two low-pass antialiasing filters (PCM mode) and three DSD Filters are available to fine tune sound signature.
A TOTL DAC Requires TOTL Supporting, and Cayin won’t settle for less than exotic with our N8ii. We have employed two extremely low phase noise (-100dBc) Femtosecond Crystal Oscillators to ensure high precision low jitter digital playback. We have implemented a solid 2×2 current to voltage I-V converter network as low noise high current output stage of the sound of current mode ROHM DACs. Last but not least, we built our circuit with 6 layers PCB to enhance signal isolation, and we covered the complete digiatl audio circuit with an alumimum heat shield, . This will lower the background noise and interference to critical components.
Balanced tube amplification with matched paired KORG Nutube 6P1
Our Vacuum Tube/Solid State Dual Timber feature shook the world back in May 2018. It was considered a miracle to portable audio industry when we managed to solve the microphonic problem with innovative techniques and for the first time, facilitates choice of vacuum tube and solid state timbre in a portable DAP. Unfortunately we can only install one Nutube 6P1 in N8, so the vacuum tube is only available to Single-end headphone output. We received loads of comment and request to make the vacuum tube timbre available to balanced output as well. Naturally, when we start our N8ii project, one of the priority requirements is to implement a fully balanced Tube Amplification circuit in N8ii.
To be frank, with the experience and track record of Cayin on design and manufacturing of vacuum tube amplifier, circuit design with Nutube in balanced configuration is hardly a real challenge. Ever since we lay our hands on KORG Nutube 6P1, we have conducted very thorough study to apply the “flat” miniature Double Triode in different circuit design. We have gone through over 30 rounds of PCB with Nutube already, which roughly tells how exhaustive we are on this subject.
Based on the feedback from dealers and users on N8 and C9, and our observations to market response in past 10 years (Cayin entered Personal Audio market since 2013), we adopt Zero Gain Negative Feedback Loop circuit in N8ii design. This will deliver strong current and impressive handling at difficult load. We have adjusted the feedback loop carefully to enhance the transparent, transient and extension that can rival the best solid state circuit but yet remain warm and mellow.
To certain extend, Zero Gain Negative Feedback Loop is not a design that is preferred by typical tube enthusiasts because this offers less tube flavor relatively. However, we believe this is more in line with the market preference as portable DAP users tend to appreciate transparent, crispy and well-defined presentation with faster transient. In our opinion, there is no right and wrong on these issues. Vacuum tube is the mean, not the end, therefore maximizing tube flavor is not necessary the most important objective. It’s our duty, as a vendor, to understand the market we serve and to provide options different needs of the bigger crowd.
Reinventing the Nutube installation.
The Dual Nutube implementation in N8ii is even more challenging than C9 because of limited space and form factor. There is not enough room to lay the two Nutube flat like N8 and C9 because we need to accommodate a bigger screen for Android implementation. We can’t lay it flat on the bottom panel either because that will reduce the space available for battery. Finally we started the process all over again and developed mechanical shock absorption and damping system to install the Nutube vertically. The new installation system involves:
- Compartmentalized CNC Aluminium chassis to create an isolated, fully damped chamber for Nutube installation
- Flexible Printed Circuit (FPC) to minimize shock transmission
- Custom Built Shock-absorption Silicon Housing to hold and damp the Nutube
- Vertical-hanged Suspension Pin to mount the Nutube and Silicon Housing into the designated chamber securely
Having a dedicated chamber to isolate the Nutube from the main PCB is a head start in dealing with microphonic and anti-interference. We are surprised by the final result of this new design, it works like a charm and we are confident that the N8ii can cover our daily activities effectively.