From A to AB!

The product was provided to me free of charge for the review purpose in exchange for my honest opinion.

Manufacturer website: Cayin.  Available for sale on MusicTeck by itself or w/N6ii.

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Intro.

The modular design of Cayin N6ii opened the door to endless possibilities of DAC/amp combinations, starting with original A01 module that implemented AK4497 DAC and following with T01 that used PCM1792A as a homage to original N6.  With a new E01 module Cayin decided to raise the bar and surprise us with something different, introducing not only a new DAC/amp combo, but also a choice of amp modes within a module.

While some were hoping for NuTube implementation (like in N8), it turned out to be challenging due to a limited space inside a module.  Instead, Cayin went for one of the top desktop quality ES9038 Pro DACs and a unique dual mode amplifier design which you can switch on the fly between Class A and Class AB modes.  After spending the last few weeks testing and comparing this new E01 module, let me share with you what I found.

Unboxing and Accessories.

Keeping it consistent with my review format, I wanted to go over the packaging and the included accessories I received with E01.

The module arrived in a compact black box with a foam cutout to keep E01 secure during the shipment.  When you remove the module, keep in mind there is a protective rubber cover over the connector, and you will need to remove it before inserting E01 into N6ii.

On the inner side of the module toward the faceplate you can see a black sticker which I had to remove as well because the fit was too tight.  If you are experiencing the same, don’t force E01 module into the DAP, remove that black sticker to make it slide in easier.

Also, included were 4 extra screws, this time inside of a small plastic capsule instead of being stuck into the foam like it was in T01 box.  A premium colorful screwdriver with Torx T5 bit was provided as well.  I don’t think everybody has Torx bits, so it was a good idea to include a screwdriver as part of the accessories, and also a manual with detailed instructions how to remove and replace the module.

Design.

As many probably figured out already, E01 stands for ESS DAC, just like A01 corresponds to AKM DAC and T01 name goes along with PCM DAC from TI.

In the heart of E01 module you will find ESS flagship 32bit 8-channel ES9038 Pro DAC, fully utilized in differential current mode output, followed by common op-amp circuits for I/V (current to voltage conversion) and LPF (low pass filtering) for Left/Right channels.  But the follow up headphone amplifier section is where Cayin decided to flex their analog design muscle with a unique DAO Mode discrete components circuit.

DAO stands for Dual Amp Operation mode where Cayin implemented both Class A and Class AB amplifier designs which you can select on the fly from N6ii menu.  There are many on-line resources, like this one where you can read more about different Classes of amplifiers.  One of the things that makes a design of these type of amplifiers unique and challenging is the manual selection of discrete transistor components, instead of op-amps, to guarantee nearly identical gain between channels.

If you take into consideration a limited circuit board space, large size power hungry ES9038 Pro, all the pre-amp circuit components, and discrete components for Class A and Class AB amplifiers, there is no extra room left to accommodate Line Out.  That is a reason only single ended Phone Output is available in E01 module since there is not enough room for LO.  The same reason why balanced output wasn’t feasible either due to lack of room to fit two DACs and to double all the discrete components.

(Cayin picture)

Some could also question that output power of 3.5mm SE (0.6ohm output impedance) is not that high: Class A, 105mW @32ohm and Class AB, 150mW @32ohm.  Based on my testing I found E01 to have more than enough power to drive earphones and efficient headphones.  And when it comes to higher impedance loads and more demanding full size dynamic and planar magnetic cans – the current output capacity of E01 had plenty of juice to drive them to their full potential.

Furthermore, considering power hungry ES9038 Pro and implementation of Class A and Class AB mode amplifier circuits, the battery life with 7.5hrs of playback time (A) and 9.5hrs of playback time (AB) was actually reasonable.  The reduced playback time while in Class A mode is expected since this type of circuit has very low efficiency due to transistor being constantly on (biased) and running hotter.

Page 2 – Sound analysis and Pair up.
Page 3 – Comparison and Conclusion.