In the wake of my Bakoon HPA-01 review, Soo in Chae checked in from Korea: "Thank you for your detailed, honest and thoughtful review on the HPA-01. I’m very happy to hear that it worked fine in your setup - and agree that our current drive circuit really is the ticket for orthos. I understand why you didn’t like the HD800 connected to the current output as much because its impedance plot (I attached the HeadRoom measurement data) varies quite a lot. It gives a hefty boost to the bass region especially around 150Hz. This makes the HD800’s frequency response via current output follow the same plot. Actually some customers and pros like this behaviour since it balances the HD800’s tendency toward the high frequencies. Anyhow, we see this is as another advantage of our current drive method since one can play with this natural EQ. I also want to tell you that we are now concentrating on two new product developments. One I already told you about in Munich. That is the 50wpc AMP-51 stereo amplifier. The other is a portable mobile headphone amplifier. The HPA-01M is targeted to debut at CanJam Europe in September. If you don’t mind, I’ll try to arrange one extra review unit for you around that time. The HPA-01M shares the same circuit as the HPA-01 but its batteries are now dual 8.4V and power output will be down accordingly. We believe this unit may become quite popular considering the latest boom of high-quality DAPs. Please keep this development secret for a while and I’ll update you along the way."

"The HPA-01M packs lots of tiny SMD parts in a relatively small solid CNC'd aluminium case. The circuit is the same as the HPA-01. You had opened its case. The top surface contained only some power supply and output stage parts whilst the rest—input, battery management—were on the bottom. For the HPA-01M, all SMD components went on the top, anything too thick or not SMD on the bottom. You can see some of those in my 3D engineering view below as well as the batteries. Basically those cover most of the surface available and are now 8.4V 2'000mAh packs again sourced from Samsung SDI. It was not easy for me to develop the case but we already have a prototype built and I like it very much in my hand. Of course not too many people carry their big orthos around but the HPA-01M will provide 'enough' power for their home listening too. It'll certainly be much better and more powerful than all the DAPs currently available. For IEMs I’ve been using the Etymotic ER4S since my high school years. It’s great on the current output socket. I believe the biggest advantage of our current drive tech is how it controls headphones so much better for a quicker response, higher dynamics and more information. Some popular high-quality IEMs also show a more or less flat impedance curve and I believe users will find the HPA-01M very suitable with those. One last advantage over the HPA-01 is that we are targeting the HPA-01M’s price to be €1'000 (excl. VAT)." Whoa! This promised to be some amazing sardine canning job, stuffing the circuit of the paperback-sized HPA-01 into a casing half that size or less to go portable, the only loss along the way some power due to smaller batteries; and a lower price."