It’s that time again. Another pursuit of perfection. Another of our own taking things into their own hands. Last time it was headphones, this time, it’s amplification. The Apex Hi-Fi Sangaku is a hybrid headphone amplifier that employs Korg’s interesting Nutube creation in an attempt to deliver the best of both worlds. It picked up interest and landed on SonnyMarrow’s radar. He liked it, but he didn’t love it. With Pete Millett’s blessing, Sonny set out to improve upon the Sangaku in every conceivable way, while leaving room for others to expand even further.
I do not recall when I hopped aboard the SonnyGaku train, but things moved quickly. The modularity of the project was amazing, and I learned quite a bit figuring out what to put in my unit. The fun part for me was picking the visual components. Landfall Systems was great in giving us tons of options and colors. I went with a black case and gold anodized face plates. Others went with unibody designs. You’ll see Flux’s along with a full review in the next few months. I use mine along with my Matrix Audio X-SABRE Pro. It also serves as a pre-amp to my FirstWatt F6 Proto.
Sonny was kind enough to chat with us and bring you details from beginning to end:
What fundamental issues did you solve with your design?
Sonny: The main issues for both the Retail and DIY Sangaku, in my opinion, stem from the power supply design. Nutubes are inherently noisy, and the power supply only added to the noise floor problem. For example, I have heard people complain that the Retail is unusable as a pre due to the background hiss.
To address this problem, I took the single power supply from the original design that is split and regulated (or tripled) into all the necessary voltages, and instead use individual supplies for each. The most important is the filament supply for the Nutubes, since they are DHTs. I used an LT3045-based solution to provide very low-noise power to the filaments, and this has proven to be a massive improvement in noise floor.
What nice to have/quality of life features did you add with your design?
Sonny: The original goal of the project was to redesign the PCB to be “modular,” and people could build one tailored to the options they want. The Sonnygaku uses a lot of plugs instead of board-mounted components for this reason. As I worked on the project, I eventually came to a “reference design” that included all the options I would want, which were incorporated into the “production” Sonnygakus built for a select few.
- The aforementioned power supply upgrades, including putting all power-related things in a separate chassis.
- I find the gain on the “stock” options to be absurdly high, so Sonnygaku has a lowered gain.
- Related to the gain issue, I could barely use a potentiometer above 9:00, so I was still in the region of bad channel balance. Sonnygaku uses a 256-step remote-controlled attenuator using 0.1% resistors.
- A screen, because screens are fun.
- All PCBs, including the nutube carrier PCBs, are on rubber standoffs to combat the notorious pinging nutubes exhibit.
- XLR and RCA pre-outs.
- Overall improvement in part quality. Most notably the coupling capacitors and the cathode capacitors. The Sonnygaku PCB has extra space to accommodate “audiophile” brand capacitors.
- Use of a JFET buffer both before and after the nutubes. The DIY can only be used with certain volume controls due to the input impedance of the nutube. The JFET buffer before the nutubes allows any volume control.
- Extra space around the opamps for the future upgrade to discrete class A opamps.
- Custom case options so everyone could make their Sonnygaku personal to them, such as your gold and black case.
What is your background in electronics?
Sonny: Nothing formal. My degree is in biochemistry, so I had some light physics and math as a good foundation to teach myself more about electronics. I’m far from an electrical engineer and consider myself a hobbyist. I enjoy designing or reverse engineering circuit, doing CAD for cases, then soldering all the components. It’s almost therapeutic for me since it gives me a creative and hands-on outlet.
What are your plans for future projects?
Sonny: As far as projects offered to the community as prebuilds, that’s hard to say. I don’t have as much time as I used to for these things, so most of what I’ve been doing post-Sonnygakus has been to create DIY projects for other people to do themselves or things for my personal use. I’ve recently been in contact with a famous amp builder that is allowing me to repair and sell a certain discontinued amp, so stay tuned for that. He had a stockpile of broken boards that are mostly assembled, so the time investment shouldn’t be that bad (famous last words). As far as personal projects, there’s a parallel single-ended tube amp in the works that will use 2a3 tubes, and I hope to build a version two of my ValveDAC for a Den-Fi writer that is currently borrowing version one. The ValveDAC is one of the most interesting audio products I’ve come across, and I’m excited to see the Den-Fi article on it in the future.
Do you have any advice for people looking to DIY their source gear?
Sonny: Invest in good tools. A decent soldering iron makes a world of difference, and all the peripheral tools (like clippers, helping hands, PCB holder) further assist in doing clean, quality work. My first electronics projects were guitar effect pedals I made using Radio Shack tools, and I cringe thinking about the solder job on those. Also, read as much as you can about a project before starting it. There are so many diy audio resources (diyaudio forums shoutout) out there, and the diy community is the best part about audio, in my opinion. So many people willing to help. I have had so many of my own horribly stupid questions answered with patience, that I feel the need to pay it forward, hence my contributions to the diy/audio community. Going into a project with a plan and your questions already answered makes the job substantially easier.
How do people get in touch with you to get their own Sonny Projects?
Sonny: I’m SonnyMarrow on basically every platform known to man, so I’m not that hard to find. However, I’m not really a store front. I take on projects for fun where I want to, so don’t take it personal if I tell you no. My actual job takes up much of my time, so I pick and choose projects carefully. If someone comes to me with something interesting, I’m more likely to take it on for selfish reasons. Recently, someone asked if I would make them a 47-step AVC preamp, which I agreed to because I have wanted to try this AVC for some time. Similar to the ValveDAC above, I loved that project which is why I’m willing to do it again.
What gear do you reach for most often?
Sonny: I currently own five headphones: HD580, HD600, HD650 (all in black silk baffle variant), Aurorus Borealis, and KSC75. The HD580 is by far my favorite, and everything I make for myself is to get the most out of them I can. I really enjoy the Borealis as well, and I use that a lot when doing A/B testing of source gear. The Sonnygaku was in part inspired by the Borealis, because due to its low impedance and high sensitivity, the normal Sangaku’s noise floor problem made them annoying to use. The tonality of the Sangaku synergizes well with Borealis, so I wanted to address the issues there and make it useable while doing silly “audiophile” upgrades to the design in the process. KCS75s are my whipping boy. First time firing up an amp? I grab the basically free headphones so if anything explodes, I’m out roughly zero dollars.
What music do you enjoy listening to?
Sonny: The only genre I wholly dislike is country. Otherwise I enjoy anything from top-40 wall-of-sound trash to classical music. My favorite is definitely more prog rock and other “rock” varieties. Currently, my overall favorite band (who just released a new album!) is The Dear Hunter, and I’ll list some other stuff in my current rotation: Protest the Hero, TTNG, Thank You Scientist, The Mars Volta, Lizzy McAlpine, Closure in Moscow, As Tall as Lions, Tides of Man.