The Objective 2 and NFB-11

I had finished up building Pete Millett’s Butte and really enjoyed it. I thought it better than the other amplifiers I’d had at the time, or at least on par.

Previous to the Butte, my high end amplifier was from a company called Audio GD (pronounced Audio Gawwwd, according to me) which is a small boutique manufacturer in China. Their website is amazing and exactly what you’d expect from something poorly translated from Chinese to English. My favorite page is titled “The babies in gestating” and describes their high quality build and QA process. All joking aside, the build quality of their gear is quite good.

The Audio-GD NFB-11

I feel this amplifier deserves a few paragraphs of thoughts, as it really did leave an impression on me and I learned something from it.

The particular model I owned was the NFB-11 and it was another combination headphone amplifier and DAC, like the Schiit Fulla and Fulla 2 I owned previously. There would be a number of revisions to the NFB-11 over the years, but I bought the original version. I had chosen it due to a lot of folks going on and on about how great it was. Words and phrases like “musical”, “excellent transients”, “hard hitting”, “fast”, and “natural” were used in the reviews I watched and read about it. Plus Zeos said it was awesome. Pretty much there was kool-aid being passed around the headphone community and I drank it.

A big highlight of the amplifier was actually ordering it. Ordering it involves emailing an @vip.163.com email address with what you wanted, waiting for a few days, getting a quote back with a possibly suspect PayPal link, and then PayPaling money. After that, you waited and prayed. A month later, a package should arrive from China and you have an amplifier. I’m not sure what would happen if you needed to return it for warranty reasons, but I’m sure that it was a similar process. I call their process for ordering The Indian Jones Process.

I went through the ordering process and after about a month, a large package containing an amplifier showed up at my door.

After spending some time with the NFB-11 I thought it sounded good, but still much like all the other amplifiers. The DAC portion actually was a pain in the ass as it required the installation of special drivers and those drivers were not easy to install. As expected, everything was in Chinese and was not as simple as opening up an installer and hitting “next” a few times. After an evening of mucking around with Google translate on some non-English speaking audio forums, I had them working and I could listen to 384khz music files. Not that I’ve ever actually heard an audible difference between standard CD-quality 44.1khz lossless files and a unicorn native 384khz file.

However, if I needed to, I could. That’s pretty rad, lol.

I feel temped to talk a bit about DACs and my thoughts on them, but I think that’s it’s own post.

The other thing I do remember about this amplifier is that it had a great volume knob and potentiometer. Silly as it sounds, I still grin when a large knob turns with just the right amount of tension and the music volume adjusts accordingly, reacting perfectly. It’s a “feeling” thing that I do believe is important in the music experience. It’s the same reason I enjoy vinyl – you must take some physical action and if that action “feels” right, it’s enjoyable. The NFB-11 definitely did that part right. It was the first amplifier I used that gave me pleasure to operate. It felt well engineered and sexy. Remembering that feeling would become important as I started to build more amplifiers and customize them to my liking.

Never fuck up the knobs. Never ever.

However, at the end of the day, it sounded like everything else I’d heard in most regards. Just it physically was bigger, looked cooler, and gave me increased audio geek cred. Plus the volume knob.

I finished building the Butte a bit after acquiring the amplifier and, due to that, had moved on to thinking about the Objective-2 amp.


This is what I was waiting for. The DIY amplifier that disrupted the headphone game. Uber disrupting the taxi cab business. Apple disrupting the cell phone. The Objective 2 (O2 from here out) disrupting headphone amplifier.

Needless to say, I had very high expectations for this one.

The O2 is interesting. NwAvGuy gave out the schematic for it freely, though partnered with manufactures to have the PCBs built. This was all done under the Attribution-NoDerivs 3.0 Unported license, which I find disappointing. Not quite Open Source, but not quite proprietary. You can make it and sell it, but can’t modify it (and then share your improved version) even with attribution. So, here is this thing I made that’s pretty cool but fuck you if you improve it and then share those improvements. None the less, a small outfit near St. Louis, JDS Labs, sold PCBs for it so I picked one up. JDS Labs would go on to build their own products, and to great success.

Again, I had a bill of materials for the O2 and ordered the parts from that weird electronics store called Mouser. For those that don’t know what a bill of materials is, most electronics projects like this will have a list of all the parts and their part numbers that are needed to build the project. Good projects will have labels on the PCB that correspond to the bill of materials so you just look at the marking on the board and match it up against the part number on the bill of materials to understand what goes where. Some projects may or may not have that last bit and the builder gets to figure it out, but in general, most of well established projects will.

Once the parts arrived I stuffed the PCB. Stuffing just means putting the right components in the right places. After that, I soldered it all in place.

My earlier fear of the components being close together and being more difficult to solder was partially right. They were closer together, but my skills were better now. I avoided any huge mess-ups and double checked, with a multi-meter, that none of the solder pads with solder caked on top were making a connection they shouldn’t. I knew this time to check polarity and the PCB had markings describing how to position anything with positive or negative pins.

The O2 also uses some Operational Amplifiers or opamps if you’re cool. Opamps are another topic that deserves their own post, but I do want to touch on them briefly.

The O2 under construction. The black rectangles with little dots on them are the opamps. Bill of materials in the background and reference IDs on the board are visible.

The opamps were in a DIP-8 package. That means the component (like an opamp) comes with a bunch of small pins (8 for a DIP-8 package) in a standardized size and shape and must positioned correctly on the PCB. Most have a small dot on one end of the part and most PCBs will have a corresponding dot printed. Line the dots up and the component be positioned correctly. Each pin on the opamp has different things going to it, like positive and negative voltage, ground, the audio signal in, and the audio signal out. Installing it upside down could cause something like DC voltage flow to a pin for audio output and, well, we could blow something up. We didn’t want that.

Everything was now soldered so I checked any solder spots that looked sketchy with a muti-meter (which I had learned to use from the almighty Google), attached the power brick, and hit the power button. A small LED lit up, it passed my “is anything burning” sniff test, and I plugged in a music source and some cheap headphones.

Not to derail the story, but one thing about the O2 is that it was meant to be “portable”. In the real world it’s not, though it can be run off two 9 volt batteries if you choose. I don’t know anyone who actually has done this outside of seeing if it works or thinking that technically batteries are a “quieter power source” and thus will make things “sound better”, as it’s just not practical given it’s size. Due to it being designed for “portable” use, the inputs are 3.5mm – headphone jacks in and out on the front panel along with the power connector. In my opinion, this is one of the more awkward designs I’ve seen and goes against “the feel” I got with the NFB-11. Using the amplifier was not “fun” and instead clunky and a pain in the ass. It looked the opposite of sexy. The default Alps potentiometer felt alright, but not as good as the larger and more sturdy one the NFB-11 had.

This is what the O2 looks like in use. Yeah. It’s a mess.

Ok, so yeah – the power light lit up and I connected a source. I was using the Sennheiser HD 600 headphone at the time and cranked the little O2 up, waiting for some magic.

Like any new toy, I listened long and hard. The amplifier certainly ticked boxes – no hiss or any sort of sound in the background. In audiophile speak it had a black background, and it was that way with all my headphones, including some earbuds and in-ear monitors. That’s a very good thing as many earphones have a very low impedance, which means many amplifiers will produce a level of noise or hiss if they themselves do not have a low output impedance and correspondingly low noise floor. For reference, the Butte produced a very small, but audible, hiss with very low impedance earphones.

Other than that, it was powerful enough for the HD 600, which is the opposite of an low impedance and highly sensitive earphone – it had a much higher impedance (300 Ohm) and thus required more voltage to produce higher volumes.

No noise, check. Power for higher impedance headphones, check.

However, the sound was actually a bit different. Not in any sort of significant way and only the kind of thing you would “feel” after spending a lot of time listening to music and then reflecting on it. NwAvGuy said his intention was for it to be transparent and get out of the way of the music. I think it probably does, but to a point of only what I can only describe the O2 as “sterile”. Things sounded as they should, I suppose, but the O2 lacked any and all character. It was surgical compared to the Butte and even the NFB-11. I wasn’t sure it was actually causing me to enjoy the music or if I was more now just trying to dissect everything with my new surgical instrument. Analyzing, rather than enjoying. I’d later realize, though I’d heard folks say it before and knew it all along, that music is art, subjective, and it’s really all up to the listener. I was learning that I preferred some character.

Why do I think most things look best in natural outdoor light? Because it is not perfect white light. It’s light from a giant ball of gas many millions of miles away that has been burning away for an eternity and traveling great distances before it reaches my eyes. It is imperfect.

The O2 is a fine amplifier. I believe it achieves it’s goal – it measures well, doesn’t really color the music, and pretty much works great for anything you can reasonably throw at it with a few notable and rare exceptions (like the AKG K1000, but lol those are special). However, it had zero character and I found myself enjoying the good ol’ Butte a lot more.

This sterility I’m talking about – is it like something where average person is going to say this? No, I’m talking about some 0.05% thing here. If I was a normal person, I’d have given zero shits, not noticed, and kept it since it ticket all these great boxes. But I’m likely not quite normal and am on a journey. No, not a journey, but a quest. Not a quest of chasing the audio dragon, but trying to figure out the various audio dragons and what that meant to me.

I ended up gifting the O2 to my mom for her birthday. As before, I 3D printed a case for it with well wishes inscribed on the bare back plate and a joking “Yerhot Audio, Love John”. She enjoys it to this day. As well as a small collection of other gear I’ve built for her.

Fin. Love you Mom.

Dammit, Pete Millett.

After more rounds of amplifier upgrades and side-grades, I kept hearing about this headphone amplifier that was a giant killer. This mysterious person from the Pacific Northwest designed it to prove a point that super expensive boutique audiophile gear was mostly just hogwash and could be beat, objective performance-wise, by some rather cheap parts and good engineering. It was the Objective 2 and I thought it was so punk rock that I could build my own “better than everything else” amplifier. Super David v. Goliath.

The mystery around the creator – a person who went by NwAvGuy – who posted to a blog for about a year, raised hell, and then disappeared was almost too good.

I spent a few evenings looking at pictures of it and watching videos of folks building it. It looked ridiculously complicated, especially given my only experience thus far was the small Frys kit I built a while back. This was supremely more complicated and involved lots of parts, most of them small and crammed next to each other. It seemed a step past where I was.

Like a lot of folks, I decided it was daunting and I didn’t have time to muck around with it. But, I had to build something now that I had the itch.

On reddit.com/r/headphones someone posted about this amplifier they’d built for their cans. It was called a Butte and I read more about it on this website that looked like it was from 1996. The designer was apparently named Pete and sold stuff on eBay. He said he had a background in electronics and his website seemed like he did. I mean, being so awful looking and full of technical information, he must know his stuff. Honestly, it all seemed sketchy as hell but he had posted stupidly detailed instructions for how to build the Butte and it seemed significantly less complicated than the Objective 2. I figured what the hell – Reddit says other people have done it and that means I can. I ordered the Butte PCB from his eBay page and ordered the pre-configured shopping cart from this weird website called Mouser. I’d never ordered parts like this before, so even that portion was an adventure.

A week later everything arrived.

As usual, I tore it all opened, printed Pete’s assembly instructions, and started on my way inserting resistors where the manual said to and putting on various connectors. After an hour or two I had it assembled and soldered. I decided to power it on with the wall wort that came as part of the preconfigured Mouser shopping cart and hoped for the best.

A little green light lit up and I got excited. A few seconds later I noticed a funny smell. Looking a little closer I noticed something weird, one of the capacitors seemed to be larger than the other. Not in a “good larger” way either. Quickly I unplugged the wall wort.

After some more looking I noticed that in Pete’s pictures the capacitors looked a little different. There are these stripes on them and they went the other way in the pictures. I guess that matters.

This is how I learned about polarity. Turns out polarity is important, folks.

I didn’t really know what a capacitor did, but I did learn that one side is positive and one side is negative. And feeding the wrong side with DC+ isn’t a good idea. I de-soldered the incorrectly placed capacitors and re-soldered them the other way around, though one was bulging out a bit.

Again, I flipped it on, the light turned on, did a quick sniff test for anything smelling funky, and finally connected it to my computer and cheap headphones. Omg it worked. And it sounded good (with super sketchy capacitors in the power supply).

The finished PCB on top the pinnacle of my non-DIY headhone amps, the Audio GD NFB-11

I also noticed that I had a few parts left over. Pete includes an optional CCS circuit that can be installed. I had no idea what this meant or really did, but I decided to install it. Basically, you’re installing a CPC3703 mosfet to make the opamp run at full tilt all the time. Class-A. Moar powwwwa is better than less powwwwa so that was a no brainer. The parts were these small little poopers and I fumbled my way through it. But, it continued to work afterwards and I felt super accomplished.

I even made a 3D printed case for it after some time. Not amazing, but it was fun and cheaper than the $50 or whatever Pete wanted for a really nice aluminum pre-drilled chassis.

Yes, I did replace the capacitors with non-blown up ones. But, wow, I really did think this amp sounded great. It had zero noise and had authority. That’s the best way I can describe it – authoritative. Am I biased because I made it? Probably. But, to this day I still think it’s a damn fine amplifier and for a total cost of less than $100 excluding enclosure, it’s right on the money.

This particular amplifier ended up going to a different home, but I love Pete Millett’s Butte so much I made another one a few years later just because. Well, not completely because – I had started to think about building chassis out of wood and needed an easy project as an excuse to try making a chassis from wood. It turned out alright and is still sitting on my audio rack today.

For a first time DIY audio project, I recommend the Butte big time. And Pete Millett, if you’re reading this, I love you. I really do. I didn’t know it then, but I’d end up building a number of your projects and each and every one is special in different ways. Thank you for being the amazing Colorado guy running a 1996 looking website full of marvelous information that you are.

This project taught me about polarity, AC/DC, and so much more. After almost blowing up (err, really I did) the capacitors and then fixing it, I spent about a week reading and testing various things out. I referenced every single component I put in that PCB and learned that resistors are not polarized, the capacitors were (but not all capacitors are), what a pin out was, where the audio signal went and how it fed into the opamp, what the mosfets I added did, and how a potentiometer is like an adjustable resistor. I feel like I learned so much building, screwing up, and then fixing the Butte that I can’t even express it. I had so much fun.

But, I still wondered about this giant killer – the Objective 2.