Reviewing the Orchard Audio BOSC™ Monoblocks

Before I get to the review of the Orchard Audio BOSC Monoblocks, let me first spend a moment on a soapbox, so to speak. If I name an amplifier type, I bet you would have a preconceived notion as to what that amplifier would or should sound like. If I list types like Class-A, Class-A/B, Class-D or an 8 Watt 300B SET amplifier, 211 output tubes, 845, or EL34, etc., just these names may trigger some notion of sound in your brain. This is a very mild form of synesthesia, or one sense triggering another. 

In this case, the amplifier type triggers a notion of sound and most likely that sound triggers some form of emotion, even very basic emotions like positive, negative, or neutral. These preconceptions drive reactions and opinions. This is a good thing, but it can also stifle the opportunity to listen to exceptional gear just because of a simple label.   

That being said, when mentioned, Class-D amplifiers generally trigger reactions and opinions of a generic, mass-market sound. And I’ll admit, I tend to not be too curious about anything based around that amplification method. But Leonid (Leo) Ayzenshtat’s Class-D amplifiers continually force me to think differently. They prove that it isn’t about the type of thing, but rather about how skillfully a thing is made. And, this should be no surprise as Leo previously designed products for several elite names such as NASA, LGS Innovations, Lockheed Martin, L3 Technologies, and Siemens before starting Orchard Audio LLC in 2017 to develop his own line of high-end audio products. 

Most recently I was able to spend a short period of time with his new BOSC Class-D monoblock amplifiers.  I think they sound just amazing, and I encourage you to give them a listen, even if Class-D amplifiers aren’t typically your thing.

How They Work

Leo’s goal with the BOSC amplifiers is to “provide the listener with a truly life-like musical experience, presented with every significant detail intact…” at an affordable price point, achieved by focusing on only what is explicitly necessary to reach this goal. 

The BOSC amplifiers use gallium nitride (GaN) technology, which is a binary III/V direct bandgap semiconductor commonly used in light-emitting diodes or in GaN MOSFET transistors. Gallium nitride is replacing silicon as a faster, smaller, less switching losses, material. Find out more about GaN in this EPC article and at this Wikipedia page. The BOSC amps also feature custom propriety dual feedback design, DC coupled for response down to 0Hz and no bass phase shift.  That is impressively low. The amps also feature a high damping factor which allows for very precise control of the speaker.

The amplifiers themselves are very small and weigh practically nothing.  You won’t need help to unbox and set them up. And because of their small size and weight they can be placed very close to the speakers eliminating long speaker cables. The philosophy is similar to powered speakers, less is more and less wire to travel means a lower degradation of quality. As such, the amplifiers also have no on/off switch and go into a low power mode when not in use. With just about any floor standing or bookshelf speaker, these amplifiers can hide right behind them, out of sight, and nearly out of mind.

Listening to these Amps

I set the amplifiers up with my PMC TBi-2 bookshelf speakers, WyWires interconnects and at first, WyWires speaker cables. I used the Orchard Audio PecanPi^TM music streamer (previously reviewed here) running Volumio connected to a half-terabyte USB solid-state hard drive with a variety of 16- and 24-bit lossless FLAC recordings on it.  

I started off with Miles Davis’ A Tribute to Jack Johnson just playing in the background while I cleaned the house. I just love the intro to this album, and the first cut, even after Miles’ trumpet steals the light from an amazing jam, is great for playing loud and making the body move. But as I was cleaning something caught my ear.  John McLaughlin’s guitar sounded really good, better than I remembered it sounding previously from my speakers. The dynamic shifts and tone forced me to stop cleaning and sit and listen.  

Once in front of the speakers, the details in the high-end pulled me into the recording. They were so clear and present without being brittle, too aggressive or fatiguing.  It was like someone had replaced the little silk dome tweeters on the PMC speakers with something similar to ribbons. It’s not that these are bad tweeters, to begin with, but they just seemed to produce more details in the high-end than I had heard previously.

Next came In Session with Albert King and Stevie Ray Vaughan, as it always tickles me to hear blues through digital gear. It kind of just seems so wrong, but with the BOSC amps it sounded really good.  It wasn’t the same as listening to Vaughan’s guitar via vinyl and a 211 tube amp out of Tannoy speakers, but it was clean and fast with great tone and separation of sounds. More importantly, it was emotional. Not in a way I was expecting, but it had soul. 

Using the Volumio app on my iPhone, I moved on and queued up Apparat’s The Devil’s Walk. Being able to stay in my chair and use my phone synced with the Orchard Audio PecanPi music streamer was, admittedly, more convenient than finding, cleaning, and flipping records. Good thing I spent all that money on records though! 

Anyway, I wasn’t surprised that listening to The Devil’s Walk was another great joy. But something happened that had not happened in some time. I could not shut it off, I mean, not that I wanted to, but if you asked me to hurry up and turn it off because we were going to be late for something, then damn it we were just going to be late! I didn’t want to breathe. I was transfixed. I had no idea these little PMC TBi-2 speakers could sound so detailed and articulate.  

I wanted to stop my heart so I could hear the music better. I was being sucked in, pushed out, and unable to focus on anything else but the music. There were all the little bird-like chimes, dancing between clicks and pings and bongs of xylophone harmonics with dry reed raspy sounds zooming in and out, floating on top of deep rolling strings and organ-like bass. I didn’t want to miss a moment of it.  And yes, while I do live on the “green” West Coast, I was transfixed but in a very sober state of mind.

Cables Do Matter

But to be honest, the low end, while dynamic, articulate, controlled and clean, just wasn’t as powerful as I wanted it to be. Was this a fault of the BOSC amplifiers? Sort of but also not really. The BOSC amps are so well controlled that they just weren’t adding more bass than there should be, and with smaller bookshelf speakers that roll off around 40Hz, the reality of the speaker design was more apparent. Whereas my EL34 tube amplifier, which has a much heavier and fatter low end, can fake its way into more bass. So without changing amplifiers, speakers, or source, how could I tweak the system to fake a bit more thump out of the low end?  Well, this is where different power, interconnects, and speaker cables can come into play.  

I was still using the WyWires interconnects and speaker cables between the speakers, amplifiers and the PecanPi DAC/Streamer, but I had other options. The PecanPi and BOSC amplifiers come with XLR connectors as well as standard RCA connectors. I had an old set of XLR cables out in the garage, so I thought I’d give them a shot.  And while with them the bass was more powerful and filled out, the loss of the high-end detail was just not going to cut it. Not that it sounded bad, as it probably would have been just fine if I had not previously heard the amps with the WyWires interconnects. The harmonics were no longer sustained and clear, dry reed sounds were more like buzzing noises, and clicks no longer snapped my attention. 

This was hardly the fault of the amplifiers. In fact, this was one of those times when I would have loved to have had one of those forum naysayers in the room to listen to the fact that cables do matter. But I digress, and I had other cables to listen to.

Having very short speaker cables and amps right next to the speakers honestly seems a bit weird to me, but this is actually how the BOSC amplifiers were designed to work.  So I figured I better use the very short, nearly jumper-like length, speakers cables that were sent with the speakers for the review. While I had not heard these cables before, they might reveal something in my search for a bit more bass. 

So, after being forced to think outside the box again, thanks Leo, I put the same Apparat album back on and got a sound similar to the sound with the WyWires cables that I had used previously.  But my listening time was cut short as other responsibilities called.  

Summing Up

I had planned to do some more listening and give the supplied speaker cables more time, and also try out my MG Audio speaker cables which tend to have a bit more depth to the low end, but unfortunately, my time with the BOSC amplifiers was up. Leo needed this pair for an event, and I had to return them much too soon.

Jack will get these amps in next week for his review. I’m looking forward to what he has to say after he has had some time to spend with them. The BOSC Monoblock Amps were definitely an exception to my so-so experiences with Class-D amplifiers. I think Leo has something special here.

Final Notes

You might have noticed that I have focused a lot of my attention on the higher end of the frequency spectrum.  I don’t want to give you the impression that this is the only good thing about the BOSC monoblocks. That would be incomplete and incorrect. It is rather that this is what stood out most from my listening time.  It isn’t that they are top-heavy, or the high end was more forward, it was just that there was more detail present than I was used to hearing, and better articulation of smaller sound variations focused my attention to this area. The mid-range and tone of the amplifiers were in balance and equally pleasant to listen to, and the low end, even though tighter and lacking a little less thump from my small speakers, sounded better, more detailed and clear. I just need speakers that extend themselves more into the low range.

There is so much out of the box and smart thinking that has gone into the BOSC amplifiers that I can’t help but say, “I can’t wait to see what Leo comes up with next.”  The MSRP for these 150W BOSC amps appears reasonable at $1,499.99. As I have said, they are meant to be hooked up very close to the speaker, imitating the benefits of direct-powered speakers, and there are no bells and whistles. There will also be a discount offered through a crowdfunding opportunity to be announced on the Orchard Audio website next month.

They are just what you need for amazing audio quality at an affordable price. If I had the ability to pair a set of the BOSC amps with the PecanPi streamer and a set of Magnepan 3.7i speakers, I think I’d have a keeper of a system that cost well under $10k and could sustain my attention for a good long time.