Author Topic: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps  (Read 822 times)

Offline mdconnelly

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A few months back, I had the opportunity and great pleasure to purchase a couple of Orchard Audio's PecanPi Streamers.  I bought them to replace an aging pair of Squeezebox Touches I had been using as Roon endpoints.  I do love Roon.  The PecanPi Streamer is a great combination of Roon endpoint and extraordinarily good DAC which sounds substantially better than the SB Touch.  They fit a perfect niche for me on two secondary systems - dining room and outside porch.  In both cases I've been using fairly inexpensive 60w stereo amps.  Nothing special, but fine for background music. 

Then along comes Orchard Audio's latest product, the BOSC mono amps. It would seem that these were made as the perfect companions for the PecanPi so I asked Leo Ayzenshtat (owner of Orchard Audio) if he had any that I could try, review and return well before they became available via his Kickstarter launch.  About 2 weeks ago, a pair of the BOSC amps appeared on my doorstep.  Thank you, Leo!

Before I go into any detail, let me say up front that these amps are something special.  Detail and clarity galore with a transparency that grabs your attention and doesn't let go.  The amps run cool to the touch and are so small that they can be easily stashed away out of site in any system.  In my opinion, they punch way above their price point and easily turn a background music system into something that cannot be easily ignored... or at least, that was my experience.

Listening Setup 1: Kitchen/Dining Room System
-- a pair of B&W DM110i speakers
-- PecanPi Streamer & BOSC amps connected via a pair of XLR cables

I installed the BOSC amps into this system early one evening and just let it play for a few hours while I was off doing other things.  When I got up the next morning, my wife was already streaming our local public radio station from it via Roon as we do most every morning. To be honest, I totally forgot about the BOSC amps in this system. That is, until the radio program started playing music.  Here I am sipping my coffee, reading the news, and damn, the music just grabbed my attention!  It sounded so much better than anything I'd heard on this system before... and then I remembered that I had installed the BOSC amps the day before.  Well, good morning!  Breakfast reinvented.

I left the amps in this rig for a week and thoroughly enjoyed it throughout that time.  In this setup, there is no "sweet spot".  It is intended to be used as mood music during meals and boogie music while cooking in the kitchen.  These amps definitely took both of these intents up a significant notch.   It made me want to sit at the table as close to the sweet spot as possible.

In discussions with Leo, he mentioned that the amps might do even better with a very short run of speaker cable.  My XLR interconnects were long enough to allow me to do this, so I swapped out a pair of 8' speaker cables with 18" of 12-gauge stranded copper wire.  To be honest, I didn't hear much of a difference on the B&W speakers at the time, but then, the 8' speaker cables I had been using were nothing special either.

Next Up!  Listening Setup 2: The Big Rig System
-- Von Schweikert VR-35 speakers
-- PecanPi Streamer & BOSC amps connected via a pair of XLR cables

My "Big Rig" is a pair of Von Schweikert VR-35 speakers normally driven by a Devialet Expert Pro 440 running dual-mono (440 watts per channel into 6 ohms).   The Expert Pro is an amazing piece of tech integrating a state-of-the-art amp, preamp, phono pre, DAC and Roon endpoint all in one.  I love it.  My intent in trying the Orchard Audio gear here was not to compare them to the Devialet, but to see just how good the BOSC would sound with the VR-35 speakers.  The Devialet Expert Pro is in a different league power and price wise and not up for replacement.  By anything.

While I normally use a pair of JPS SC3 speaker cables with the VR-35 speakers, I initially hooked up the BOSC to them using the 18" 12-gauge wire.  When I turned on the system to listen, I was... disappointed.  The sound was a bit hard and edgy.  Definitely not as refined and relaxed as I was used to hearing from these speakers.  But I then remembered the many times I compared speaker cables in the past with occasionally similar results.  Out went the cheap 18" wires and back went the JPS SC3.  Wow, what an improvement.  Who says wire doesn't make a difference?!   Let the listening commence!

Just as with my B&W DM110i speakers, what I noticed first and foremost was transparency across the board and extraordinary detail and delicacy of the top-end.  Voices and instruments were presented in an oh-so engaging way.  The extended harmonics and fast transient response were startling from the start.   It was easy to just get lost in the music.  The soundstage was big, wide and deep with voices and instruments well defined within it.  Tiny details normally not noticed were there in abundance… fingers on strings, the shimmer of a cymbal, room ambience of the recording venue… life-like but never distracting from the music.   As good as it sounded, I did notice that the bass and lower register music was not quite as full and impactful as I was used to via the Devialet.   I’m tempted to say that music via the BOSC was leaner, but it never sounded lean.  Bass was tight and tuneful and integrated well within the overall sound presentation.   

Hey, in a prior life I worked sound for a couple cover bands and I learned that you can't really tell how good something sounds until you crank it up, right?   In truth, I was kind of expecting the sound to turn hard and edgy as I increased the gain.  On the contrary, these BOSC amps can bring it!  As volume went up, so did their ability to boogie.  To these ears, bass had more of a physical presence and the top-end continued to do what it does best.  Given their, size, weight and power, I can’t help but think these would also be great amps for a DJ.

Listening Setup 3: a different front end
-- Von Schweikert VR-35 speakers
-- Sonore microRendu (Roon endpoint) & Schiit Multibit Bifrost DAC
-- BOSC amps connected to Bifrost via RCA cables and RCA/XLR converters

In this case, I wanted to hear how well the BOSC amps would perform with a front end other than the PecanPi Streamer. I no longer own a traditional preamp, but do have something that replicates what the PecanPi Streamer does.  The Sonore microRendu is an ethernet-to-USB streamer and an excellent Roon endpoint.  The Schiit Bifrost is a very nice USB DAC.  The only thing missing was the volume control of the PecanPi but that was easily managed in software via Roon. Just to note: the combined price on the microRendu and Bifrost is several times that of the PecanPi.   

To these ears, I heard very little difference. The sound was as elegant and engaging as ever and sounded very similar to what I heard using the PecanPi Streamer which I think speaks volumes about just how good the PecanPi is.   I certainly can’t speak for all preamps, so if your intent is to use a different front-end and are concerned, touch base with Leo.  I have found him to be very easy to contact and converse with.  He's far more an expert engineer/designer than a salesman, and that is a sincere compliment!   

With any amps that strive to be as transparent and life-like as Leo’s BOSC amps, there is a risk that they can turn on you with poorly recorded music.  In my opinion, the BOSC amps most noticeable strength is their top-end transparency.  You hear everything the recording has to offer and it is incredibly mesmerizing with good recordings.  But beware of recordings of less merit. 

Bottom line: I thoroughly enjoyed my time with the BOSC amps and think they form an amazing combo with the PecanPi Streamer.  Their strength for me is that they were able to take what was a background music system at best to something far, far better.   I have no doubt that they will shine best when matched with a high-quality pair of speakers.   If you like your music open, honest, highly engaging with life-like detail readily conveyed, I think these are absolutely worth a listen. 


Offline rollo

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #1 on: August 28, 2019, 08:40:19 AM »
  Well written. Looks like Leo is bringing it on.


charles
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Online orchardaudio

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #2 on: August 28, 2019, 09:43:46 AM »
Thank you for taking the time to do this writeup.

Offline Guy 13

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #3 on: August 28, 2019, 04:08:08 PM »
Thanks.
Interesting write-up.

Guy 13
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Offline poseidonsvoice

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #4 on: August 31, 2019, 06:05:56 AM »
Morning fellas,

I hope mdconnelly doesn't mind if I tag along my own mini review of the BOSC Class D GaN amplifier monoblocks. I had the pleasure of listening to them a few days ago for several hours before shipping them off to the next person in the tour. For those of you who know me, I am extraordinarily picky about amplifiers, particularly with regards to measurement criteria. Prior to accepting these monoblocks I had a look at the measurements provided by Leo, because it isn't worth my time to review a product unless it actually has the 'potential' to make the grade. I am not saying that measurements are the end all be all, but I am saying that over the years I have been able to separate the wheat from the chaff so to speak. Given the flat THD versus frequency and extraordinarily low THD and IMD measurements it appeared worthy. My main 2ch amplifiers are designed by Tom Christiansen, the Modulus 286, all SMD designed, 4 layer boards and again, extraordinary measurements. They are my references.

Other gear in my system include:

  • Roon with everything upsampled to DSD 256
  • Auralic Aries G2 streamer
  • Matrix Audio X Sabre Pro (MQA) - output voltage of 4.5V RMS
  • Poseidon's Voice/Bent Audio TAP-X (fully differential silver autoformer based preamp)
  • Poseidon's Voice Moksha/GedLee NA12 loudspeakers (96dB efficient)
  • Behringer DCX 2496 w/AMB Kappa DCX modificiations for a quad set of subwoofers
  • The room is fully custom, fully treated, and of course the entire system has been measured and optimized using REW, etc....

The noise floor of the room is low. Using a NIOSH app on my iPhone XR, with C-weighting, it rests at about 28 dB. So yes, details are heard in galore.

System details: https://www.audiocircle.com/index.php?action=systems;system=1184

3 amps were used for the evaluation:

A DIY Sony VFET Class A design (15-30 watts/ch Class A, overall gain of 16dB) - on loan.
Modulus 286 (~60-100 watts/ch Class AB, overall gain of 20dB)
BOSC Class-D GaN monoblocks (150 watts Class D, overall gain of 16.8dB, this is the 8 ohm version)

Gain differences between the 3 amplifiers were completely accounted for by the 1dB volume settings on my TAPX. In addition, gain settings were accounted for the multiple sub configuration as well.

I would like to echo nearly everything said by mdconnelly. This is an extremely good amplifier, something I could live with easily if I didn't own the Modulus 286. The noise floor is very low, and you hear tiny details into the background on many recordings. The amplifier is very similar sounding to the Modulus 286 which is a major compliment! Big, bombastic dynamics, excellent tight very well delineated bass and yes, ethereal high end. Soundstaging was wide, and performers were well placed, such that you could easily distinguish the differences between them. At no time was power a problem, and this is really because my main speakers are very efficient, they loaf at 10-20 watts. I was listening at 80-100dB spl's without a hint of strain, and my listening position is about 12 feet away.

The major difference between Modulus 286 and BOSC Class-D GaN monoblocks are:

- BOSC is a bit more 'forward' sounding. This isn't a negative per se, and is quite system dependent.
- BOSC bass although well delineated was slightly less impactful than the Modulus 286. Interestingly enough, they both have very similar damping factors as well as measurements, so this may be all in my head.

Would I be able to tell the difference in a blinded situation? Probably not.

How about the PASS DIY Sony VFET? Sadly this amplifier fell in last place. Although very good sounding in its own right and actually, more detailed than many of Pass' DIY designs, there were major differences in bass detail, realism, imaging density and overall believability. Relative to the other 2 amplifiers, there was smearing and bleeding of images within the soundstage instead of fine delineations. You could easily walk away from the system with the Pass amps whereas with the Modulus 286 or BOSC amps you were fastidiously held in the listening seat. You could say that the Modulus 286 and BOSC designs gobsmack you immediately. They are that good. Mind you, that the finely delineated stages exhibited by the Modulus and BOSC amps are not at the expense of TONALITY. Tonality is quite neutral and very natural.

A few observations and nitpicks. I think it is important that audiophiles understand and particularly Leo understands the importance of good system integration here. Note that the input impedance of these BOSC amps are 5k ohms and 7k ohms for the 8 ohm and 4 ohm versions respectively. So no tube preamps or passive preamps with high output impedances need to apply. In addition, do take into account the overall closed loop gain of these amplifiers; they are somewhat on the low side of 14-17dB. They will most likely EASILY work in a system with fine DACs that have adequate voltage swings along with sensitive speakers. But if you have the 4 ohm version of the BOSC, along with Magnepans, guess what, you will most likely need a preamp with some gain, and low output impedance. In addition, for you vinyl enthusiasts, you will most definitely need a preamp and phono preamp of course. The final nitpick is that the amplifier has no power switch whatsoever. You just plug it into the wall, and you need to be careful about making sure your preamp or DAC is on first and that speaker cables are already connected to the amplifier prior to plugging it into the power outlet.

All that being said, the sonics of this amplifier are truly excellent to spectacular. I put the BOSC amps in the league of other greats like the Modulus 186, 286, 686 series, the Benchmark AHB2, Hypex NCore designs, etc...

Leo is a fine audio engineer and has definitely done his homework. Sonically, I have little to no concerns. From a reliability standpoint, and given how small the chassis is, I would like to see measurements on how hot the chassis gets with high powered situations as I was a little surprised with how heat can be dissipated even after taking into consideration how efficient Class D amps are. So some measurements at 8 ohms, 4 ohms , and/or an FTC 1974 torture test. 1/3rd of rated power for an hour, then five minutes at full power. That would be interesting to see. I understand that these amplifiers are designed for music systems and not sinewave generators, but reliability is just as important as sonics in my opinion.

Thank you Leo for lending your amplifier design. It was a sonic splendor and I feel that it is an even better effort than my PecanPi streamer! Best of luck to you in this new venture!

Best,
Anand.
« Last Edit: August 31, 2019, 07:32:09 AM by poseidonsvoice »
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Offline Guy 13

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #5 on: August 31, 2019, 07:49:56 AM »
Thanks.
Another good and informative write-up.
One question, would the BOSC give good results with
the new Schiit Asgard,
I would-will use my ASUS PC tower computer
to the Asgard and then to the BOSC
I don't need 100wpc, my speakers
are 95db efficient.

Guy 13
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Lot more stuff on storage
prior to moving back to Canada.

Offline mdconnelly

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #6 on: August 31, 2019, 07:55:41 AM »
Anand - great writeup.   It's great that you have the technical depth to properly review these awesome sounding amps.

Guy 13 - I had very good luck using my Schiit Multibit Bifrost with these amps.

Online orchardaudio

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #7 on: August 31, 2019, 11:05:32 AM »
Thanks.
Another good and informative write-up.
One question, would the BOSC give good results with
the new Schiit Asgard,
I would-will use my ASUS PC tower computer
to the Asgard and then to the BOSC
I don't need 100wpc, my speakers
are 95db efficient.

Guy 13

Based on the Asgard's spec of 0.2ohm output impedance it will have no issue with driving BOSC.

BOSC has best performance in the 10 to 25W range so it will pair well with the 95dB speakers. This is exactly what Anand had.

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #8 on: August 31, 2019, 11:12:08 AM »
Anand,

Thank you very much for your time. Wow you have a very well setup and quiet listening room.

Offline Folsom

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #9 on: August 31, 2019, 12:40:39 PM »
Great praises!

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Re: 2 weeks with the Orchard Audio BOSC HiFi Monoblock Class-D GaN Amps
« Reply #10 on: September 14, 2019, 05:08:14 AM »
Kickstarter launching next week. Check out the project video:
https://youtu.be/qo4ssUfE4rg.

Sign up for our mailing list to learn when Kickstarter project goes live:
www.orchardaudio.com/bosc