Orchard Audio BOSC Mono block Class D Amplifiers

Cassettes excellent? Dolby-less hiss was terribly intrusive although bearable with properly calibrated Dolby B. I admit the hf response limitations weren't an issue, but there was always a loss when recording CD's for the car back before cheaper in-car CD players came along. Metal tape took more energy to get the signal on the tape and a lot more playings to remove it but ferric tape was awful after just a few playings. I could never go back to that medium now. As for vinyl, I have a lot of LP's and 12" singles I'd like to play again regularly one day.

No need to be sorry Dave, it's usually me arguing, when others are saying something is overpriced.  Don't bring in NVA as an example, as Brookie said "he's taking the piss".  I just looked at these amps expecting the price to no more than £500 for the pair. I'll happily wait for Oli's review, although I'd like to try em against my A60, or even my brother's monos.

That's Antonio there. I have home-made NVA based power amps here and the larger one, based on the AP70 integrated, does seem very good and more 'straight laced' sounding than the colourful and charming character smaller models I was making, up until RD passed away.

Lord, I wish I wasn't so bloody far away from the 'action' these days. 'Up North' has had a keen do-it-yourself presence in audio for decades now and people seem able to travel hundreds of miles up and down very busy roads and railways to attend bake-offs which I just can't do (waily waily). That's why I spend so much time on bloomin' forums - cough.....

Orchard Audio – BOSC Class D Monoblock Amplifiers PART 1

The BOSC is the brain child of Leo, who has been developing his OA brand for the last couple of years. The amps are all analogue and have a total output of 150w.

Diminutive in size, barely bigger then a CD Jewel case on the face and maybe 2 inches deep, they are designed to be on short speaker cables and hidden behind your speaker, an antidote to ego stroking big brand mentality.

The amps were left running and in place for 48hrs prior to any critical listening.

The system consisted of a DCB1 preamp, Pioneer CS-77A Speakers, Allo Boss & RPI streaming via JRiver and Spotfire Cables throughout, which although isn’t the ideal setup, is the only setup I had available to use. Real world situations exist here so I felt it served a purpose.

I started the listening with a few well know (to me) tracks and although I felt the amps were incredibly clear, I wasn’t feeling particularly “connected” to the songs. I tried a few tracks and I just wasn’t getting into the songs in the same way as usual. I decided to try a meatier set of cables, so I dug out my Spotfire “Emeralds” from the garage and plumbed them in. The Emeralds have a chunkier sound, so it was a good start that the BOSC demonstrated what I knew to be true already.

I put a few tracks on and straight away I felt a bit more involved but still felt like a bit of something was missing. I contacted Leo and explained that, and he said if I was to use shorter speaker cables, all would be well. I hadn’t got anything sufficient at this time, so I thought I’d just listen and get something sorted out later.

I put on Dave Brubecks “Take 5” and sure enough, the bit that was missing was some “slam”
The kick drum that forms the start of the song didn’t quite hit me in the chest in the way I have become accustomed to. However, before I knew it, I had just finished the whole album and hadn’t noticed the last hour or so had passed.

Hmm, I thought in a puzzled way.

Donavon was next. Universal solder to be precise. Donavon’s vocals soared out of the speakers in a way I haven’t experienced before. They were so clean and clear that I was genuinely taken aback. I sat here listening to the songs, one after another and again, the last song of the album came on and yes, I’d listened to every track intently, but the time had flown. I thought I had better write a few things down and decided to start with the gob iron (harmonica)

The gob iron and Donovans vocals were absolutely crystal clear. I will say this now……….OPEN WINDOW

I haven’t had an amplifier here that gets you as deep into to the recording as the BOSC. Stunningly transparent and neutral. I was hearing the tape “warble” on the second guitar track. I was hearing fret buzz, contrasting harmonics from the strings on the guitar, the plectrum land on the strings, you name it, if the mic picked it up, I was getting it here. Revelatory.
I played a plethora of acoustic guitar tracks and every one of them drew me in and captivated me.

I needed to change genre and did so.

Madness – Greatest hits.

House of fun started up and yes, superb clarity and transparency but the lower registers were slightly recessed, and I wasn't really “feeling” the bass line. Don’t get me wrong, the detail from the bass is there but its not punching my chest. I am a huge believer that the bass line underpins everything else, so if that’s not right, we ain’t gonna get on!

I must try something loud.

On went Metallica – The God that failed.

Unfortunately, in this instance it was the amp that failed, failed to give me sufficient levels of chest vibrations.

Again, I am hearing details and layers of this track that I have NEVER heard before but IMO its missing the weight I know this track gives and more importantly, I am not wanting to smash the house up and scream the lyrics at my neighbours wall. This is a problem.

I decide to do a bit more experimentation and play a few tracks via vinyl. For almost everything, the bass issue isn’t and issue via vinyl and again, I have spent at least 2 hours just letting albums run through and enjoyed every second of them.

I decide to see whether the amps would sound as good via Volumio. As suspected and in accordance with my experience, Volumio “fattens” the sound somewhat and this is very apparent here.
I played “Talk Tonight” by Oasis and by god, the hairs stood up on end, but it lost some nuances, micro detail and a bit of the imaging, likely caused by the lack of up-sampling without JRiver. I was streaming at 32/96 and now we’re at 16bit. Once again, the whole Oasis back catalogue is at risk of being auditioned and I must get up and walk away for a few minutes to get my brain around what I have heard.

SO, what do I think?..........

The BOSC are phenomenal imagers. I played some classical music via vinyl and sat here feeling like I was at a Royal tea party. It was all very polite and dignified. An air of prim and proper about it. Delightful, but not dramatic, Safe not stirring.

I played some acoustic guitar tracks and I heard deep into the recording. I was absorbed and engrossed. I played some metal and whilst being dazzled by the amount of detail and new things I hadn’t heard before, I didn’t feel very metal at all. No head banging, not screaming at the neighbors and the family were all relatively unperturbed by my behavior.

Truth is, I loved most of my music via the BOSC but it seemed to me that the experience varied, alum by album. On the good stuff, they were phenomenal. Bass was tight and dynamic, and the clarity was unbelievable at times. However, on other stuff, it was like the bottom end had been rolled off and the emphasis was on the HF. I’d like to say that it was poor mixing or something but I have material here that is deliberately mixed to have a hump in the mids and it sounded “normal”.

29 Palms – Robert Plant being one of them. I have this track for this exact reason and yet through the BOSC, it sounded normal....balanced.

The Beatles 50th anniversary Sgt. Pepper always sounds a little bass heavy here, regardless of amplifier and again, it just didn’t.
So there are a couple of reasons why this could be….

1) The BOSC need shorter speaker cables as advised or

2) The BOSC are a little lean.

Tomorrow I will investigate further.

To be Continued.

No they don't Dave.

I'm still sitting here listening and the more I do, the more convinced I am becoming that they are completely transparent, tonally.

Things will get interesting when the Neurochrome turns up. My moneys on it being closer to the Orchard Audi’s, but with a bit more bottom end.

From a technical point of view they are. Whether that is audible, or is even a good thing, are different questions

I rather think we've gone beyond that stage now, but there are definitely some popular amp makes that have added character that owners find difficult to live without.

It's only taken a few years but you and I are agreeing Dave lol

Definitely feeling like Krell, Mcintosh and the like managed to do this.

Bruno Putzeys suggested he could make his amps sound like any other brand, but he didn't want that. He wanted the straight wire with gain that I have here with Leo's stuff.

This is most likely what Oli is describing as the damping factor of this amp is very high > 600.

If this is the case putting the amp on even shorter wires would only make this effect more apparent.

Impedance matching is something I have thought about. I will try and get up to yours for a couple of hours.

I'll PM you when I've had a chat with the gaffer about plans.

Hes right, beyond a certain ratio all the damping factor in the world doesnt add anything more. Same with headphone amps and output impedance related frequency shifts, once youre under half an ohm it makes no difference if its 0.1 ohm or 0.0001

If the damping factor is 600 changing the length of the cables to the speakers shouldn't make any difference, at least not if they're unconditionally stable...