[HAL]

The Orchard Audio BOSC amps have arrived to demo with The Monoliths speaker system.  These will be the BG NEO10 driver amp in the system for trials.
 
Made a custom set of 2' speaker cables for direct connection to the driver terminals.

Balanced inputs on the amps, so easy connection to the dspMusik 2x8 digital crossover. 

A slight change in Parasound A23 tweeter amp levels to match the BOSC amp gain.  Very simple change to the crossover.

[poseidonsvoice]

Hope you enjoy them!

Best,
Anand.

[HAL]

Anand,
Will give the BOSC amps a good try.

Got them installed and ready for dspMusik crossover adjustment.

[orchardaudio]

Looking forward to your findings.

[HAL]

The BOSC amps are up and running in The Monoliths system.  They are powering the BG NEO10 mids, so a very sensitive frequency range of 200Hz to 2.6KHz. 

Checked DC offset since both the BOSC amps and dspMusik 2x8 are DC coupled.  Highest channel DC offset was 24mVDC, very similar to other amps here.  Very good for fully DC coupled!

First listening with everything from start is that they are very good.  The rest of system will be coming up to temperature and more listening once it is stabilized.  Class A/B amps take awhile here as usual. 

More as listening continues.

[Tyson]

Love that the amp just fits right behind the drivers.  That's about as short a path for speaker wire that's possible.

[poseidonsvoice]

HAL,

I don’t know which amps you may be referencing to in your previous post but the BOSC design is not class AB. They are Class D.

And I found they needed little to no “warm up” time.

It’s too bad you don’t have a pair for your tweeters. The BOSC amps do very well in that region as well and probably better than your Parasound units to be honest.

Best,
Anand.

[orchardaudio]

It’s too bad you don’t have a pair for your tweeters. The BOSC amps do very well in that region as well and probably better than your Parasound units to be honest.

He can do both, on one speaker and try it mono.

[HAL]

The system normally has a pair of Parasound A23 stereo amps vertically biamping the mids and tweeters.  I have replaced the mid channels with the BOSC amps.  The A23's are Class A/B, I understand the BOSC are Class D.  The A23's need warm-up time.

There is a difference of 12.2dB of voltage gain between the A23's and BOSC amps.  That has been corrected for in this version of The Monoliths crossover by attenuating the tweeters and subs and running the BOSC's through the same exact crossover as the A23's.  This is the best way to compare in this setup.

Back to listening.

[HAL]

From the first listening, the BOSC amps are much quieter than the A23's.   Background noise level is below hearing from the mids where before there was a background noise level.  The BG NEO10 is 92dB/1w/m sensitivity, so most amps have a residual noise level.  Not with these.

The lower gain of the amps helps to use more of the DAC's output voltage range compared to the higher gain amps.   Gives better overall SNR for the system.

Nothing stands out as wrong.  Everything is clean and distinct without being analytical.  Very nice with big orchestral pieces or complex rock music.  Acoustic instruments sound very realistic.  There is an immediacy that having direct connection with very short speaker cables makes possible.  Transient edges have excellent attack and nice decay. 

Very happy with the amps in the system so far and lots of listening to do.

[maty]

Nothing stands out as wrong.  Everything is clean and distinct without being analytical.  Very nice with big orchestral pieces or complex rock music.  Acoustic instruments sound very realistic.  There is an immediacy that having direct connection with very short speaker cables makes possible. Transient edges have excellent attack and nice decay.

Why?

https://www.diyaudio.com/forums/vendor-s-bazaar/340236-bosc-hifi-monoblock-class-gan-amp-post5924997.html

Acoustic instruments -> without phase shift at audio band like good/very good class A and class AB amps. Bruno Putzeys' recent explanation did not convince me.



BTW, PURIFI 1ET400A has 1º at 20 kHz. Hypex NC400 about 14º 16º. IcePower 1200AS2... "a ton".


Complex music -> without harmonics at -90 dB. H2 predominant like acoustic instruments.



BTW, PURIFI 1ET400A is H3 dominant, with only -130 dB.


It is clear to me that not only superb measurements have been sought, musicality has also been taken into account in the BOSC design.

[orchardaudio]

Background noise level is below hearing from the mids where before there was a background noise level.  The BG NEO10 is 92dB/1w/m sensitivity, so most amps have a residual noise level.  Not with these.

The residual noise of the amp itself is only 32uV, then whatever noise your DAC makes will be added to the 32uV multiplied by the Amp's gain. Since the gain of the amp is low relative to others the overall output noise will also be very low and should be completely inaudible.

[poseidonsvoice]

The residual noise of the amp itself is only 32uV, then whatever noise your DAC makes will be added to the 32uV multiplied by the Amp's gain. Since the gain of the amp is low relative to others the overall output noise will also be very low and should be completely inaudible.

Yup!

Best,
Anand.

[Tomy2Tone]

Anand-

How do these amps with the GaN compare to other class d amps you’ve had in your system.

[poseidonsvoice]

Tomy,

When only comparing Class D amps, i.e. NCORE NC400, NC1200, and ICE EDGE AS1200, the differences I hear are:

NC400: The NC400 has a bit more of an upper midrange “bite”
NC1200: Similar to NC400, a tad quieter sounding
ICE EDGE AS1200: Not as “gobsmacking” and the bass is not as well delineated

I believe for the Kickstarter price that Leo is selling the BOSC amps for and if you need that kind of power and want an amp that runs cool, the BOSC is a good deal. You just have to make sure it is compatible with your system from an electrical standpoint, ie input impedance, overall gain, and output power. This is also a “set it and forget it amplifier”...there is no power switch and you also should not turn off your preamp. Leo did this to save some costs which is understandable.

Best,
Anand.

[HAL]

Second listening session was Jazz and Orchestral with Miles Davis Kind Of Blue and Pomps & Pipes on Reference Recordings.  Dynamics are excellent and mids are clean and musical with the BOSC amps.  Hard to beat that absolutely black background with just recorded room ambience sounds. 

From this listening so far, looks like I will put in for 2 pairs of BOSC Monoblocks for the system in the kickstarter campaign.  These deserve a full up system to test.

[poseidonsvoice]

Second listening session was Jazz and Orchestral with Miles Davis Kind Of Blue and Pomps & Pipes on Reference Recordings.  Dynamics are excellent and mids are clean and musical with the BOSC amps.  Hard to beat that absolutely black background with just recorded room ambience sounds. 

From this listening so far, looks like I will put in for 2 pairs of BOSC Monoblocks for the system in the kickstarter campaign.  These deserve a full up system to test.

Nice to know you like them HAL!

Best,
Anand.

[Tomy2Tone]

The residual noise of the amp itself is only 32uV, then whatever noise your DAC makes will be added to the 32uV multiplied by the Amp's gain. Since the gain of the amp is low relative to others the overall output noise will also be very low and should be completely inaudible.

Hi there, do you have plans coming for a stereo version of the BOSC amp?

[orchardaudio]

That would defeat the purpose of what these amps are trying to achieve.

For the next product I am planning USB DAC based on PecanPi.

[HAL]

Last day with the BOSC amps in the system.

Friends coming over for a listening session before the ceremonial reboxing and shipment back to Orchard Audio.