• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

BOSC - HiFi Monoblock Class-D Amp

orchardaudio

Active Member
Joined
Aug 24, 2018
Messages
241
Likes
245
Location
Succasunna, NJ
#21
Some updated BOSC performance plots for 8 ohm load, these will most likely be the same as the final measurements. I really like the way that BOSC sounds right now and don't plan to make any more tweaks to the production version.

SNR (A-Weighted)
Signal to Noise Ratio 8 ohm (A-Weighted).JPG


SNR (No Weighting)
Signal to Noise Ratio 8 ohm (No Weighting).JPG


THD Ratio vs Measured Level
THD Ratio vs Measured Level 8 ohm.JPG


THD+N vs Frequency @ 10W
THD+N Ratio vs Frequency 8 ohm (10W).JPG


THD+N vs Frequency @ 1W
THD+N Ratio vs Frequency 8 ohm (1W).JPG


64k FFT @ 10W Output
FFT @ 10W Output 8 ohm.jpg


Frequency Response
Frequency Response 8 ohm.JPG


IMD vs Measured Level
SMPTE Ratio vs Measured Level 8 ohm.jpg
 
Last edited:

DonH56

Major Contributor
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
2,927
Likes
3,391
Location
Monument, CO
#22
Can you run a wideband FFT to show out-of-band spurs? I expect them to be very small, just curious.
 

orchardaudio

Active Member
Joined
Aug 24, 2018
Messages
241
Likes
245
Location
Succasunna, NJ
#23
Can you run a wideband FFT to show out-of-band spurs? I expect them to be very small, just curious.
64k Wideband FFT 1kHz at 10W
FFT @ 10W Output 8 ohm (wideband).jpg
 

DonH56

Major Contributor
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
2,927
Likes
3,391
Location
Monument, CO
#24
Thank you! Very clean!
 

orchardaudio

Active Member
Joined
Aug 24, 2018
Messages
241
Likes
245
Location
Succasunna, NJ
#25
An awesome review for the BOSC amp:

"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."

"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."


Read the full review here:
https://theaudiobeatnik.com/reviewin...sc-monoblocks/
 

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
2,255
Likes
3,479
Location
Gold Coast, Queensland, Australia
#29
Instead of picking a best case (or near to best case) THD at some random power output (7W) and single frequency for your headline figure, how about specifying THD properly and in line with FTC standards?

The standard is: THD less than X% for any power from 250mW to Rated Power over the bandwidth (min) of 20Hz-20Khz.

1565991026274.png


Example:

1565991102883.png


The customer then knows the worst case advertised THD over the power output and frequency range instead of a cherry-picked best case number.
 
Last edited:
Joined
Aug 24, 2018
Messages
241
Likes
245
Location
Succasunna, NJ
#30
Instead of picking a best case (or near to best case) THD at some random power output (7W) and single frequency for your headline figure, how about specifying THD properly and in line with FTC standards?
Is this better for you?
1566145592922.png


It has been updated on the website.
 

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
2,255
Likes
3,479
Location
Gold Coast, Queensland, Australia
#31
Is this better for you?
Marginally. The specification at 75W is still only half rated (150W) power.

The FTC mandated Amplifier Rule is crystal clear and has been for nearly 45 years. Any amplifier over 2W output power must state any power output claims in accordance with the Rule conditions to be sold in the US.
1566165266049.png


And the test period is 5 minutes minimum after preconditioning.
1566165685165.png


The headline specification advertised is the worst case THD from 250mW to full rated power across the frequency range specified. It cannot be best case or cherry picked numbers.

https://www.ecfr.gov/cgi-bin/retrie...ty=HTML&h=L&r=PART&n=pt16.1.432#se16.1.432_13
 
Joined
Aug 24, 2018
Messages
241
Likes
245
Location
Succasunna, NJ
#32
What that standard is asking, is not a real word scenario.

First of all there is no such thing as running an amplifier at 150W for 5 minutes when playing audio.

It is also extremely unlikely that a person would play anything through any amp that would even peak at 150W, as your ears would not be able to handle that.

A very realistic scenario is audio that peaks in the 10 to 25W range. This is where BOSC will have the best performance.

If all amplifiers are specified based only on that standard it would actually not tell consumers how the amplifier performs at levels that they will be using it.
 

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
2,255
Likes
3,479
Location
Gold Coast, Queensland, Australia
#33
What that standard is asking, is not a real word scenario.

First of all there is no such thing as running an amplifier at 150W for 5 minutes when playing audio.

It is also extremely unlikely that a person would play anything through any amp that would even peak at 150W, as your ears would not be able to handle that.

A very realistic scenario is audio that peaks in the 10 to 25W range. This is where BOSC will have the best performance.

If all amplifiers are specified based only on that standard it would actually not tell consumers how the amplifier performs at levels that they will be using it.
It doesn't matter whether you like, or agree with, the established standard. Lobby the FTC to change the rule if you think it is flawed in any way. Otherwise, advertise your products in accordance with the various ratings requirements if you are selling those products into markets where such adherence is mandatory (pretty much all countries AFAIK). It's very straightforward, and hundreds of respected manufacturers have been doing so for 45+ years.

Manufacturers have tried in the past to water down the amplifier rule and apart from some very minor concessions, the FTC has left the standard as it is. There is good reason for that- it keeps manufacturers honest and ensures customers get what they paid for.

It seems you want the perceived legitimacy of using an industry standards based AP analyzer, but aren't prepared to specify the amplifier according to the industry standard required for advertsing power and THD. Can you see the irony?
 

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
2,255
Likes
3,479
Location
Gold Coast, Queensland, Australia
#34
And here's an example of how to specify power the correct way. This may help you avoid making mistakes going forward.

1566181701561.png


Notice the main specifications are bold and in clearly larger print.

The other specifications cover THD at lower levels (which happen to be less than half the headline number) and the burst/short term powers etc.
 
Joined
Mar 1, 2018
Messages
2,255
Likes
3,479
Location
Gold Coast, Queensland, Australia
#39
Thanks Orchard audio. See, it's not that hard to finally come clean.

The compliant specification would therefore be:

With 8 ohm loads, from 20-20,000Hz, 150 Watts minimum RMS with no more than 0.015% THD from 250mW to rated output.
 
Top Bottom