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Here2Learn

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Anyway, the BOSC name will be changing to Starkrimson (another pear variety). This is because of a trademark issue with Bosch Gmbh.

I believe the amp case uses a top plate? If so, it may be beneficial from a customer support perspective to notify the owner's of amps already shipped and offer a new top plate with "Starkrimson" at cost (inc shipping, P&P, taxes). The reasoning behind this is that people receiving a version with BOSC on it, may feel they will end up with an amplifier that is no longer mentioned online a few months from now and therefore loses resale value if they want to sell it in the future.

Maybe an easier way is have the "Starkrimson" product page always mention that early but identical production units were called BOSC and this was changed due to a trademark dispute with Bosch Gmbh, but there is no technical difference whatsoever.

Or do both.
 
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orchardaudio

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I believe the amp case uses a top plate? If so, it may be beneficial from a customer support perspective to notify the owner's of amps already shipped and offer a new top plate with "Starkrimson" at cost (inc shipping, P&P, taxes). The reasoning behind this is that people receiving a version with BOSC on it, may feel they will end up with an amplifier that is no longer mentioned online a few months from now and therefore loses resale value if they want to sell it in the future.

Maybe an easier way is have the "Starkrimson" product page always mention that early but identical production units were called BOSC and this was changed due to a trademark dispute with Bosch Gmbh, but there is no technical difference whatsoever.

Or do both.

Thank you I will take this into consideration, it all depends on what I am allowed to do per the final agreement with Bosch.
 

restorer-john

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Thank you I will take this into consideration, it all depends on what I am allowed to do per the final agreement with Bosch.

The world is indeed a strange place when a company like Bosch makes it difficult for you to name a product after a botantist who cultivated and had pears named after him over 200 years ago. The name predated Robert Bosch himself by six decades.

I would have told them exactly where to go.
 
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Matias

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@orchardaudio could you please post THD+N versus power for 1kHz in 4 ohms, and also the power where it reaches 1% with 1kHz into 4 ohms?
Thanks.
 
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@orchardaudio could you please post THD+N versus power for 1kHz in 4 ohms, and also the power where it reaches 1% with 1kHz into 4 ohms?
Thanks.

It will never get to 1% distortion with the provided power supply. This is because the power supply will shut down due to overcurrent before that happens.

I will post the other info later.
 
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orchardaudio

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"At 1 W into an 8 Ω load, the BOSC’s distortion is below the Audio Precision analyzer’s measurement capabilities."

I did a loopback test on my APX525. Clearly, at some voltages, it has better performance than at others. You can clearly see the spikes in distortion when the automatic gain control kicks in.

As an example when an amplifier is outputting 11Vrms (~15W in 8ohm or ~30W into 4 ohm), the THD+N the analyzer can measure will not be any better -105dB (0.00056%).

THD+N Ratio_Loop_Back.jpg
 

SIY

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I did a loopback test on my APX525. Clearly, at some voltages, it has better performance than at others. You can clearly see the spikes in distortion when the automatic gain control kicks in.

As an example when an amplifier is outputting 11Vrms (~15W in 8ohm or ~30W into 4 ohm), the THD+N the analyzer can measure will not be any better -105dB (0.00056%).

My current workaround, which I’ll use on the next thing you send me, is a super low distortion external oscillator (Vicnic) and a twin T filter. That gets me down to the ppm level.
 
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orchardaudio

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Starkrismson is now the new name of BOSC. Also, I am very happy to report that I have changed the input impedance of the amplifiers to 44k, without any degradation to performance.

THD Ratio vs Power into an 8-ohm load @ 1kHz
THD Ratio vs Measured Level 8-ohm.jpg

Multitone:
FFT Spectrum.JPG

Wideband FFT of with -60dB input:
Wideband FFT Spectrum -60dB Output.jpg

THD+N Ratio vs Frequency @ 10W:
THD+N Ratio @ 10W.JPG
 

Lord Victor

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The power of the bose is still too small. Hope to release 8/4/2Ω GaN Class-D with 400/800/1600W respectively
I have to agree - the 150 watt has me a bit apprehensive about buying a pair, compared to the competition; purifi already seemed a little low to me, since its on the low side for some of my inefficient speakers - not to mention I just generally prefer some 'headroom' on principle.
 
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orchardaudio

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I have to agree - the 150 watt has me a bit apprehensive about buying a pair, compared to the competition; purifi already seemed a little low to me, since its on the low side for some of my inefficient speakers - not to mention I just generally prefer some 'headroom' on principle.

Just to make sure you know it is 150Wrms so that is 300Wpeak.

Also I have 2 week return policy.
 

Lord Victor

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Just to make sure you know it is 150Wrms so that is 300Wpeak.

Also I have 2 week return policy.
I get that, I suppose I may just have been enamoured by the performance of a 400/800 RMS @ 8/4 Ohm circuit from Pascal which has been beating all the competition so far.
I appreciate the return policy, though being based in Europe does make that tricky - especially if I were to make a DIY version using the boards (I prefer having the PSU and the board in a more substantial case - just personal taste).

A question for you by the way, what is the slew rate of these amps? I've seen some mention that this should be one of the benefits of GaN FET?

I'm looking for a reference system for developing speakers, as well as listening, and I've been comparing a lot of Class D circuits lately; Klank, Hypex nCore, Purifi, Pascal L-Pro2, ICE etc. and whilst all of them to varying degrees beat the class A/AB amps I had on hand, some of the ones highly recommended like the Purifi, though a natural progression of the nCore in sound, disappointed me due to having a comparatively slow/muddled sound, which I found surprising - the Pascal being leagues ahead. So when I came across the GaN FET, proclaimed as the future of class D, I got very curious how it would compare.
 
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orchardaudio

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I get that, I suppose I may just have been enamoured by the performance of a 400/800 RMS @ 8/4 Ohm circuit from Pascal which has been beating all the competition so far.
I appreciate the return policy, though being based in Europe does make that tricky - especially if I were to make a DIY version using the boards (I prefer having the PSU and the board in a more substantial case - just personal taste).

A question for you by the way, what is the slew rate of these amps? I've seen some mention that this should be one of the benefits of GaN FET?

I'm looking for a reference system for developing speakers, as well as listening, and I've been comparing a lot of Class D circuits lately; Klank, Hypex nCore, Purifi, Pascal L-Pro2, ICE etc. and whilst all of them to varying degrees beat the class A/AB amps I had on hand, some of the ones highly recommended like the Purifi, though a natural progression of the nCore in sound, disappointed me due to having a comparatively slow/muddled sound, which I found surprising - the Pascal being leagues ahead. So when I came across the GaN FET, proclaimed as the future of class D, I got very curious how it would compare.

Per my calculation 73.51V / 3.7uSec = 19.86V/uSec or 2.5A/uSec or 2500A/mSec (8ohm load). This is with the audio analyzer bandwidth limiting to 1.2MHz, in reality, it will be faster. Where I am located right now I don’t have the equipment to measure with higher bandwidth. This is at the amplifier output. The switch nodes will have much faster slew rates, this is where GaN excels as you say.
Acquired Waveform.jpg

By the way did you see this?
https://audioxpress.com/article/fre...d-audio-bosc-and-purifi-audio-eigentakt-eval1
 

Lord Victor

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Thank you - was rather curious about that...

Any particular power supply you would recommend for EU users for the DIY board, to get the maximum performance @orchardaudio ? Is there anything better than what you offer with them as stock on the market?
I know so many people go on about linear vs. switching supplies etc.
I might just have to give these a try, sooner or later...
 
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orchardaudio

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Thank you - was rather curious about that...

Any particular power supply you would recommend for EU users for the DIY board, to get the maximum performance @orchardaudio ? Is there anything better than what you offer with them as stock on the market?
I know so many people go on about linear vs. switching supplies etc.
I might just have to give these a try, sooner or later...

You can use one of these
CUI / SDI250-56 - this is power supply that comes with my mono amps
Murata / PQC250-54 - this is power supply inside my integrated amp

The amp tests identical with both of those supplies. You can use any power supply between 45.6V and 58.8V. Stay in the 250 to 300W range.
With 48V you get 100W clean into 8ohm.
With 54V you get 150W clean into 8ohm.
 
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