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Yesss thanks amigo
I've done several speaker projects and it's been super informative.
Thank you, @daniboun, you may have missed this....
- To ask and if you do not mind (further) clarifying, how would you suggest that this (graph) shows minimal load dependence, (possablely) its Linearity regardless of input frequency (0/20-45Khz) or power level? If you could further clarify that would be fabulous, thank you :=)
- What are your thoughts of the Crosstalk measurement?
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I'll try to answer you with an analogy, by sharing three results. Let's take the best Class D amplifier tested by Amir, then the Topping B100 (the most exemplary), and finally our FDA. I gridded the graphs to make them easier to understand.
This is what you could get from a SOTA amplifier, regardless of the frequencies, we have a linear response
And we can see that the harmonic distortion is almost linear from 1W up to 100W
Let's take nowone of the best Class D amplifiers tested and see what we get:
As Amir explains, below 1 kHz, the frequency dependence is minimal.
But above that, things start to get messy, and that's a bit of a common problem with Class D amplifiers.
If we now consider our FDA, its behavior is more linear, and quasi indepent of the frequencies.
We can see that the distortion is more pronounced at lower volumes, especially below 15 kHz
Roland68
Major Contributor
The noise is the sum of the Axign chip, the STA516BE, the feedback from/with the Axign (ADC), and all other components in the signal path (coils, etc.). Leaving aside the components in front of the Axign chip and the power supply.
If we now consider our FDA, its behavior is more linear, and quasi indepent of the frequencies.
We can see that the distortion is more pronounced at lower volumes, especially below 15 kHz
Thank you, @daniboun, a conundrum/dilemma with this graph. The A30a excels in the Bass region (<100/125hz), yet, the graph (-47db/1W, -55db/5W) does not suggest that it should, does it? Also, the amp is very quiet/silent, even when music is playing (between tracks, 92db Speakers/6.4R min)?
- Would you be able to provide an explanation for this, thank you :=)
The explanation is right there in the picture: “Rather high ultrasonic noise though. Wider bandwidth lowers SINAD”
This just means that the amps has significant amounts of ultrasonic noise.
Given this, we really don’t exactly know the distortion vs frequency behavior, because the noise drowns the distortion. One should then use a 22 or zo kHz filter and redo the measurement.
This just means that the amps has significant amounts of ultrasonic noise.
Given this, we really don’t exactly know the distortion vs frequency behavior, because the noise drowns the distortion. One should then use a 22 or zo kHz filter and redo the measurement.
Thank you, Yes, @voodooless, how relevant would you consider this Graph/Measure?
It's nice to see issues at higher power for certain frequencies.
In the end, it's silly to point to one graph as the most important because they all can show different issues with varying impacts. But if I really had to pick a single one, it would probably be the 5W multitone. It shows distortion, noise, and IMD all in one go, and with the right load, also load (in)dependence.
Thank you, Yes, @voodooless, the 5W multitone graph (no ASR VMV/A2 5W multitone graph) but perhaps if the Power/W v N/D only showed 20-20Khz (with a 22 or zo kHz filter and (perhaps) a couple more Freqs) then it also could be a pick/relevant, especially for most people, does that seem reasonable?
VMV A2 1/10/100W Multitone graphs, for consideration....
L7Audiolab - 4R1WMultitone ........................... L7Audiolab - 4R10WMultitone ........................ L7Audiolab - 4R100WMultitone
Perhaps this should also be considered....
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Normally you shouldn't even worry about it with well done Class amps.
Class D amps are susceptible to high level of ultrasonic switching noise at very high frequencies (above 20 Khz). Ultrasonic sound is the part of the sound wave spectrum that ranges from 20 KHz to 10 MHz
Theoretically, humans are not affected...
It isn't. You are looking at a graph that shows the results of ultrasonic noise - you don't need to worry about ultrasonic noise - you can't hear it.
Why?
Thank you, @daniboun, appreciated :=)
- Thank you, Yes, an optimized PFFB (and Spread-spectrum modulation, if utilised), despite the Filter components and/or Capacitive Load and/or EMI/SWF/Ultrasonics, can minimize these effects. Note, the above line is removed (to avoid confusion) :=)
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Thank you, Yes, @antcollinet, the Multitone graphs confirm this, is that correct, although the 45Khz BW can be misleading, especially as you mention, the ultrasonic noise is not audable and no need to worry about it (not important). As @voodooless has mentioned, for the Power/W v THD+N/db graph (20-20Khz), a 22 or zo kHz filter should be utilised, sound reasonable :=)
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1- what have any of those got to do with high levels of ultrasonic noise causing the problem.
2 - Where is your evidence for these phenomena? I've never seen any tests which suggest these things are an issue - have you extracted that text out of an AI?
This a capacitive load not ultrasonic noise. As you have mentioned, both are very different. Although, my thoughts were focused on capacitive load and the way that ultrasonics might/would combine with a capacitive load. Apologys for any confusion, I did not take notice of the references that I was reading but I will try to (again) find them :=)
Tryed but I cannot find that reference again (probably too old, anyway), so I shall remove it from the original post. PFFB renders the comment/s unnecessary, anyway :=)
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GiBo61
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It's curious that now that they've discontinued production of the Sabaj A30a amplifier, so many posts are being published in this thread. I was almost thinking of buying a second one from a seller who still has a few in stock (Amazon?), but honestly, I find it difficult to justify the purchase.
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