Hi fellas,
Wanted to update this thread with some measurements of my Alpha Nirvana in my NPXP chassis. Recall that my Alpha Nirvana version has +/-24V rails, gain of ~20dB and about 1.3A bias. I recently purchased a Quantasylum QA403 and I am loving it! You can compare my measurements with those published on page 13 but do note that my vertical scale is in dbV and not dbFs. I do not know of an accurate method of converting the two but keep that in mind they are not equivalent. Moreover, my build uses dual SLB’s and I see that I only used 10mF capacitors in the supply not 15mF! In any case, I’m disassembling my NPXP to put a new module in and will be adding a 32,800uF cap bank per channel.
Unweighted noise
My 60Hz is at -107 to -108 dbV which is about 4 microvolts RMS. That’s pretty much inaudible (my speakers are 95dB sensitive for reference). Also note that this is on a bandwidth of 20Hz to 20khz. If I had hauled out my bench meter that has a 100khz bandwidth, the number would be roughly 5 times worse. That being said, 20 microvolts RMS (@60Hz) is still quite low. The goal for any amplifier design is to be comfortably less than 1mV (1000uV) RMS overall and this one obviously is.
A-weighted:
Of course when you add an A-weighting filter as most manufacturers would, everything looks even better. The belief is that this correlates most with how the human ear perceives relative ‘loudness’ of these frequencies. Depending on your age, due to presbyacusis, your own weighted filter might be more at 4khz on up. Some manufacturers will list CCIR weighted curve which is different and said to be a bit more accurate rendition of what the human ear perceives with regards to ‘random noise.’
1 watt/1khz/8 ohms:
2 watts:
5 watts:
10 watts:
20 watts:
Clipping/30 watts/1% distortion:
That’s all folks. Those of you on the fence should just build this amplifier. It’s a single ended Class A design that‘s very, very polished and a gift to diy’ers. I hope that one day Hugh will share the fruits of his knowledge with a complementary/push pull design but the fella is still pushing it at his age and needs to make a living!
Best,
Anand.
Wanted to update this thread with some measurements of my Alpha Nirvana in my NPXP chassis. Recall that my Alpha Nirvana version has +/-24V rails, gain of ~20dB and about 1.3A bias. I recently purchased a Quantasylum QA403 and I am loving it! You can compare my measurements with those published on page 13 but do note that my vertical scale is in dbV and not dbFs. I do not know of an accurate method of converting the two but keep that in mind they are not equivalent. Moreover, my build uses dual SLB’s and I see that I only used 10mF capacitors in the supply not 15mF! In any case, I’m disassembling my NPXP to put a new module in and will be adding a 32,800uF cap bank per channel.
Unweighted noise
My 60Hz is at -107 to -108 dbV which is about 4 microvolts RMS. That’s pretty much inaudible (my speakers are 95dB sensitive for reference). Also note that this is on a bandwidth of 20Hz to 20khz. If I had hauled out my bench meter that has a 100khz bandwidth, the number would be roughly 5 times worse. That being said, 20 microvolts RMS (@60Hz) is still quite low. The goal for any amplifier design is to be comfortably less than 1mV (1000uV) RMS overall and this one obviously is.
A-weighted:
Of course when you add an A-weighting filter as most manufacturers would, everything looks even better. The belief is that this correlates most with how the human ear perceives relative ‘loudness’ of these frequencies. Depending on your age, due to presbyacusis, your own weighted filter might be more at 4khz on up. Some manufacturers will list CCIR weighted curve which is different and said to be a bit more accurate rendition of what the human ear perceives with regards to ‘random noise.’
1 watt/1khz/8 ohms:
2 watts:
5 watts:
10 watts:
20 watts:
Clipping/30 watts/1% distortion:
That’s all folks. Those of you on the fence should just build this amplifier. It’s a single ended Class A design that‘s very, very polished and a gift to diy’ers. I hope that one day Hugh will share the fruits of his knowledge with a complementary/push pull design but the fella is still pushing it at his age and needs to make a living!
Best,
Anand.
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