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Old 8th November 2005, 05:35 PM   #11
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Why all this attention to THD? The numbers are nice though!

But what about IMD? Way more important in relation to perceived sound quality.
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Old 8th November 2005, 05:53 PM   #12
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I have even lower THD on the loudspeaker, then on the 4om resistor, at least in highs.

PS: Reducing THD by the huge loop gain, IMO, is not so much intelligent approach. I have said "STOP" to myself, when could not provide flat THD/Freq more, it's occured at 50db loop gain and no more then 500-550KHz idle switching, because i still prefer cold amp. But if i could develop the discrete amp with 30db loop gain and .005% THD at 10W etc, i would be really proud.
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Old 9th November 2005, 03:15 PM   #13
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How do you measure THD and do you include noise? If the noise is not included it is not uncommon to reach those levels but if the noise is included I am impressed.
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Old 9th November 2005, 03:18 PM   #14
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What do you really mean by loop gain of 50dB? Do you mean the ratio between the modulating signal and the supply rails? If the loop you are using is hysteresis modulated I assume that you are using an integrator and this will naturally give a loop gain that falls by -1 or -2.
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Old 12th November 2005, 07:06 PM   #15
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Yeah, integrator in use of course, i tend to call it PID even.
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Old 12th November 2005, 08:13 PM   #16
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IVX: Have you published your circuits somewhere? I am curious to see how you get your results, and how you calculate your loop gain.
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Old 13th November 2005, 02:15 PM   #17
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Have you published your circuits somewhere?
I have not such plans so far, though it's would be simple (TDA8939) and no bad amp to build by DIYers.
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