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Author Topic: What input stage clipping looks like  (Read 1483 times)

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Offline jerryfreak

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Re: What input stage clipping looks like
« Reply #15 on: August 27, 2020, 11:18:52 PM »
im not familiar with the MKIII but heres what doug had told me about it in the past

The MKIII is not as well made and they made 2 significant steps backward in the redesign of the preamp. The Chinese MKIIs were of Japanese design and produced at high end Chinese factories. In the MKIII, the preamp voltage rails went from +/- 6 volts to a single supply 4 volts. The other simplification employed to reduce cost was in the MIC ATTN circuit. In the MKII, a clever switch circuit was used to alter the value of feedback resistors in the gain stage of the preamp. This gave the preamp more headroom, working much like the trim knob in a recording console. In the MKIII, the preamp gain is fixed and the MIC ATTN setting are post preamp. That makes it easier to overload the preamp while fixing THD+N at the highest end of the chip's range, not optimal. In all of the 661s, they use the same JRC2122, not capable of 16 bit performance. One good thing about the simplification is they removed the CMOS chip used in the MKII for selecting the internal mics. It's the same circuit Sony uses which limits dynamic range. So by using a very low THD+N chip that will work with a single supply, you can get higher performance without having to bypass a CMOS chip. Of course, with the original and MKII, you get even better performance with the CMOS bypass MOD due to the higher voltage rails. I sold a lot of those to researchers and birders who run computer based analyses on the data. A few audiophiles also run that MOD. You get high end performance at a modest price. Finally, in the MKIII they use a 32 bit A/D converter vs 24 bit for the MKII.
« Last Edit: August 27, 2020, 11:20:54 PM by jerryfreak »
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