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Old 16 October 2016, 18:16   #89
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Join Date: Jun 2010
Location: NL/PL
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Originally Posted by Stratosplat View Post
Totally unnecessary and unlikely to outperform a high quality opamp even when running on low voltage supply rails without vast complexity and expense.

Designing opamp circuits properly is a science, not a crapshoot.
True and as such most of situations OPAMP are overhyped marketing blahblah - OPAMP only make circuit simpler as they can be used almost like black box without knowing science by anyone, even by marketing people - they will not magically improve audio as usually modern OPAMP has sufficiently high parameters itself and they are frequently ruined by improper application (for example in Amiga reference voltage for DAC is created by dividing in resistor divider general digital supply voltage by half - this short way to inject power supply noise to output signal - for any analog circuitry you use separate clean power line and separate ground plane).
Amiga is also different when compared to consumer DAC (in Amiga time) as Paula feed samples with over 3MHz sample rate - this is very high sample rate and some slower OPAMP working as in Amiga case in first stage may distort signal (DAC produce series of pulses where level of pulses depends on sample value and length of pulses depends on volume set in AUDxVOL - for small values like 1 in case of 14 bit mode this may be important - also it is not clear what kind of DAC is used in Paula - current or voltage [but CD32 schematics suggest that it may be current type DAC] - current DAC need additional current to voltage conversion which can be very tricky itself with slow OPAMP).
All this may impact analog signal quality (like hearing FDD or HDD in analog audio line not uncommon).
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