15 October 2016, 20:26 | #81 | ||
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Aren't you calling sample rate what should be called bit rate ? |
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15 October 2016, 20:57 | #82 |
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Another thing to consider is the quality of the opamps in Amiga models. I'm quite sure they would have been chosen on price and not audio quality! There's only top notch sound cards that will have decent opamps in.
With the LED filter off, there's no filter at all is there? That'll be why it doesn't sound as good as it could (16-bit 44KHz listening tests), well that and no oversampling. |
15 October 2016, 21:01 | #83 |
son of 68k
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15 October 2016, 21:07 | #84 |
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I have an 80's cd player, Aiwa. I don't play cd's through it though because it sounds SO BAD. Not all digital gear is sparkly and perfect.
I have a clock port Prelude sound card in my A1200 and that sounds superb...I simply can't fault it. |
15 October 2016, 21:19 | #85 |
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16 October 2016, 00:46 | #86 |
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I guess there is a big difference between processed samples from a given source and a recorded sample. You get better results when convert 16 to 8 bit or direct 8 bit calculation. There are some variables that can make 8 bit records sound bad (mostly noise added). But it depends on source quality. So I don`t see much sense in measure comparing because at the end you hear what you hear and that differs from person to person.
If you record the analog Amiga output that plays a 16 bit sample via 14 bit calibration. What do you think you can measure or what result will expected? |
16 October 2016, 01:52 | #87 | ||||
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This is not only functionality. Quote:
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This is not a big problem, more important is PCB routing and power quality. Side to this you can easily replace older OPAMP in Amiga for something new like TLE2084 or similar. And IMHO those OPAMP hype is a bit exaggerated - if you need HQ design then you need to go for discrete and higher voltage. And Amiga have at least two filters - one that can't be switched of - call this filter reconstruction filter - it remove PWM from AUDxVOL. Quote:
Not sure what to expect - THD+N between 60 and 70dB maybe better... Last edited by pandy71; 16 October 2016 at 02:05. |
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16 October 2016, 12:51 | #88 | ||
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What many don't seem to understand is that it's also important to ensure that an opamp's surrounding component values suit it unless it's clearly specced as a higher quality direct drop-in replacement for the original. Not selecting a suitable opamp or not making the appropriate component value changes if necessary can often make matters far worse than just leaving it alone, although placebo effect will frequently tell someone otherwise. Designing opamp circuits properly is a science, not a crapshoot. Last edited by Stratosplat; 16 October 2016 at 13:58. |
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16 October 2016, 18:16 | #89 | |
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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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16 October 2016, 22:34 | #90 |
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Yes. The worst thing about the audio output stages on an Amiga is everything else apart from the chosen opamp.
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17 October 2016, 13:17 | #91 | |
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http://www.diyaudio.com/forums/chip-...fferences.html https://e2e.ti.com/support/amplifier...udio-equipment But once again - yes, even if you trying to be sarcastic there are bigger issues in Amiga than OPAMP - replacing them by four high end modern ultra fancy marketing hypes OPAMP's will not brings Valhalla to your ears... btw some of people like old uA739 sound... -*-*- Promised test files for Amiga - generated by AP tool (APx Waveform Generator Utility v4.2) as 32kHz, 16 bit, 2 channel, later converted by SoX (re-sampling to 28604, 8 bit, 16 bit and 14 bit, no dither applied, 8 bit version use native Amiga 8svx format). https://ulozto.net/!KokppftoNZdU/8364-test-7z archive 15.6MB large, after unpacking it should be around 154.6MB. |
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17 October 2016, 18:08 | #92 |
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I was actually agreeing with you. The entire audio circuitry is incredibly poorly implemented. It would be hard to have made it any worse on purpose let alone by accident. It seems to be a classic example of what happens when you trust digital design engineers to design analogue signal stages.
Preferring the sound of one opamp over another doesn't mean that it's better. The same applies with power amplifiers where many audiophiles prefer the sound of some ancient designs with clearly audible distortion over modern designs where distortion can be orders of magnitude too low to be audible. I was talking about actually being better rather than just giving a warm fuzzy feeling of "I've changed it and it sounds different so it must be better". There's so much crap floating around on the voltage rails, reference rail and in the signal itself that the minor noise and distortion introduced by even a cheap opamp is going to be irrelevant by comparison. |
17 October 2016, 18:51 | #93 | |||
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17 October 2016, 19:44 | #94 | |
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But on my a1200 with ide-cf i can't hear any disk activity, even with volume pushed. |
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17 October 2016, 19:49 | #95 |
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17 October 2016, 20:05 | #96 |
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@pandy71
There must be something going on with your system to have audio interference from fdd and hdd accesses. Just for the heck of it, I plugged one of my A1200 (no RF shield, cf for hd, apollo 1230 accelerator) to my KRKs and I can't hear a thing, copying right now as I'm writing about 1gb of whdload stuff from internal cf to pcmcia. My ear to the woofer, nothing's there. |
17 October 2016, 20:25 | #97 | |
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Connect Amiga audio RCA out to amplifer, don't play anything on audio, raise volume on amplifier, start using FDD or HDD - enjoy sound created by current ripple in speakers... |
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17 October 2016, 20:53 | #98 |
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17 October 2016, 21:14 | #99 |
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17 October 2016, 21:27 | #100 |
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Motherboard revision may also affect. At least on some Amiga 600 motherboard revisions PCMCIA and IDE activity can be literally seen from the composite out picture. Quite annoyingly even. Some motherboard revision do have manually soldered ceramic cap to prevent this and later ones have that designed in.
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