17 October 2016, 23:26 | #101 |
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@pandy71
They're active studio monitors, as I said, dead silent, volume at max. Transcend CF 32gb internal, 1gb sandisk on pcmcia, simple chinese cf2ide adapter. Motherboard rev is 2b with the usual capacitor fix for compatibility, but no recapping or anything else. PSU is from an A500, rca cables are of the simplest/cheapest type. Last edited by vulture; 17 October 2016 at 23:35. |
18 October 2016, 10:18 | #102 | |
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As Meynaf pointed earlier - FDD/HDD are mechanical and they use significantly more power than SSD/CF/SD etc - as such current ripple is way higher and this current ripple will propagate also to Paula and as final effect to audio output. Hope you see difference between 100mA and 1.0A - formally such thing is called PSRR http://www.analog.com/static/importe...als/MT-043.pdf - in Amiga voltage reference for DAC is taken directly from power lines trough very minimalistic low pass filter - in decent audio equipment you have at least dedicated low noise voltage regulator (as people complain for noisy voltage regulators such as LM317) to improve PSRR. http://tech.juaneda.com/en/articles/lm317.html http://www.tnt-audio.com/clinica/reg..._noise2_e.html http://www.diyaudio.com/forums/power...egulators.html https://hifiduino.wordpress.com/2011...se-regulators/ Somehow you trying to convince me that noisy power supply with low quality power distribution, with variable load between 25 and 30% (in peaks) of maximum power supply capabilities and very simplistic circuit used to feed voltage reference source have no impact on audio quality. |
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18 October 2016, 11:15 | #103 |
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But are they on the same power line input ?
Don't mechanical parts take 12V where paula uses 5V ? |
18 October 2016, 11:24 | #104 |
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I'll try loading a floppy game tonight and see how it goes. And I'm not trying to convince anyone about anything, it's what happens. |
18 October 2016, 12:53 | #105 | |
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Side to this Amiga audio path using both lines ( i.e. 5V, 12V also -12V is used) - Vcc (5V) is used to supply Paula (digital and analog part share same voltage pin), Vref is created in resistor divider from Vcc, there is separate analog ground, OPAMP are directly powered from +12/-12V lines - there is only few capacitors and resistors working together as very simplistic filters. This is not bad but definitely not the most optimal way - however it is justified for computer where cost of production was sensitive - just enough but not 14 or more bit - if you really wish to have HQ audio then all those problems need to be addressed properly, audio supply and ground need to be clean, proper PCB layout etc. |
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18 October 2016, 14:34 | #106 | |
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It's passably OK for the intended job, but it could have been so much better at the minor expense of dedicated audio stage voltage regulation and correct signal ground referencing. Also, setting up a guard band around the audio stages would have been very easy and quite effective at keeping radiated digital noise away from the audio signals. All of this was standard practice at the time on high quality audio equipment. Show the schematics and PCB layout to any competent electronics design engineer and they'll tell you exactly the same thing. I suspect that penny-pinching is partly responsible as doing it properly can be very cheap, but not quite free. I'm happy to accept it for what it is as I don't use the Amiga for any serious audio work, but I certainly wouldn't attempt doing so without at least a partial circuit redesign. I re-capped my 2B A1200 at the weekend, so I know they're not responsible in my case. The incoming supply rails are as clean as can be expected from the fairly crude (by modern standards) external PSU design, so I'm happy that nothing is broken per-se. Please note: I am not moaning. This is exactly what I'd expect to see from the hardware that's sitting in front of me. I'm under no illusions that high quality audio will be delivered or should be expected. |
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18 October 2016, 14:46 | #107 |
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Well, it appears we have some folks here who talk about schematics, voltage, noise, audio theories, etc, and try to explain why our miggy's sound is so damn piss poor (in their opinion), while not having actually listened to the real result.
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18 October 2016, 15:30 | #108 | |
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It makes perfect sense to listen first (as your ears tell you everything you need to know about what you actually hear) then investigate after if you feel the need, so that's precisely what I've done. It's exactly what I'd expect based on my own independent listening tests and backed up by 35 years knowledge and experience of digital and analogue electronic circuit design. Sounding good to certain individuals doesn't negate the fact that it's actually very poor in terms of circuit design and implementation, hence the fact that it does sound fairly awful to certain others with good enough equipment and ears to notice. Another contemporary example is MP3 where a high quality encoding may sound identical compared to the source to one person, yet very different to another. There is no 'black and white' when it comes to what different people can hear and find audibly acceptable. Please show me where I said that the Amiga's sound is "so damn piss poor", or is that in reference to someone else's reply that I've missed? I have no problem with others being perfectly happy with it, so why do you have a problem with others who aren't so impressed? Chill. Last edited by Stratosplat; 18 October 2016 at 16:00. |
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18 October 2016, 16:03 | #109 | |||||||
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Problem : i never actually heard that noise. Quote:
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But please plug an Atari ST on a hifi equipment and listen. Then you will know what 'noise' and 'incredibly poorly implemented' really mean. |
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18 October 2016, 16:07 | #110 |
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I'm quite obviously saying the complete opposite of what you're claiming I'm saying in at least one of the above quotes, plus you seem to be denying that psychoacoustics which differs between individuals determines what a person does or doesn't hear.
You're clearly putting your own spin on my words for some reason that I don't understand. On that basis, I shall take no further part in this conversation. Last edited by Stratosplat; 18 October 2016 at 16:27. |
18 October 2016, 16:29 | #111 | |
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Honestly - I don't trust your ears and i have limited trust to mine. Why not using something not so subjective? And as i can't listen your Amiga (used by you as reference to justify your claim) then perhaps you can record sound from your Amiga (for example using samples provided in this topic) for example on PC with Line In input? Will be nice if you can place those samples in uncompressed or compressed losslessly (FLAC?) somewhere where i can download them and i can hear your Amiga same as you (then i will be able to hear same signal as you with proper Amiga and proper software). For today as i can't hear your Amiga I can tell only one thing 68 or 72dB is not 14 bit as electric current is not simple arithmetic in 68k registers and assumption that you feeding 16 or 14 bit to two 8 bit DAC's where one of them has introduced -36dB doesn't mean that they behave like 14 or 16 bit DAC and all this without even involving other problems related to audio circuits design. If you reject this opportunity to answer questions then i have proposal to stop talking what you or i can hear (or not) until i will be able to measure in objective way Amiga audio output (of course after all you can be a real audiophile and reject scientific approach claiming that theory is meaningless). |
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18 October 2016, 17:21 | #112 | |||||||
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I will ignore this - looks too much like personal attack. Quote:
If the ear, either yours or mine, can't perceive it, then it's just too subtle and not worth talking about in depreciating terms such as those that were written. If you want some not subjective way, just make it heard by enough people. Sound quality can't really be measured - you can only measure accuracy but accuracy isn't equal to quality. Quote:
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(and forget what calibrated output is all about) Quote:
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18 October 2016, 18:20 | #113 |
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@pandy71: Reading back through this thread again, it would appear as though meynaf is picking fights with almost everyone on the basis that he is right and they are wrong no matter what they say. Don't let him wind you up.
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18 October 2016, 18:26 | #114 | |
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(appears some really do not like being proven wrong...) |
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18 October 2016, 18:42 | #115 | |||||
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This completely not true - this is simple conclusion after your last comments. I never wrote about poor Amiga audio quality and it was not me suggesting that i never hear Amiga.
I'm vaccinated and immune to FUD. Quote:
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I hope you not suggesting that bad audio circuit with poor measurement results will provide good sound quality - however if you think it is true i will be glad of some examples for such situation. Accuracy can be measured and indirectly can be used to quality assessment. I hope you not trying to suggest that Amiga is somehow high end audiophile source. Once again i highly recommend http://www.harman.com/sites/default/...dioScience.pdf - He (Floyd E. Toole, Ph.D. Vice President Acoustical Engineering, Harman International Industries, Inc) cover some of things you wrote about measure, science, theory - there is no electronics there but rather sound quality remarks and how subjective testing is complementary to objective, it is nice paper written with simple and understandable language - you may find it interesting. Quote:
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Why i should stop talking with you? I assume you are mature (you 43 me 45) to have sane discussion where we are able to present different point of view, where there is a place for exchanging arguments and where at some point we can discuss some objective data and as a programmer you (i hope) appreciate that 2+2 will give you 4. Last edited by pandy71; 18 October 2016 at 18:59. |
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18 October 2016, 19:44 | #116 |
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ok, so I'm formatting a floppy disk and I can still hear no noise/static/hiss from the speakers.
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18 October 2016, 20:32 | #117 | ||||||||
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However if you're vaccinated then why not just stopping here and try to discuss something more interesting. Quote:
If you want to experiment oversampled 8 bit with dithering and aggressive noiseshaping, you can tell me exactly what computations have to be made on the signal, and i can try coding it. I have the code (somewhere) to play audio by cpu poking AUDxDAT. Quote:
So with all this, what do you want to do ? Quote:
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But having plugged it into some big amp where normal music with volume knob set to 8 would have been enough to make the neighbors come, i set it to 40 and still got only silence. Let's be honest : i was very surprised to hear nothing ! Maybe you're right and it's not good by todays standard. Yet it sounds good in everyday life. If you play 24-bit samples on super accurate 24-bit D/A, will you hear the difference with regular 16-bit ? Where's the point in which it starts to count ? If 14-bit doesn't sound different than 12-bit then maybe we only have 12-bit dynamics while playing 14. But then whether we have 12,14,16 or more, doesn't matter (at least for me). Quote:
Anyway, we have to remember that we communicate in english, which i don't regard as a very good tool, especially when neither is a native speaker. So many misunderstandings can occur. |
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18 October 2016, 23:08 | #118 | |||||||||
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From my perspective this very amusing part of science applicable as in theory you can imagine such software approach (you should like this - there is no hardware but pure software) to beat limitations of hardware - for example deliver audio quality beyond Amiga designers imagination. List thing more interesting than breaking old HW limits - i think this is important especially for you as a software guy - i have own ideas about improving HW but it is real art to not change main HW architecture yet bend limit beyond imagination only by using clever software. Quote:
Computation you can check for example SoX or ffmpeg code (ffmpeg use SoX part but they added coefficients for some common sub-Nyquist sample rates - disputable if they improve or not perceived quality but they exist). Someone provided code for using Copper (as my assumption is that Copper will provide jitter free sampling) but even using HW DMA and sample rate like 56kHz with proper signal processing i think Amiga can easily match dynamic of the 16 bit system (with respect to Gerzon-Craven theorem). Quote:
There are some techniques to deal with problems, temporal averaging to remove uncorrelated with signal noise is one of them. And also we note measuring particular sample values (albeit it possible and it is used with some DAC calibration techniques). Quote:
Wise people not say f**k theory - i live long enough to experience situation when good theory perfectly match real life. Quote:
Oscilloscope will be highly unsuitable for this as very limited dynamics present in typical oscilloscope - they usually use not more than 8 bit AD converters and with typical sample rates around 100MHz efficient number of bits is usually somewhere around 6 or less - definitely very bad for 14 bit audio. Quote:
I have A1200 and A3000 (CPU capable to run 68020 code) - in 3 -4 weeks i should e able to use A1200 (need to buy IDE>SD adapter and restore system disk), A3000 is slightly more challenging as i need to rework some problems on MB and buy a keyboard - as you can imagine it is impossible to buy A3000 keyboard nowadays. Quote:
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And from beginning quite clearly stating that my listening experience telling me that Amiga is somewhere between 60 and 70dB which is not bad and i will be very positively surprised to see better numbers. Quote:
And there is large group of people seriously deliberating on superiority of Analog Devices AD8597 over AD797 - referring to Amiga - there is no magic - simple OPAMP replacing will not magically change sound - many thing need to be addressed to improve sound - this is another interesting topic for Amiga - after checking what is better - 14 bit or 8 bit with oversampling and NS there will be time for some improvement on Amiga to even improve audio more. And i agree on language (my English is really self learned - i know that my vocabulary and grammar are poor), i agree on stopping discussion to the point where some objective data will be known so i t will be easier to see some picture and discuss something more real than our impressions. Once again - i respect you even if sometimes it is not easy to discuss with you. Last edited by pandy71; 18 October 2016 at 23:18. |
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19 October 2016, 09:53 | #119 | |||||
son of 68k
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I had two A1200 and none made any hearable noise. I could, however, hear a significant quality loss when using the calibration file of one machine on the other. |
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19 October 2016, 10:18 | #120 |
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@audio discussion:
Is it really that relevant wether or not an Amiga can compete with modern PC audio hardware which is 25 years newer and leans heavily on technologies which where either not available at all or not available for any reasonable cost back in 1985? Of course we have better audio these days. And no, that is not at all relevant when looking at the Amiga audio out quality. It'd be much more interesting to know how it compares to audio produced back in the day by PC's and such and much less in current day high end studio performance. The Amiga is not a high end audio device. Then again, neither was a PC back in the 90's (I'm pretty sure Soundblasters where actually quite a bit worse in the actually produced signal to noise ratio department until the AWE32*), so again why is this relevant at all? *) as opposed to the stats on the box, which never held to any serious scrutiny. If we're going to compare DAC performance, it should be done fairly - compare it to other DAC's from the 1980's, available for similar prices as Paula (i.e. a few dollars max). Comparing the Amiga against high end audio stuff is hardly fair (and outright silly when doing so against stuff from 2016!) and doing so does make it seem like the goal is to make the Amiga look bad (IMHO anyway). |
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