Non Oversampling Vs Oversampling - diyAudio
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Old 7th April 2002, 12:22 AM   #1
jkeny is offline jkeny  Ireland
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Default Non Oversampling Vs Oversampling

HI all,

It would be interesting to be able to change from non-oversampling to 2, 4,8 oversampling without having to re solder, etc.
For instance the Marantz CD4000 operates in 4 times oversampling (through the SAA7378 decoder) and I would like to hear how non-oversampling would sound on this CDP before I embarked on a non-os project.

I have downloaded software from www.daisy-laser.com which should allow a PC to communicate via DSA protocol with any decoder, digital filter using this protocol - so you can completely control the CDP - play any track, change DAC format, etc

But I have not got it working yet - the software seems to work ok but I suspect that my cable connections are wrong - or Windows is wobbly? All instructions for wiring the cable and using the software are given in the links below.

Lets see if we can get this working and have a very interesting tool for experimenting with our CDP's

The link is http://www.daisy-laser.com/tech2b.htm

and the software is at
http://www.daisy-laser.com/download.../dsaprogram.zip
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Old 7th April 2002, 12:33 AM   #2
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And I assume you have a way to easily change the analog filter every time you go "lower" down the o/s ladder to get rid of all the ultrasonic garbage that will come out.

Or you could buy a Wadia. [joke]

Jocko
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Old 7th April 2002, 01:03 AM   #3
jkeny is offline jkeny  Ireland
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I know oversampling was designed so as to avoid a very steep and expensive analogue filter but from what I've read of non-os this does not seem to be a problem. Have you first hand experience of this ultrasonic garbage?
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Old 7th April 2002, 05:23 PM   #4
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YES!!!!!!!!!

Take a spectrum analyzer to the output of any digital circuit. There are "birdies" all over the place in low order filters. The steep o/s types get rid of it.

Example: say you have a 10 kHz signal. There will be a"birdie" at around 34 kHz.

Wadia is the best example of this problem. The SAA7220 isn't that great either. Probably due to the zero in the transfer function they put there to cancel out one of the 3 poles in the post-filter. No a good idea.

Jocko
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Old 7th April 2002, 06:16 PM   #5
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Exclamation NON-OS vs. OS debate

Hi Jocko,
But you accept severe ringing and overshoot on a square wave of 1kHz right in the middle of the audioband?! {no joke}.
The non oversampling DAC has a perfect square wave!
Paul McGowan once said: <B><I>"If we submitted an analogue amplifier with the kind of square-wave response that CD manufacturers proudly publish, we'd be laughed off the face of the earth."</B></I> the Absolute Sound, Vol 10, # 39, 1985.
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Old 7th April 2002, 07:30 PM   #6
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Yes, it comes from the fact that every single bit put on a CD goes through a brick-wall filter on the A/D side. Can't make a recording without one.

The Gibbs phenomenon is what it is called, and there is no way around it.

Jocko
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Old 7th April 2002, 09:34 PM   #7
jkeny is offline jkeny  Ireland
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Default Non os Vs Os

Yes Jocko,

But what does this ultrasonic garbage sound like???

John
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Old 7th April 2002, 10:01 PM   #8
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Default But what does this ultrasonic garbage sound like?

BAD, that is why we call it garbage. Audio circuits are non-linear (that distorting for those in Rio Linda) at RF frequencies.

"If we submitted an analogue amplifier with the kind of square-wave response that CD manufacturers proudly publish, we'd be laughed off the face of the earth." the Absolute Sound, Vol 10, # 39, 1985

And yet PS audio marketed a DAC after that and I believe Paul McGowan has not left the planet!

I really don't understand this retro frenzy for non oversampling DACs. The new DACs sound and measure better. Why the hell does everybody think oversampling was invented? If you want to do something "retro chic" go design a 6SN7 into something. That way Jocko can stop ranting about this and go rant about something else.

H.H.
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Old 7th April 2002, 10:45 PM   #9
jkeny is offline jkeny  Ireland
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Default NON-OS software

I just started this thread because I thought ther was a quick and easy way (namely software control) to hear for myself what non-os sounds like. I am able to make up my own mind about waht sounds good and what sounds bad.

So maybe we could get back to the thread

Has anybody tried this software - if so please respond. I am interested in following this independent of others opinions whoever well informed they are - after all this is what the hobby is about

John
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Old 8th April 2002, 12:45 PM   #10
ergo is offline ergo  Estonia
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Harry, Have you experimented with non OS yourself???

I was also very sceptical about that and only browsed the DAC schematics which were oversampled, digitally filtered etc. etc. and skipped the minimalistic type ones.

Then one of my friends did a project with CD-Pro transport and TDA1541 (non OS). There was something in the sound that dropped my mouth open when I first heard it. I had tried to create a slid and 3 dimensional soundstage tweaking my Marantz CD67 for about two years, but his project managed to top mine by a huge margin with version 1 !!!

After that I have heard other non OS projects (CS8412 + TDA1543 and my own PCM1702 project etc.) and all these share the same beauty regarding the "air quitar factor" and depth in the soundstage. I consider these qualities to be very important and if these designs make it possible and the rest of my system (JLH96 or LCAudio The End Millennium amps and Dynaudio speakers) handles it without any noticeable problems then I consider it a solution worth to try.

On the techical side, if this is done over I2S interface as jkeny suggest, it creates a very simple and short signal chain. That will make it simpler to run data tracks, creates less problems with earthing, better for clock distribution etc. All this might well make it more suitable for DIY projects as an advanced DAC with latest techniques will be very difficult to build as there are so many factors in circuit design and PCB design which, if not done right, might create a lot of problems and the advantages are thus nullified....

Ergo
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