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Old 20th December 2003, 06:37 PM   #1
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Question TDA5141 oversampling or non-oversampling ?

Hi,

what is better ?

These TDA1541 + CS8412 schematics that ghost around in the forum, are they oversampling or not ?

I read one very technical thread ( yes, I have searched ), but that did not give me an answer.

What is the best schematic for this chip ?


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Old 20th December 2003, 07:20 PM   #2
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Default Should be easy for you to figure out....

Since I don't have the schematics that you refer to, if there is filter chip between the RX chip and the DAC chiop, then it is more than likely set up to be o/s. Hard to be o/s without one of those filter chips in there...............

The best?? Really is no such thing. Just like any other type of engineering: it is a series of compromises. You need to decide which ones you want to emphasize at the expense of others.

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Old 21st December 2003, 11:59 AM   #3
rah is offline rah  Australia
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Default TDA5141A oversampling or non-oversampling ?

I was going to ask that question too, which way is better?

TDA5141A oversampling or non-oversampling ?

It’s not hard to tell that non-oversampling is popular between the DIYers here, but has any one tried a good oversampling implementation with the TDA1541A ?

From what I know from reading around on the forum, the old CD players did oversampling with it, but most of the implementations were bad, SAA7220 sharing same supply with TDA1541A, jitter on the clock, cheap op-amp I/V conversion. Has any one tried this properly?

The Sugden Masterclass CD player does this way, with the TDA1541 S1 DAC and the SAA7220 filter, and it’s known for good sound quality. Damn expensive too, as I just found out.

Sugden Masterclass CD player:

http://www.jesugden.co.uk/masterclass_cd.htm

Review:

http://www.hifichoice.co.uk/review_print.asp?ID=2372
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Old 1st September 2004, 05:53 AM   #4
Fin is offline Fin
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Default Does this help?

Found this article while looking for something else. Could this be part of the reason some people like Non-Oversampling - or the removal of SAA7220?

Quote:
One of the most amazing experiments I ever did was with the Magnavox [CD player] chip set—the Philips SAA72220 and TDA1541 DACs. One of our customers told me they were using that chip set in a professional piece of gear they were making. I had measured the Magnavox CD players and they had horrendous linearity errors. I said, "How can you be using this chip set? I've measured them and they don't work very well." And he told me that you just have to know how to hook them up. They work real well if you know what to do. They are really sensitive to ground-noise problems, and to glitching on the waveforms coming in. I said, "Do you mean the D/A [converter chip]?" He said, "No, the interface between the signal coming in [to the DAC] and the oversampling filter." I was pretty amazed that the logic signals coming into the converter from the oversampling filter could make a difference.

But evidently it does. You have to buffer the lines, trim them up, make them nice and clean without any large amounts of ringing or overshoot or undershoot. They have to be nice, firm, well-controlled squarewaves coming into the D/A converter or you'll get bad linearity errors. This was a guy I had a fair degree of faith in, who would have some reason for saying what he said. When I got back home I took a friend's CD player, measured it, opened it up, got out the Philips data books, and looked at the interfacing. I cut the lines and put in a CMOS buffer and some RC networks that shaped the waveforms so they were nice and clean, and they looked real good on the 'scope.

I measured the player again. The linearity improved by something like 6dB. Instead of being 9dB out low levels, it was now out 3dB. I was amazed. I am not a golden ear—I wouldn't swear to you that I heard a difference before and after, but I could swear to you that I measured a difference before and after. But when I tell people that there were differences in the logic lines—all I did was shape the waveforms on the logic lines before the D/A converter—they were amazed.

I knew another person who had a Magnavox CD player and did the same thing. It's real. It's repeatable. So there could easily be differences between two players, at least between converter interfaces—how to hook them up or the care in power supplies or grounding. Because the converter was obviously latching bad data based on what it saw previously with glitches or overshoots. These two chips were designed and made by the same manufacturer and designed to hook to each other, but if you just hooked them to each other they didn't work very well.
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Old 1st September 2004, 10:27 AM   #5
guido is offline guido  Netherlands
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Default Re: Does this help?

Quote:
Originally posted by Fin
Found this article while looking for something else. Could this be part of the reason some people like Non-Oversampling - or the removal of SAA7220?

Read this on the inputs of the 1541 and much more on this chip.

http://www.diyaudio.com/forums/showt...849#post369849

As for OS without filter chip, it is possible by using two dacs and delaying data to one of them. Works for me.
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