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Differences in ROMs for Audio
Differences in ROMs for Audio
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Old 13th June 2007, 02:06 PM   #1
Zero One is offline Zero One  Australia
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Default Differences in ROMs for Audio

Some time back I posted regarding using CD Roms as the basis for an audio player and since then I have played around with three different ROMs and thought some findings might be helpful to some out there in tweaky DIY land.

In the long term it is my intention to use the ROM with an external DAC, most likely the new Monica USB from DIY Paradise, but I wondered how much difference there might be in the sound of the ROMs as they are.

First up I created a battery power supply with 10,000 uf caps for both the 5V and 12V supplies.

The batteriy supplies sound far nicer than the SMPS that comes from a PC and transforms the upper reaches of the audio spectrum whilst at the same time seeming to give much tighter bass.

The really surprisiing thing is the vast difference in the quality of the audio from all three players I tested, obviously there would be but it is far more than I predicted.

The three players I tried were all older units, an Aopen, Samsung and a Sony, all had the extra button so they could skip tracks. Remember this is the analogue output not digital.

The Aopen proved to be quite woeful, the highs being veiled and the bass muddy, bascially pretty much like a lot of cheap cd/dvd players. The Sony runs at higher than normal speed and I found it had some circuit noise compared to the other two and produced clean highs and reasonable bass, but overall lacked ambience, it sounded a little better than a cheap CD/DVD player. The samsung runs at normal CD speed when playing audio and sounds really good, a great surprise, the bass was tight, highs extended and ambience really quite good, overall it was very listenable. Unfortunately this ROM died, it keeps speeding up and slowing down and the read laser moves back and forth at random, I have no idea why but it only cost $2.00 so it doesn't matter.

The point is that there are quite big differences and as a basis for a CD player some may be far better suited to the task than others. Of course once using the digital output the differences might be very slight, I can't really say what caused the variations here, it could be the drive end of things or the DAC or the analogue section, but overall it tells me this is something to look at.

It is worth noting that of the three units the samsung was the best made internally, it seems to have good shielding and layout etc, just a pity it died.

It would be interesting to hear other folks experiences with ROMs.

I think I will further investigate this issue, as I have a friend who is an computer repair guy with lots of old drives, so I am hoping he can drop off a few and I can run some comparisons.
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Old 26th June 2007, 03:54 AM   #2
ozziozzi is offline ozziozzi  Australia
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Thumbs up CDROMS and DVDROMS as audio drives

Hi Zero One, I like your idea of battery drive for CDROMS, must try it. I have only used separate SM computer powersupply to play around with these drives. Have you heard about Playstation 1 's as audio drives? The very early models seem to be popular according to the forums I have read.

I have also experimented briefly with old CDROMS and DVDROMS ex-computer and in older style DVD players. I found them cheap from recyclers like Revolve or AussieJunk in Canberra or from garage sales (typically $0.50-$2). One thing I found recently at the Salvos is an "Akashai"(sp??) brand DVD player that contains a thick, shielded computer-style DVDROM drive. Even the analog out on that sounds good to me. Pity I didn't find the remote with it.
The beauty of starting with a unit like this is that you may be able to substitute similar CDROM or DVDROM drives that sound even better. All the control and display work has been done for you (on large, well spreadout separate PCBs!!!) and it has both analog and optical digital audio out, even a Dolby 5.1 decoder if you are into HT. Separate Switchmode power supply is *easily* substituted/modded.

BTW a computer/electronics tech I know suggested that computer drives probably have lower jitter and error rates than domestic entertainment products--maybe that's part of the performance boost compared with domestic CDPs.

Please let us know if you find a particularly good drive.

Of course I need all those speakers in the garage.
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Old 26th June 2007, 10:09 AM   #3
Zero One is offline Zero One  Australia
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Hi Ozziozzi

I haven't gome any firther with the roms, too much tweaking of my TT and phono cart, but I am on the lookout for some better drives.

I think what you say about the drives being probably better is likely correct, a couple of techs have told me the same thing and I know from pulling a few CD players and Roms apart there is no contest between them in terms of construction quality so that must account for something.
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Old 28th June 2007, 03:07 AM   #4
Leolabs is offline Leolabs  Malaysia
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Good to know people interested who are interested in CD/DVD ROMs as source.

I have a Lite-On CDROM(4 years of usage) powered from an industrial grade SMPS,besides not good at driving difficult loads(analog output),nothing to complain in term of sound,really outperform those el-cheapo DVD players.

Regarding DVDROMs made for DVD players,DVS from South Korea(esp their DSL710 series) is possibly the most popular among manufacturers(ranging from mid to high end,from a few years back till now).
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Old 28th June 2007, 03:52 AM   #5
FastEddy is offline FastEddy  United States
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I for one would not bother using CD mechanisms at all, but would favor the DVD mechanisms, mostly 'cause DVD-A discs and DVD video discs have such a much better sound (24 bit v. 16 bit) ...
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Old 28th June 2007, 06:48 AM   #6
fmak is offline fmak
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Default Re: Differences in ROMs for Audio

Originally posted by Zero One

The really surprisiing thing is the vast difference in the quality of the audio from all three players I tested, obviously there would be but it is far more than I predicted.

Have you looked at the TTL/converted spdif signals?. Some are very poor indeed.

Also some CDRoms clocks deviate from the +-100 ppm spec, making narrow pll jitter reduction impossible.

Try listening after ensuring low jitter output with good output waveform.
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