There is much touting about early CD-Players from Philips and Marantz, i.e for modding them for NOS or better decoupling of the TDA-IC´s.
But I am wondering: Theoretically the power supplies should be a mess:
Digital and analog grounds are not seperated, no seperated transformer windings, one voltage regulator provides power for the servos, decoding and analogue output - how comes nobody seems to have adressed the issue
and tried modifications here?
The CD 304´s PSU - same scheme for CD-104 and probably many more:
But I am wondering: Theoretically the power supplies should be a mess:
Digital and analog grounds are not seperated, no seperated transformer windings, one voltage regulator provides power for the servos, decoding and analogue output - how comes nobody seems to have adressed the issue
and tried modifications here?
The CD 304´s PSU - same scheme for CD-104 and probably many more:
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You are spot on Salar. I have bought two old Philips players for modification to transport only. These are very very good players but the production cost had to be held down for sales reason. Huge potential for improvement as you have noticed. One is TDA5141 and one is TDA1543 Dac version but that does not matter. The error correction and interpolation of playback errors is just magnificent.
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I don't know the answer to your question. I also wonder why there seems to be no-one modifying layouts to separate power and signal grounds from one another. One guess is people doing mods like them to be simple substitutions (like for example opamp rolling) rather than anything complex requiring EE levels of understanding.
You're right Salar, there's a lot of potential for improvement. Most Philips CD players (especially those with a TDA1543) were fairly low cost consumer appliances, with more effort put into simplicity that audio quality.
However, what you've described would require designing a whole new mainboard for the player. It's possible, but it would take a lot of skill to make something the works, and even more to make something actually better than the original.
A better idea might be to start with a player that's better as standard. Something like an Arcam Alpha already has a lot of the problems you mentioned addressed.
However, what you've described would require designing a whole new mainboard for the player. It's possible, but it would take a lot of skill to make something the works, and even more to make something actually better than the original.
A better idea might be to start with a player that's better as standard. Something like an Arcam Alpha already has a lot of the problems you mentioned addressed.
On the other hand, where is the audible effect? Tested a Philips CD-304MKII
with a silent CD-track, ramped the audio volume all way up - and heard nothing from the servo circuitry despite the fact that theoretically there must be
some interference. I remember this effect very much from portable players...
with a silent CD-track, ramped the audio volume all way up - and heard nothing from the servo circuitry despite the fact that theoretically there must be
some interference. I remember this effect very much from portable players...
Well take a look at this thread. He has even done this for TDA1541. Do the AD844 modification and listen for yourself. A very good I/V stage.
http://www.diyaudio.com/forums/digital-line-level/227677-using-ad844-i-v.html
http://www.diyaudio.com/forums/digital-line-level/227677-using-ad844-i-v.html
I doubt those frequencies go high: With Philips, it is a 650hz wobble frequency and the hiss of the focus servo the latter we hear already directly.
Anyone out there with an old Philips or Sony Player and a spectrum analyzer?
I could also check with my scope if someone tells me what frequencies to look for...
Of course....Any useful modifications or repairs are impossible without a suitable FFT Analyzer. There is nothing interesting (quality limiting) to see, when measuring very old CDP like Sony CDP550, the ancient CDP101 or Philips CD160, CD104 etc. You will not be able to see any remarkable influence of the servos in the analog signal, when playing for example 997Hz, -90 dBFS
But in my opinion there is NO good reason to use one of these vintage players nowadays, except you like the vintage looks or the mecanical quality of the tray etc.
SQ does improve using a better I/V configuration.
But on the early Philipses (TDA1540 and TDA1541A DACs) just adding two 6k8 resistors (onnected to the -15V) to the capacitor of the DEM oscillator improves SQ also by removing the noise in the DEM clocksignal.
Decoupling of the PSU can easily be improved by replacing some resistors by small inductors (say 100uH). Far easier improvements than redesigning the entire PSU..
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And this is why I use them too ! Currently enjoying Nagaoto badged version of Kyocera DX-710 as a transport.
Direct track select via illuminated buttons is great and seems to have been dropped from designs after remotes became commonplace. Yeah, much more satisfaction from using older machines for me.
For the 304 (schematic I own) it's C2564 and C2599 (SMD types underneath the PCB) for the DEM clock... The values are 820pF. Connect both sides (on DAC pin 8 and 9 ) to the line connected to DAC pin 11 (-16.8V). This is the "simple" DEM-mod. So you'll need 4 6k8 5% resistors (through hole types 0,125W or 0,25W) and a steady hand soldering
Be careful not to desolder the SMD capacitors..Best place is to solder the resistors underneath the PCB... out of sight.
Compact disc is less or more ancient and there will be only very few high quality Players in future. But it is no problem to buy a solid transport without going back in the very early days. Most (all) Philips CDP are imho really ugly and the quality of build ist also not remarkable.
Even if your unit is producing some noise while playing a -60 dBFS Track and
listening with very high gain over headphones....It will not be "enough" to have any influence under normal listening conditions.
Your Player also maybe faulty?
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