This is probably a stupid question..........
.................but that is nothing new (from me)!
I hope I am asking this in the correct thread as it is also applicable to Optimum decoupling in digital IC's.
Here we have been discussing the addition of extra transformers to separate sections of the CDP and break up ground loops.
If a new tf is added and the ground of the new supply is connected to the appropriate star ground for that circuit - how does that influence decoupling?
For example, a decoupling capacitor is connected as close to the supply pin as possible - but where is it connected to ground?
Is it best to connect it directly to the main groundplane, or via a trace to the star ground (which is connected to the new tf)?
.................but that is nothing new (from me)!
I hope I am asking this in the correct thread as it is also applicable to Optimum decoupling in digital IC's.
Here we have been discussing the addition of extra transformers to separate sections of the CDP and break up ground loops.
If a new tf is added and the ground of the new supply is connected to the appropriate star ground for that circuit - how does that influence decoupling?
For example, a decoupling capacitor is connected as close to the supply pin as possible - but where is it connected to ground?
Is it best to connect it directly to the main groundplane, or via a trace to the star ground (which is connected to the new tf)?
Mediocraty is relative.
Where is Jean-Paul when I need him???????
It doesn't have to be the best, have CDM1 stamped on it, have S1 or S2 printed on it (genuine or fake), or have the lowest noise and distortion as measured on your scope, for it to be worthwhile and fun to improve and listen to.
The CD624 was probably one of the cheapest implementations of the CDM4/19. It is unlikely that the CDM4/19 is the limiting factor in this project!!
Surely the crappy Bitstream DAC, poor ground plane, sub-standard power supplies, inferior decoupling, non existant shielding, flimsy plastic case and jitter ridden clock are all far worse than the mechanism/laser!!
What constructive suggestions do you have for me, Bernhard?
Originally posted by Bernhard
The most mediocre swing arm transport I'm aware of, with brush motor and missing ceramic cap across motor psu pins
Where is Jean-Paul when I need him???????
It doesn't have to be the best, have CDM1 stamped on it, have S1 or S2 printed on it (genuine or fake), or have the lowest noise and distortion as measured on your scope, for it to be worthwhile and fun to improve and listen to.
The CD624 was probably one of the cheapest implementations of the CDM4/19. It is unlikely that the CDM4/19 is the limiting factor in this project!!
Surely the crappy Bitstream DAC, poor ground plane, sub-standard power supplies, inferior decoupling, non existant shielding, flimsy plastic case and jitter ridden clock are all far worse than the mechanism/laser!!
What constructive suggestions do you have for me, Bernhard?
Re: More on the power supplies.
Konnichiwa,
No, but I did. And the Op-Amp indeed has an "AC Ground" Pin (or perhaps better called signal current loop return) which in MOSt (but not all) Op-Amp's is the negative supply.
If you have them, try working out the pin assignements etc. by yourself, good excercise in analytic thinking and electronics.
I don't. They are supposed to be "audio grade" with OFHC Copper leads, but I don't like any 'lytics in audio coupling applications, so I don't use them at all.
If it can be done, great. I always tend to solder my SMD Cap's directly next to the IC body on the IC pin's, for non SMD Chips.
Again, try to make as much sense as possible yourself.
If that means getting Horrorwitz & Hell "Art of Electronics" and reading it (actually, the Authors are Horrowitz & Hill IIRC), so be it...
Sayonara
Konnichiwa,
Fin said:Also - I never said the op-amp had a ground pin - but thanks for the clarification.
No, but I did. And the Op-Amp indeed has an "AC Ground" Pin (or perhaps better called signal current loop return) which in MOSt (but not all) Op-Amp's is the negative supply.
Fin said:I can send them to you if you like............................
If you have them, try working out the pin assignements etc. by yourself, good excercise in analytic thinking and electronics.
Fin said:So - where would one use Os-Con SG series?
I don't. They are supposed to be "audio grade" with OFHC Copper leads, but I don't like any 'lytics in audio coupling applications, so I don't use them at all.
Fin said:If the Vdd and Vss pins are not next to each other - but are on adjacent sides of the IC - what do you think of using an axial 10nF ceramic directly across the pins?
If it can be done, great. I always tend to solder my SMD Cap's directly next to the IC body on the IC pin's, for non SMD Chips.
Fin said:Again, I can send them to you if you like............................
Again, try to make as much sense as possible yourself.
If that means getting Horrorwitz & Hell "Art of Electronics" and reading it (actually, the Authors are Horrowitz & Hill IIRC), so be it...
Sayonara
Here's another drawing.
Is this the correct layout? (of course, the prereg is missing)
The shunts will be placed close to the ICs; but still on a small separate board (since the main PCB isn't designed to house them)
When the prereg will be added, where will his ground go? To the most critics IC's ground, or to the gridge's ground?
Is this the correct layout? (of course, the prereg is missing)
The shunts will be placed close to the ICs; but still on a small separate board (since the main PCB isn't designed to house them)
When the prereg will be added, where will his ground go? To the most critics IC's ground, or to the gridge's ground?
Attachments
Konnichiwa,
Pretty much so, with your added qualifications.
The answer of course is neither.
Remember, ask yourself where the current flows, the complete loop, the whole loop and nothing but....
For the whole powersupply in effect a "BUS" wire system applies up to the point where it feeds the actual circuit. I would retain a local star ground around the pre-regulator for the adj pin resistor and capacitor plus the output load and input bypass capacitor (if used), as this defines the local AC loops for the regulators.
Sayonara
Bricolo said:
Pretty much so, with your added qualifications.
Bricolo said:
The answer of course is neither.
Remember, ask yourself where the current flows, the complete loop, the whole loop and nothing but....
For the whole powersupply in effect a "BUS" wire system applies up to the point where it feeds the actual circuit. I would retain a local star ground around the pre-regulator for the adj pin resistor and capacitor plus the output load and input bypass capacitor (if used), as this defines the local AC loops for the regulators.
Sayonara
More on the power supplies.
Hi Thorsten
I have the datasheet for the DAC and the schematics for the CDP. The implementation of the DAC is slightly different in both documents - mainly just the values of the decoupling capacitors. In the datasheet they are 47uF lytics with 47nF ceramics. In the CDP schematics, they are 33uF lytics with 100nF ceramics.
If anyone is interested:-
SAA7322-3.PDF
Pin 22 (Vdd1; +5V for digital section) and Pin 23 (Vdd2; +5V for crystal oscillator) share one supply network which is different in structure to the other (analogue) supplies to the dac. This supply contains a network of resistors and an inductor.
The supplies to the analogue pin 39 (Vdda; analogue logic), pin 11 (Vddal; analogue left) and pin 42 (Vddar; analogue right), are simpler and only comprise of a resistor and decoupling.
The supply to pin 15 (Vddref) is the same as the analogue supplies.
I assume that the two digital supplies are most sensitive as they been given more attention. The fact that they have a different supply network would suggest that they could benefit from being separated from the analogue supplies,
However, Rotelian has just highlighted the following two statements in the datasheet:
Does this place a limit on the extent to which the supplies can be separated?
Is this the type of "analytic thinking" that you suggest?
The dac is a SMD IC - but I think it may be possible to get close to it.
I will look for this book.
Hi Thorsten
I have the datasheet for the DAC and the schematics for the CDP. The implementation of the DAC is slightly different in both documents - mainly just the values of the decoupling capacitors. In the datasheet they are 47uF lytics with 47nF ceramics. In the CDP schematics, they are 33uF lytics with 100nF ceramics.
If anyone is interested:-
SAA7322-3.PDF
Pin 22 (Vdd1; +5V for digital section) and Pin 23 (Vdd2; +5V for crystal oscillator) share one supply network which is different in structure to the other (analogue) supplies to the dac. This supply contains a network of resistors and an inductor.
The supplies to the analogue pin 39 (Vdda; analogue logic), pin 11 (Vddal; analogue left) and pin 42 (Vddar; analogue right), are simpler and only comprise of a resistor and decoupling.
The supply to pin 15 (Vddref) is the same as the analogue supplies.
I assume that the two digital supplies are most sensitive as they been given more attention. The fact that they have a different supply network would suggest that they could benefit from being separated from the analogue supplies,
However, Rotelian has just highlighted the following two statements in the datasheet:
Does this place a limit on the extent to which the supplies can be separated?
Is this the type of "analytic thinking" that you suggest?
The dac is a SMD IC - but I think it may be possible to get close to it.
I will look for this book.
Re: More on the power supplies.
Konnichiwa,
I had a look at the datasheet. Not to discourage you, but rather than spending a lot of time modding this player I would think it is better to dispose of it apropriatly and to get a sensible modification basis, maybe a pre CD720/21/22 (the 723 seems less desirable due to the prescaling prior to the digital filter).
An old and inherently compromised swing arm mechanism, a DAC chip with unbypassable Op-Amp's of the "not so hot" variety on chip and with in general poor sound (I remember this generation) is best safely deposited in a nearby recycling plant where the plastic and metal can be reclaimed....
Sayonara
Konnichiwa,
Fin said:
I had a look at the datasheet. Not to discourage you, but rather than spending a lot of time modding this player I would think it is better to dispose of it apropriatly and to get a sensible modification basis, maybe a pre CD720/21/22 (the 723 seems less desirable due to the prescaling prior to the digital filter).
An old and inherently compromised swing arm mechanism, a DAC chip with unbypassable Op-Amp's of the "not so hot" variety on chip and with in general poor sound (I remember this generation) is best safely deposited in a nearby recycling plant where the plastic and metal can be reclaimed....
Sayonara
So considerate!
Hi Thorsten
You didn't have to agree with me!!!!!!!
You just did!
Along with everyone who owns:- Philips AK601, AK630, AK640, AK729, CCD310, CCD320, CD110, CD115, CD130, CD140, CD162, CD164, CD210, CD230, CD340, CD380, CD480, CD482, CD500, CD502, CD582, CD583, CD584, CD600, CD604, CD608, CD610, CD614, CD615, CD618, CD624, CD634, CD780, CD781, CD820, CD824, CD830, CD834, CD840, CD850, CDC586, Marantz CD40, CD41, CD42, CD50, CD52, CD60, CD62, CD65II, CD72, CD583, CD593, CD883, Technics SLP177A, SLP202, SLP212, SLP222, SLP277A, SLP377A, SLP477A, SLPG100A, SLPG200A, SLPG400A SLPG420A, SLPG440, SLPG500A, SLPG520A, SLPG540A, SLPJ24A, SLPJ24A, SLPJ26A, SLPJ27A, SLPJ28A SLPJ325A, SLPJ37A, SLPJ46A, SLPS620A, SLPS740A, Rotel RCD855, RCD955, RCD965, Micromega Trio Mk1/MK2, Micromega Leader, Meridian 203, Meridian 206, Arcam Alpha........................
Put it in the bin rather than see what is possible????
Go for an easier option???????
Isn't a "pre CD72X", a CD6XX?
The newer ones are better???????
Look again at pins 10 and 44 (maybe even pins 1 and 9).
Starting with something that already sounds good is not really a challenge and doesn't have as much room for improvement.
Hi Thorsten
Originally posted by Fin
The CD624 was probably one of the cheapest implementations of the CDM4/19. It is unlikely that the CDM4/19 is the limiting factor in this project!!
Surely the crappy Bitstream DAC, poor ground plane, sub-standard power supplies, inferior decoupling, non existant shielding, flimsy plastic case and jitter ridden clock are all far worse than the mechanism/laser!!
You didn't have to agree with me!!!!!!!
You just did!
Along with everyone who owns:- Philips AK601, AK630, AK640, AK729, CCD310, CCD320, CD110, CD115, CD130, CD140, CD162, CD164, CD210, CD230, CD340, CD380, CD480, CD482, CD500, CD502, CD582, CD583, CD584, CD600, CD604, CD608, CD610, CD614, CD615, CD618, CD624, CD634, CD780, CD781, CD820, CD824, CD830, CD834, CD840, CD850, CDC586, Marantz CD40, CD41, CD42, CD50, CD52, CD60, CD62, CD65II, CD72, CD583, CD593, CD883, Technics SLP177A, SLP202, SLP212, SLP222, SLP277A, SLP377A, SLP477A, SLPG100A, SLPG200A, SLPG400A SLPG420A, SLPG440, SLPG500A, SLPG520A, SLPG540A, SLPJ24A, SLPJ24A, SLPJ26A, SLPJ27A, SLPJ28A SLPJ325A, SLPJ37A, SLPJ46A, SLPS620A, SLPS740A, Rotel RCD855, RCD955, RCD965, Micromega Trio Mk1/MK2, Micromega Leader, Meridian 203, Meridian 206, Arcam Alpha........................
Put it in the bin rather than see what is possible????
Go for an easier option???????
Isn't a "pre CD72X", a CD6XX?
The newer ones are better???????
Look again at pins 10 and 44 (maybe even pins 1 and 9).
Starting with something that already sounds good is not really a challenge and doesn't have as much room for improvement.
Ahem, I don't want to interrupt you people but I happen to own a CD634 and I modded some CD624 models. There is not much wrong with these players except for the plastic case that does not deserve that name. CDM 4/19 still beats a lot of newer transports, I would not call it an inherently compromised swing arm mechanism. It is old, that's true but I've seen many new transports that fail at very young age so age itself does not need to be a problem. If it would be crap it wouldn't have functioned for nearly 15 years. I saw and heard some quite good DVD transports recently that sounded good apart from video quality, especially when combined with Wolfson DACs. Nevertheless their longevity is not comparable with older swingarms, lots of RMAs anyhow. I haven't found a quality alternative for CDM 1/4/9 yet to be honest, it plays nearly everything I throw at it so I'll continue using them for a while.
The 1 bit DAC has its weaknesses in the highs ( smearing at peak signals ) but really sounds OK overall. The machine needs work as any Philips cdplayer and is a good base for starters. It is not high end but what can you expect for that price. The SAA7321/22/23 are one of the better sounding 1 bit DAC types Philips produced. IMO better than the newer DAC 7 ( TDA1547 ) types. Believe it or not not but these cdplayers sound better than Teac VRDS 10, both in unmodded state
So throwing the cdplayer away seems a waste of capital to me, certainly when it is in good working order. An excellent cdplayer for learning how to mod and to gain experience in the field.
The 1 bit DAC has its weaknesses in the highs ( smearing at peak signals ) but really sounds OK overall. The machine needs work as any Philips cdplayer and is a good base for starters. It is not high end but what can you expect for that price. The SAA7321/22/23 are one of the better sounding 1 bit DAC types Philips produced. IMO better than the newer DAC 7 ( TDA1547 ) types. Believe it or not not but these cdplayers sound better than Teac VRDS 10, both in unmodded state
So throwing the cdplayer away seems a waste of capital to me, certainly when it is in good working order. An excellent cdplayer for learning how to mod and to gain experience in the field.
Re: So considerate!
Konnichiwa,
Well, maybe drastic....
No. The CD-720 is what I am talking about. I meant pre 723 CD 71X/72X.
Well, their lasers are pretty new, their chipsets are adjustment free and they have a much better (sounding) Multibit DAC (TDA1545).
Yes, there is a really cheap and nasty Op-Amp (not even NE5532 grade) hardwired inplace as I/V converter and no, it cannot removed from the circuit either, so this Op-Amp is the absolute limit of the Analog stage quality, no matter what you do behind it. Of course, as the DAC is a very early Bistream device (and as Philips never yet managed to make a decent sounding Bitstream DAC chip - they seem to get worse with every subsequent generation) the limitation in the Ananlog stage is likely not to matter much anyway.
Starting with something where the foundation is not at least competent and competently implemented is a complete waste of time, in my view.
In many attemps I have yet to get good CD sound out of ANY of the various Bitstream DAC's (Philips, BB, AD,Cirrus,AKM) that have their own on-board analog filters and Op-Amp's. When I say "good sound" this is meant in direct comparison to well implemented Bitstream (NPC) or Multibit (Philips TDA1541, BB PCM 63/1702/1704 especially). Hence my take at "safely dispose".
Sayonara
Konnichiwa,
Fin said:Put it in the bin rather than see what is possible????
Well, maybe drastic....
Fin said:Go for an easier option???????
Isn't a "pre CD72X", a CD6XX?
No. The CD-720 is what I am talking about. I meant pre 723 CD 71X/72X.
Fin said:The newer ones are better???????
Well, their lasers are pretty new, their chipsets are adjustment free and they have a much better (sounding) Multibit DAC (TDA1545).
Fin said:Look again at pins 10 and 44 (maybe even pins 1 and 9).
Yes, there is a really cheap and nasty Op-Amp (not even NE5532 grade) hardwired inplace as I/V converter and no, it cannot removed from the circuit either, so this Op-Amp is the absolute limit of the Analog stage quality, no matter what you do behind it. Of course, as the DAC is a very early Bistream device (and as Philips never yet managed to make a decent sounding Bitstream DAC chip - they seem to get worse with every subsequent generation) the limitation in the Ananlog stage is likely not to matter much anyway.
Fin said:Starting with something that already sounds good is not really a challenge and doesn't have as much room for improvement.
Starting with something where the foundation is not at least competent and competently implemented is a complete waste of time, in my view.
In many attemps I have yet to get good CD sound out of ANY of the various Bitstream DAC's (Philips, BB, AD,Cirrus,AKM) that have their own on-board analog filters and Op-Amp's. When I say "good sound" this is meant in direct comparison to well implemented Bitstream (NPC) or Multibit (Philips TDA1541, BB PCM 63/1702/1704 especially). Hence my take at "safely dispose".
Sayonara
Konnichiwa,
Well, compared to those in the better Philips/Marantz gear they are rather awful. Just compare this CD-624 (I know know the kind of machine this is) to a Marantz CD-94 which is nowadays going 2nd hand for a song. Why bother with this plastic rubbis with a bad transport and DAC if a better basic design is readily and cheaply available?
Which is not saying much, in my view. The 1547 is awful.
Not much of an achievement, thanks to the CD7 DAC's in the 10.... ;-)
Okay, pass it on to a friend or relative.
Only in the mechanical sense. In the sonic sense the basic platform is sufficiently crippled (IMNSHO) to merit summary dismissal, a fate that arguably applies to practically all Bitstream/Delta-Sigma DAC equipped players out there. Very few have even the slightest potential, those with NPC DAC's being one of the very few exceptions to the rule (especially marantz CD63/67 and certain Arcam types, not sure about the recent Wolfson DAC's, no played with them, but Cirrus, BB and AD Delta/Sigma are mostly best avoided, especially the lower end stuff).
Sayonara
jean-paul said:
Well, compared to those in the better Philips/Marantz gear they are rather awful. Just compare this CD-624 (I know know the kind of machine this is) to a Marantz CD-94 which is nowadays going 2nd hand for a song. Why bother with this plastic rubbis with a bad transport and DAC if a better basic design is readily and cheaply available?
jean-paul said:
Which is not saying much, in my view. The 1547 is awful.
jean-paul said:Believe it or not not but these cdplayers sound better than Teac VRDS 10, both in unmodded state
Not much of an achievement, thanks to the CD7 DAC's in the 10.... ;-)
jean-paul said:
Okay, pass it on to a friend or relative.
jean-paul said:
Only in the mechanical sense. In the sonic sense the basic platform is sufficiently crippled (IMNSHO) to merit summary dismissal, a fate that arguably applies to practically all Bitstream/Delta-Sigma DAC equipped players out there. Very few have even the slightest potential, those with NPC DAC's being one of the very few exceptions to the rule (especially marantz CD63/67 and certain Arcam types, not sure about the recent Wolfson DAC's, no played with them, but Cirrus, BB and AD Delta/Sigma are mostly best avoided, especially the lower end stuff).
Sayonara
Back to Mechanics....
Here are my plans for mechanical mods:
Make a base out of 2 pieces of 9mm MDF with neoprene sandwiched in between, these layers will be glued. The upper sheet of MDF will be cut into two sections so that the transport has its own section mechanicaly decoupled from the rest of the player. The 4 bent metal tabs that currently support the mech will be removed and I will use 15mm dia wooden dowel in their places (glued to the transport's decoupled MDF section).
I hope this all makes sense, anyway the idea is to provide some decoupling of the transport from the rest of the player and from the whole player to the equipment rack, without adding excessive mass (energy storage) or making the thing look truly hideous. I guess I'm going for the Sondek approach rather than the Trio LO7D (the hideous comment relates to an MDF monster not the LO7D).
I have searched the wonderful WWW and cannot find a really good objective explanation of mechanics for CD players (there's plenty of marketing drivel and speculation) so it looks like I'm going to have to take a punt on the above approach.
Any opinions or ideas before I get the tools out?
BTW, I looked at the data sheets for the LM1085 - the transient response looks poor compared to LM317 i.e. 30uS versus 5 uS to recover from full load to 100mA (50mA for the LM317). Ripple rejection at HF is also inferior. From the data sheets it looks like LM317 is a better choice. Maybe I should use some NOS samples of LT1038CK (date code 8512) I found in the loft - these are almost vintage (might be corked by now??).
Here are my plans for mechanical mods:
Make a base out of 2 pieces of 9mm MDF with neoprene sandwiched in between, these layers will be glued. The upper sheet of MDF will be cut into two sections so that the transport has its own section mechanicaly decoupled from the rest of the player. The 4 bent metal tabs that currently support the mech will be removed and I will use 15mm dia wooden dowel in their places (glued to the transport's decoupled MDF section).
I hope this all makes sense, anyway the idea is to provide some decoupling of the transport from the rest of the player and from the whole player to the equipment rack, without adding excessive mass (energy storage) or making the thing look truly hideous. I guess I'm going for the Sondek approach rather than the Trio LO7D (the hideous comment relates to an MDF monster not the LO7D).
I have searched the wonderful WWW and cannot find a really good objective explanation of mechanics for CD players (there's plenty of marketing drivel and speculation) so it looks like I'm going to have to take a punt on the above approach.
Any opinions or ideas before I get the tools out?
BTW, I looked at the data sheets for the LM1085 - the transient response looks poor compared to LM317 i.e. 30uS versus 5 uS to recover from full load to 100mA (50mA for the LM317). Ripple rejection at HF is also inferior. From the data sheets it looks like LM317 is a better choice. Maybe I should use some NOS samples of LT1038CK (date code 8512) I found in the loft - these are almost vintage (might be corked by now??).
Re: Back to Mechanics....
Konnichiwa,
I recommend instead solid needlewood or needlewood ply.
Remember, damping resonances usually makes them more audible with music, so consider leaving the neoprene out at this juncture.
Good idea. Make a "large" overall solid wood section for the whole chassis and a seperate section for the Transport, preferably using string suspension (the large plate can supply the frame) and enlarge the holes in the chassis so the transport is (string) suspended on it's own platform.
The ripple rejection at HF is indeed orse, but the load transient plots are not directly comparable, you MUST use a fairly large Cadj with the LT/LM1085 and LM317 to compare. Peruse the Linear Tech LT1085 datasheet for that plot, which shows a much smaller deflection of the Output with a full current (3A there) step.
As usual, one must be able to correctly interporet datasheets to be able to draw conclusions from them. Often different companies show different ways of generating what appears to be the same (and hence comparable) plot.
The LM1085 will substantively behave identically, other than that, go for it.
Sayonara
Konnichiwa,
Dave S said:
I recommend instead solid needlewood or needlewood ply.
Remember, damping resonances usually makes them more audible with music, so consider leaving the neoprene out at this juncture.
Dave S said:
Good idea. Make a "large" overall solid wood section for the whole chassis and a seperate section for the Transport, preferably using string suspension (the large plate can supply the frame) and enlarge the holes in the chassis so the transport is (string) suspended on it's own platform.
Dave S said:
The ripple rejection at HF is indeed orse, but the load transient plots are not directly comparable, you MUST use a fairly large Cadj with the LT/LM1085 and LM317 to compare. Peruse the Linear Tech LT1085 datasheet for that plot, which shows a much smaller deflection of the Output with a full current (3A there) step.
As usual, one must be able to correctly interporet datasheets to be able to draw conclusions from them. Often different companies show different ways of generating what appears to be the same (and hence comparable) plot.
Dave S said:
The LM1085 will substantively behave identically, other than that, go for it.
Sayonara
Thanks Jean-Paul
What an interesting thread this is turning out to be.
Actually, with a little bit of ingemuity and thinking "outside the box" (pardon the pun), the plastic case can be viewed as a bonus. The internal bracing provides quite good structural integrity and can be useful for attaching additional parts/components. Also, these braces can be used to nicely sheild off sections of the pcb. They just happen to line up perfectly with positions that you would want to place shielding to separate the various sections of the circuit board. By simply attaching copper foils (and some damping material) to each of the vertical faces of the plastic braces and deviders, it is easy to produce a structure that should rival most others on sheilding and resonance.
Also - this plastic case has a very nice separate section to the left of the pcb. This can again be sheilded with copper foil and used to accommodate all the additional transformers and power supplies that Thorsten mentions - sort of like an internal/external PSU.
Alternatively - this space could be used to place a new audio board for a different (filter), dac and output stage. Maybe even Thorsten's Thermionic Valve stage could fit in there - just have to be careful with the heat - it could melt the plastic!
For those who don't want to go to all this trouble, just placing a brick in this empty space should work wonders by increasing weight and stability.
Yes Jean-Paul, my understanding is the with most things mechanical/electromechanical, quality is inversely related to date of manufacture.
Specially designed for those of us who dare to be different.
Even if it is as bad as some suggest - then it is virtually impossible to not have a positive result for first time modders.
What an interesting thread this is turning out to be.
Actually, with a little bit of ingemuity and thinking "outside the box" (pardon the pun), the plastic case can be viewed as a bonus. The internal bracing provides quite good structural integrity and can be useful for attaching additional parts/components. Also, these braces can be used to nicely sheild off sections of the pcb. They just happen to line up perfectly with positions that you would want to place shielding to separate the various sections of the circuit board. By simply attaching copper foils (and some damping material) to each of the vertical faces of the plastic braces and deviders, it is easy to produce a structure that should rival most others on sheilding and resonance.
Also - this plastic case has a very nice separate section to the left of the pcb. This can again be sheilded with copper foil and used to accommodate all the additional transformers and power supplies that Thorsten mentions - sort of like an internal/external PSU.
Alternatively - this space could be used to place a new audio board for a different (filter), dac and output stage. Maybe even Thorsten's Thermionic Valve stage could fit in there - just have to be careful with the heat - it could melt the plastic!
For those who don't want to go to all this trouble, just placing a brick in this empty space should work wonders by increasing weight and stability.
Yes Jean-Paul, my understanding is the with most things mechanical/electromechanical, quality is inversely related to date of manufacture.
Specially designed for those of us who dare to be different.
Even if it is as bad as some suggest - then it is virtually impossible to not have a positive result for first time modders.
So considerate!
Hi Thorsten
I appreciate your honesty and understand that you think I might be setting myself up for failure. However, in this situation, I think this one is worth a go. Jean-Paul has had good results and I hope I can too. Besides, I don't have a lot of choice. You guys in the UK and Europe are spoilt for choice when it comes to finding good machines a reasonable prices. A quick look on eBay Australia will highlight my point. If ever there is anything half decent, the bidding goes so high that it gets ridiculous.
I think so!
This CDM4 has hardly been used.
How often would adjustment be required?
The SAA7310 decoder has 1*fs I2S out and the SAA7321 DAC has 4*fs I2S out - allowing the use of many multibit DACs, and O/S or Non O/S. Maybe extreme - but it could even be possible to have three different approaches to D/A conversion in one CDP.
The advantage I see to this CDP is that you can progressively move backwards through the signal path and improve or bypass one stage at a time. This could start with the existing opamp output satge, then the final on-board opamps could be bypassed, then the D/A part of SAA7321 could be bypassed, then the filter part of the SAA7321 could be bypassed..............until you find a sound you like.
All this in one CDP with only one outlay for a good clock, transformers, power supplies, mechanics improvements, etc.
I think I read something similar near the start of this thread!
So - if I skip all of the experimentation and connect a TDA1541 to the SAA7321 or SAA7310, or a SM5842/PCM63 combination to the SAA7310, then it could be a worthwhile project?
Hi Thorsten
I appreciate your honesty and understand that you think I might be setting myself up for failure. However, in this situation, I think this one is worth a go. Jean-Paul has had good results and I hope I can too. Besides, I don't have a lot of choice. You guys in the UK and Europe are spoilt for choice when it comes to finding good machines a reasonable prices. A quick look on eBay Australia will highlight my point. If ever there is anything half decent, the bidding goes so high that it gets ridiculous.
I think so!
This CDM4 has hardly been used.
How often would adjustment be required?
The SAA7310 decoder has 1*fs I2S out and the SAA7321 DAC has 4*fs I2S out - allowing the use of many multibit DACs, and O/S or Non O/S. Maybe extreme - but it could even be possible to have three different approaches to D/A conversion in one CDP.
Originally posted by Kuei Yang Wang
Yes, there is a really cheap and nasty Op-Amp (not even NE5532 grade) hardwired inplace as I/V converter and no, it cannot removed from the circuit either, so this Op-Amp is the absolute limit of the Analog stage quality, no matter what you do behind it. Of course, as the DAC is a very early Bistream device (and as Philips never yet managed to make a decent sounding Bitstream DAC chip - they seem to get worse with every subsequent generation) the limitation in the Ananlog stage is likely not to matter much anyway.
The advantage I see to this CDP is that you can progressively move backwards through the signal path and improve or bypass one stage at a time. This could start with the existing opamp output satge, then the final on-board opamps could be bypassed, then the D/A part of SAA7321 could be bypassed, then the filter part of the SAA7321 could be bypassed..............until you find a sound you like.
All this in one CDP with only one outlay for a good clock, transformers, power supplies, mechanics improvements, etc.
I think I read something similar near the start of this thread!
Originally posted by Kuei Yang Wang
In many attemps I have yet to get good CD sound out of ANY of the various Bitstream DAC's (Philips, BB, AD,Cirrus,AKM) that have their own on-board analog filters and Op-Amp's. When I say "good sound" this is meant in direct comparison to well implemented Bitstream (NPC) or Multibit (Philips TDA1541, BB PCM 63/1702/1704 especially). Hence my take at "safely dispose".
So - if I skip all of the experimentation and connect a TDA1541 to the SAA7321 or SAA7310, or a SM5842/PCM63 combination to the SAA7310, then it could be a worthwhile project?
Re: Back to Mechanics....
Hi Dave
I'm sorry for causing your thread to be diverted somewhat - it was not my intention and it just developed that way. Actually it is really Bernhard's fault - things were fairly relevant, or at least gerenic, until he opened the can of worms about the CDM4. I hope you find some of our discussion interesting anyway. Maybe it should be moved to a new thread, but I don't know how to do that.
Dave S said:
Hi Dave
I'm sorry for causing your thread to be diverted somewhat - it was not my intention and it just developed that way. Actually it is really Bernhard's fault - things were fairly relevant, or at least gerenic, until he opened the can of worms about the CDM4. I hope you find some of our discussion interesting anyway. Maybe it should be moved to a new thread, but I don't know how to do that.
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