Agree entirely !
I just would not want to be on the wrong end of his vitreol
Looks and sound quality - completely irrelevant
This thread is about a multi changerand op amp swapping - then it extends to ' just drop in this and that ' high end smart **** stuff
The player is simply not worthy of the rest of the mods we could advise.
Just let the guy swap op amps and enjoy himself for pete's sake.
I did once upon a time and it was fun
LM 49710's rock..... drop them in kvholio and see for yourself !!
Smart guy, the thread changed when a Denon cdplayer was discussed. Calling a 3 Euro DAC chip high end !? Not my words, although the chip is capable of extremely good results.
The Denon has outdated ( =mediocre) sounding PCM DAC chips also with way too much opamps in the output stage and the solution I proposed costs less than the easy way out: changing opamps. This also counts for the cd changer, a cheaper and better solution which has a higher price/quality ratio is a better solution. Why invest in expensive opamps if it is not necessary ?
I am experienced enough to know that wire nests and stacked parts with long wires won't make stuff better i.e. good looking means "technically good looking" for those that could not understand that. Short wires, decoupling caps close to the chip they need to decouple etc.etc. If you reread my post you probably will see that I asked the same question as you did.
Back to the original subject: personally I would not even bother to mod a cd changer as they're the ones most prone to failures of the mechanical parts. There must be reliable ones out there but I haven't seen one yet.
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this thread
The original post was to point out that a highly rated expensive cd player looked quite poorly built. Not only was it praised for its sound, but also for it's build quality. Back in the mid nineties, made in China was a crap shoot. The Denon was better build but was the cheaper of the two. The Adcom was the better sounding of the two. Again, what is the important aspects that make good sound. The Denon had better quality parts that lasted through time, the Adcom had many failed parts. The Denon had all it's part properly place and neatly done, the Adcom is just a mess. So maybe the spaghetti mess may sound good.
The original post was to point out that a highly rated expensive cd player looked quite poorly built. Not only was it praised for its sound, but also for it's build quality. Back in the mid nineties, made in China was a crap shoot. The Denon was better build but was the cheaper of the two. The Adcom was the better sounding of the two. Again, what is the important aspects that make good sound. The Denon had better quality parts that lasted through time, the Adcom had many failed parts. The Denon had all it's part properly place and neatly done, the Adcom is just a mess. So maybe the spaghetti mess may sound good.
Or the people that did evaluate their sound where influenced by other factors like... price? Personal self respect? Once you have paid some 700$ on it is hard to accept that doesn NOT sound better than a 200$ CD. Reviews that I read now, show mostly unreability, not audio quality (it does not mean that it didn't sound good).
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Of course people doing a subjective evaluation are influenced by price, appearance, manufacturer reputation etc.
Thinking you can 'switch off' these influences when listening is a mistake imo.
The only way known to me that excludes these influences are double blind tests.
/offtopic
i think i'll go ahead with trying different opamps, to be honest i don't think it's useful to anyone if i report my subjective findings.
It also has been done before a million times so i don't think opening a thread would bring anything new to the table.
Jean-Paul's suggestion of replacing the DAC sounds like an interesting option, if i decide to try this it could be useful to others to show the way i implemented it, or discuss technical issues.
Best regards,
Klaas
Thinking you can 'switch off' these influences when listening is a mistake imo.
The only way known to me that excludes these influences are double blind tests.
/offtopic
i think i'll go ahead with trying different opamps, to be honest i don't think it's useful to anyone if i report my subjective findings.
It also has been done before a million times so i don't think opening a thread would bring anything new to the table.
Jean-Paul's suggestion of replacing the DAC sounds like an interesting option, if i decide to try this it could be useful to others to show the way i implemented it, or discuss technical issues.
Best regards,
Klaas
Hey, go right ahead and tell us how you get on - I'll be watching.
We're a friendly bunch and it's always nice to hear someone else made some improvements.
Try and damp as much of the plastic parts and case as you can ( bitumen sheet / silicon sealant... carefully ) and if you must do things that need loads of wiring...........Jean Paul is correct ( gulp )
The LM 497.... op amps are very nice in the context of what they do and in relation to most others out there ( but it's all personal taste - before someone steps in and we have an op amp argument - hahah )
You could beef up the main power supply smoothing capacitors and change the existing bridge rect diodes to something fast / soft recovery ( cheap ones are the uf 4007 as an example )
The above won't break the bank and will absolutely change the sound.
Apologies to Jean Paul if I seemed a bit rude - we are in agreement anyway I think
Andrew
We're a friendly bunch and it's always nice to hear someone else made some improvements.
Try and damp as much of the plastic parts and case as you can ( bitumen sheet / silicon sealant... carefully
) and if you must do things that need loads of wiring...........Jean Paul is correct ( gulp ) The LM 497.... op amps are very nice in the context of what they do and in relation to most others out there ( but it's all personal taste - before someone steps in and we have an op amp argument - hahah )
You could beef up the main power supply smoothing capacitors and change the existing bridge rect diodes to something fast / soft recovery ( cheap ones are the uf 4007 as an example )
The above won't break the bank and will absolutely change the sound.
Apologies to Jean Paul if I seemed a bit rude - we are in agreement anyway I think
Andrew
Welll , it took some time to replace the opamps and stick all the bitumen inside the Denon
Just kidding, bitumen is fine for roofing and dampening loudspeaker-enclosures,
i'm not sure it will do any good inside a cd-player that's already built like a tank.
The opa2134's are an improvement, but i've been thinking a dedicated regulated powersupply for them could improve things even more.
I prefer the idea of regulators close to the opamps over having a bulky supply located far away from the opamps.
I designed a small pcb that could be plugged in to the opamp's sockets,
with simple 3-leg regulators onboard.
The opamps will still use the existing circuitry on the main pcb.
Since space is really constricted, the pcb i designed had to be really small, what i came up with sofar has roughly the size of a stamp.
Please note that the groundplane isn't attached to anything yet, despite doing some reading on the subject,
i must admit i'm still kinda lost on the subject of using groundplanes.
Comments and advice are greatly appreciated
Regards,
Klaas
Just kidding, bitumen is fine for roofing and dampening loudspeaker-enclosures,
i'm not sure it will do any good inside a cd-player that's already built like a tank.
The opa2134's are an improvement, but i've been thinking a dedicated regulated powersupply for them could improve things even more.
I prefer the idea of regulators close to the opamps over having a bulky supply located far away from the opamps.
I designed a small pcb that could be plugged in to the opamp's sockets,
with simple 3-leg regulators onboard.
The opamps will still use the existing circuitry on the main pcb.
Since space is really constricted, the pcb i designed had to be really small, what i came up with sofar has roughly the size of a stamp.
Please note that the groundplane isn't attached to anything yet, despite doing some reading on the subject,
i must admit i'm still kinda lost on the subject of using groundplanes.
Comments and advice are greatly appreciated
Regards,
Klaas
Attachments
Personally... I wouldn't.
The fact the regs are some didstance away isn't in itself an issue when current draw is constant. What matter is a low impedance supply at the opamps and that is achieved with correct decoupling.
Identify your problem before trying to fix it
I suspect adding a separate PCB and regs will be difficult because you need to decide exactly where the ground returns have to be in order not to inject noise where it is not wanted.
I would at most think of adding something like a 0.1uf perhaps in series with a 1 ohm across the supply of the opamps.
The fact the regs are some didstance away isn't in itself an issue when current draw is constant. What matter is a low impedance supply at the opamps and that is achieved with correct decoupling.
Identify your problem before trying to fix it
I suspect adding a separate PCB and regs will be difficult because you need to decide exactly where the ground returns have to be in order not to inject noise where it is not wanted.
I would at most think of adding something like a 0.1uf perhaps in series with a 1 ohm across the supply of the opamps.
Thanks for your comments, i agree that having the powersupply at some distance from the opamps isn't necessarily bad.
However, when i look at the Denon's schematic, the dacs are also fed by the same supply (still have to verify this by measurement)
The symmetrical 12v-supply has a much bigger electrolyt at the output of the negative rail, 2200 uF for the negative rail instead of 100 uF for the positive rail.
Maybe because current-draw is asymmetrical ?
It hardly looks like an ideal powersupply for the opamps to me.
It actually surprises me that there's so little investment in the powersupply,
maybe it was more important for the manufacturer to invest in dead weight
Main reasons to consider my approach are that it is easily reversible and small.
Where to place the ground returns is also something that bothers me.
Regards,
Klaas
However, when i look at the Denon's schematic, the dacs are also fed by the same supply (still have to verify this by measurement)
The symmetrical 12v-supply has a much bigger electrolyt at the output of the negative rail, 2200 uF for the negative rail instead of 100 uF for the positive rail.
Maybe because current-draw is asymmetrical ?
It hardly looks like an ideal powersupply for the opamps to me.
It actually surprises me that there's so little investment in the powersupply,
maybe it was more important for the manufacturer to invest in dead weight
Main reasons to consider my approach are that it is easily reversible and small.
Where to place the ground returns is also something that bothers me.
Regards,
Klaas
Interesting thread.
Before I started my DIY fun, I threw away my GCD-700 when the CD changer mechanism went south. Now I regret that I didn't salvage the working drive. Anyhow, it is a looong weekend here in US, so I decided to recap all the mid '90 era CD player just for the break.
It is kind of interesting that the low cost CD players at this time didn't have any 3 legs regular, and most of them are like Klaas said, have asymmetrical filter caps for the +/- rails. However, in my Denon DCD-815 and DCM-460, the +ve side have bigger filter caps (same for the Sony CDP-361).
The 2 Denon's use PCM61P-L and have essentially the same circuit design. Comparing to the DCD-1015 (higher model number implies higher end) with the same DAC, there is no opamp after the DAC. It is basically one (cheap) output cap after the LPF. I wonder can someone educate me the pros and cons of the types of "Dac outputs"?
The service manual is too big to upload, but I can email to whoever wants to see the detail.
Thanks!!
Before I started my DIY fun, I threw away my GCD-700 when the CD changer mechanism went south. Now I regret that I didn't salvage the working drive. Anyhow, it is a looong weekend here in US, so I decided to recap all the mid '90 era CD player just for the break.
It is kind of interesting that the low cost CD players at this time didn't have any 3 legs regular, and most of them are like Klaas said, have asymmetrical filter caps for the +/- rails. However, in my Denon DCD-815 and DCM-460, the +ve side have bigger filter caps (same for the Sony CDP-361).
The 2 Denon's use PCM61P-L and have essentially the same circuit design. Comparing to the DCD-1015 (higher model number implies higher end) with the same DAC, there is no opamp after the DAC. It is basically one (cheap) output cap after the LPF. I wonder can someone educate me the pros and cons of the types of "Dac outputs"?
The service manual is too big to upload, but I can email to whoever wants to see the detail.
Thanks!!
First point, having unconnected copper pours on a PCB is bad practice, connect it to ground.
Understand how currents realy flow and getting to grips with ground (return path) will follow somwhat, electrons dont drift very far or very fast in terms of current flow, the waves are important. Ground planes quite often become a necessity for EMC reasons, such as controlling the ever increasing RF pollution we endure.
http://www.x2y.com/filters/TechDay0...log_Designs_Demand_GoodPCBLayouts _JohnWu.pdf
And Henry Ott (the EMC master, and the BEST resource for grounding issues):
home page
Understand how currents realy flow and getting to grips with ground (return path) will follow somwhat, electrons dont drift very far or very fast in terms of current flow, the waves are important. Ground planes quite often become a necessity for EMC reasons, such as controlling the ever increasing RF pollution we endure.
http://www.x2y.com/filters/TechDay0...log_Designs_Demand_GoodPCBLayouts _JohnWu.pdf
And Henry Ott (the EMC master, and the BEST resource for grounding issues):
home page
The PCM61(essentially identical to AD1860) has an internal opamp for i/v conversion, and the 8x oversampling meant that they could get away with no additional output stage. The Denon DCM444 magazine changer(far better than the carousels for reliability, as it's a proven Pioneer mech) uses exactly the same output scheme, and actually sounds pretty damn good. I'd rather have this configuration than a cheaply implemented additional opamp output/lpf stage in the way. The PCM61/AD1860 is a very sweet sounding dac when done halfway well.
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