| Dave S |
I have a CD723 with all the "Chris Found" mods plus:
KC-7,
AD826 I/V
Schottky PSU diodes
Separate transformer with emitter follower type power supplies for the OpAmp and DAC (cut down version of the Audionote PSU).
Servo 11V is still supplied off the original unregulated supply.
Output caps 22uF 63V FCs bypassed with 10nF Wima polypropylenes
Chassis damping
In varying amounts, most of the mods made improvements to the sound of the player. However it is still some way behind my lightly modified Arcam Alpha+ player (Trichord clock and a few component upgrades) and a long way behind my friend's Cambridge Audio CD2, both of which are 10+ years old. I reckon the CD723 is comparable with a decent modern £400 CD player.
Any suggestions to make the CD723 better, or have I reached the limit with this very cheap machine??? |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Dave S
I have a CD723 with all the "Chris Found" mods plus:
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Hmmm.
| quote: | Originally posted by Dave S
KC-7,
|
I hope it is well implemented. I would expect the layout to be critical, much more so than the actual circuit.
| quote: | Originally posted by Dave S
AD826 I/V
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Why? You like bad sound?
| quote: | Originally posted by Dave S
Schottky PSU diodes
Separate transformer with emitter follower type power supplies for the OpAmp and DAC (cut down version of the Audionote PSU).
|
Hmmm. Nothing wrong with that, but again implementation is critical.
| quote: | Originally posted by Dave S
Servo 11V is still supplied off the original unregulated supply.
Output caps 22uF 63V FCs bypassed with 10nF Wima polypropylenes
|
Why? You like bad sound?
| quote: | Originally posted by Dave S
Chassis damping
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In what sense?
| quote: | Originally posted by Dave S
Any suggestions to make the CD723 better,
|
Yes. Analyse the Circuit. identify the weaknesses and address them. You seem to have left most of the in place, the same style it is often done by "boutique" modders who like sell expensive modules and pretend that an excellent clock and analogue stage will makie a world class player out of any mediocre piece of rubbish.
| quote: | Originally posted by Dave S
or have I reached the limit with this very cheap machine???
|
I don't think so.
Sayonara |
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| Elso Kwak |
| quote: | Originally posted by Dave S
I have a CD723 with all the "Chris Found" mods plus:
KC-7,
AD826 I/V
Schottky PSU diodes
Separate transformer with emitter follower type power supplies for the OpAmp and DAC (cut down version of the Audionote PSU).
Servo 11V is still supplied off the original unregulated supply.
Output caps 22uF 63V FCs bypassed with 10nF Wima polypropylenes
Chassis damping
In varying amounts, most of the mods made improvements to the sound of the player. However it is still some way behind my lightly modified Arcam Alpha+ player (Trichord clock and a few component upgrades) and a long way behind my friend's Cambridge Audio CD2, both of which are 10+ years old. I reckon the CD723 is comparable with a decent modern £400 CD player.
Any suggestions to make the CD723 better, or have I reached the limit with this very cheap machine??? |
Hi Dave,
You could try the OPA2604 or the OP275 for IV.
Jung like regulators seem to better suited for the analog stages in my experience.
A balanced power 1:1 transformer improved the sound of my Philips CD931.
Ultrasoft recovery diodes worked better for me, but this is clearly player dependent as all mods. In the Philips CD650 I heard a big difference, in the CD931 not.
:cool: |
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| sreten |
"you have to be cruel to be kind"
Mods improve matters but there's no way you can expect
to be able to bypass total high quality build practises.
You can't turn a cheap CD player into a giant killer.
:) sreten. |
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| jean-paul |
| Say that again to the Tjoeb guys ! |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by sreten
Mods improve matters but there's no way you can expect
to be able to bypass total high quality build practises.
You can't turn a cheap CD player into a giant killer.
|
Actually, you can. Here is what is wrong with the CD-720/21/22/23:
1) Powersupply - complete joke. Fit seperate transformers/supplies for Analogue Stage & DAC (+/-12V & 5V), one for the Servo circuitry (+/-12V), one for the clock (5V) - use the basic Tent Audio Module - hard to implement it wrong if you use a fully insulated supply, fit correctly & forget and one (5V - might be 3.3V on the later verions) Supply for the main CD processor.
Build well implemented and de-noised supplies and clean up the original supply to only supply "utility" digital circuitry (uP/Display/Remote etc.). All the transformers used to supply especially the digital section should be chosen for minimal leakage between secondary and earth and suitably phased/ploarised to minimise further any leakage. Then add an external 1:1 insulation transformer and filter, non of this needs a lot of power.
2) Chassis - complete joke. For a minimum fit a serious solid wood bottom plate (spruce plywood) and fit some decoupling feet like the String Suspension thingies you get. Add solid hardwood sidecheeks and a plywood rear panel, plus a nice solid vented top cover made from thin spruce ply, for fun make the vent openings in the shape of Violin Vents. C37 laquering of wood and PCB's are optional.
3) Fit a nice superfast Op-Amp (LM6182 is still my choice) in the analog stage (more or less original circuit adjusted for 2mA Full Scale Current), no capacitor in the feedback loop and follow by a simple low impedance 1st Order LPF (I used 100R/15..22nF IIRC) and a suitable (passive) offset adjustment to get rid of the output offset.
Now the above can be done well on a fairly tight budget, within the existing case so on. For more extreme versions a string suspended drive for a toploader might be worth a try.
The Digital Filter and DAC in the CD-723 are "good enough for CD", if you make sure to eliminate the other problems.
Sayonara |
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| sreten |
| quote: | Originally posted by jean-paul
Say that again to the Tjoeb guys ! |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
Actually, you can. Here is what is wrong with the CD-720/21/22/23:
1) Powersupply - complete joke. Fit seperate transformers/supplies for Analogue Stage & DAC (+/-12V & 5V), one for the Servo circuitry (+/-12V), one for the clock (5V) - use the basic Tent Audio Module - hard to implement it wrong if you use a fully insulated supply, fit correctly & forget and one (5V - might be 3.3V on the later verions) Supply for the main CD processor.
Build well implemented and de-noised supplies and clean up the original supply to only supply "utility" digital circuitry (uP/Display/Remote etc.). All the transformers used to supply especially the digital section should be chosen for minimal leakage between secondary and earth and suitably phased/ploarised to minimise further any leakage. Then add an external 1:1 insulation transformer and filter, non of this needs a lot of power.
2) Chassis - complete joke. For a minimum fit a serious solid wood bottom plate (spruce plywood) and fit some decoupling feet like the String Suspension thingies you get. Add solid hardwood sidecheeks and a plywood rear panel, plus a nice solid vented top cover made from thin spruce ply, for fun make the vent openings in the shape of Violin Vents. C37 laquering of wood and PCB's are optional.
3) Fit a nice superfast Op-Amp (LM6182 is still my choice) in the analog stage (more or less original circuit adjusted for 2mA Full Scale Current), no capacitor in the feedback loop and follow by a simple low impedance 1st Order LPF (I used 100R/15..22nF IIRC) and a suitable (passive) offset adjustment to get rid of the output offset.
Now the above can be done well on a fairly tight budget, within the existing case so on. For more extreme versions a string suspended drive for a toploader might be worth a try.
The Digital Filter and DAC in the CD-723 are "good enough for CD", if you make sure to eliminate the other problems.
Sayonara |
I simply don't care. My bog standard Cambridge Audio
CD4SE is miles better than any modded cheap CD player,
tubes added or not, and as far as I'm concerned thats it.
:) sreten. |
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| Nuuk |
| I got clear improvements with thorough mechanical modifications as described HERE .;) |
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| jean-paul |
| quote: | Originally posted by sreten
I simply don't care. My bog standard Cambridge Audio
CD4SE is miles better than any modded cheap CD player,
tubes added or not, and as far as I'm concerned thats it.
:) sreten. |
If you don't care why react in this thread ? You can't compare apples and pears but there are really a lot of possibilities with cheap cdplayers. Especially if you dont like to watch tv in your spare time and have a soldering tool waiting.
For bog standard more or less expensive cdplayers without needed work you're on the wrong forum ;) Besides that there are plenty expensive cdplayers with excellent build quality that sound absolutely mediocre. The fun with DIY can be making a very good cdplayer with a cheap basic model and some hard earned knowledge.
I don't want to challenge you but your remark "miles better than any modded cheap CD player" is like walking on thin ice. |
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| Nuuk |
| I had a CD4SE and they are excellent CDP's but I don't know if it is that much better than my modified CD723 (which cost me about half of what the CD4SE did! ;) |
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| sreten |
| quote: | Originally posted by jean-paul
If you don't care why react ? You can't compare apples and pears but there are really a lot of possibilities with cheap cdplayers. Especially if you dont like to watch tv in your spare time and have a soldering tool waiting.
For bog standard more or less expensive cdplayers without needed work you're on the wrong forum ;) Besides that there are plenty expensive cdplayers with excellent build quality that sound absolutely mediocre. The fun with DIY can be making a very good cdplayer with a cheap basic model and some hard earned knowledge.
I don't want to challenge you but your remark "miles better than any modded cheap CD player" is walking on thin ice. |
Except the CD4SE is allegedly accepted to be a "giant killer".
(At ~ twice the cost of a budget CD player at the time.)
IMO if you want the best don't make it difficult for yourself.
You can improve a cheap CD player, this I'm not arguing.
But you can't IMO mod a basic CD player into the "ultimate".
What I'm suggesting is take a good / very good CD player and
adding mods that should improve matters is surely easier than
trying to take a cheap (but more to the point average design)
CD player to somewhere it will eventually refuse to go.
:) sreten. |
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| carlosfm |
| quote: | Originally posted by sreten
IMO if you want the best don't make it difficult for yourself.
You can improve a cheap CD player, this I'm not arguing.
But you can't IMO mod a basic CD player into the "ultimate".
|
Who said so?!:eek:
You should take a listen to my old Marantz CD52 SE with internal TDA1543 NOS Dac and dedicated trafo/PSU.:up:
And Tent clock.
Well, yes, it's useless to loose much time on a player with a bitstream Dac (like my Marantz), but you can easily do something very special out of it.
THIS is giant killer, miles ahead of your BUDGET Cambridge CD4SE.
And I spent much less money than you, with all this.:p
Deam it, these days people use "giant-killer" and "high-end" too easilly, banalizing this words.
You haven't heard anything yet.:devily: |
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| Fin |
| quote: | Originally posted by carlosfm
You should take a listen to my old Marantz CD52 SE with internal TDA1543 NOS Dac and dedicated trafo/PSU.:up:
And Tent clock.
Well, yes, it's useless to loose much time on a player with a bitstream Dac (like my Marantz), but you can easily do something very special out of it.
|
I wonder what the results would be like if the same level of attention was given to the original Bitstream DAC???? |
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| sreten |
| quote: | Originally posted by carlosfm
THIS is giant killer, miles ahead of your BUDGET Cambridge CD4SE.
And I spent much less money than you, with all this.:p
|
Unlikely for both cases, my CD4SE is completely standard.
I think its very good, but reputation is its outstanding.
:) sreten. |
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| Fin |
| quote: | Originally posted by sreten
Mods improve matters but there's no way you can expect
to be able to bypass total high quality build practises.
You can't turn a cheap CD player into a giant killer.
|
What are those "high quality build practices"?
And
Who said anything about "bypassing" them?
Looking at Kuei Yang Wang's recommendations, I don't see any evidence of short-cuts. Every aspect of the player's build/design is addressed.
| quote: | Originally posted by sreten
I simply don't care. My bog standard Cambridge Audio
CD4SE is miles better than any modded cheap CD player,
tubes added or not, and as far as I'm concerned thats it.
|
How do you know this?
| quote: | Originally posted by sreten
Except the CD4SE is allegedly accepted to be a "giant killer".
(At ~ twice the cost of a budget CD player at the time.) |
"Allegededly accepted whom"?
A "giant killer" at twice the cost of a budget CDP???
Is this a contradiction?
The giants that it is killing must be even more expensive. How did it manage to do this? - By somehow bypassing the "high quality build practices" of the very expensive machines??
| quote: | Originally posted by sreten
IMO if you want the best don't make it difficult for yourself.
You can improve a cheap CD player, this I'm not arguing.
But you can't IMO mod a basic CD player into the "ultimate". |
What is "the best" and how do you know when you've got it?
Doing that which is difficult is what this forum is all about. For most of us, there is a certain satisfaction in taking a machine with humble beginnings and turning it into something much better. We are not bypassing high quality build practices - we are trying to identify the short-cuts and cost cutting that the manufacturer has made, and then address those items.
| quote: | Originally posted by sreten
What I'm suggesting is take a good / very good CD player and
adding mods that should improve matters is surely easier than
trying to take a cheap (but more to the point average design)
CD player to somewhere it will eventually refuse to go. |
How does one know that the designer of the more expensive CDP has got it right? These players are still built to a price point and will still be compromised in some way. Yes, the more expensive machine may sound better than the unmodded budget one - but once the modding process starts, a lot more innovative ideas and best sounding or engineering practices can be implemented in the more basic models. For instance, a mid priced CDP may have some reasonable quality componentry or sections. It is less likely that you would rip these out to replace them with the best options. If you do rip them out, then you have wasted you money in the first place by paying for their inclusion in your CDP. It is also possible that the more expensive machines rely more heavily on the selection of specific components and less on the critical layout. |
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| Nuuk |
Forunately for all of us, the designer of the CD4SE seems keener on promoting DIY modding than Sretin. ;)
Actually, the CD4SE was not really suitable for upgrading (electronically) as it was already extensively 'modded', hence the excellent sound quality. Much better for a DIYer to start with something like the CD723 which is basic and cheap!
As ever the last words should be 'each to his (or her) own!' :yinyang: |
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| carlosfm |
| quote: | Originally posted by Fin
I wonder what the results would be like if the same level of attention was given to the original Bitstream DAC???? |
Of course it was.
And I have two independent RCA outs on the player, I can even A/B.
There's no comparison between a bitstream Dac, the better that it may be, and a good multibit Dac.
Yes, the TDA1543 is good.
Forget the specs, well done it's very good.;)
Bitstream Dacs always sound undynamic to me.:rolleyes: |
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| sreten |
Hmmm......
I don't know why I'm being given a hard time for trying to answer
the original question, and after all these are my opinions, not
statements of absolute fact.
If you think differently fine, they are my considered opinions.
:) sreten. |
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| Nuuk |
I'm not trying to give anybody a hard time! Life does that well enough for all of us. ;)
But the original question was how could the CD723 be modified to sound better. You introduced the subject of starting off with a 'better' product. That's fine if the person asking the question was enquiring about how to get a good CDP from scratch. But he already has his CD723 and has spent time and money on it.
For my part, I was just saying that having heard the CD4SE and a modified CD723, I would prefer to go with the CD723 from a modders point of view.
If I just wanted to have a really good sounding CDP without opening the case, I would take your suggestion and try to hunt out a CD4SE although they are rare as hens teeth and I doubt any owners are prepared to sell theirs - would you?
I also speak from experience in saying that the CD4SE is not a good CDP for modding!
I greatly respect your vast knowledge of speaker building and if you came on a thread about speakers and put me right, I wouldn't think that you were giving me a hard time ;) |
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| carlosfm |
| Unfortunately, the sad news is that if you want a really good sounding CDP without opening the case (can you resist?:D ), you'll have to spend much more money than that CD4SE costs.:bawling: |
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| Bernhard |
| quote: | Originally posted by Kuei Yang Wang
no capacitor in the feedback loop
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Just tried that in my 880, no change. |
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| Fin |
| quote: | Originally posted by carlosfm
Of course it was.
And I have two independent RCA outs on the player, I can even A/B.
There's no comparison between a bitstream Dac, the better that it may be, and a good multibit Dac.
Yes, the TDA1543 is good.
Forget the specs, well done it's very good.;)
Bitstream Dacs always sound undynamic to me.:rolleyes: |
Thanks Carlos - it's good to hear from someone who has given both types of DAC a fair go. I will probably end up doing something similar to you - ie. take the SAA7321 in the CD624 to it's max, and then do a good multibit dac for comparisson. The idea of being able to A/B two DACs in one CDP is great. Do you run them off the same Tent Clock at the same time? |
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| Fin |
| quote: | Originally posted by sreten
Hmmm......
I don't know why I'm being given a hard time for trying to answer
the original question, and after all these are my opinions, not
statements of absolute fact.
If you think differently fine, they are my considered opinions.
|
That's fine Sreten - everyone is entitled to their opinion. However, you did challenge almost every DIYer on the Digital forum. Your statements telling us that we are all wrong were presented as "absolute fact".
| quote: | Originally posted by sreten
You can't turn a cheap CD player into a giant killer. |
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| carlosfm |
| quote: | Originally posted by Fin
Do you run them off the same Tent Clock at the same time? |
Yes, it feeds the 7310, the digital filter, and the bitstream dac separately.:cool:
The TDA1543 gets (NOS) I2S from the 7310. |
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| Dave S |
They have given me some more things to try.
I will try some of the KYW mods in the not too distant future.
I note with interest his comment about the C Found mods as I also had some doubts e.g. CF recommends changing the -11V PSU cap from 3,300u to 4,700u to match the +11V, (quote) "this balances the loading of the mains transformer windings and allows for a slightly higher current dissipation". Impressive stuff!!!!
The KC-7 is built on Elso's pcb and fitted <5cms from the signal processor - maybe I should connect it to BCK at the DAC as well (do I need to disconnect the original BCK i.e pin 48 of the SAA7378 from BCK input, pin 1 of the TDA1545?).
Elso - thanks for the OP275 recommendation. I replaced the OPA627s I/V in my Arcam with a pair of OP176s and was surprised to get a worthwhile improvement. The OPA627 is better than the OP176 in the o/p filter but it seems to be the other way round in the I/V. I will try an OP275 next time I open up the CD723.
My approach with the CD723 is in line with the points made by Fin and Jean-Paul - it's a bit of cheap, clean entertainment to see what can be achieved. Better to peel a few tracks off this pcb than a Wadia! Expectations are low so if it turns out good then that's just fine with me.
On another point - discrete I/V stages - I'm sure many will recommend this. However I had a bad experience with the LC audio ZAPfilter. The minimal instructions are wrong and eventually LC more or less agreed that the thing cannot accomodate unipolar current output without an external bias current.
Anyway, I ran the thing as a line stage to see how it sounds and was unimpressed, it's some way behind an OPA604 run off even the most basic of power supplies!
Might be tempted by KYW's OPA660 I/V circuit if I can find a decent pcb to accommodate it (haven't got time to design one 'cos I need to finish quite a number of projects).
Cheers
Dave |
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| carlosfm |
| Try the LM6172 for I/V.;) |
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| Kuei Yang Wang |
Hi,
| quote: | Originally posted by Dave S
I note with interest his comment about the C Found mods
|
I happen to know the gentleman, nuff said.
| quote: | Originally posted by Dave S
The KC-7 is built on Elso's pcb and fitted <5cms from the signal processor
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Seperate (galvanically) PSU with low earth leakage for that?
| quote: | Originally posted by Dave S
maybe I should connect it to BCK at the DAC as well
|
No, don't.
| quote: | Originally posted by Dave S
I will try an OP275 next time I open up the CD723.
|
Try an LM6182 please. No reactive components in the feedback loop, just one resistor and adjust teh values for 2mA 0dbf on the TDA1545 (see datasheet).
Sayonara |
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| Dave S |
Quote: "Seperate (galvanically) PSU with low earth leakage for that?"
1) Elso recommends using the digital +/-10V rails, not a separate PSU.
2) Given that Elso may be fallible, how do I get low earth leakage? Do I need an E-I core transformer rather than a toroid?
I added an IEC mains input, which means I have the possibility to earth the chassis - is this worthwhile?
Dave |
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| Dave S |
LM6182 is discontinued, not sure if I can find NOS. Can I use AD812 in the same way?
Other duals in my bitbox: OP275, RC4227, NE5532, AD8620 (SO8) - any of these worth a try?
LM6172 looks viable if I can find one (not listed in Farnell, RS or Digikey), OTOH the feedback resistor, 3K3, seems a bit high for such a fast amp.
Should I change the o/p circuit from CF's, which is:
3K3 feedback resistor with 470pF polystyrene in parallel
47uF pana FC // with10nF Wima on opamp output (you aready told me to change this)
1K series resistor and 470uH and 820pF in shunt (after the coupling caps).
Thanks |
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| rbroer |
| quote: | Originally posted by Kuei Yang Wang
Originally posted by Dave S
maybe I should connect it to BCK at the DAC as well
No, don't.
|
Please do so :cool:
The BCK "happens" to be 8.X MHz.
There's enough time margin to prevent metastability problems (BCK output of decoder is lagging a bit with respect to clock input).
To be really sure, with the KC7 you can connect "normal" output to TDA1545A, and the inverted output to the servo/decoder chip.
IME the performance gain is higher than just connecting to the SAA737X servo/decoder only. |
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| carlosfm |
| quote: | Originally posted by jkeny
can the player ever get beyond mediocre?John |
I tested the TDA1387, scavenged from an old SB AWE64 Gold soundcard (much better than any Live IMHO).
This Dac is much alike the TDA1545A, and sounds very good indeed.
I could never find where to buy the TDA1545A, but listening to the 1387 I imagine this is a very good Dac.
The 723 has this dac, so it MUST be possible to make it sound VERY good.
Even if you have to take the chip out of the original PCB and make a new one.:tilt: |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Dave S
1) Elso recommends using the digital +/-10V rails, not a separate PSU. |
If that is done ground loops and ground bounce seems unavoidable. It is one of things that cause me problems with the claims that external clocks actually lower jitter. If you supply it locally the implementation must be handeled very carefully, with minimal loop areas to not cause problems.
If you supply it from a seperate supply connecting this supplies ground via a AC milliamp Meter (or even better a small resistor with a differential 'scope probe across it) will show just how much current "leaks" into the (clock) signal ground line.
| quote: | Originally posted by Dave S
2) Given that Elso may be fallible, how do I get low earth leakage? Do I need an E-I core transformer rather than a toroid? |
Among those I have tested the lowest leakage items had 2-Chamber safety construction with a dairly thick plastic in the thing and in general small size. I find that you need to actually try a few locally available brands and you should find a good one. Often doubling up the transformers and wiring winding out of phase can get you a drastic improvement as you now have capacitances et all better balanced and leakage in opposite polarity between the two transformers. It's a bit of "black art.
| quote: | Originally posted by Dave S
I added an IEC mains input, which means I have the possibility to earth the chassis - is this worthwhile? |
Measure, with the Player in system using a good fully floating 'scope.
| quote: | Originally posted by Dave S
LM6182 is discontinued, not sure if I can find NOS. Can I use AD812 in the same way? |
The AD812 appears to be the cmpatible AD part. Go for it.
| quote: | Originally posted by Dave S
Other duals in my bitbox: OP275, RC4227, NE5532, AD8620 (SO8) - any of these worth a try? |
EVERYTHING is worth a try, if only to confirm a negative fact.
| quote: | Originally posted by Dave S
LM6172 looks viable |
The 6182/812 will be a better choice.
| quote: | Originally posted by Dave S
Should I change the o/p circuit from CF's, which is:
3K3 feedback resistor with 470pF polystyrene in parallel
47uF pana FC // with10nF Wima on opamp output (you aready told me to change this) 1K series resistor and 470uH and 820pF in shunt (after the coupling caps).
|
Of course. First change the resistors on the DAC's reference for 2mA full scale current. Then you need an I/V resistor of 5.656V/2mA = 2k8, no parallel capacitors or RLC circuits.
Then feed a suitable (positive) current into the inverting input to bring the output down to zero Volts from the around 3.3V it is at (this is well implemented is stable and fit & forget, no servo needed). IIRC I used a seperate 317 Reg (15V) from the raw supply some extra RC filtering and then simple resistors to each inverting input, with a +/-10% trim in series (you need to experiment to find the right fixed resistor value first) to trim out sample variation in offset.
BTW, I also used a 317 (5V) with added RC for the DAC and 317/317 (+/-15V) without RC filtering for the OpAmp, of course low impedance bypass cap bypassing the Adj pin to ground in all cases, the negative voltage was actually an identical 15V positive (317) regulated voltage run via seperate wiring to the main PCB ground near the DAC where everything was "stared" for DAC & Analogue Stages.
Then a 100R build out resistor that forms the same LPF as previously in the feedback loop, so 15nF on the Output to ground, use a nice low inductance, audio grade type like Silver Mica or low inductance Polystyrene.
The actual Circuit remaind in my case completely on the CD-720 (I did this ages ago) Board and used original traces etc.
All that came from that board to the added supply board and transformers where two ribbon PSU cables one to carry DAC, Offset and Op-Amp +/- Supplies from one small EI Transformer, the other carying +/-12V (317/337 regged, classic symmetrical supply, again small EI transformer) to near the supply section where it fed the only the Servo Portion of the player.
Another transformer and regulator supplied the various Digital Decoder & servo IC's, I simply retained the original clcock arrangement de-noised on the supply lines and with a real X-tal instead of the ceramic resonator.
So in total I added 3 pcs small PCB mount transformers and a batch of regulators (8 or 9 pcs, would have to check my notes) on a Veroboard PCB to a CD720 and made a few small changes on the main PCB, plus I fixed the dreadful chassis. The result with a nice external mains conditioner sounded jolly decent, good enough to make a later bought Marant CD-67 SE to sound completely "declasse" in comparison.
Sayonara |
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| Bricolo |
| quote: | Originally posted by Kuei Yang Wang
If that is done ground loops and ground bounce seems unavoidable. It is one of things that cause me problems with the claims that external clocks actually lower jitter. If you supply it locally the implementation must be handeled very carefully, with minimal loop areas to not cause problems.
|
Hi Thorsten,
I was thinking about this carefull implementation. I've been scratching my head for a while, and can't decide what's ok or not.
The PS pins of the clock will be connected directly after the diode bridge, that's sure. There's no other choice.
But where to connect the ground??:confused:
-at the transformer's ground
-at the nearest ground from the decoder (where the clock is connected)
-other? |
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| Elso Kwak |
| quote: | Originally posted by Dave S
They have given me some more things to try.
I will try some of the KYW mods in the not too distant future.
I note with interest his comment about the C Found mods as I also had some doubts e.g. CF recommends changing the -11V PSU cap from 3,300u to 4,700u to match the +11V, (quote) "this balances the loading of the mains transformer windings and allows for a slightly higher current dissipation". Impressive stuff!!!!
The KC-7 is built on Elso's pcb and fitted <5cms from the signal processor - maybe I should connect it to BCK at the DAC as well (do I need to disconnect the original BCK i.e pin 48 of the SAA7378 from BCK input, pin 1 of the TDA1545?).
Elso - thanks for the OP275 recommendation. I replaced the OPA627s I/V in my Arcam with a pair of OP176s and was surprised to get a worthwhile improvement. The OPA627 is better than the OP176 in the o/p filter but it seems to be the other way round in the I/V. I will try an OP275 next time I open up the CD723.
My approach with the CD723 is in line with the points made by Fin and Jean-Paul - it's a bit of cheap, clean entertainment to see what can be achieved. Better to peel a few tracks off this pcb than a Wadia! Expectations are low so if it turns out good then that's just fine with me.
Cheers
Dave |
Hi Dave,
I sometimes feel like crying in the desert here but a frog would not survive in such an environment. ;)
Glad you like the OP176 though I am not sure the OP176 is exactly one half of a OP275. Maybe Scott Wurcer can shed light on this as the OP176 is obsolete. Where did you buy it?
I found the OP275 more harmonically right and subjectively having less distortion than the OPA2604. It sounds a bit like musical instruments are better in tune now. Also the OP275 has better and more firm bass.
As for the supply of the KWAK-CLOCK I tried both ways i.e. the raw digital supply of the player and a dedicated separate transformer and bridge rectifier and smoothing caps. The first approach sounded better and this was confirmed by several emails from guys who have built the clock. I second Rudolfs suggestion using both outputs of the comparator.
Where can I find the Chris Fountain mods?
I once "balanced" the raw supply in my Sony by providing equal 4700µF caps but ideally the current draw should also made equal with a ballast resistor.
;) |
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| pburke |
| quote: | Originally posted by sreten
I simply don't care. My bog standard Cambridge Audio
CD4SE is miles better than any modded cheap CD player,
tubes added or not, and as far as I'm concerned thats it.
:) sreten. |
well, you should hear my modded Cambridge player :) It's actually a pretty flimsy cheap player once you start poking around in the guts of it. Amazing that it does sound so good to begin with.
Peter |
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| Dave S |
Hi Elso,
I emailed you the CF article - it's no longer available on the web.
I am fairly sure that the OP176 is 1/2 of an OP275 - they have almost identical specs and both use the Butler front end. I got the 176s as samples 2 or 3 years ago.
Regarding balancing of the + and - loads - you are correct that it is not sufficient just to have the same value caps but the current drawn from the supply needs to be equalised by some means.
I do wonder what "higher current dissipation" means, maybe it's related to current woppling:cannotbe: |
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| Kuei Yang Wang |
Konnichiwa,
No CD Player utilising Digital Filters is "bit accurate" on the analogue output. As for your link, this is about the digital output, which on this particular Philips Chipset seems tapped of after a few stages of Digital filtering and volume control, If I gathered it right.
Sayonara |
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| Elso Kwak |
| quote: | Originally posted by Dave S
Hi Elso,
I emailed you the CF article - it's no longer available on the web.
I am fairly sure that the OP176 is 1/2 of an OP275 - they have almost identical specs and both use the Butler front end. I got the 176s as samples 2 or 3 years ago.
Regarding balancing of the + and - loads - you are correct that it is not sufficient just to have the same value caps but the current drawn from the supply needs to be equalised by some means.
I do wonder what "higher current dissipation" means, maybe it's related to current woppling:cannotbe: |
Hi Dave,
I compared the photo micrographs of both chips and they are not exactly similar.
Thanks for the article. I already had seen it on a French forum.
I do not understand what is meant by "higher current dissipation". Did I write that?:confused: |
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| Dave S |
| quote: | | I do not understand what is meant by "higher current dissipation". Did I write that? |
Absolutely not!
It's in the C Found article. |
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| Elso Kwak |
| quote: | Originally posted by Dave S
Absolutely not!
It's in the C Found article. |
Ok I will read the the article. Did not have the time yet.
;) |
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| carlosfm |
I always thought that the single OP176 is the same as double OP275 too.
Anyway, my Audio Alchemy DDE v3.0 originally had both.
It uses the OP176 on the analog stage, biased in class A, and two OP275s as the PSU for the OP176s.:eek:
I/V is discrete.
Some years ago I removed the OP176s and put OPA627s.
Much better.:D
Never tested the 176 for I/V though. |
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| Dave S |
Carlos,
I agree, in the usual noninv op-amp config I always find OPA627 is better, that's why I was surprised that OP176 worked well in I/V.
I would welcome other's feedback on this, I have been known to be wrong in the past (frequently:) ). |
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| Bricolo |
| quote: | Originally posted by Bricolo
Hi Thorsten,
I was thinking about this carefull implementation. I've been scratching my head for a while, and can't decide what's ok or not.
The PS pins of the clock will be connected directly after the diode bridge, that's sure. There's no other choice.
But where to connect the ground??:confused:
-at the transformer's ground
-at the nearest ground from the decoder (where the clock is connected)
-other? |
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|
|
| Geoff |
| quote: | Originally posted by Dave S
Hi Elso,
I emailed you the CF article - it's no longer available on the web.
|
Just to set the record straight, and in case anyone else is interested in reading it, Chris Found's article on modifying the CD723 is still available on the web via his new URL:
http://www.cfmedia.org
or you can access the pdf file directly:
http://www.cfmedia.org/mods.pdf |
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| Nuuk |
| quote: | | Just to set the record straight, and in case anyone else is interested in reading it, Chris Found's article on modifying the CD723 is still available on the web via his new URL: |
And I still have thesame info HERE on Decibel Dungeon.
On CD723 modder I know has found a pair of 5534's work best for him and believe me, he tried most of the options! ;) |
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| Geoff |
| quote: | Originally posted by Nuuk
One CD723 modder I know has found a pair of 5534's work best for him and believe me, he tried most of the options! ;) |
Tim, by any chance? |
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|
| carlosfm |
| quote: | Originally posted by Nuuk
On CD723 modder I know has found a pair of 5534's work best for him and believe me, he tried most of the options! ;) |
Comparing to what?:confused:
I find this very amusing: (from the pdf)
"First, change the op-amp (NJM4560D) to a NE5532 ( Signetics type only), this improved the sound performance over the much faster NJM that seems to get confused by out of band noise."
:eek:
Of course the NE5532 is better than the NJM4560D, but the explanation is :cool: :bawling: .
:clown: |
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| Fin |
| quote: | Originally posted by Dave S
My approach with the CD723 is in line with the points made by Fin and Jean-Paul - it's a bit of cheap, clean entertainment to see what can be achieved. Better to peel a few tracks off this pcb than a Wadia! Expectations are low so if it turns out good then that's just fine with me.
|
Dave - even if you end up putting a bit of money into it, most of what you build or buy (clock, psu, etc....), can easily be moved on to another project. |
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| Nuuk |
You name it Carlos, this guy tried it. He is extremely methodical in this sort of work!
It's strange to me that any mention of the 5534 bings this sort of incredulation. They are opamps and quite good ones at that. !n this guys set-up they sound the best to him.
The person concerned is also a classical musician with perfect pitch hearing so I trust his judgement in these matters. He goes for accuracy rather than 'wow factor'.
Remember that this is what this game is all about - achieving the sound that we like the best - not about building hi-fi with the highest spec! ;) |
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| Audiofanatic |
| quote: | Originally posted by jean-paul
Say that again to the Tjoeb guys ! |
Hi Jean-Paul,
I couldn't agree with you more.
This is something I can not understand, this is a product that may not be sold as consumer electronics.
Best regards,
Audiofanatic ;)
BTW Jean-Paul, I now have a CD80 and I'm gona modify it and report to you later if this one is better than the VRDS transport/player ;) |
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| matjans |
| quote: | | EVERYTHING is worth a try, if only to confirm a negative fact. |
good point.
| quote: | | Remember that this is what this game is all about - achieving the sound that we like the best - not about building hi-fi with the highest spec! ;) |
at the risk of confirming about each and every prejudice against the dutch... add (in my case):
"for as little money as possible."
and in that respect the cd723 is a sound investment. ;)
i've done most of the tweaks on nuuk's site and i must say that they improve the cd723 to a point where it's no longer the bottleneck in my sysem. now, my loudspeakers and room are... |
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| carlosfm |
| quote: | Originally posted by Nuuk
!n this guys set-up they sound the best to him.
|
That's fine, OK.
| quote: | Originally posted by Nuuk
The person concerned is also a classical musician with perfect pitch hearing so I trust his judgement in these matters. He goes for accuracy rather than 'wow factor'.
|
Don't take me wrong on what I'm gonna say, please.
The last classical-music-only-lover I've been with happens to be owner of an hi-fi store.
He was demonstrating me (and a friend of mine) an espen$ive system with choral music and some strings.
The sound was OK.
But my friend had asked me to go with him because he was thinking in buying those speakers.
Of course I took two CDs of mine.
Stop with choral music and put something really serious for a system test.
Unbearable:bawling: , unlistenable:bawling: , bass was overblown, muddled everything.:bawling:
I guess this guy sells plenty of systems demoing with that kind of music, that is the music he loves and it happens that it doesn't have any dynamics, any bass.
He could put a cheap Nad driving some Apogees and love the sound.:dodgy:
So Nuuk, I guess this is really a matter of taste, audio is subjective and the fact that he likes more the NE5534 doesn't tell me much.
As I'm not in the mood to discuss this, because it's always very polemic and some people take things personally, each one to it's own.;)
Just wanna tell you all that my NOS Dacs have much more out-of-band noise than the 723 but there's no reason that I should change the op-amps I love for some "slower" ones.:clown:
BTW I know the NEs very well.;) |
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| Nuuk |
| quote: | | As I'm not in the mood to discuss this, |
I thought that you just had Carlos :D
My friend is a classical musician but his taste in music is quite broad!
But the bottom line is exactly as you stated, it's personal taste that counts! ;) |
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| Elso Kwak |
| quote: | Originally posted by Dave S
Carlos,
I agree, in the usual noninv op-amp config I always find OPA627 is better, that's why I was surprised that OP176 worked well in I/V.
I would welcome other's feedback on this, I have been known to be wrong in the past (frequently:) ). |
Hi Dave,
Also my experience. The OPA627 is one of the best as a line amp or in a phono amp though bettered by a discrete FET inputstage.
There seems to be some "misunderstanding" regarding the connections of my clock to the CD-player in question and the formation of ground loops. Only one groundlead is connected from the clock PCB to the PCB in the CD player.
:cool: |
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| Bricolo |
| quote: | Originally posted by Elso Kwak
There seems to be some "misunderstanding" regarding the connections of my clock to the CD-player in question and the formation of ground loops. Only one groundlead is connected from the clock PCB to the PCB in the CD player.
:cool: |
Hi Elso,
If you're reffering to my post:
Sure, it only needs one ground connection. But my question was more "where to connect the clock's ground?". Near the decoder's ground, or near the transformer's center tap? |
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| Elso Kwak |
| quote: | Originally posted by Bricolo
Hi Elso,
If you're reffering to my post:
Sure, it only needs one ground connection. But my question was more "where to connect the clock's ground?". Near the decoder's ground, or near the transformer's center tap? |
Bricolo,
No, I was not referring to your post but it can be done both ways.
Not sure which one is better.:rolleyes: |
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| Dave S |
| quote: | Bricolo, No, I was not referring to your post but it can be done both ways.
Not sure which one is better. |
I would recommend connecting the clock ground at the point of lowest impedance i.e the PSU star point. Otherwise you may provoke ground bounce.
I did say I'm frequently wrong:
I went back to OPA627 for I/V in the Arcam. The OP176 was a bit too aggressive for my tastes and in my system.
I also felt the same about the OP275 in the CD723 and replaced it with RC4227 - I'm not saying this dual OP27 device is great, but even though it has less resolution than the OP275 it also lacks the aggression of the 275.
Horses for courses. |
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| carlosfm |
Yes, the OP176 and OP275 sound aggressive to me.
Midband and treble are a little on the "digitalitis" side.
A little more dynamics in the bass than the NE5532/4, but the rest is very similar.:D |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Dave S
I would recommend connecting the clock ground at the point of lowest impedance i.e the PSU star point. Otherwise you may provoke ground bounce. |
If you do, the ground level of you clock will be shifted compared to the IC to which it is applied depending upon the ground(signal) routing for that IC. The problem, if you use the local PSU you are between a rock and a hard place and either way you add notable levels of jitter.
If this makes the result sound better we have perhaps another indicator that "low jitter" as such is not inherently a desiriable design goal, outside akademia.
If low jitter is desired we need to handle the clocks PSU noise current locally and return the ground to the ground of the IC fed the clock. This suggest a clock of the style implemented by Guido Tent for such applications.
If you use a seperate "master clock" with a complex PSU arrangement and you want low jitter, you MUST use a low leakage galvanically seperate PSU for the clock. Of course, low jitter may not "sound good" to some (just as flat frequency response with extended HF does not not neccesarily sound good to everyone).
Sayonara |
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| Bricolo |
Thank you for your reply, you made things clear now.
BTW, what's a low leakeage psu? Is it a special transformer or something?
And now, how would the grounding have to be with a complex clock distribution? (like a master clock feeding a decoder, a filter and a dac) :D |
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| Dave S |
| quote: | Yes, the OP176 and OP275 sound aggressive to me. Midband and treble are a little on the "digitalitis" side.
A little more dynamics in the bass than the NE5532/4, but the rest is very similar. |
I normally try to avoid too much subjective discussion on these boards but I have to agree that this description is spot on! |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Bricolo
BTW, what's a low leakeage psu? Is it a special transformer or something? |
I refer to a PSU as "low leakage" is there is not much current flow between earth and the secondary. Hifi/audio gear is usually earthed somewhere, somehow, so such current always flows. The presence of these current loops in conjunction with single ended RCA connections is also the main reason for audible differences between mains cables.
You can achieve low leakage in many ways. With toroidal transformers it often works to use a pair of them, both mounted identical to the chassis with non-conductive screws and wiring one primary out of polarity with the other, secondaries wired normally. The leakage is usually identical but now out of phase, around 20db reduction in leakage current are possible.
| quote: | Originally posted by Bricolo
And now, how would the grounding have to be with a complex clock distribution? (like a master clock feeding a decoder, a filter and a dac) :D |
The jitter matters most at the DAC, however it is the DAC's WORDCLOCK that determines the jitter output for multibit DAC's, while for Delta/Sigma DAC's the main clock tends to be the system clock. How all of this works out depends hence upon the DAC and other chips used.
Ideally we re-clock the Wordclock of the Multibit DAC, hence we ground our clock signal (hopefully the clock has a seperate supply so that we do not need to worry about PSU line currents) at the re-clocker. If we use the same supply for reclocker and clock again we ground at the reclocker. For a Delta-Sigma DAC we clock directly the DAC and pull our joint supply from the DAC too and we do not connect ANY grounds at the other clock fanout receivers, only the signal.
Retro-fitting such clock distribution systems to existing gear is often messy, as the grounding is not designed for it.
BTW, if you start to implement multiple re-clocking also track down all other clocked devices (Microcontrollers for drive functions, displays etc.) and slave them to an integer multiple of the main clock. Genertaing the main closk from a very high multiple (eg. 33....MHz instead of 16.93MHz) allows dividing down to the commonly found 12 & 8MHz clocks on such PIC's easily.
Once ALL clocks are fully synced (as I did on my "giant killer" CD-67) and all supplis maximally insulated against crosstalk you start hearing what CD is actually capable of in terms of resolution, on both good and bad recordings.... ;-)
Of course, given that I rarely use CD for "serious" music listening I could not care less, really and prefer hence pleasant sounding, visually stunning Digital gear over boring looking but excellent sounding black boxes.
Sayonara |
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| guido |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
The jitter matters most at the DAC, however it is the DAC's WORDCLOCK that determines the jitter output for multibit DAC's,
Sayonara |
Not always (e.g. tda1541 / tda1545 clock on BCK).
I guess reading the datasheet of the particular dac you wanna use is a good idea. It is anyway :D
Greetings, |
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| TimA |
Dave,
I would suggest you consider using some film/foil capacitors in place of the output electrolytics. With speakers flat to 21Hz, 3.3uF was the lowest value to which I could go without noticeable impact on low bass, though the input impedance of the following preamp might influence your results.
Can you be more specific with regard to what you term as ‘mediocre’, it is not much to go on.
Tim. |
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| Dave S |
Tim,
Firstly, your spellling is better than mine!!
Secondly, expanding on mediocre:-
In my experience cheap CD players sound either soft and lacking in detail or harsh and bright. I can make the CD723 sound either way but it still lacks any real resolution and depth. The bass is boomy and thin rather than full and tight, instruments lack tonal colouring, treble is thin - "common digitalis".
Maybe I'm being hard on the poor little CD723 because I thought a Naim CD5i I demo'ed had the same problems (erring on the soft side) and nearly all (new) sub £1500 players do. That was why I asked the original question - is this machine worth further effort?
Sreten thinks not. KYW etc thinks I can do better than my 1st round of mods. Time will tell (although it might be quite a while). |
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| jean-paul |
If you want the thread title changed because of spelling, just say yes and I'll do it.
Too late, I've done it already... |
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| Audiofanatic |
Hi Jean-Paul,
I have the wonderfull CD80 now and want to modify this monster, can you give me some hints, I've search the forum allready, I just want to know if you might have other mods under your hat.
Cheers,
Audiofanatic ;)
P.S. If you can help, send me a PM :angel: |
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| carlosfm |
| quote: | Originally posted by Dave S
Sreten thinks not. KYW etc thinks I can do better than my 1st round of mods. Time will tell (although it might be quite a while). |
Dave, have you installed a good clock there?
It will always sound bad without a good clock.
You'll hear some good bass.:)
You may try the Tent clock, cheap and very good.
Also, I don't like the AD826.:rolleyes: |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by carlosfm
Dave, have you installed a good clock there?
|
I am not Dave, but to quote:
"I have a CD723 with all the "Chris Found" mods plus:
KC-7,
AD826 I/V"
KC-7 here stands for Kwak Clock 7.
| quote: | Originally posted by carlosfm
It will always sound bad without a good clock. |
This is exactly the kind of hype that get's me annoyed. I know quite a bit of Ditital gear that relies on bog standard clocks (single gate on a big LSI Chip) and merely feeds them with a clean supply and guess what, it sounds just fine AND measures in < 200pS region for Jitter.
I wish people would stop this "Add clock - great", "No new Clock = Bad sound" nonsense. This new clock business reminds me by far too much of the Emporers new Cloth & Groove.
Yes, in virtually ALL cases changing the clock will change the sound. To the better? Sometimes. Often add-in clocks actually worsen the jitter levels (not reducing them as claimed) and plenty of digital gear sounds just fine without them, plenty more can be modded to sound great with a "Clock". True, fitting correctly a proven low jitter clock module CORRECTLY can reduce jitter and improve the sound, but such is rather rare.
Sayonara |
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| Dave S |
In order to start on the new mods I have reversed some of the old mods. I removed the emitter follower type supplies and lashed in a 7815/7915 PSU (liberated from some pro-audio piece of kit only 7 years old but already obsolete!!) just to power the I/V, all the other supplies are back to the original. The change in sound was minimal, possibly indicating:
a) I'm deaf
b) I did something wrong with the EF supplies
c) Power supplies don't matter
d) 7815/7915 ain't that bad.
e) Bigger problems elsewhere.
Oh well here we go, at the risk of starting an argument.....
Next I removed the KC-7 and refitted the original clock components (even those horrible axial 22pF caps), the same crystal was used (the original). The sound improved significantly with the standard clock arrangement, although it is still has some of the red book upper mid glare, the resolution, dynamics and general musicallity is much better.
The KC-7 was built on Elso's pcb and fitted under the ECO-SL board with a short clock connection to the sig processor and the 3 supply wires were connected at the main smoothing caps on the DAC board. The only deviation from Elso's recommendations was that the 1uF caps were naked stacked film polyesters not polypropylene - in order to keep the unit low profile.
The next step is to try KYW's current f/b I/V stage (AD812 in lieu of LM6182) but I need a bit more help here. KYW suggests selecting the DAC reference resistors for 2mA full scale current. The data sheet shows 1mA and R(ref) is 11K, with 22K from VDD to Vref and 33K from vref to Pin 7. My CD723 has the corresponding values - 11K (internal to the DAC), 15K and 10K.
I've read the data sheet about 10 times and the explanation is not at all clear to me, so how do I calculate the resistor values neccessary for 2mA FS current?
Thanks,
Dave |
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| TimA |
Dave,
With your initial (I notice you have just made some progress so I hope this is not too late) CD723 criticisms in mind, here are some thoughts based on my own experience with this player and in comparison with a slightly modified (for a dc-coupled output) Marantz CD17KI.
Output capacitors...
10uF Oscons (bypassed with small polyprops) were reasonably good although there was a degree of congestion and harshness coupled with a ‘small’ sound. My own preference here is for paper-in-oil types but from what you have written and again from experience an Audyn tin-foil ’KP-SN’ could suit your requirements nicely, being not so glassy in the treble as a Hovland Musicap for example and sounding more spacious than Oscons and other electrolytics.
Op-amps…
I wonder if you might like the NJM2114, significantly more dynamic than the NE5534 and in many ways more refined, though to my ears a little harsh in the treble. My preference is for the NE5534 (of recent Philips manufacture) though I got fine results from a pair of LM6171s (with 500nF across the +/- pins). I have tried 1980s Signetics NE5534s in other circuits with disappointing results. The OPA627 was impressive but I couldn’t live with it. I find a 2mA constant current source on the op-amp output usually leads to a noticeable improvement in refinement, though sometimes a very slightly diminished amount of bass ‘drive’ accompanies this – not a problem for me, but for you…?
Regulation…
I echo those who suggest regulating the digital supplies. There is a rather light-weight, flimsy, diluted quality to the sound without regulation. This was particularly noticeable through an external DAC when compared with the digital output of CD17KI, though it was not unpleasant. I regulated the existing supply to around 10V (if I remember correctly) for the servo circuits with a feed off this to a shunt regulator for the 5V supplies. Further listening between the two digital outputs proved a waste of time, any remaining differences between the two circuits were now so small as to be insignificant.
Other changes…
Removed output muting transistors, some A.N. tantalum resistors here and some Elna Silmics there.
The end result…
The CD723 became (after C.F.’s recommended changes and after adding the regulation) subjectively indistinguishable from the CD17KI when their digital outputs were fed to an external DAC. The analogue sound of the CD17KI remained the more analytical while the modified CD723 (NE5534/paper-in-oil) became the more musically involving. Fitting an NJM2114 into the CD723 output narrows the gap between the two considerably, making the CD723 more ‘up-beat’, many people would prefer this.
Tim. |
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| carlosfm |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
This is exactly the kind of hype that get's me annoyed. I know quite a bit of Ditital gear that relies on bog standard clocks (single gate on a big LSI Chip) and merely feeds them with a clean supply and guess what, it sounds just fine AND measures in < 200pS region for Jitter.
Sayonara |
Sorry Kuei, I forgot he was already using an external clock.:rolleyes:
Anyway, I think you can always do better with a good clock, that's my experience.
On my CD650 I double-regulated the 7220 and, still with the original clock, bass was not tight at all, mucked the whole music.
Only when I put a Tent clock (with dedicated trafo/PSU) things got much better.
The same happened to several other CDPs I own.
But you may have your tricks, don't discuss that.
And each circuit may be a different thing and a different approach. |
|
|
| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Dave S
I removed the emitter follower type supplies and lashed in a 7815/7915 PSU (liberated from some pro-audio piece of kit only 7 years old but already obsolete!!) just to power the I/V, all the other supplies are back to the original. The change in sound was minimal, possibly indicating:
a) I'm deaf
b) I did something wrong with the EF supplies
c) Power supplies don't matter
d) 7815/7915 ain't that bad.
e) Bigger problems elsewhere.
|
I think it's a mix. First, your current Op-Amp's are fairly tolerate to PSU problems. Second the really nasty drive and digital section supply really causes troubles.
| quote: | Originally posted by Dave S
Next I removed the KC-7 and refitted the original clock components (even those horrible axial 22pF caps), the same crystal was used (the original). The sound improved significantly with the standard clock arrangement, although it is still has some of the red book upper mid glare, the resolution, dynamics and general musicallity is much better. |
Okay. Now, if you take my recommendation get a simple clock (like the cheap Tent Module) and give it it's own supply, low leakage transformer for the supply and a really nicely low noise supply, then the correct logic level to the Servo Chip.
And for goodness sake give the actual Player logic it's own well regulated and clean 5V supply plus a nice solid regulated (7812/7912 is fine) supply for the servos.
| quote: | Originally posted by Dave S
The KC-7 was built on Elso's pcb and fitted under the ECO-SL board with a short clock connection to the sig processor and the 3 supply wires were connected at the main smoothing caps on the DAC board. |
Using this hookup will maximise all possible problems with ground noise etc to maximise jitter. A typhical example why "Clock" is nowhere near the "cure all digital ills" many claim it to be.
| quote: | Originally posted by Dave S
The next step is to try KYW's current f/b I/V stage (AD812 in lieu of LM6182) but I need a bit more help here. KYW suggests selecting the DAC reference resistors for 2mA full scale current. The data sheet shows 1mA and R(ref) is 11K, with 22K from VDD to Vref and 33K from vref to Pin 7. My CD723 has the corresponding values - 11K (internal to the DAC), 15K and 10K. |
The Datasheet (it is on page 9 Note 5) suggests two 11K resistors. Why you are at it, the capacitor on the Reference section is also quite critical for sonics. I'd use 47uF/6.3V BG NX-HiQ (I do occasionally use BG's, where they actually work). With the above the feedback resistors for the OPA (as discussed previously) become ideally 2K8 or 2K87.
Sayonara |
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| Kuei Yang Wang |
POST SCRIPTVM....
| quote: | Originally posted by Kuei Yang Wang
The Datasheet (it is on page 9 Note 5) suggests two 11K resistors. |
I would probably start with a trimmer and adjust the final value to give 2V RMS with digital full scale....
Sayonara |
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| zygibajt |
| quote: | | You can achieve low leakage in many ways. With toroidal transformers it often works to use a pair of them, both mounted identical to the chassis with non-conductive screws and wiring one primary out of polarity with the other, secondaries wired normally. The leakage is usually identical but now out of phase, around 20db reduction in leakage current are possible. |
Thorsten,
How can I easy and quick find the polarity of windings of transformer?
| quote: | | Among those I have tested the lowest leakage items had 2-Chamber safety construction with a dairly thick plastic in the thing and in general small size. I find that you need to actually try a few locally available brands and you should find a good one. Often doubling up the transformers and wiring winding out of phase can get you a drastic improvement as you now have capacitances et all better balanced and leakage in opposite polarity between the two transformers. It's a bit of "black art. |
Could you describe more precisely what is 2-Chamber safety construction with a dairly thick plastic in the thing and in general small size? Sorry but it might be language barrier that I don't quite understand what you mean.
Do the two transformers have to be mounted in special way to each other to achive better canceletion?
What about leakage if we apply balanced separate transformer on the mains.I mean the one with dual 115VAC windings for 230V and ground taken from center tap?
Bartek |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by zygibajt
How can I easy and quick find the polarity of windings of transformer? |
Dual trace 'scope?
| quote: | Originally posted by zygibajt
Could you describe more precisely what is 2-Chamber safety construction with a dairly thick plastic in the thing and in general small size? |
No, that is about as precise as it gets. Many transformers wind secondary and primary over each other. "2-Chamber Safety" Type transformers have seperate chambers for primary and secondary and often fairly thick plastic (and air) between the windings and the core.
| quote: | Originally posted by zygibajt
Do the two transformers have to be mounted in special way to each other to achive better canceletion? |
Symmetrical to even the capacitances.
| quote: | Originally posted by zygibajt
What about leakage if we apply balanced separate transformer on the mains. |
If our equipment mains transformer is not balanced too we will have some improvement in leakage, but not much.
Sayonara |
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| Fin |
| quote: | Originally posted by TimA
Regulation…
I echo those who suggest regulating the digital supplies.......
I regulated the existing supply to around 10V (if I remember correctly) for the servo circuits with a feed off this to a shunt regulator for the 5V supplies......
Tim. |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
I think it's a mix. First, your current Op-Amp's are fairly tolerate to PSU problems. Second the really nasty drive and digital section supply really causes troubles.
And for goodness sake give the actual Player logic it's own well regulated and clean 5V supply plus a nice solid regulated (7812/7912 is fine) supply for the servos.
Sayonara |
Hi Tim and Kuei
This is something I am really interested in doing in my CD624. At present, the unregulated +/-10V supply for the servos and the regulated +/-5V digital supply share the same output from the transformer, rectifier and smoothing capacitors (6800uF for +, and 1000uF for -). There is a separate rectifier, smoothing caps (330uf and 470uf) for the +/-15V supplies for the analogue stage. This will be redundant as a new transformer and supplies will be added for the opamp and DAC.
What is the best way to improve and regulate the +/-10V and +/-5V supplies from the original transformer?
Should the entire +/-10 servo section be supplied from the old +/-15 supply - leaving the other rectifier/supply for the +/-5V digital section?
If this is the way to go, what changes need to be made to the capacitors (6800uf, 1000uf, 470uf, 330uf)? |
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| carlosfm |
Fin, the PSU of the analog stage (+/- 15v) may not have enough current for the mechanism.:cannotbe:
They are usually very weak, some 100ma or even less.:xeye: |
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| Rotellian |
| Fin, Carlos is right - that would be my main concern. (however thats not to say that the now redundant +/- supply cant be used to supply other things :) |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Fin
What is the best way to improve and regulate the +/-10V and +/-5V supplies from the original transformer? |
Don't bother. You really need to add a few extra transformers (they need no be huge size) and build seperate supplies. Working of the original shared supplies is just by far too much compromise. Leave the original supplies o power only Display/Control uP & Remote control circuitry, all other supplies should be build new from scratch and be galvanically insulated, so you can break up several bad ground loops and feed each and every section optimally.
For Players of the CD-720/21/22/23 ilk (to which yous also belongs IIRC) I'd implement as follows:
1) 2 X 15V (seperate supplies only joined to for +/-15V at the DAC's Starground) with a further +15V tapped off the positive supply to null offset and +5V tapped off the positive supply to power the DAC.
All regs. in this supply should be at least LM317 better LT/LM1085, adj pin bypassed and good "audio grade" output capacitor, lower than common value "set" resistor chains to draw at least 50mA standing current through the regulator (more is better within reason).
Diodes Schottky, PSU Cap's small value and raw voltages fairly high, ideally with some added RC filtering, something like 3R3 470uF - 10R - 4,700uF - Reg with a 18V transformer and schottky bridge and the regulators (+15V Op-Amp, 15V Offset Null, +5V DAC each set around 50mA ballast current (27R resistor from Adj to output). Use a Transformer 18V 1A + 18V 1A.
2) 2 X 12V (seperate supplies only joined to for +/-12V at the Servo Motor Drivers Starground)
The regulators are a little less critical, 78XX/79XX types should suffice if on a budget. Due the potentially quite high burst currents when the laser focuses etc the supply should be fairly solid, so put a substantial value capacitor before and after the Regulator. Again, adding some "Ballast resistors" to draw extra current can be a good idea. A 12V + 12V 1.5A Transformer or bigger would be a good idea.
3) 1 X 5V for the Digital Player sections (Decoder, Digital filter etc.). If you use standard type transformers with two secondaries you could use the second secondary to power a clock module. The rest of the supplies I'd arrange similar to those for the +/-15V Analog supply.
I hope this helps.
If you need to due to insufficient space inside the player, you can install all the supplies detailed above in an external case and add a Sub-D25 connector on the back of the player which allows with a short circuit plug the player to run of the internal supply but which otherwise breaks the supply lines to Analogue stage, DAC, Servo and Digital circuitry and connects the external supply. | | | |
