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Old 18th September 2004, 09:47 AM   #1
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Question clock experts...a little help?

so modding of my 3.99 sony cdp-591 has begun...nothing to drastic so far..

i've replaced and doubled the size of the supply line caps going to the DAC,from 47uf to 100uf across each line.

i reused some of the removed 47uf's to add some filtering to the supply lines going to the output opamps..since they had no local supply caps other than .022uf ceramic bypass's[would have used more 100uf's but space is pretty tight].

i've also removed the muting transistors...

the results?a slightly warmer smoother sound with a bit fuller midrange and much less "bite" in the top end...overall i think it's better but it still lacks any real bass kick or image depth,still pretty flat and uninvolving...i plan to add some more spare parts in the next round,i have an old audio alchemy PSU laying around,the freebie that came with the original units[+/-12V@150ma]...i figure if i can seperate the traces i'll see about using it to power the output stage amps and see how that goes

now if you've read this far...we now come to the clock question,i've examined the circuit sony installed in this machine...but there seems to be some "extra parts" that tho designed into the board i guess they didn't feel the need to include in production...i've attached a quickie schematic drawing to show how things are set up,i'm pretty sure this is how it connects together and the component values are included[please excuse my drawing skills ]...the parts shown in red are labled on the board and have thier traces as i've shown...but are not installed...another cap and an inductor...

can anyone who is familier with these type of circuits[i'm not]tell me what these would do?are they a possible addition/refinement of the existing circuit or are they maybe for some other configuration alltogether???if anyone can recognize and/or make sense of the entire circuit...can you calculate or tell me how to calculate possible values for the missing components???and if you can go that far ...would you say it would be a worthwhile thing to add them as far as performance goes?or were they left out for a reason??any other possibilities for mods to this simple circuit or the entire machine are more than welcome as well...
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Old 18th September 2004, 02:35 PM   #2
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Ive looked at your schematic, this is just an additional filter
for the clock , from my knowledge of RF circuits the
inductor would be 2 or 3 turns of .5mm wire on a ferrite
bead and the capacitor no more than say 27pf.

I wouldnt get too excited about this , the existing circuit
without these components is more than adequate,
unless this part of the circuit is unshielded, where
additional filtering might be called for.

You have here a common circuit in CD players , next
you need to find the Clock output from this ic . look
up schematic diagram.

I already have 2 or three replies running about an
article I had published in Electronics World June of 1997
concerning overcoming SPDIF in digital transfer.
The ideas there are fairly transportable to other
parts of CD players: heres a brief explanation

Using interpolation ( assembling new information )
via a common ic called a flip flop Part 74AC74
enables clock comparison to lower frequency
signals. Schmidt triggers are also useful as buffers in
tidying up digital waveforms. The idea then is
say you have a 16Mhz clock ( in your case 48Mhz )
you can provide this to clock input of a flip flop
any individual signal you wish to gain interpolation
advantage from is input into data of said flip flop
which then provides an output and inverted output
via pins labelled Q and Qbar.

In theory if you input a signal at 2MHz the flip flop enables
an 8 times comparison advantage if the clock runs at 16 Mhz. Having inverted and non inverted outputs invites balanced operation There are housekeeping pins such as set and
reset and of course 5v+ and gnd for voltage supplies.

You would also need to look at manufacturers data for
current limits on outputs and arrange loading resistors
to suit, or look at a buffer circuit if routing these signals
over long lengths using transmission techniques ie 75 ohm
loading ( say 20cm )


Cheers / Chris
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Old 18th September 2004, 02:52 PM   #3
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Rodzilla: The red parts is a fundamental mode filter. It is supposed to make it possible to use cheap 3rd overtone crystals instead of the more expensive (ASAHI) fundamental mode crystal.

If the red parts are not mounted, it only means you already have the good crystal.

If the red parts were in, they would have prevented the 3rd overtone crystal from resonating on the fundamental frequency of 1/3 of 45.1584 MHz. (15.05 MHz). It would then be forced to oscillate at the intended 45.1584 MHz.

Best regards

Lars Clausen
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Old 18th September 2004, 03:09 PM   #4
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Lars
That explains it well


Cheers / Chris
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Old 18th September 2004, 04:45 PM   #5
DIAR is offline DIAR  Finland
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Rodzilla,

I have Sony DVP NS900 player.
I just changed coupling caps from analogue output to Black Gate 0.47 uF Super-E-Caps configuration. I ordered them from LC Audio and it took about three or four days to arrive (VERY fast )

Id say that the most noticeable changes was stronger and deeper bass and wider and deeper soundstage. A very good value for the money and effort.
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Old 19th September 2004, 12:47 AM   #6
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thanks for the replies guys...i thought maybe these bits might be for some other config,but i had to ask.RF and related tuned frequency circuits are a bit beyond my skills...i won't worry about them

Chris-i would love to get a look at the schematics/datasheets for this thing...it's an older player tho and they seem to be virtually unobtanium...altho sony did inform me of a canadian supplier to order replacement parts from if i need them[laser heads,motors etc],no useful info seems to be forthcoming from sony,either for free or for sale...alltho i used to know where the sony repair depot was here,and i'm planning to visit,to see if i can't buy,borrow or even bribe someone there to get me one if they still have access to it...it's worth a shot,but from the sound of things,i may need to be heavily armed and hold the place up to get it out of them...it doesn't look good

the board in this player is fully labled,and was probably used in several models,the missing bits from the clock circuit are not the only parts MIA..there's also a digital output that needs perhaps a handful of parts of unknown values and jumper switched to be activated,there's another "unfilled" input/output that looks like possibly a remote control bus that holds no interest,as well it would seem there was an option to run the board as a dedicated transport with no onboard D/A..there's an unused alternative clock circuit laid out and labled for this purpose["No D/A"]as well as various jumpers around the board to activate or bypass the various options...a service manual/schematic would be mighty useful indeed!

Diar-i will replace the output caps eventually,but in my experience while it's definately a useful upgrade to a circuit that already sounds half decent...it won't fix one that doesn't..i think this thing needs to sound a bit better than it does before i'll get much out of just replacing the caps[tho if i had some decent ones on hand i would anyway] replacing the coupling caps is more of a final touch than a "fix",even cheap generic caps can produce quite decent sound if the circuit they're connected to is good...and currently that's still debatable
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Old 19th September 2004, 03:48 PM   #7
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Link to the picture of the insides of a CDP-591 I once owned:

http://www.diyaudio.com/forums/attac...&postid=141420

Although it sounded decent in the end, it is not really a machine that deserves the attention and the effort. After all the energy spent it still was beaten by old TDA1541A machines. Nice object to learn modding though. Be careful with placing the topcover, the plastic hooks of the frontcover break off easily. Better leave it open till it's finished.

If you Search for the thread you can read what I did to make it better. Especially placing a regulated supply for the opamps was an improvement.
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Old 19th September 2004, 06:48 PM   #8
alfsch is offline alfsch  Germany
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You have a 3.overtone crystal there, i can give you a circuit to make a clock and see, what this makes better soundwise, if you wanna test this. the original on chip osz is not very good...
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Old 20th September 2004, 12:47 AM   #9
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jean-paul - i know it's far from a great player...i only paid 4 dollars for the thing,it's whole reason for existance now is just to have something to mess with...if it turns out sounding decent,great!if i blow it up...that's ok too.it's not my main player,it's just something to play "mad scientist" on,and it's totally disposable if it comes to that.

i have already read through your other thread...if you search google for info on the DAC in this player,it's about the only halfway useful link that pops up!as i said i do plan to add another PSU for the outputs maybe later tonight when i have time,the new PSU is self contained but unregulated at the moment...it's fairly well filtered but i can build a regulator board for it as my next little project,i'll see how it works out[will likely have to drop it from +/-12v to +/-9v regulated tho]

alfsch - i'm not sure i follow you,Lars sez the circuit is capable of running a 3rd overtone crystal with the extra bits but isn't,and you seem to be saying it is running one if i read you right???...regardless,any ideas for a better replacement or improvement are more than welcome
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Old 20th September 2004, 09:34 AM   #10
alfsch is offline alfsch  Germany
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right, its on 3.harm
the osz could (!!) have l+c added, to make a tuned resonant osz at 3.harm, but cheaper is to add a low parallel resistor, like its here 5k, to prevent the fundamental and the osz will run on next higher resonant freq, which is 3.harm.
you could test this, if 5k --> 300k or so, osz will run at 15meg, if you think iam wrong.
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