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Help needed for implementation of ο1 in Marantz CD40

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Help needed for implementation of ο1 in Marantz CD40

Postby franjam » March 2nd, 2018, 1:06 pm

H Ti,

As opposed to the Marantz CD63 the clock in the CD40 isn't connected to the DAC TDA1541, but to the preceding chip, SAA7220. For the CD63 you said the inverter was in the DAC and I should therefore connect to XTO. I'm having trouble working out the scenario for the CD40 as the clock seems to go back again to yet another chip, SAA7310. How do I know where the inverter is ? And where is the best place to connect? can you explain how this scenario works?

here's a pic :)
Marantz CD40 DAC-clock.jpg


I am tempted to connect to XIN on SAA7310 pin26 and cut the track from pin 9 on SAA7220, is this completely wrong? XOUT pin 25 is floating... so looking the other way "to circuit" what does this signify? there is also "to circuit" on the DAC chip after "oscillator" pins 16/17.....?

(Just for information although i dont think it makes a difference I have implemented the oversampling mod which means that pins 123 on SAA7220 are directly connected to pins 123 on TDA1541 and the relevant intervening tracks have been cut).
By the way I have just finished connecting the o78 to the TDA1541 plus a separate 0785 to each of the other two preceding chips, Sounds great :D

Thanks for your help :)
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Re: Help needed for implementation of ο1 in Marantz CD40

Postby amb » March 3rd, 2018, 4:06 am

The diagram appears to be a block diagram rather than a full schematic. I wonder what is the box labeled "X-TAL OSCILLATOR" between X-IN and X-OUT, internal to the SA7220. I don't think it's actually an oscillator in there, as there is a quartz crystal externally. Might it be the inverter gate? If so, which way does the output of the inverter pointed? I "think" it's the X-OUT pin "TO CIRCUIT", so the appropriate place to inject an external clock would be X-IN, after removing the crystal and the two capacitors. This also goes through an internal buffer and then out to XIN on the SA7310.
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Re: Help needed for implementation of ο1 in Marantz CD40

Postby franjam » March 3rd, 2018, 1:19 pm

XIN seems to be the answer ;) otherwise there would be no sound right :?:

All sounds pretty good to me :D
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Re: Help needed for implementation of ο1 in Marantz CD40

Postby amb » March 3rd, 2018, 1:33 pm

Note that I was referring to X-IN at the SA7220, not XIN at the SA7310.
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Re: Help needed for implementation of ο1 in Marantz CD40

Postby franjam » April 2nd, 2018, 6:20 am

Absolutely, that's the way it's done ;-)

CD40 clock and regs.jpg


CD 40 full mods.jpg


So to close this particular chapter : I obtained the CD40 much cheaper than the CD63, about 40 euros with the postage. The pcb is simpler in its layout and cap population ; the cd drive is of better quality. I spent less money and less time on it, partly due to experience, but there are also less caps to replace/renew. It is easy and quick to Dremmel modifications and holes in the casing as it is largely plastic and there's lots of room to work with. I finally used 2.2uF Mundorf aluminium oils for the output caps supplied from the first stage of the op-amps, ( which I replaced with NJM2068's 'cos i fried one without understanding how ; the NJM's were what I had around..). It looks like crap, the CD63 looks a lot better aesthetically.
With largely identical mods ie. complete cap renewal, o1 clock and o78 on DAC and 7805's on key chips, the CD63 sound great and is worlds apart from what it was, the sound is clear open very detailed and well balanced. The CD40 beats the pants off it ! It has all the previous qualities but is simply more dynamic and engaging, more "musical". The difference back to back on the same sytem is immediate and obvious, you don't have to think about it, so the TDA1541 myth seems to be true...I just had to find out :).
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Re: Help needed for implementation of ο1 in Marantz CD40

Postby minimaliszt » June 18th, 2018, 8:20 am

Saw the xtal freq was 11.2896Mhz in the schematic. What oscillator did you use for this? I have a project with the same value, and I've been very briefly poking around the right device.
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