Reclocking in a TDA1541 (zero-oversampling) CD player

[Dr.H]

Hi All,

I own a heavily modified Rotel 955 (zero oversampling with the TDA1541 fed directky from the SAA7210) and am interested in implementing the reclocking of BCK or all lines between SAA7210 and the DAC.

A few questions:

Any schematics I can look at anywhere? I am not really sure about connections. Another contact mentioned feeding the " inverted clock" from the 74HC74 back to the SAA7210. Any ideas on the meaning and implementation of this?

Is the best 74xx the 74HC74?

Does the 74HC74 require a clock independent of the one I have in the CDP (11.xxxMHz)?

ANyone have experience of the sound impact of reclocking in a TDA1541 based CDP?

Thanks for any help
Ryan

 

[Elso Kwak]

Asynchronous Reclocking

Hi Dr.H. Ryan,
I can send you the schematic of my Asynchronous Reclocker. Basically it is a low jitter clock with a 100MHz crystal and 74VHC74 flip-flops. Two flip-flops are used in series to catch any missed transistions.
74VHC74 sounds better than 74HC74 or 74AC74 I found.
A higher frequency indepent (asynchronous) clock sounds bettter than the clock from the player.
Also note that the ASR does not make a low jiitter masterclock superfluous.

 

[rbroer]

Hi Ryan,

Like we discussed before, it is quite easy.
Here's a little sketch showing you how to do it.
I've implemented this succesfully with a TDA1543 and SAA7310, TDA1541 and SAA7210 shouldn't be any different.

The system clock is11.2896 MHz, BCK is running at 2.8224 MHz in your non-oversampling application.
The reclocked BCK will shift a little, but not as much as to violate setup timing.
The inverted masterclock feeds back into the SAA7210, otherwise you'll have masterclock going up while BCK is just transitioning, resulting in metastability problems.

Let us know how the results are;
I for one do like the improved bass en attack a lot.

Cheers,

 

[Dr.H]

Kwak clock

Thanks Rudolf,

So it looks like I'll have to make a purchase of teh KWAK clock to get the inveretd clock outout then.


As my system stands now, I have a crystal (11.xx MHz) which I purchased from Guido Tent and which is being fed from its own clean supply. This runs to the 7210. (used to go to the SAA7220, but I found that you can feed directly to the SAA7210 in the non-oversampling situation).

Is there a way to generate the inverted clock in my current set-up (i.e. just crystal and power supply) without buying the KWAK clock? I'm trying to avoid the international mailing system (which routes via Singapore remember?)

Ryan

 

[Elso Kwak]

Asynchronous Reclocking

Hy Ryan and Rudolf,
What I meant was this:
http://home.student.utwente.nl/f.s.bouwman/audio/images/nonoz-schematic.gif
(This is from Feddes website). Fedde found just as me that reclocking al three signals DATA, BITCLOCK and LATCH gives the best sound in a NON-Oversampling DAC
The Asynchronous Reclocker can also be implemented in a one box CDP. This has been done by Marco Amboldi in a Philips CD960, who is very enthusiastic about it.
Marco's website:
http://members.xoom.virgilio.it/hi_fi/index.htm
Ryan, You don't have to buy the KWAK-CLOCK. The schematic is available for DIY use by sending me a email. Please note that the metallic square box supplied by Guido Tent is not a crystal but a complete crystal oscillator. You have to add only a supply. I am not sure what you mean by the Singapore connection. The email system on this forum works again! But you have my emailaddress.

 

[Dr.H]

My email address

Hi Elso,

I have posted you via diyaudios system, but yes I would be interested in the schematic, my address being rl_hill@yahoo.com.

Many thanks for the assistance.
Ryan

 

[George Kubitsch]

max clock freqvency

Hi Elso!

Thanks to your help, I made the AsynchronousReclocker3 with a 57,9x MHz crystal.
I had to change the capacitors to 30-60pf and the source resistors to 40 - 60 ohms to make the oscillator working.
My scope has about 40MHz working range, so I can not measure it correctly. It drives the 74hc74s D flip-flops correctly.
Before I put the circuit between the CS8412 and TDA1541 two questions occurred to me:
1. Is this clock jitterless enough, how can I check it?
2. The datasheets of 1541, 1543 say maximum 10-12 MHz input clock freqvency, 57 or 100 MHz is not too much?

Thanks in advance
George

 

[Elso Kwak]

Asynchronous Reclocker

Hi George,
I am not familiar with your crystal, so it is difficult to give advice.
To answer your other questions
1. The clock is driving the clockinputs of the 74VHC74's NOT the TDA1541 !
2. See above.
I don't own equipment to measure jitter. All my clock circuits are developed "by ear".

 

[George Kubitsch]

asynchronous reclocker

Hi Elso,

You are absolutly right, I did not think it over.

Thanks
George

 

[Malefoda]

...otherwise you'll have masterclock going up while BCK is just transitioning, resulting in metastability problems.

Hi there, here I go with a problem of TDA reclock and it can be that...

Before:
I have a PFM Flea clock, powered by a dedicated PSU, from only a R at the XO's output pin, 2 wires, one for the SAA7310 and one for the SAA7220, then the ground to the Filter's ground.
Works like clockwork (!).

Now:
Then I fitted a LM317@5V, a +10V from the player's PSU, grounded to a local ground passing by. Shows a solid 4.98V.
A FlipFlop 74HC74 is fed by a pair of wires, ground and +5V from that reg, a 10µF 35V and a 100nF X7R between the 7 & 14 pins.
A new R (100R; PRP), is set at the XO's output pin, via a coax, soldered at the Clock pin of the flipflop, pin 3.
Another coax goes from pin 5, or 6, to pin 2,

I've tried it with Q and Q_, with the RC 1K/10pF wich works fine with SAA7220 OEM data lines, 100R, always with pins 4 & 2 linked on PCB.
No sound in any case, slight buzz sometimes.

Then found this thread and fed the Data pin of 74HC74 with BCK from the SAA7220.
I've played this Q and Q_ and the RC in data line.
In every case, depending on swith on/off and the mood of the player : sometimes plays well, sometimes higly distorted and even changing to almost no sound.
A sync problem or soemthing like that?

Don't know what to do, any idea is welcome gents!

Thanks,
Matthieu

 

[Malefoda]

...sometimes plays well, sometimes higly distorted and even changing to almost no sound.
A sync problem or soemthing like that?

Hi,
here it goes with a almost working setup:
BCK reclocked with main XO/2, then feeding the TDA1541A wia a 33R (the 10pF cap still here, won't harm).

So the only time it's out of sync (I name it like that even if it's something else) it's when the player is switched off for a while, say from 5 to 60 minutes.

Off all the night: OK when main socket on in the morning (I don't switch any device, just the socket),
Off for a while: NOK, a second switch on/off (at the CDP's switch) and it's OK
Off for few seconds: OK

A cap feeding a PSU for minutes and don't let the XO or the FlipFlop to reset?
A need to wire "reset" at the 74HC74?

Thanks,
Matthieu

 

[Malefoda]

Hi there,
of course people are allowed to answer

It's not stable, sometimes it starts badly, then within 5 sec of playing settles fine. Today for the first time it's always drift... off!
No idea how to perform that...

Thanks,
Matthieu

 

[Fantasio]

IMHO, some of the power supplies take too much time to set up the required voltage, so that the power up reset and startup conditions are not met for some of the chips. That would explain why a brief switch off then on cures the problem.

Otherwise check wether your the reclocking gates or flip flop meet the fan out and timing requirements. Could also be a defective part.

 

[Malefoda]

Hi,
the fact that it refuses to work again pushed me to setup like factory. It's dead silent now, think it's fired... :'(