TDA1541 DEM reclocking - diyAudio
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Old 4th March 2003, 08:43 AM   #1
rbroer is offline rbroer  Netherlands
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Default TDA1541 DEM reclocking

Anyone successfully implemented the Henk ten Pierick DEM reclocking for the TDA1541 ?
I've tried, but I can't get it working. Get noise & distortion, guess the active divider isn't working.

I'm using 4*fs (non-oversampling application),
and BC557B's for the PNP's
The negative voltage is -6.1V
I measured -10V DC voltage on pins 16 & 17.

The FF indeed has the 4fs signal on it's outputs and there is some sawtooth on the DEM pins (noisy), but no luck.

Anyone ?
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Old 4th March 2003, 09:40 AM   #2
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i'm workin' on it too....but i haven't populated my pcb's yet....!
as i recall, the original dem is set up to work with 11,2 mhz - but you are using nos - then you don't have that clock......just a guess.....!

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Old 4th March 2003, 11:48 AM   #3
rbroer is offline rbroer  Netherlands
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It's in a cd player, so I do have the 11MHz.
As I menioned, the divider and FF work ok,
I have the 4*Fs square waves on the FF outputs.
In fact I have tried 8*Fs as well.
If you're interested I send you some scope shots of what I'm seeing.

The original DEM with capacitor:
Measuring a pin to ground shows a sawtooth; there is a phase difference between the two pins resulting in a triangular signal when measuring between the two pins of +/-0.5Vac @ -10Vdc

With the DEM reclock circuit:
Measuring a pin to ground shows something like a sawtooth; like the inverse of the signal that is shown in the picture. But there is a lot of "noise" like small oscillation superimposed that signal.
Also the AC value is at least halved.

I've also tried with 2.2k and 3.9k in stead of the 2.7k
With higher resistors, the ac value goes up in amplitude, but the sawtooth ramp rate stays the same, resulting in a bigger "step" when the other transistor is switches.
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Old 10th March 2003, 08:22 PM   #4
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i'm sorry but i don't have the time to dig deep into this subject at the moment, but i will be back.
later troels...!
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Old 11th March 2003, 11:37 PM   #5
BrianL is offline BrianL  United States
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Exactly where can one find info on this
DEM reclocking? I.E., where does Mr.
Pierick have it posted?
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Old 13th March 2003, 06:36 PM   #6
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Wink DEM Reclocking

Hi ,
I don't think Henk ten Pierick has posted his scheme on a forum or website. Best contact him directly by email.
His emailaddress is in the picture of the schematic. (leftunder)
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Old 14th March 2003, 10:12 AM   #7
rbroer is offline rbroer  Netherlands
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The DEM reclocking is working now
Was a problem unrelated to the circuit as supplied by Henk ten Pierick.

Im must admit, didn't expect a lot from it, but the improvements are not subtle at all.

Two things pop out:

First the clarity of voices and instruments, they sound clearer, easier to follow and differentiate.

Basses seemed less at first, but they sure were faster and much tighter. The TDA1541A imho always had a bit of woolly bass compared to other dacs, but not anymore.

Minor improvements:
Treble seems to have less roll-off
Agility factor improved, it's quicker in a positive way.


I've implemented the 4*FS DEM reclocking for a non-oversampling TDA1541A-S1. I've not implemented the BCK reclocking yet, as I wanted to do the mods seperately to hear their effects.

My next implementation will be a little different;
use the VHC series logic 74VHC74 without any need for inverters since my Kwak-Clock has inverted clock output as well.

I would say an improvement as big as installing a low jitter clock or getting rid of opamp I/V stage

Cheers,
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Old 14th March 2003, 11:30 AM   #8
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good to hear that you succeded.......keep it up !!!!!

best regards,
troels

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Old 9th September 2003, 08:00 AM   #9
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Default DEM mod very worthwhile

Hi All,

Finally got around to doing this DEM mod for the TDA1541 and yes, it is worthwhile. My observations are as follows:

1. Much better detail retrieval, especially stuff that was unresolved before.
2. A better sense of intimacy and musicalness in recordings
3. Notes have more separation and individuality.
4. Bass seems tighter, and again there seems to be more individuality to notes instead of the usual smearing.
5. Guitars, etc have more immediacy

The board (I have made several) also provides an option to reclock BCK.

This is in my heavily modded Rotel 955:
1. Zero-oversampling, i.e. SAA7220 bypassed
2. TDA1541 uses TL431 based power supplies
3. IV conversion as per rbroers "simple IV converter". He posted schematics here some time ago.
4. Seperate transformers and AC-DC for 1541, 7210 and processor
5. High speed diodes for rectifying
6. Ferrite beads and inductors (0.2 ohm DC) used in CDP
7. KWAK CLOCK v 6

Other things to do include:
1. Use of CMC coils in the power supplies
2. Optimising the TL431 based PS
3. Improving the IV converter to DC-coupled
4. Adding an output buffer along the lines of BUF04

My 2c.
Ryan
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Old 8th December 2003, 02:09 AM   #10
moemoe is offline moemoe  Singapore
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Hi All,

I'm trying to implement DEM reclocking as well. I have one question on the schematic which I hope the guys who have implemented the DEM reclocking successfully can share their thoughts on.

Is there any purpose to connecting pins 3 & 4 (D0 & D1 for ws_in) and pins 2 & 5 (Q0 &Q1 for ws_out) together? It would appear to me that ws_out is now a 10V clock whose voltage is double (due to the summation of Q0 & Q1) that of the normal ws clock. Wouldn't this have any adverse effect on the TDA1541A chip?

If there's really no purspose to the above, why not just use D0 for ws_in with its corresponding Q0 for ws_out only. For those thinking of reclocking BCK as well, just use D1 with its corresponding Q1 to do so.

I sent an email to Mr. Henk Ten Pierick but have yet to receive words from him. Anyway, I thought it may benefit all to have the discussion on DEM relocking here on the forum.

Best regards,
Moe
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