Opinions on NOS mod for vintage TDA1541-based CD player - diyAudio
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Old 17th February 2016, 02:37 PM   #1
KanedaK is offline KanedaK  Belgium
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Default Opinions on NOS mod for vintage TDA1541-based CD player

Hello fellow members,

I acquired a ReVox B226 cD player a few weeks ago.
It's a 25 or 30 years old player in need of a refresh (altough it sounds surprisingly good as it is now).

I've decided on a global recap (all the electrolytics and probably also the output coupling caps) + replacement of the output stage NE5532 opamps with Sparkos Labs SS3602 dual discrete opamps.

while I'm at it, as the board will be out and all, it seems to make sense to upgrade the clock as well - as such a thing might be a great leap forward in sound quality, according to internet sources (haven't heard what a proper clock can do).

Looking for an affordable clock module I keep bumping on all-in-one, low-jitter reclock and NOS modules that solder in place of the SAA7220 chip found in TDA1541 based players. Those modules are supposed to be "plug and play" and require no further modification of the board, wich sounds appealing.

So here are my questions:

1) does it make sense to NOS an existing player designed for 8 times oversampling and sounding quite good that way?

2) is a NOS dac configuration compatible with a tripath-based power amplifier (knowing I'm using a conventional SS preamplifier between the CD player and the power amp), or is there a risk of instability or other problems due to spurious very high frequencies "garbage" that will be left unfiltered at the player output?

3) does NOS modification bring any real upgrade in SQ (in general and on this particular ReVox B226 player) or is it more like a change in flavour and a matter of taste?

4) If I would decide to keep the oversampling, and keep the SAA7220 chip active, wich clock module would you recommend knowing that I need something not too expensive and easy to implement, and if possible reversible (no destruction of board tracks)?

Thanks a million!
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Old 17th February 2016, 02:43 PM   #2
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From what I understand the SAA7220 mostly causes problems because it usually shares the powerline with the DAC chip, and giving it its own power supply has a better effect on sound quality than turning it to NOS mode. The oversampling itself is not the problem, it's there for generally good reasons.
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Old 17th February 2016, 03:15 PM   #3
DF96 is offline DF96  England
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NOS probably means abandoning any attempt to reproduce the signal before the original ADC. Remember, oversampling was meant to be an improvement, as it allowed easier implementation of analogue filters.

Unless the original clock is quite bad (unlikely with Revox?) the unsophisticated connection of a 'better' clock is likely to result in more jitter, not less.
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Old 17th February 2016, 04:44 PM   #4
poynton is offline poynton  United Kingdom
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As the owner of 8 Revox B126 / B226, be careful when playing with the power supply / DAC board.

The clock is a very basic implementation using the 7220 and a crystal.
Almost any "external" clock will be an improvement.
Take care where you take the power from due to the standby switching.

I agree that a better option would be to give the 7220 its own supply.
Again, take care where you get the supply for the 5v regulator.


Andy
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If it ain't broke, break it !! Then fix it again. It's called DIY !
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Old 17th February 2016, 08:46 PM   #5
Eldam is offline Eldam  France
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I believe also the jitter issues of the SAA chip is more important in the result than oversampling problematic... You may think to swap the original Crystal as well !
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Old 19th February 2016, 08:11 AM   #6
danico is offline danico  Hungary
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I followed Ecdesigns work from the beginning. And using some of his tweak in my Revox B225 improved the sound with a huge margin.

since you have the tda1541A chip you can adapt them as well.

For an easy step i would do the latest DEM clock mode.
Its only 2 resistor of 6K8 taken from -15V to the DEM cap legs on the chip.

secondly the I2S attenuation brings another big step to the sound.
I made it into the place of my oversampling chip SAA7030.
you design a bit different maybe you cannot eliminate the 7220 completely.
You can use resistors instead of diodes. both works fine. different size resistors for 3V or 5V data lines!!
Attached Images
File Type: png i2sattdemclockfor33v.png (324.2 KB, 110 views)
File Type: jpg image-1.jpg (57.1 KB, 107 views)

Last edited by danico; 19th February 2016 at 08:15 AM.
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Old 19th February 2016, 04:43 PM   #7
Eldam is offline Eldam  France
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Danico,

If 2.2 n between pin 16&17, doest it mean you have to leave free the 14 DEM caps (unpopulated) ?

I stayed on the same shematic but with 100 pF at DEM Clock & 0.33 uF for the 14 DEM caps !

Btw, did you noticed difference between résistors in serie with pin1 & pin 3 with carbon, metalic, SMD "MIFL"... reversed diode ?

A good way is also to feed the clock with a low impedance battery à la IanCanada with LiPoFe4 (less than 6 M ohms ESR... your local decoupling cap may have more impedance )
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Old 19th February 2016, 08:04 PM   #8
danico is offline danico  Hungary
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Hey Eldam,

Sorry I did not checked the supplied pictures good enough.
I just tried to find something to describe the upgrade.

Ignore the 2,2nf and just leave the original cap on the dac pins.
or use any of these size for:
235.2 KHz, 350pF
256.58181 KHz, 318pF
282.24 KHz, 300pF
313.6 KHz, 260pF
352.8 KHz, 250pF
403.2 KHz, 203pF
470.4 KHz, 180pF
564.48 KHz, 145pF
705.6 KHz, 122pF
The capacitors need to have tight tolerance (1%).
So the C giving 176.4 kHz fDEM might be around 465 pF.

I used old vishay draloric mk2, but I do love the carbon resistor sounds AB or Beyschlag. I use them in the signal line most of the time. Metal film resistor works good with high freq, but you never know.

Did you tried out already the dem mod? how it sounds for you?
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Old 19th February 2016, 08:08 PM   #9
danico is offline danico  Hungary
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did not heard about this battery powering. sounds interesting.

I tried to keep my cd player as original as I can, so I just chanced every caps to oscons and elna silmic II and Claritycap ESA after the opa627.

Cant ask for better performance for this price:-))
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Old 19th February 2016, 08:12 PM   #10
danico is offline danico  Hungary
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Quote:
Originally Posted by Eldam View Post
Danico,

If 2.2 n between pin 16&17, doest it mean you have to leave free the 14 DEM caps (unpopulated) ?

I stayed on the same shematic but with 100 pF at DEM Clock & 0.33 uF for the 14 DEM caps !

)

Ok. I just realized you asking about the 14 caps around the dac. of course you need them. it was a simplified picture focusing on the dem resistors.
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