JACQUES HIFI PAGES

UPDATES ... At last : my preamp for tda1541 dac

1- The collector solution

As you may know if you read my website, I never did my preamp to take direct tone from the legendary tda1541 from our friends at Philips.
Well this is no more : I just came up with a new idea ---the use of hybrid Szikai pair---that works great directly from the AOL and AOR outputs of this chip.
In my solution , you just have to steal these 2 points ( pins 6 and 25 ) and the +12v from any ( or best, one for each channel ) output opamp ( here it's pin 8 of LM833 ) , and you're done. I don't touch or disconnect anything : the good thing about my solution is that it's non-destructive and your cd player can return to stock in 25 seconds. Good if you're a collector.

I usually use the following or preceeding component to solder my stealing points, bigger and more solid .
Here a cap following the tda1541 output and a resistor feeding the LM833 opamp.

Of course , all wires should be eventually shielded because of the high gain of my circuit . You can see the GAIN pot which is used to set precisely the output volume exactly like the other cd player it is compared to . To make a close A/B test, output volumes must be the same.
The control is wide as at max the sound will distort. I love this feeling to have power under the hood....this comes from my guitar effect pedals work I suppose.... but no more talk here is the schematic so you can do it yourself at home :

It's easy and very cheap. So try it and tell me if you like it. For me, it's really an incredible tone, which gives even more prestige to the legendary tda1541...for example , it blows away a 24/192 modern chip , upsampled and taken directly. Specially in stereo image and human voices reality.

2- The 'pure' solution

If your cd player is not a collectable AND has tda1541 as a dac, you will of course prefer the pure solution.
This time you need to isolate pin 6 and 25 of tda1541 completely from board . I do it crudely by cutting the pins and float them like this :

I also isolated the +DC from the opamp , just to be sure my circuit receive a good 12v or more.
Then the schematic of my preamp is slightly different because you need to do yourself the I/V conversion , with 90ohm resistors .
Thank you Mr.Lampizator for having calculated this resistor value for us !
The gain pot is no longer useful as the it should be maxed to be at line level.
But it's exactly at line level , which is no small feat because the tda1541 is not known for being loud . I am quite proud of my circuit .
Here is the modified schematic :

Here we are , with a 25euros budget, beating all 5000euros cd players from high-end with such an ease it's ridiculous.
They should have stopped at 1541. I include myself. Your comments are welcome at tda1541@ts808.com .

Here in my cd50 from marantz , where the access from the back is much easier , I have cut the traces from pins 6 and 25 of tda1541a and coming to the opamp , here a mighty 14v . The cuts are circled in red.

Then I could put my circuit on the crate .
I have noticed only the wires from the tda1541 need to be shielded. It's not critical for the outputs .

3- The Mykono2

Here in this philips cd782 I have tried another solution with 100% silicium classic transistors ---derived from my mikonos---- I called Mykono2 ,
which can't be read but look nice typed.
I found that this tone has a little bit more punch and dynamics, but it's a question of taste. It gives the human voices more physical presence to my ears.

4- La totale / The Full Monty

Maybe you remember my marantz cd40 I modified non-oversampling . This tone, raved by audio diyers, while incredible, has issues with loud records .
It's somehow strange nobody else noticed that...you can do the experience with Tori Amos' 'Scarlett's walk' ---money well spent as this record is beautiful---. On track 1 , you can hear slight but ugly and numerous distortions certainly coming from the aliasing --- I refer to Rick Matthews webpage which is about digital pictures but I think it's the same problem --- . If you stick with old style recordings , it's kind of ok but knowing this disturbs me.
Anyway, I had to try my new mykono2 combined with nos mod.

The addition of the mykono2 circuit took me 5mn , as it was ready for mykonos, including DC taken from a removed opamp.
Just had to cut the traces from pin 6 and 25 of tda1541 at the same place than in the cd50.

Well, tone is fabulous--too weak a word-- but, no surprise, the aliasing problem is still here. I'll keep this cd player for classical music.

5-tda1540 :' I-can't-believe-it's-not-16bit !'

After this great experience, and being sure the stock output stage of philips cd player was that bad,
I felt I had to try the I/V conversion and mykono2 on the venerable tda1540 .
Nothing prepared me to that surprise .

I just did exactly what I did on tda1541 players, i.e. : dump one of the opamp to use its DC ( red wires ) , take ground ( brown wire ) and isolate pins 22 of each chip ( the tda1540 is mono ) but cutting their traces and steal the Iout signal ( vintage shielded white wires from french army ).
I eventually found the same tda1541 I/V preamp circuit works with tda1540 ...really similar chips.
And .... I could not believe my ears ....

Usually , tone of 1540 cd players is quite wooly .
Logically I thought , like everyone else , that was because sampling is only 14bit oversampled to get 16bit redbook correct.
But it's not .
Now I have an incredibly detailed sound with a stereo image and reality that leaves all stock cd players WELL behind.
Try this and tell me it's not true.
This means collectable 1st cd players are now even more valuable , because they are incredibly well manufactured ( see my marantz cd73 ) and have a drive that will make 20000euros Esoteric new drives blush with jaleousy.
Only drawback is I hope this article won't make their price go up...and I hate the faraday cage philips built over the circuitry of these wonderful ancestors.
Here I made my 1st experiment on cd150 , which is cheap and a joy to disassemble.

Somewhere I knew Philips engineers were geniuses.
Let's not forget that everything here is Philips-made here EXCEPT the output opamps !!!
Anyway, the tda1541 , with the same mod , is better but not where I expected . I could describe this supremacy with a more realistic tone.
But what's new for me is that the modified tda1540 beats tda1541 stock and it's not a small feat.

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