Modding of a CD player with TDA1541

Gary Indiana

Active Member
A couple of weeks ago I picked up a Philips CD-40 for $4.99 at a local Goodwill. It is a single disc CD player made mostly of plastic in Belgium in 1990. Not knowing exactly what would be inside I had pretty good feelings about it, and I was right. :D

The player has the coveted TDA1541A DAC chip which has been discontinued for many years but remains so famous and desired that fakes of it are still being made and sold on ebay.

I made a few simple modifications (mods) to the player to squeeze the best of its sound. And it was WELL worth it. The biggest surprise to me was switching the player to non-oversampling (NOS) operation. The sound became MUCH BETTER. Piano on CD now sounds like a piano, ovation sounds like ovation, all the obnoxious "digital" pollution disappeared! I read about NOS mods but wouldn't really know until I heard one with my own ears.

I posted all this in the thrift store mega-thread, but I do not want it to stay buried in there. It is a gem worthy of exposure, and an experience worthy of sharing. The mods are very simple and the results are very DELIGHTFUL.

And so here it is:
 
===== Posted March 6 2010 =====

Another v. good & cheap CD player joined my growing collection today. Philips CD-40 (exactly the same as Marantz CD-40) for $4.99 at GW. I plan to modify it to get the best possible sound, but even as is, this thing put instant smile on my face the moment I took it for a spin. :D

It has modest plasticky looks, but a TDA1541 DAC inside, made 1990 in Belgium, and has addictively beautiful sound even without any mods.

philipscd40.jpg



Compare the looks with Marantz CD-40 (random pic from the web):
marantzcd40.jpg


==== Edit April 7, 2010 ====

I came across another version of Marantz CD40 with a Yamaha DAC and transport inside and without TDA1541.

The Marantz CD40 sans TDA1541 is Made in Japan (vs. Made in Belgium for the good one). It has simple 2-digit green LED display (vs. multi-digit turquoise tube display). and it has no IR remote sensor.

I'm posting a picture of it, so people would avoid buying it on ebay and such. Philps CD40 with TDA1541 is in the bottom, and the good Marantz CD40 should look almost exactly like that Philips (compare with picture posted above). But if it looks like the Marantz CD40 sitting on the top of the Philips posted below, it will have some Yamaha DAC and not the TDA1541 inside.


Click on the thumbnail above, and then click again to see detailed full image.

Bad Marantz CD40 on the top of good Philips CD40:
marantzcd40.jpg
 
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===== Update March 8 2010 =====

I made the first quick mod on the CD-40 and with very worthwhile results.

I got a bunch of quality 100 nF caps - Japanese Matsushitas - to replace the original surface mounted 100 nF ceramics around the DAC chip.

First, I followed the suggestion by Lukasz Fikus of Lampizator fame, to leave the little SMD caps in place and add new caps in parallel. This is what I did:
smdcapsinplace.jpg


The result was noticeably muddy sound. The ugly coloration of audio was so bad that I couldn't listen to more than about three songs untill I pulled the cords and fired up my soldering iron again.

I removed the little SMD caps and left only the new Matsushitas in place:
smdcapsgone.jpg


And again, the result is noticeable difference in sound; but this time for the better. Very addictive crispy clean audio. I also connected the top and bottom panels to the ground. The CD-40 player was so cheaply made that they saved on grounding wire.

The next, and probably the final, mod will be replacement of the original op amps for OPA2604s. This player is a little too cheaply looking to tempt me into spending on it too much. What else I might do is test it in a NOS mode.
 
===== Update March 11 2010 =====

My OPA2604 came this morning and I put them to test right away.
I ordered from Mouser - an authorized TI dealer. The chips from ebay are a few bucks cheaper but might be fake.

The original LM833N opamps in the CD player are very good, and there is no urgent need to upgrade, but if you have a spare $14 burning hole in your wallet then go for it. :D

The chips came in antistatic foam:
49557786.jpg
36908386.jpg


Original opamps still in place:
75488905.jpg


Replaced with DIP-8 sockets, which will allow me to move my "investment" around whenever I wish. I chose the cheaper Dual-Leaf kind because it is easier to unplug the chips from them:
59195165.jpg


OPA2604 opamps in their new home. The old JRC feeds the headphones outlet:
80206461.jpg


The sound is better, more detailed. Highs got crispier. The player is connected to NAD 705 (which I like a lot) and DIY speakers with Vifa woofers and Seas tweeters. I expected more of the Mosfet tube-like warmth from the opamps but I got more detail instead. The difference is not huge, but noticeable enough to make me want to stick with the new setup. I enjoy it and it was worth the few dollars and some time IMO.
 
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===== Update March 13 2010 =====

I made a couple of mods again. The non-oversampling mod (NOS) is very simple and well worth it IMO. It does require soldering skills to play with tiny SMD parts and traces.

Having followed all kinds of tips on the web I made three tiny incissions on the PCB, thus cutting three traces marked with red arrows. Then I connected three first pins of TDA1541A with three first pins of SAA7220:
nonosmod.jpg


The mute jumper is more tricky because the traces are tiny and squeezed together:
mutemod.jpg


Then I decided to upgrade the audio output a bit by replacing 100 Ohm series SMD resistors with metal film ones. They are in muting circuit necessary to prevent loud pops when you turn off the power while playing CD:
resistormod.jpg


I like the outcome of the modifications a lot. Each mod resulted in slightly better audio and was definitely worth it IMO. My $5 Goodwill player became a multi-$thousand sounding machine. After the NOS mod I immediately noticed more individual instruments than I ever heard before. All the above mods are to stay in my player, and I might upgrade parts of the power supply in the future. Better clock? I don't know yet.

Now, after listening to the NOS modded player for a couple of hours I HIGHLY recommend it. The NOS sound is detailed, more "musical" and just plain delightful. :D I know, I will never be going back to oversampling. For best acoustic results it needs to be a combination of good DAC, good past-DAC audio stage (good opamps, fets or tubes) and NOS. Oh, and a well-recorded CD helps, too.
 
Nice work there , great to find a deal and make it sound like a big buck spinner I guess ? I think my AR CD-06 shares that DAC and the Philips drive , nice sounding unit . Picked up a Philips 921 player a month or so ago , stand alone sounds not too bad also . I was hoping to use it with my DAC but it doesn't send the HDCD data to the dac . It's in the kitchen now hooked up to a minisystem with a dead cd player so all is good . Doing the dishes is not so bad now :D
 
Just checked the list , my AR uses the tda1541 + the cdm 2 drive . sound's pretty tuntable-y I think ?
 
Nice work there , great to find a deal and make it sound like a big buck spinner I guess
It sounds really clean & NATURAL. I'm working on a tube amp out of a 1960's console. I expect even better results when that's finished and hooked up to the modded CD player.

Side note: the whole over-sampling idea is a really weird one. I can't understand why no one auditioned a CD player with and without it back in the day when it was first designed. Or why would they not include a switch to turn OS off?
 
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Now that you have those dip adapters, try different opamps. My favorite ones are the TI Burr-Brown OPA-2134 and OPA-627. The 627 are very expensive at about $25-30 each and probably an overkill for your model.

Also replace the larger electrolytic capacitors near the output area, those will measure fine with a DMM that has capacitance measurement, but as you know, a true measurement can only be made with a larger setup with sinusoidal input, scope and so on. I replace anything over 1/4" in diameter. I also replace the main power filter caps too. You can use Panasonic/Nichocon from Digikey or Mouser, but I prefer the Elna Silmic II and Black Gates.
 
Now that you have those dip adapters, try different opamps. My favorite ones are the TI Burr-Brown OPA-2134 and OPA-627. The 627 are very expensive at about $25-30 each and probably an overkill for your model.
Thanks for the suggestions. OPA627 are $18.37 for the AP ver. and $26.62 for BP ver. at Mouser. The difference is in input bias current and Voltage gain, which is really a non-issue when these are fed from a DAC chip. The OPA2134 are only $2.59 at Mouser. The distortions are at interesting levels: 0.00008% for 2134 and 0.00003% for the 627. My already installed OPA2604 have max. THD 0.0003%; so, I should've bought the OPA2134s for half the price of 2604s.

BTW, the original LM833N have max. THD 0.002%.
Also replace the larger electrolytic capacitors near the output area...... I prefer the Elna Silmic II and Black Gates.
These are non-polarized 100 microF so they may be little harder to get [Edit: I found the caps at local Frys].
And where do you buy the good caps, like Black Gates?
 
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I am an engineer, and tended to go by SPECS since that's what we do in that trade. But please give more credit to your ears as they are the most important sensor and input to this whole thing. Yes, I love the fact that the OPA627 has the lowest noise levels than anything, but hearing them are much better than any other specs.

This chart got me started but I now buy them and try them. I suggest you do the same instead of taking my word.

http://tangentsoft.net/audio/opamps.html

wsjoe
 
Does anyone have an opinion on the LM4562 op amps. Maybe compared to the OPA2604's.
I haven't tried them. A quick google says: they cost $4.82 from DigiKey - which is about the same as OPA2604 from Mouser. The LM has some very impressive audiophile specs. But, as wsjoe says, your ears will always be the ultimate judges.

In my Philips CD modding project I still plan to try simple discrete two FET transistors preamps in place of the opamps, and then a triode buffer instead of buying different new opamps. I hear a lot of good things about the simple circuits.
 
Fantastic job. I'm always amazed at the ability of you guys. Something I hope to learn one day. Thanks to tutorials like this I'll be able to search in the future when I'm ready and find threads like this.

Thanks to you and AK!
 
Today I tried the modified CD player with a simple two-tube output. The preamp comes from Hong Kong. Cost me $41 shipped. Separate pair of different tubes were purchased for $11.90 directly from mother Russia - for which transaction I used a limited debit Visa card instead of my regular CC. This is what I'd highly recommend whenever buying something on a Russian website.

I described details of my preamp in this thread.

And here is what my temporary setup looked like:
cd40wtubes.jpg


The sound is very beautiful, although different from the opamps. It is more mellow, lost a bit of punch and a bit of crisp, but it is even more analog-like.

I like it a lot, but would rather have a switch to change between opamps and tubes for different types of music. And I still want to try FET transistors on the output.

The tube preamp will become a separate unit in its own enclosure so I can use it or test it easily with different audio sources.

Edit: It's either the tubes burning-in or my ears are burning-in to it, but this thing with tube pre-amp sounds VERY lovely now. The difference isn't huge, it is subtle and sweet and addictive. To fully enjoy it a good amp and good speakers are essential.

Edit 2: I just tried, this afternoon, to upgrade the audio path of an 1996 Onkyo with SM5872 DAC, but the outcome just isn't the same. Too much digital noise comes out from the DAC that will not go away without heavy filtering. So, there was not much to improve from the factory design. Now I know why everyone is raving about the good old TDA1541A.
 
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