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TDA1541A



The Fikus Transport 1,0 in ten simple steps



This project is inspired by the incredible success of shigaraki transport. If these guys can achieve so much with a 5 Euro mechanism from Sanyo - I can do similar job with another player. Let's try.

In fact this is the project I do for YOU dear readers, not for myself. (And by the way - first project fully funded by donations from readers !!!)
I want to prove that with some time and patience everybody can make a transport, which will - if not beat - at least approach the best transports of the industry, including ANY one you pick from the millionaire's wish list.

My pick is a cheap, popular and simple player  (well, at its time it was a TOP Philips model) Philips CD-940  (identical to CD-930 which I had as a double) chosen by me  because of its very nice CDM9 mechanism.  I chose it because it plays well, it works fast, it can be bought for little money, it reads every CD without problems and there are thousands of them out there. I bought two just in case and I paid 50 Eu each - in mint condition but without a remote.

Important disclaimer: I don't KNOW how to do it - I am learning in the process. After examining 100+ players and their schematics I pretty well know what's hot and what's not. So I will do my best.  Lets evaluate for example my sixpack - I picked the powering points by intuition. Maybe 5 will be unimportant - but ONE will be of paramount importance. So be it. I want to try my best.


Philips CD 940

(I must admit I LOVE LEGIBLE DISPLAYS !!!  Some Japanese makers adjust their displays to Japanese size of rooms (JVC, Pioneer). I hate that - I CANT SEE !


I decided to tweak this player to the limit,  but with a reservation that I will be using ONLY engineering methods with proven effect. No spikes, cones or granite oil. I decided to stay under a total budget of 200 Eu to keep the project in the sane bracket. I may add a digifetishizator output buffer or maybe a digilampizator, low esr os-con electrolytes scattered in critical places, every power  "consumer"  on the board will have a new dedicated power supply - transformer, regulation and filtration. This applies to the laser, the spindle motor, the servo, display, demodulator, microcontroller and S/PDIF transmitter.  Clock from Kingwa. Bituminous felt, new oversized transformers, new AC filter, etc. That was the plan, now I will confront it with reality.
I will try to l isten to the player after every major step.
Again, I am building  A TRANSPORT so I optimize my actions around that task, not around making it a well sounding player, but who knows. I will try the analog outputs too.
If I fail to make good sounding transport - that will be another lesson to learn.

Finally, if I feel that the transport has a good potential - I will take it to the Battle Of Six Transports and eventually - to challenge the CDM9 based Mephisto 1 from Pierre Lurne.



If you share my philosophy of ten steps and no nonsense tuning - you may repeat it with ANY player you like, I mean ANY player. The cheaper - the better.


Above - the finished transport on top of Lampized LITE DAC-AH.



Why CDM9 ? Because it is the last mechanism from the wonderful swing-arm range. The last one. After that - it's goodbye magnetic, hello plastic. (In my opinion, even the CD-PRO2 mechanisms are plastic BS covered in heavy alloy decor. They are faking the orgasm. What a shame.)

CDM-9 mechanism list of "users":

ARCAM ALPHA 5
ARCAM DELTA 270
AUDIOLAB 8000 CDM
AURA CD-50
BURMEISTER 979 (pro version)
EMT 982 PROFESSIONAL
Forsell Air Reference Air Bearing (Pro)
JADIS JD-1
KRELL KPS 20i
MARANTZ CD-23 (Pro)
METAXAS MAS PHOS
MISSION-Cyrus dAD7
NAIM AUDIO CD2
NAIM AUDIO CD3
NAIM AUDIO CDI
PHILIPS CD950
PHILIPS LHH100M
PHILIPS LHH300
PS AUDIO LAMBDA 2
QUAD 66
ROTEL RCD-975
T+A CD1400AC
T+A CD3000R
THETA DATA BASIC

Now I hope you approve my choice of CDM9.

Of course the list is courtesy of Vasili from Minsk, who keeps the best list on the net, updated daily !

http://www.vasiltech.nm.ru/files/cd-players/CD-Player-DAC-Transport.htm

If that is not a list of good players - than what is ? Even Jadis, Krell and Forsell is here. Burmeister, Quad, Theta - the whole ELITE.

So lets try to make something that is close or - who knows - better ?

For those interested in Transport related issues, quality, s/pdif etc - you can read more from me  HERE


You can read the Transport comparison "BATTLE" - HERE

I found this S/Pdif article here






Above - general  look and the mechanism in the centre. All electronics except  display are on one green PCB. It is an okay board, not too neat and not too messy. No premium parts in sight. No resistors in straight rows. Just  "a pcb".

By the way - the drawer is of the cheapest possible kind. Absolutely nothing comparable to the old metal drawers from Sony and Philips. Nothing like Bang Olufsen CD5500  either.
The swing-arm is a far reminiscence of the CDM1 but it is still a magnetic field swing-arm that holds the laser. BUT the turntable motor is the shitty type - the Mabuchi 3 USD toy motor. Not even a far far cousin of the CDM1 magnetic haal motor. That one is today the industry standard - from sony to sanyo to philips - everyone uses cheap motors from china.
The CDM9 mechanism is soft suspended on 4 rubber hangers.





The power supply input - at least has a decent noise filter - a choke (the little thing that looks like a transformer) and the orange capacitor. That is really nice of them.

There is some extra room for my "stuff".



TEN STEPS TO  (S/PDIF) HEAVEN




STEP ONE: sniffing around with the buzzer



Yes, the buzz function of the DMM meter is one of best tools for our hobby. (I mean the meter beeps when the probes are in short circuit.)
My routine is this: slightly bend the electrolytes on the PCB to gain access to their legs. I held one probe at the 5V regulator output leg and with the other probe I poked the positive capacitor's legs. My GOD this is supposed to be the top player from most reputable company - and guess what - almost ALL CAPS BEEPED !  At least 3/4 of all caps are fed from JUST ONE regulator - and the cheapest simplest one - 7805. It supplies almost every function of the player. This way the consumers of electricity are joined with each other on common +5V line. They interact with each other, talk to each other like hell. There are not even chokes to interrupt the common line and separate chips. everything is made in such vulgar primitive manner that I am speechless. How can a DAC be fed from the same line which feeds the laser and SP/DIF generator and display ???
The conclusion: intuition tells me that there is huge potential for improvement.

STEP TWO - chip checklist

By going to my favourite web site www.alldatasheet.com I try to gather the data about the chips.
This player uses many integrated circuits, almost all from Philips. The control of laser - motor - reading and data pre-formating is done by the TDA8808 chip. That one definitely  deserves its own power supply.
Next, the raw data is going to the error correction. That is important too. So we add second power supply.
Next the data is interpreted by the so called demodulator - our well known and very popular saa7310. No compromise here from Philips side. That is a key chip and it will get third dedicated power supply.
The next chip - xxxx is actually the one which generates S/PDIF so for transport quality it is mission-critical. Ooouups there goes the fourth power supply.

Next is the DAC - SAA7350  itself - and since it interacts with preceding chips up the chain - (for example by clocking them) - it deserves the supply too. Maybe it will  also sing well - who knows. The VAC DAC sung VERY well with similar dac. So the fifth supply is taken.

It  leaves me with one spare 5V supply left plus the old one - the 7th supply on board will supply everything that's left like display, infrared circuit, etc.


























The above digital demodulator receiver chip is standard of Philips - used in every machine produced after they ceased SAA7210. It is used in some very capable machines like Grundig 9009, Naim CD3, and many Marantz players too. It should be also excellent here.

Speaking of my beloved mighty Naim CD3 - it shares with the Phillips 940 more than you think - mechanism, laser, controller, receiver/demodulator, RAM, servo - 90 % it is the same.
Well - almost - because NAim has 9 regulators and Philips only 3.
Until today that is.
Because adding the sixpack - transforms the Philips into Naim. I am serious. It is the same principle - one regulator per every consumer !




Above the DAC I never tried. It is very integrated chip, unlike the dinosaurs like TDA1541 or 1540. But after I heard it inside VAC DAC - I know it has potential. Especially in trebles.
It is a V out dac so no need for any opamps of any kind.
It may be lampized with just a cathode follower buffer.





The above photo shows the most important chip that controls the functions of the transport part - laser, data reading, etc.
Unfortunately - the space around these chips is so tight - on both  upper and lower sides of the PCB - that we can not squeeze any oscons in the proximity. The power arrives from far away.

I can only upgrade the main caps far away which supply this critical chip. Or wait a minute - I have 100 uF SMD tantalums somewhere .... I could add a few to the power input pins !


Philips CD-940

On the picture above - red tape markers indicate caps and chips which respond to the buzz test from the 5V regulator - all on common line. That is BAD SCENARIO. Too many devices on one 5V rail. No good at all. I am going to select 6 most important ones and apply the sixpack pure power there, disconnecting the old 5V supply.
The less important consumers will get the old supply - now FREED from 6 consumers and also well osconed and tantalized . So the old supply becomes by comparison much better.







Reverse side of the dual layer PCB - again - plus 5V consumers marked with red tape.






Above on the right - the "famous" hero of my story - one common regulator chip 7805 attached to a large heat sink.  5V output is on the third right-most leg marked with an arrow.







STEP THREE : best toilet time reading - the schematics.


For me the use of the schematic is optional - I like to sniff around on my own, (I mean around the schematics, not around the toilet) but for the project of this calibre I will read the schematics like a pro should.
It only confirms what I found out already: the player has five supply voltages: +12, -12, -5, +10 and +5V. The latter one feeds 3/4 of the player functional consumers and from S/PDIF point of view (transport) - all of the vital functions are fed from just one 5V. It is one shared common line. In my opinion it is not adequate, not elegant and not kosher at all.
I sustain my decision to add 6 new supplies.

See the MODULE BLOCK DIAGRAM of the player HERE

The schematics part 1 is HERE
The schematics part 2 is HERE
The schematics part 3 is HERE (transformer)
The schematics part 4 is HERE
The schematics part 5 is HERE
The schematics part 6 is HERE






Photo:  SPDIF trace in stock form.
What can I say - it is the worst square I ever saw and by a wide margin. It does not automatically guarantee to play bad music, but it shows the Philips approach to their top player. Messy engineering was tolerated in the 90 ties in Eindhoven. The trace has overshoot, much limited low frequency response (falling flat line part) and tons of refflections.

On the other hand - HOW MUCH ROOM FOR IMPROVEMENT for me !


Listening in stock form: as a transport and as a player

As a stock transport against the Theta - Read HERE

As a stock unmodified  Philips CD940 transport  I used it with my own very good lampized LITE  DAC-AH with CS8416 receiver.  - it plays quite well. I would say - better than most players used as transport. Theta is still a touch better in every area: bass is deeper and stronger, space is better in all 3D aspects, trebles are more airy, it is more musical and more pleasant. But difference is not night / day - just a liiiiittle bit. Overall - stock Philips CD-940 makes very nice transport, especially for the money (usually circa 75 Euro).



As a stock stand alone player - it plays OKAY, nothing is wrong, it is quite clean, bass is not deep or strong, trebles are clean, sound is listenable but not impressive. NOTHING compared to lampized TDA1541 or any other lampized player for that matter. (CD 940 and 930 which is the same player, only 940 is from Belgium and 930 from Singapore)
I would say - the stock philips plays better than most stock players and ergonomy is very good, especially large legible display, fast access to tracks, perfect operation.
I can attribute the clean and nice sound to the fact that there is in the analog section after DAC -  ONLY ONE op-amp per channel. Not 10 like in most other players.



STEP FOUR - NEW POWERHOUSE SIXPACK


I will start from adding a new power transformer. The old one (very small indeed, maybe 20 VA in total of its 3 secondaries and the core is a cheap one really)  will be relieved from 75% of its duty so it will in a way become adequately sized for the remaining 20 % of the  job. It will continue to supply the less critical functions like: the  drawer, phone output, analog section opamps, muting transistors, etc.
I add a 160 VA toroid with one 12 V AC secondary. That is a 15 AMP secondary !
I will rectify it by a diode bridge and I will feed 9900 uF raw supply capacitor bank. (That is already more capacitance than the whole player put together contained before modifications).



I moved the old transformer to the side and added the huge 160 VA  toroid.



From the raw supply of (roughly) 16 VDC (rectified from 12 V AC)  I will split the feed into six parallel lines by means of six small ferrite chokes.

After the choke I put a tantalum cap - 1 uF by 35V per each feed.
Then the signal will go to the input of a low drop low noise high quality regulator LM2940CT (not from the 7805 family  ) with 5V DC outputs. I hope I can get away with having no radiators because demand is small per each regulator. (assumption confirmed - all regulators are stone cold under nominal load of their consumers)
I expect the current capability of these regulators to be between 10 and 50 x over the real demand, even peak.
After the regulator I added again a 33 uF /25 V tantalum cap. It is so small only because there will be an oscon down the line.
Thats all - the powerhouse is ready to rock'n'roll. Literally. So I mounted it on the universal PCB and installed in the free space. I took 6 wires to reach the old existing electrolytes which feed the individual chips.
The old caps were fed by a protective resistor between the cap positive and the power source. In all cases - they used 6,8 Ohms. I guess that up to 16 Ohms is good.
So I experimented - supply direct to Os-con/chip from Sixpack and B) power via that resistor (lifted to interrupt the old supply). On the scope and also by the ear - the resistor should be INCLUDED - it acts as a high frequency filter - forming a typical PI CRC.



On the above photo - during experimentation stage - the wires were going wrongly  to the oscons directly. Later I re-soldered all 6 of them to the free end of resistors which stand lifted.


Philips does it this way: power line +5V -> resistor of single ohms -> duo consisting of 47 uF electrolyte and a 100n foil bypass -> consumer power input leg. So scenario is very simple:

1. We replace the electrolyte with the oscon
2. We lift the resistor to get rid of old circuit influence
3. We attach the wire to the lifted end of resistor which will feed the positive leg of oscon. Resistor is in the circuit as before.
I decided to use my 330uF/6,3V oscons which I had at hand. One per each line. Later I decided to go for SEPC -470/16 - the  much better oscon. Oh Yes - MUCH better.







The cost so far: 12 tantalums = 6 Eu. 6 Oscons = 6 Eu. 6 regulators = 4 Eu. Diodes 1Eu. Transformer = 20 Eu. PCB = 2 Eu. Chokes 4 Eu. Electrolytes = 3 Eu Subtotal:  46 Eu.
As you can see - the sixpack became a seven pack because I added dedicated line for the clock.





After some time I decided to use the best newest and most advanced caps probably ever made - os-cons from the new ultra low esr line - SEPC.








Above: sixpack's  6 outputs measure EXACTLY 5 V DC as they well should. Bravo Fikus. Point for you !



The red tape here shows the  selected  six points where I will connect my sixpack. Caps that feed the power consumers which I consider the most critical. These points will become power inlets for sixpack. I will install there the os-con best caps.



Os-cons SEPC are visible here - the silver cans with purple edges. One per every consumer point to be powered from the sixpack.



Photo: Sixpack installed.



The two big power supply caps were up-sized to 10 000 uF from 4700 and to 6800 from 3300.
On the right we see an os-con near the regulator chip. All supply has been significantly upgraded.



power sixpack regulator


Very nice up-market version of the noisy 7805 - the superb LM2940CT -5  producing +5VDC.






I know I know it looks vulgar and messy but it is very practical approach - I glued the Sixpack  PCB vertically just near all these consumers. It stands on two wooden feet.







BEFORE I installed the sixpack I did just the os-cons. The new SP-DIF signal  - stolen from the source chip  (see point 6 below)   and SEPC super low ESR oscons made the player (as a transport) -  very smooth and musical. Six-pack power supply is not yet installed but the sound of transport is much smoother, analog-like and more charming. I like the change so far. The analog outputs (unmodded) after these mods I did to the digital part - are showing HUGE improvement. Shocking good in fact.


STEP FIVE - THE CLOCK.

Since the clock strongly affects (I hope) the SPDIF performance, I will replace the standard cheap quartz with the more sexy and more precise superclock from Kingwa. It has its own power supply and a 11,2 Meg output for Philips standard. Of course you can use any other clock in the same way.

The clock works well. I powered it from raw unregulated supply of the sixpack - 16 VDC . This change in sound is quite questionable. It is very very small. Sound becomes smoother, more liquid and more analogue, but less sharp and immediate. It lost some bite perhaps. I am not sure really.
I suggest that you use the stock clock which gives 95% of the final result. Buy the clock only after everything else works perfect.

Photo: clock output

Photo: clock mounting

Photo: old clock removal and connection point.



The blue wire is cut off. When I don't know which hole is good input of new clock - I install two wires and test them both. One plays, the second - doesn't. So I cut the non-playing wire.  The yellow is the clock going from Kingwa to the old circuit. Two SMD caps were removed on the bottom side of the PCB.


STEP SIX - the digital output

I traced the digital output signal upstream, looking for its pure form at the source, to he first point where it is already formed (digitally speaking, not electrically). It can be captured here:

Photo: schematics of the SPDIF generator and surroundings.


I have picked the signal at the source

The trace after wiring the blue wire to RCA via a resistive L-pad at this point of my work looks like this:



Of course the trace is infinitely better than stock horror. The amplitude is 1 V peak to peak. It is okay. No overshoot, no reflections, just very good square trace. Upper line is FLAT.  Overall - one of the best I know.

I wired the signal directly to the s/PDIF output - my newly installed RCA socket.
I tried it with the series cap and without, with the 75 resistor and without, and the conclusion is that no cap solution sounds best.
I used - starting  from the source -> a wire, an L-pad to reduce the output by 1:4, ->   270 Ohms series to pin of RCA hot and from there ->  75 Ohms to ground,.
I eliminated the capacitor in series and the ugly signal transformer. Who needs transformer here ! It only distorts the signal. Who says galvanic isolation is necessary? This is not a telephone line buried under the desert.



STEP SEVEN - the PCB tuning

Since the new powerhouse does not feed all of the player, I decided to upgrade just the caps of non 5V feeds with tantalums, which should be good for digital circuits.
I have a handful of 47uF  Roedenstein caps with 35V rating (not from this photo but similar) so they are excellent for this purpose.



I replaced all but the analog section caps.

Additional cost: 10 Eu

All electrolytes on main PCB are now replaced with the tantalums except the ones which get power from the sixpack. This brings additional smoothness to the sound and accuracy of tracking. Not big improvement but important one.


The arrows show which caps were upgraded to tantalum 33uF/35V -(  brown balls) and the remaining +5V supply caps - with the standard purple oscons. All marked in red.

STEP eight - THE GROUND STAR

I made an assumption that the ground is connected with far too thin ground traces and there is no star, and all the chips can interfere and cross talk over the noisy ground,
so I decided to cut the ground around each new consumer with the utility knife and wire it to the star point, together with RCA grounds of sockets, with the chassis, with the "rest of PCB" ground, with the powerhouse negative pole.
So I will join 10 lines in a star. The star will be located close to the old power supply negative point on the original PCB - and attached to the chassis by a screw (paint stripped first).


In fact I discovered that the earth in this player is on the ground plane - the whole upper surface of the PCB. This solution is the best possible, everything is grounded nicely, no need for tweaking or star  scheme. I leave it as it is.
Sixpack ground is wired to the nearest upper plane connecting point.

STEP NINE - the digi fetishizator OUTPUT

This step is unnecessary because the S/PDIF is coming straight from a chip buffer. No need to amplify it further. I leave it as it is with bypass over the digital output stage - capacitor and transformer for galvanic isolation. This is unnecessary because we don't send the signal over a kilometre distance, only few tens of centimetres . Galvanic isolation is not a problem at all.

STEP TEN - vibrations


Just to please everybody I decided to decorate the interior of this thin and flimsy player with some pieces of bituminous felt, used normally to damp the car doors. It gives the player some extra weight and a VERY positive change of the feel. It is no longer behaving like an empty beer can.
To really kill bad vibrations in the player - I supported the main PCB with a piece of cork.  It will no longer vibrate like before ! This cost- free trick  does 100 x better for the vibration damping than all cones, spikes, plinths, platforms of this world. A 1000 Euro high end shelving system will not be as effective as a half of wine cork under the centre of the PCB.










Plinth and new legs.


To add anti-vibration measures to the player - and I know vibrations affect the sound - I decided to add a wooden plinth. It is not merely a shelve (which vibrate themself like hell) but it is INTEGRAL with the player floor chassis.
I ordered an inch thick hardwood board, veneered the edge with solid mohogany, sprayed the surface flat black and I GLUED it to the entire floor. So the floor is now damped by the soft glue (never hardens a'la silicone) and the plinth.
I removed the four feet and I glued them to the plinth. See this job below:















Philips CD 940




The dog is listening very carfuly !



Without going nuts - thats about it that I can do about the vibrations control. The player responded with better order on the scene, cleaner notes, better ability to play well at very high volumes. I think this in not illusion - it does play better.

This mod can be recommended to all players out there, and DACs, preamps, amps - glue the plinth, forget shelves and spikes.





Additional works:



Output RCA's






Power cable of 3x thicker cores (not chinese fakes but real Polish Copper 25 Amp rated power cord. It is soldered inside directly under the flimsy connecting socket on PCB.







CONCLUSION

Am I in heaven by now? I am definitely poorer by 160 Eu and some change, including the player , sixpack, clock, plinth and all my mods.  Was it a good exercise? I hope yes. Have we learned something ?
Oh yes we did.
Power is everything.
Oscons are fantastic, especially SEPC line
CDM 9 is fantastic pickup mechanism. It is my champion of fast reading of ANY disc in my collection.
The player sounds great as transport but even more - as player. DAC chip is excellent and one op-amp does a great job. It sounds like a million dollar player.
I recommend the CD930/940/950 to everyone looking for reliable and well sounding player/transport. It is worth every penny especially after tweaking.
Minimum job is to put oscons everywhere - this alone gets you 80 % to heaven.


Do we beat the highenders - Lets see ........


JUMP TO THE BATTLE OF TRANSPORTS



THE NEXT DAY

The next day I examined the very good player - Marantz CD67. Similar to CD63 but better.
I took the S/PDIF signal from the source - much improving the sound of this player as a transport.



This is the stock SPDIF trace on my scope. Horrible indeed.
I found that apart from the cheap signal transformer, the signal was passing by the ultra long PCB track - almost one metre of track, resistors, caps, bridges and jumpers. I hooked myself directly to the SAA7372 chip leg 31.
It looked like this:


Already much better.
To adjust the signal level I used L-PAD from two resistors: I divided the signal  1:10 by 750 Ohms series and followed by 75 Ohms to the ground. I picked the signal from mid point of resistor connection. It has 0,5 V volume - perfect for the DAC.




The signal is present at the jumper U172 and the ground is everywhere on the ground plane - just scratch off the paint nearby. as I did.
U172 sees the 750 Ohms plus 75 Ohms to the ground, so the load is 825 Ohms. The signal comes out from the twisted ends - it is reduced 10 times from 5 V to 0,5 V.


Parts for this project

Another transport project - FISHER

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TDA1541A