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TDA1541A

Pioneer PD-S703 player

It is my fourth pioneer so I will not write anymore about the stable platter mechanism etc.

The reason I like this player is that:
1. It ies very easy to buy - Pioneer made millions of this PD-S series. It is also cheap because People don't know how good it is.
2. It is reliable - I have never seen a Pioneer fail or skip tracks
3. It always reads all CD's, what a nightmare is reliability with Philips based machines. This Pioneer will read scratched CD-R recorded at 24x speed in miliseconds.
4. It has good design: elegant , plain, mature, ergonomic, intuitive buttons, etc etc. Not too many functions, always easy to hit the right button
5. It has plenty of room inside for lampizator. WOW, it has abundance of free space!
6. It is simple to work on - no gymnastics like with some players, Meridian 207 being THE WORST.
7. It has only one opamp per player - very simple indeed.

The reasons to complain - are:
1. The box is made of metal so thin as a beer can. You can flex it with one finger. So the player is very wobbly and makes lightweight impresssion (even if it looks like a mean manley machine)
2. The power switch does not operate on 230, it works on low voltage so it cant switch Lampizator on and off
3. All player works from single common regulator chip - A BIG BIG NO_NO !
4. There is no SP/DIF, only toslink.
5. The DAC is relatively unknown and un-documented.
6. Display is rather small (but at least it is switchable off or dimmable too.)

Not much to complain, is it?
We can address the complaint list and work point by point to change the weaknesses into strengths.

Description of the guts of the Pioneer PD-S703

Inside Pioneer we find VERY small but good quality transformer , power supply PCB, separate main PCB with the Pioneer's own DAC named Legato Link PD2029A, I think the top of their own production. I am not aware of a higher Legato Link DAC ever made.

Look, which other modells used it:

PIONEER PD-9700	2 x PD2028A	PEA1030 Stable Platter
PIONEER PD-F705	PD2029A	PEA1179
PIONEER PDR-05	2 x PD2028B	Writer – Stable Platter
PIONEER PD-S503	PD2029A	PEA1179
PIONEER PD-S504	PD2029A	PEA1179 Stable Platter
PIONEER PD-S505	PD2029A – PD0236AD - CXD2507	PEA1291 Stable Platter
PIONEER PD-S506	PD2029A – CXD2507	PEA1030
PIONEER PD-S602	PD2029A	PEA1179 Stable Platter
PIONEER PD-S603	PD2029A	PEA1179 Stable Platter
PIONEER PD-S604	PD2029A	PEA1179 Stable Platter
PIONEER PD-S605	PD2029A – PD0236AD - CXD2507	PEA1291 Stable Platter
PIONEER PD-S702	PD2029A	PEA1179 Stable Platter
PIONEER PD-S703	PD2029A	PEA1179 Stable Platter
PIONEER PD-S705	PD2029A – PD0236AD	PEA1291 Stable Platter
PIONEER PD-S801	2 x PD2028	PEA1030 Stable Platter
PIONEER PD-S802	2 x PD2028B – PD0116A	PEA1179 / PEA1285
PIONEER PD-S901	2 x PD2028B	PEA1030 Stable Platter
PIONEER PD-S904	2 x PD2028B – PD7009A	PEA1179 / PEA1285
PIONEER PD-T04	2 x PD2028B – PD0116A	PEA1179 Stable Platter
PIONEER PD-T06	2 x PD2028B	Magnetic Stable Platter
PIONEER PD-T07	2 x PD2028B	Magnetic Stable Platter
PIONEER PD-T09	2 x PD2028A / B	Magnetic Stable Platter

But NOBODY outside of Pioneer own stables used this chip. Shame because it is a great one !
I added to the list also the 2028 because it is almost identical.

Coming back to our PD-S703 - the DACdoes not have any fame, cult, or anything like that. real high-emders and audiophiles would not even discuss it. They are too busy discussing Burr Brown 1702 DAC and so on.

In my opinion, sonically - the Pioneer is one of the best DACs ever made, definitely beating B-B PCM1702, PCM58, 56, and a couple of others. It is THAT GOOD.
And some of these above players can be had for as little as 10 Euro on ebay.de today. Nobody seems to like them (in stock form that is).

The main board is nothing to write home about. It is the weakest part of this player. It has great looks, great DAC, decent transport - but shitty PCB. The cheapest possible piece of PCB like in a boombox.
It has poor topology, poor ground arrangements, VERY VERY poor regulation. and cheap parts.
If you crank up the volume, (during pause) you will hear all consumers sharing power line with the DAC: the spindle motor, the tracking motor, the laser head - EVERYTHING is audible - through the speakers. Because one lausy regulator feeds them all, plus some 5 other chips. Horror.
I suggest to add a 7805 near the DAC, float the DAC supply lines and give him his own power (with a blackgate or Oscon cap).

What I did was a simpler solution - I increased all caps by the factor of 10 and bypassed them with a 1 uF tantalum orange drop. That improves things quite a bit.

Pioneer 703

In order to install the clock, you de-solder the oscillator (silver can) and C403, C404, R401.

The Sony digital filter chip IC301 is hiding underneath the square, the black arrow shows SP/DIF origin place.

Pioneer 703

The Stable Platter mechanism is VERY LIGHT AND CHEAP looking. It is not a high end transport, but I like it because it does the job well.
Note that the tracking is made with plastic gears, but the laser pickup is first class (and hard to get). The whole thing is NOTHING comparable to Sony KSS190A, BU1 or other heavyweight champions like Philips CDM-1 or Hitachi MAgnetic. But - in my experience -in practical terms nothing works better than this mechanism. It operates like a dream and reads everything.

Pioneer 703

The whole mechanism is mounted on a thin light piece of steel. Here I would add some goo or felt or other damping.

After removal of pickup and tracking - we expose the turntable. It is mounted inside a "milkcrate" type of plastic subchassis. Not too highendish really.

All motors are simple and very cheap Mabuchi types with brushes.

The power supply section - I havent touched it, but it is begging for bigger caps, AC filter (CLC) ferrite rings and so on. I leave it to you to decide.

Re-working of the Pioneer

My plan was the following:
1. To install the lampizator using SRPP tube system and 6H6P tubes
2. To install the precision clock
3. To upgrade power supply electrolytes
4. To install SP/DIF coax output
5. To deaden the sheet metal cover
6. To clean the laser

AD1. I analyzed the circuit and I concluded that this DAC is a ballanced type, voltage out type and stereophonic (one piece used only).
I knew from PD-S904 that the DAC is very noisy so I decided to keep the CRC filter which is installed between DAC and first opamp.
I removed the opamp completely and gained a clean unused source of +12V DC for the clock.
I tapped the signal from op-amp empty now pins 2 and 5 representing stereo signal - L+ and R+

AD2. To install precision clock I removed the el-cheapo 16 Meg cristal, two associated picofarad capacitors and one resistor. Then you connect PLUS of power supply of the new clock to 12 VDC (from unused iopamp supply - now available) and ground to ground . Then you try the CLOCK output - in one hole after the cristal has been removed , and in the other hole. In one of the holes it will work.
The clock should be as close to the old cristal as possible but not any closer.
Mounting the clock on soft suspension is a good idea, but I used the screw.

The clock small PCB visible on the right wall.

Clock from behind.

AD3. The typical Japanese made PCB from such LOW BUDGET player will benefit from clock upgrade.
remember how they decided the original sizes ?
First the engineers calculated the proper size, then to be cost concious they specified 1 size smaller ones. In reality, cap suppliers lied and the real caps were again one size smaller than advertised. Then the accountants forced downsizing by a factor of 4. Then 15 years later - they dried by half. That leaves us with not much capacitance left.

So the first good step is to use fresh, quality caps and bigger by factor of at least two compared to oryginals.
Second level job is to use LOW ESR caps which will improve performance.
Third level is to use premium caps - Tantalums (lots of airy treble, plankton in spades) or Os-Cons (liquid liquid liquid) or Black-Gates - $$$ but in some circuits - magical.

My advice is:
Low ESR TEAPO EVERYWHERE - all PCB
except digital demodulator - filter chip supply - Os-Con
and DAC gets - you guessed right - the Black Gate in power supply.

AD4. Since there is SP/DIF in the form of ugly Toslink (a NO-NO) but no electriucal coax, I decided to remove toslink. The SP/DIF is on one of its three legs. One leg is gnd, one is +5 DC and one is SP/DIF. But to improve things I traced the spdif back aaallllll the way to the source in digital filter chip. I have stolen the SP/DIF before it gets distorted by thin long trace and many passive parts. I mounted the new RCA socket in place of toslink one. Despite a square hole - the RCA fits perfectly !!! And Voila - we have a real transport !

Pioneer PD-S703

New SP/DIF digital out socket installed in place of Tosling optical one.

Pioneer PD-S703

Red circle shows silkscreen descriptor of SP/DIF signal. Yellow ring shows the tapping point - the earliest possible point we can steal clean sp/dif. The first part is a resistor so in order to float the tapping point (remove old unused circuit) we can lift one leg of this resistor.

Pioneer PD-S703

This is SP/DIF stealing shown on the upper side - same thing as one picture above. The screened coax is connected to GND (black screen) and white center goes to R321 (previously lifted on the leg away from the chip.)

Lampizator enters the building

Ideal place for toroidal Lampizator transformer is in the corner where it collides with the foot of the player. So I decided to join the foot and the trafo by common screw. It requires some 4,5 mm drilling in the foot but it WORKS.

I steal 4 signals from the opamp socket: L-, L+, R- and R+. After - I empirically chose the matching pair - stereo and in phase. Wether you choose negative or positive pair makes no difference ! It is the same signal. You are free to experiment with a circuit like Broskje or other - which will utilize all 4 outputs but IMHO it achieves something at he cost of simplicity and elegance so may not be worth it. Simple single-ended connection already works great and the SRPP does the trick.

Pioneer and Lampizator make me smile

The whole tuning job took me 1 hour, and lampization - 4 hours more. In the whole process I did not find any nasty surprizes. Everything went smoothly and worked from the first start.
I used 6H6P because it is very good tube which has a character opposite to that of DAC Pulseflow.
DAC is strong, powerful, rich in bass and trebles. 6H6P is a midrange tube, with laid back presentation.
The combination of the two is JUST IDEAL! They go together like Ginger and Fred.

You may notice that there is extra set of RCA on backplate left side and a pot and a switch because the lampizator in this system works also as a high end preamp. It can accept a third party source like a tuner or a turntable.
I
All grounds are joined in star fashion. MANY lines, in excess of 10.

There is no problem with HEAT - tubes are comfortable in such large spacious box.

For the inputs of signal I used decoupling caps - 0,56 uF MKP and bypass of 10 uF Tantalum. Seems to work very good together.

For the output decoupling I used 2,2 uF MKS from roedestein.

The SRPP has 140 VDC supply, and cathode resistors (all four) of 200 Ohms.

LISTENING to the lampized Pioneer CD player

I must admit that this player sounded awful in stock form. Like a lof bitrate MP3. Really shitty.
After lampization the music exploded. It fills the entire room. It is live, vibrant, colorful and dynamic. It is full of detail without forcing them. It has depth that is so big it has its own echo.
Bass is top class and trebles as well. It is one of the best CD sounds period. With good SET amp it made me drool. Cd after cd after cd.
It is in same class as lampized Kenwood DP 5090 or NAD 541i or AMC CD6 or even Cambridge Azur 540C.
VERY VERY RECOMMENDED.

(the black thing under the Pioneer is Theta Transport monster.)