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Sony 337ESD mods.

Mike P

Mike P

Trade: Pickwell Audio
It’s a horrible wet and windy day here in Sheffield so I thought I’d take some time to share with you my Sony 337ESD vintage CDP upgrade project.
I wasn’t sure whether to put this post in the classic or DIY section or if it should even go in the system pics thread. The moderators can feel free to move it as they see fit.

The 337ESD is a formidable beast dating from the late 80’s back when CD was king and the big audio companies were making CD players built like battleships. The Sony 337ESD is one of the top models from Sony at that time and probably only comes second to the even mightier 555ESD.
This player is huge and incredibly solidly built. The pictures don’t really convey the scale but it’s about twice the size of my old Arcam Alpha 5 and probably four times as heavy!

The 337ESD uses my favourite DAC chip, the TDA1541A. Actually, in the 337ESD there are two TDA1541A DAC’s arranged in what Sony call ‘staggered parallel’ configuration somehow supposedly giving 18 Bit performance.
The laser mechanism is the simply superb Sony KSS190A which uses linear motor on magnetic rails for tracking rather than the more common nasty plastic gears. The laser head slides on polished steel rails and rests in a cast aluminium baseplate. The spindle motor is a brushless hall effect item and has a beautifully machined all metal clamp. In fact pretty much everything on the laser mech is all metal. The whole mechanism then sits in what Sony called the “Gibraltar” chassis which is a special vibration dampening composite of polyester and calcium carbonate.

More info on this player can be found here: http://www.thevintageknob.org/sony-CDP-337ESD.html
And here: http://www.lampizator.eu/lampizator/REFERENCES/Sony 337ESD/sony337.html


Anyway, here are details of my efforts to make the already wonderful Sony 337ESD even better! I’ve been very careful not to do anything irreversible and I’ve carefully saved all of the original parts in case I ever want to put the player back into stock spec again.

First up here’s an overview:

Underside of the laser mech:


Left to Right: Beefed up capacitors in the digital/servo power supply (Panasonic FC and FM). Schottky diodes for the output stage/analogue section. Huge 6800uF Elna Duorex filter caps for the output/analogue section. Copper heatsinks housing Fidelity Audio Spower discrete voltage regulators (analogue +/- 15v). 1000uF Elna Simlics after the regs.


The business end! Left to right: Unbranded axial polypropylene film caps on the output in DC blocking role. The black boxes are muting relays (not transistors!). The turquoise coloured resistors downstream of the DACs are Takman metal film with the exception of IV feedback resistors which are Charcroft Naked Z foil. Op-amps are Burr Brown OPA2604 soldered direct (no sockets) and the power supply rails for the op-amps are decoupled by 100uF Elna Silmic.

Hidden under the heatsinks are the DAC chips which have been swapped to matching serial number Taiwanese manufactured TDA1541A from 1998 which to me are the best sounding. The bit decoupling caps are 220nF polyester with 1uF polyester on the MSB pins. The DEM oscillator caps are 560pF Wima FKP polypropylene film/foil.
Each TDA1541A has its own voltage regulators and caps for the +5v and -5v supplies. The voltages regs have been upgraded to Fidelity Audio Spower HC and the decoupling caps are Elna Silmic 220uF.
A better view of the voltage regs for the DACs.


There are also lots of hidden mods under the PCB too. Here you can see some extra decoupling caps for the -15v supply on the DACs (100uF Silmic). The 15uF Oscons tie the -5v and -15v rails of the DAC chips together and the resistors tie each leg of the DEM oscillator cap to -15v (pin 15) to create a simple circuit which is supposed to reduce ‘jitter’ on the DEM oscillator. Some local decoupling caps for the digital IC’s have also been upgraded to small surface mount NPO/COG ceramics mounted under the PCB.


The voltage reg on the left supplies the digital filter chip, and clock circuit. This again is a fancy Spower reg . The caps for the section have been upgraded to 1500uF Pansonic FM, 330uF Elna Cerafine and Sanyo Oscon SP 33uF. The voltage reg is now fed from its own dedicated transformer, rectifier, smoothing cap and is pre-regulated to 12v by an LM317 before being regulated down to +5v by the Spower.

Here’s a close-up of the PSU which supplies the digital filter and clock etc. I fabricated this alloy panel which is mounted on brass standoffs and uses only pre-existing screw holes.



I purchased a decent used Tektronix oscilloscope especially for doing the laser alignment adjustments on this player. Focus bias (RF eye pattern), focus balance, tracking gain and focus gain have all been checked and carefully adjusted until ‘just right’ and the laser mech was treated to a full strip-down clean and re-lube.
I also bought a frequency counter so that I could check and adjust the PLL frequency. To help get this exactly right I fitted a nice new sealed multi-turn trimpot to replace the old single turn one. You’ll notice that all of the small electrolytics have also been replaced with top quality new ones and in some cases upgraded to Oscons or film.

My next plan for this player is to fit a upgraded low jitter clock and dedicated PSU which will probably mean losing the small toroid and 317 reg at the top left of the player in order to create some room. I’ll keep you posted.
Happy modding!
Mike
 
Looks very smart, nice work Mike. I really like the sound of the TDA1541A players, I'd definitely recommend the clock upgrade, it really opens the sound up.
 
Thanks, I've started looking at clocks and aim to fit one in the near future.
 
Excellent, it should be easy to hear differences with the rest of the mods you made.

How do you find it compared to stock? I have a Marantz CD65 II that I have done alot of modifications to and it is a night and day difference compared to a stock Arcam Alpha CD (same ABC chips and transport)
 
I'm not very good at describing the sonic differences but if I had to describe the standard player in one word it would be "smooth" and the modded player "powerful".

I've been messing with TDA1541A machines for years and I still find it amazing how swapping out just a few components for another type can completely change the character of the sound. For example the difference between say, Elna Silmic caps and Sanyo Oscon SEPC on the TDA power pins is huge. Both are excellent but they give very very different flavours to the sound.
 
Such a pity that an expensive battleship player couldn't run beyond single layer pcbs.
Clock jitter is much easier to control with a ground plane
 
OK, I need some help.

Please can someone tell me how I need to connect the clock i.e. which components to remove and where to connect the ground and clock signal wires.

Here's the schematic:

 
All sorted now. I just needed to select the 5v clock signal output by connecting a little solder jumper.

Will report back later with pics and listening impressions.
 
As promised here's some more details of the clock install.

To power the Tentlabs clock I wanted to use a nice compact Net Audio clock PSU which I had left over from my old Arcam Alpha 5 project. The Net Audio clock has an output of 9.45vdc and the Tentlabs clock needs 10 -20vdc so I had to modify the PSU to give me a higher voltage output.

First I removed the 9v transformer and replaced it with a 12v one. I also took the opportunity to increase the VA rating a bit too for better regulation.

12x 1.414 = 17v so I swapped the 2000uF 16v rated Nichicon filter cap to one with a higher voltage rating. I chose a 3300uF 25v Rubycon ZLH.

The output voltage of the LM317 reg on the Net Audio PSU is set with a zener diode so to get just over 12v output this was swapped to a 11v zener. I also swapped the bypass cap on the adjust leg from 10uF to a 22uF Elna Starget too as minor upgrade.



NB: After this pic was taken the 100uF Nichicon FG went back in instead of the Pana FC.

Here's the rebuilt PSU in its new home. I fabricated this alloy shelf for it to sit on. Note the tightly twisted red/black wires in and out which are teflon insulated silver plated copper solid core.



And here's the Tentlabs XO2.2 clock in situ, again on an alloy shelf and mounted on brass PCB standoffs. As with the PSU I made use of existing threaded holes so nothing irreversible has been done.



At first I couldn't get the clock to work but after contacting Guido Tent for advice I found that I needed to set the clock for 5v output rather than 3.3v. This is done by means of a solder jumper.

Fitting the clock has been a superb upgrade and has made the sound more effortless and liquid and has eliminated any harshness. Bass is super dry, deep and articulate and details shine through more clearly. Most excellent!
 
I like the neat and tidy way you've done the mods Mike. I'm thinking that these mods could equally apply to my Naim CD3 as it uses the same chip set. I modified my CD3 so it now has an SPDIF out which I run through a Musical Fidelity M1 DAC. I find this arrangement preferable to using the internal dac. I was going to get the Avondale mods done to the CD3 but I couldn't raise the money and as I already had the MF dac this seemed the easiest thing to do. I'm having other thoughts after reading this and the enthusiasm for the 1541 chip. How about a stand alone dac built around a 1541 chip or does such a thing already exist?
 
Thank you for the kind words folks.

The Naim CD3 is an excellent player with some really solid engineering (nice big ground planes, execllent output stage etc).

All in one box CD players tend to be better than a transport + DAC because they suffer less from jitter but of course it all depends on the quality of the supporting circuitry. The advantage of an external DAC is that it can be used for multiple sources.

There are plenty of TDA1541 based DAC's out there, both vintage ones and newer kits. Some are much better than others.

Martin Clark on this forum is very knowledgeable with regards to the Naim CD players, I'm sure he'd be happy to share some ideas on how to improve the CD3.

As for my Sony 337, well I've got a few more ideas for further fine tuning. Watch this space.
 
Since my last post on this thread I've been working on some small but very important details.

First of all I've been paying some attention to the decoupling capacitors around the digital filter chip and the clock distribution IC's. As standard the bulk/electrolytic capacitors are 1000uF, 470uF and 33uF Elna Duorex. Under the PCB where two 100nF ceramic radial caps but these were stuck out on long legs far too far away from the IC pins! I wish I'd taken a picture to show you how bad it was.

Up top I'd already fitted a Panasonic 1500uF replacing the 1000uF Duorex, a 330uF Cerfafine replacing the 470uF Duorex and a 33uF Oscon SP to replace the 33uF Duorex.

Underneath the PCB is where the real improvements have been made:

  • The legs of one of the 100nF radial ceramic caps have been cut down to the minimum length.
  • The other radial ceramic has been swapped to a 47nF SMD COG ceramic.
  • A second 47nF SMD COG has been added to the other IC (which didn't have it's own ceramic decoupling cap).
  • The digital filter chip also now has its own 15uF Oscon SP soldered directly from the power supply pin to the ground pin(s) under the chip.



I've also just finished implementing some HF RC filtering on the DATA and WS lines between the CXD1144 digital filter chip and the DAc chips. Thankfully the Sony already had 1K series resistors on these lines (R700, 701, 704, 705). To implement the RC filtering I added separate 10pF COG ceramic caps from the DAC side of each of these resistors and terminated them back to digital ground by the CXD1144. I used a mix of axial and radial caps for easiest fitting.



I'm still getting my head around the result of this latest mod. The difference is profound....and in a good way!
 
Another small mod today - four more resistors downstream of the DACs changed to frighteningly expensive Charcroft VAR naked Z-foil jobbies. Positions R403, R404, R503, R504.
 
Just catching up on this - interesting to read your results on the data/WS line filtering in this particular instance, Mike. Kind of backs-up the original logic :)

How's the expensive-resistor-swap working -out for you? Not something I've ever tried, TBH, anywhere, though I have a couple of places in my system overall I might yet convince myself it's worth a go on a potential rather marginal s:n gain.
 
Hi Martin, thanks for dropping by. Those z-foil resistors are superb, give them a try!
 
I've been hugely impressed by the Charcroft CAR resistors, so much so I've gone ahead and fitted another six. Unfortunately to make room for them I've had to replace the big axial poly coupling caps with some much more compact 10uF Wima MKS, at least as a temporary measure until I've figured out a satisfactory way of installing something better.



I do love these big old Sony ESD CD players.....as you can see!

 
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