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Alternative Transport Mod

12.247.43.125

Posted by jhietbrink on April 15, 2003 at 18:15:00

I’ve been trying hard not to look at the transport section of the SCD-1/777ES. But I read good things about Richard Kern’s transport mod and I couldn’t stop myself any longer. For those of you who haven’t heard about this mod, Richard replaces a large number of chip-type electrolytic capacitors on the Main and RF Boards with Black Gates. More can be found by searching this section of the Asylum and there is an article about the mods by David Robinson in the latest issue of Positive Feedback Online (Issue 6).

Maybe I’m lazy, but I wasn’t really in the mood to do as much work as Richard is doing. I also don’t the idea of replacing surface-mount chip type capacitors with radial lead caps. Some of the advantage of replacement would be lost to lead inductance and the mod wouldn’t be all that mechanically sound. And as I started to look at the circuit diagrams, I began to realize that capacitor size might be more of an issue than capacitor quality.

First we should digress to the “digital” power supply that serves the Main and RF Boards that are located under the transport mechanism. There are three separate supplies on the Power Supply Board fed from the “digital” transformer: a 12V, 5V and 3.3V supply. The supplies are nearly identical in design: a packaged rectifier, 10,000uF, 25V Elna LPO Standard Audio Grade capacitor, 3-pin regulator, and a 2,200uF, 25V Elna Silmic capacitor. The 12V and 3.3V power supplies have Rohm 1 amp regulators and the 5V supply has a better performing 2 amp NEC regulator.

The 12V supply feeds the motors and motor control chips (loading motor drive, tilt motor drive, sled motor drive, spindle motor drive, focus/tracking coil drive). The 5V supply feeds the optical pick-ups and RF amp (the signal begins in the analog domain), as well as a bunch of ancillary digital chips. The 3.3V supply feeds the ARP and DSD decoder chips and an inverter, the only digital chips in the direct signal path. On the Main and RF Boards, all of the electrolytic capacitors are of the low-inductance, surface-mount, chip type. Most of the electrolytic caps are 22uF, 16V, although there are a couple 33uF caps on the DSD Decoder and some 10uF caps as well. I haven’t been able to determine the manufacturer of these caps, but they appear to be regular electrolytics rather than organic semiconductor (oscon) types. The electrolytic caps are extensively bypassed with .01uF ceramic chip caps.

A couple of things that you may be starting to notice are that (1) there isn’t much capacitance on the Main and RF Boards – and that (2) there is a large gap in cap sizes between the 2,200uF regulator output caps on Power Supply Board and the 22uF caps on the Main and RF Boards. The relatively small amount of capacitance is a somewhat minor issue for the low power digital chips, but a bigger issue for the much higher power motor control chips, lasers and RF amp chip.

Rather than upgrade a bunch of itty bitty caps, I decided to add capacitance to the Main and RF Boards. I added three 220uF, 25V Elna Silmics to the “MOT12V”, “RF5V” and “ARP3V” supplies. I had these caps lying around since I removed them from the digital supplies on the Audio Board and replaced them with Sanyo Oscons. Of course, there is no place to put them on the Main and RF Boards – so I soldered them to the wiring harnesses, very close to the Main Board. The cap on the 12V supply I tie-wrapped to a nearby transport support, and the other two are held in place by the wiring harness. Adding the caps to the wiring harnesses makes this a relatively simple mod.

I’m not given to superlatives -- but this mod makes a stunning difference in audio performance. I’m enjoying one old disc after another – even CDs that I had written off as poorly recorded. The great mechanics of the transport are apparently hobbled by the stock power supplies.

I added each of the capacitors sequentially, breaking in the caps and listening after each one. I started with the cap I thought would be most effective (the 12V motor supply) and ended with the cap I thought would be least effective (3V ARP supply). My premonitions proved to be correct, but each cap made an important difference.

Adding a cap to the 12V motor supply improves bass response, dynamics and the overall sense of pace. Adding a cap to the 5V RF supply makes a more subtle, but no less important change. Volume levels are subjectively higher at the same volume setting – and the sound is fuller with background sounds being more obvious and clear. Individual instruments are better delineated. I wasn’t expecting much of adding a cap to the 3V ARP supply. However, this cap added a better sense of clarity and ambience – especially on SACDs. String plucks became more crisp – and more harmonically rich.

Unless you happen to have 220uF, 25V Elna caps lying around, you’ll have a hard time finding them in the US (they are not available from Sony as replacement parts). I’m sure that Black Gates will work fine or even Nichicon type KZ. I used the Elnas because I had them, they are very good caps, and I’m not a big fan of mixing cap types.

I could have added two more caps – and I might still if I can find space for them. The 5V and 3V power supplies have two sets of leads running to the Main and RF Boards – bi-wiring of a sort. Adding a cap to the “DIG3V” leads that feed the DSD Decoder may be worthwhile and adding a cap to the “DIG5V” leads may be of some value too.

Other SCD-1/777ES Mods and Information

Analog Signal Path

Replaced RCA jacks with Vampire OFC jacks
Replaced output wire with Kimber AGSS
Revised grounding creating a star ground for audio board
http://www.audioasylum.com/forums/hirez/messages/41691.html

Replaced AD712s in the output buffer stage with hi-spec OPA2132s
http://www.audioasylum.com/forums/hirez/messages/78259.html

Replaced resistors and capacitors in I/V conversion stage
http://www.audioasylum.com/forums/hirez/messages/93363.html

Set filters to “custom”

Power Supplies

Revised grounding, AC polarity, analog supply bypassing
http://www.audioasylum.com/forums/hirez/messages/107304.html

Removed choke on analog power supply
http://www.audioasylum.com/forums/hirez/messages/32357.html

Transport

Added capacitance to the “Digital” (Transport) Power Supplies
This post

General Description

Analog Signal Path
http://www.audioasylum.com/forums/hirez/messages/33130.html

Accessories

Electraglide Reference Glide power cord
Chang Lightspeed HT1000 power conditioner (w/upgraded capacitors)
AudioDesk Systeme CD Lathe
Aurio Pro Media Isolation Bearings w/optional tungsten carbide balls

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Schiit Audio

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