Acoustic Precision EIKOS CD-Player

Ruach · 3rd March 2005, 02:19 AM

Hi guys,

I have been searching for information regarding this cd player, which is a stock Pioneer PD-S904 that was heavily modded by Tom Evans.

http://www.tnt-audio.com/sorgenti/eikose.html

Information is scant and I was hoping that you can provide me with some details on the type of electronics mods that was done to this cd player.

All I know was that a Tricord clock was added, and the voltage regulators changed.

Btw, does anyone have the service manual for the Pioneer PD-S904 ?

Thanks

Spartacus · 4th March 2005, 10:39 AM

Hi,

I spoke with Tom Evans about his mods a few years ago, and can remember some details ...

Tom Evans uses a new output stage for the Eikos, powered by his super regs. The standard pioneer stage is based on a NE5532 as a SIL package - could easily be replaced using an adaptor.

Other mods are to fine tune the servo focus, pay attention to noise/decoupling of the servo, filter and DACS, bond a non resonant platform to the base of the player and build a high capacity outboard PSU.

Also, IIRC, all data and clock signals in the DAC are buffered with 1K resistors to reduce noise on the PSU lines. However it may pay to replace the bit-clock resistors with mayber 47 ohms in order to speed up the rise-time and reduce jitter. Tom removes them all, but I'm not sure that's a good idea.

Hope this helps.

Ruach · 7th March 2005, 12:30 AM

Thanks.

That's quite a lot of work.

To fine tune the servo focus, pay attention to noise/decoupling of the servo, filter and DACS.. one who need a scope for that.

Only a 100 set of the Eikos were produced by Tom and I have yet to see an Eikos at my part of the world.

Spartacus · 7th March 2005, 09:43 AM

Well, the Eikos costs a alot more than the stock pioneer, so MR. Evans has to justify that.

The main benefits will come from clocking and replacing the op-amps with something like LT1364s. You don't need a scope for better decoupling - try just fitting some OScons/Blackgates etc. at key locations. If I remember correctly, the laser board on top of the transport has a tantalum decoupling cap that can beneficially be replaced with something like an OScon.

If you change the op-amps, try removing the output coupling caps if DC offset isn't too high. In general, just do one mod at a time and learn as you go.

Ruach · 7th March 2005, 06:48 PM

Thanks for the info. They have been very helpful. Best regards.

typeo · 20th December 2005, 08:29 AM

I have one of these players. I purchased it second hand as they are very hard to get hold of now. When I bought it the player was still at base spec. There were three extra upgrades to the player:

Lithos A - which upgraded the analogue circuits
Lithos D - which upgraded the digital circuits

And a power supply upgrade, which I believe seperates the power circuits for the audio circuitry from the main player electronics circuits.

Obviously one of the upgrades includes a later version of the Trichord clock upgrade.

Even though the player was a few years old I contacted Tom Evans and had all the upgrades done. At the time he was working on the Pulse Power Supply (a two box PSU) for the Vibe amp and he reckoned this would work extremely well with the EIKOS CD player to reduce even more noise. So I had a Pulse Power Supply fitted as well. The complete upgrade cost around £2500 from what I remember.

hifi · 20th December 2005, 09:55 AM

Do you know anything more specific about what they did to the player?

Im currently rebuilding a PDS-904 into a transport myself.

typeo · 20th December 2005, 10:04 AM

I'm afraid I don't know much about the electronics, and I've not taken the lid off it. There are some pictures of the insides of one of these players in one of the earlier issues of Hi-Fi+ magazine. I'll see if I can find it for you.

As you may remember the EIKOS is fitted with a special base, I'm not sure what this is made from. It also doesn't have the standard PDS-904 feet, but 4 yellow dot squash balls that it sits on!!

Ruach · 20th December 2005, 10:08 AM

Hi hifi,

Is that a picture of the insides of an Eikos?

Quote:

Originally posted by hifi
Do you know anything more specific about what they did to the player?

Im currently rebuilding a PDS-904 into a transport myself.

hifi · 20th December 2005, 10:39 AM

>> Ruach

No, its from the rebuild of my player.

3rd March 2005, 02:19 AM	#1
Ruach diyAudio Member Join Date: May 2003 Location: Singapore	Acoustic Precision EIKOS CD-Player Hi guys, I have been searching for information regarding this cd player, which is a stock Pioneer PD-S904 that was heavily modded by Tom Evans. http://www.tnt-audio.com/sorgenti/eikose.html Information is scant and I was hoping that you can provide me with some details on the type of electronics mods that was done to this cd player. All I know was that a Tricord clock was added, and the voltage regulators changed. Btw, does anyone have the service manual for the Pioneer PD-S904 ? Thanks

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4th March 2005, 10:39 AM	#2
Spartacus diyAudio Member Join Date: Jan 2002 Location: Cheltenham	Hi, I spoke with Tom Evans about his mods a few years ago, and can remember some details ... Tom Evans uses a new output stage for the Eikos, powered by his super regs. The standard pioneer stage is based on a NE5532 as a SIL package - could easily be replaced using an adaptor. Other mods are to fine tune the servo focus, pay attention to noise/decoupling of the servo, filter and DACS, bond a non resonant platform to the base of the player and build a high capacity outboard PSU. Also, IIRC, all data and clock signals in the DAC are buffered with 1K resistors to reduce noise on the PSU lines. However it may pay to replace the bit-clock resistors with mayber 47 ohms in order to speed up the rise-time and reduce jitter. Tom removes them all, but I'm not sure that's a good idea. Hope this helps.

7th March 2005, 12:30 AM	#3
Ruach diyAudio Member Join Date: May 2003 Location: Singapore	Thanks. That's quite a lot of work. To fine tune the servo focus, pay attention to noise/decoupling of the servo, filter and DACS.. one who need a scope for that. Only a 100 set of the Eikos were produced by Tom and I have yet to see an Eikos at my part of the world.

7th March 2005, 09:43 AM	#4
Spartacus diyAudio Member Join Date: Jan 2002 Location: Cheltenham	Well, the Eikos costs a alot more than the stock pioneer, so MR. Evans has to justify that. The main benefits will come from clocking and replacing the op-amps with something like LT1364s. You don't need a scope for better decoupling - try just fitting some OScons/Blackgates etc. at key locations. If I remember correctly, the laser board on top of the transport has a tantalum decoupling cap that can beneficially be replaced with something like an OScon. If you change the op-amps, try removing the output coupling caps if DC offset isn't too high. In general, just do one mod at a time and learn as you go.

7th March 2005, 06:48 PM	#5
Ruach diyAudio Member Join Date: May 2003 Location: Singapore	Thanks for the info. They have been very helpful. Best regards.

20th December 2005, 08:29 AM	#6
typeo diyAudio Member Join Date: Dec 2005 Location: UK	I have one of these players. I purchased it second hand as they are very hard to get hold of now. When I bought it the player was still at base spec. There were three extra upgrades to the player: Lithos A - which upgraded the analogue circuits Lithos D - which upgraded the digital circuits And a power supply upgrade, which I believe seperates the power circuits for the audio circuitry from the main player electronics circuits. Obviously one of the upgrades includes a later version of the Trichord clock upgrade. Even though the player was a few years old I contacted Tom Evans and had all the upgrades done. At the time he was working on the Pulse Power Supply (a two box PSU) for the Vibe amp and he reckoned this would work extremely well with the EIKOS CD player to reduce even more noise. So I had a Pulse Power Supply fitted as well. The complete upgrade cost around £2500 from what I remember.

20th December 2005, 10:04 AM	#8
typeo diyAudio Member Join Date: Dec 2005 Location: UK	I'm afraid I don't know much about the electronics, and I've not taken the lid off it. There are some pictures of the insides of one of these players in one of the earlier issues of Hi-Fi+ magazine. I'll see if I can find it for you. As you may remember the EIKOS is fitted with a special base, I'm not sure what this is made from. It also doesn't have the standard PDS-904 feet, but 4 yellow dot squash balls that it sits on!!

20th December 2005, 10:39 AM	#10
hifi diyAudio Member Join Date: Mar 2001 Location: sweden	>> Ruach No, its from the rebuild of my player.

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