CD Transport Experience

[fmak]

I spent the last few months improving the digital output of several sacd players with new clocks, very low noise ps (3 to 20 nV/sqrt Hz ), 75R BNC sockets, matching cable impedances etc.

The above measures improved the palyers both as transports and players and I have been using a Tent XO3 relock board on a Sony SCDXE670 with good results.

However, when the transport is used to feed a dCS 972/952 system with upsampling to 24/192 and DSD, there was something missing in musicality., although the playback was undoubtedly hq.

I replaced the transport with my Sony SCD777ES and had quite a shock. The unit blew all the others I have tried away - there was no comparison. Bass was much more extended, the sound stage was simply superior, and treble smoother but very clear. The same characteristics are clear on CD replay and SACD repaly from the player, as well as upsampled 24/192 with the dCS. I am also hearing small percussions sounds not evident on other transports. Those tried so far consist of Marantz CD23 with swing arm and Sony moving laser. I shall try the TEAC VRDS transport later.

The Sony has been modified to remove ground loops, replaced with Vishay resistors in the analog sections, and the digital section capacitors replaced with SG OSCON s. The I/V opamps were replaced by fast AD826s (preferred to OPA627 and AD825). The CD ouput connector was replaced with a Canare 75R as a BNC socket won't fit.

Lesson so far:- improving a lesser transport on the digital output side is not enough. The mechanism matters - in this case a fixed laser with moving platform. Don't just concentrate on clocks and opamps.

[Dr.H]

Can you direct me to any worthwhile mods I can perform on my transport (a Proceed PDT3), especially the SPDIF output. Would simply replacing the phono plug at the output with a "true" 75 ohm BNC plug make any audible difference?

Thanks
Ryan

[fmak]

[QUOTE]Originally posted by Dr.H
[B]Can you direct me to any worthwhile mods I can perform on my transport (a Proceed PDT3), especially the SPDIF output. Would simply replacing the phono plug at the output with a "true" 75 ohm BNC plug make any audible difference?

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Try the Guido Tent XO3 which is a low noise ps, low jitter clock, and allows the output to be relocked and outputted at controlled impedance. The price is reasonable and performance good. You can also try other clocks; do a search here.

Some people claim that the replacement of a phono socket with a BNC improves sound. I think that this depends on how well the spdif output is engineered. For example, the Krell 20i doesn't have a good output.

[A 8]

I've been tweaking cdp's and transports since 1988 and I fully agree.

"Fiddling" with the laser circuit, servos, receiver diodes power supply, RF circuits, decoders, grounding etc will have a direct impact on the end result irrespective of using relocking or fifos, asrc and what not....go figure....

I wish I was a professional ee designer and not just a eager tweaker (ET) so that I could come up with a plausible explanation.

I read a post once on this forum by a percieved to be very "guruish" member saying that bass punch could only be affected on the analog side of a dac.....man that is so wrong.... you can even affect it by tweaking the freaking laser curcuit and moving on to digital powersupply....it will have a significant impact on ANY sonic aspect.

Sorry I know I am going to get beaten up but I am bored.....

[fmak]

Lesson so far:- improving a lesser transport on the digital output side is not enough. The mechanism matters - in this case a fixed laser with moving platform. Don't just concentrate on clocks and opamps. [/B][/QUOTE]
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More evidence.

For a few months I used the SCDXE670 with Tent XO3 to feed the dCS system, comparing DSD with 24/192 and 16/44.1. The result was that DSD was much warmer than 24/192 and not liked.

With the 670 replaced by the SCD777ES, DSD has come into its own and comparable to 24/192, although there are still differences. This is with exactly the same set up bar the CDPs.

CD has become very good indeed thru the Sony whilst it was previously not good on lessers players.

It seems that the data coming out of the transport is as important as the interfacing of that data.

I wonder if we can't use some of the computer programs to do analyses of CD transports?

[Guido Tent]

Originally posted by A 8
I've been tweaking cdp's and transports since 1988 and I fully agree.

"Fiddling" with the laser circuit, servos, receiver diodes power supply, RF circuits, decoders, grounding etc will have a direct impact on the end result irrespective of using relocking or fifos, asrc and what not....go figure....

I wish I was a professional ee designer and not just a eager tweaker (ET) so that I could come up with a plausible explanation.

I read a post once on this forum by a percieved to be very "guruish" member saying that bass punch could only be affected on the analog side of a dac.....man that is so wrong.... you can even affect it by tweaking the freaking laser curcuit and moving on to digital powersupply....it will have a significant impact on ANY sonic aspect.

Sorry I know I am going to get beaten up but I am bored.....

dear all,

The jitter (even the pit jitter) at the RF is very important. It all starts there. Depending on concept and implementation and quality of (re)clock circuitry (and rest of driove, induced jitter by servo's is a known one....), a certain jitter will remain at the SPDIF output or DAC chips.

That is what you actually listen to....

Among that, analog aspect counts as well

I am looking at building newer, better slicers for the EFM comming from the OPU

regards

[fedde]

That's were the triple buf circuit of Meridian comes to play...

I think that a CD-P should be designed around a FIFO buffer, with a fixed and precise clock. Ideally, all data should be read in multiple times. If the buffer gets almost empty, the player should read in more data (or faster). After this FIFO buffer, some extra reclocking buffers could be placed with the same clock and separate supplies. This to further reduce the jitter because of input dependance...

Fedde

[fmak]

[QUOTE]Originally posted by fedde
[B]That's were the triple buf circuit of Meridian comes to play...

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Interestingly, Meridian pays no attention to 75R socketry - they use cheap phono sockets even forn the 518 dejitter/digital processor. Does this mean that interface may be less important than is sometimes made out?

[A 8]

I've got a cd player fitted with a asrc that includes a FIFO and separate reclocking before spdif out. All voltage supplies are individually supplied ,regulated and decoupled.
Spdif then goes through toslink on to the dac that again has a FIFO and asrc (complete reclocking) and guess what.......I can still hear changing a decoupling cap in the transports rf circuitry?
This goes way beyond my eager tweaker mind ....it is still just ones and zeros and as long as they get to the dac in the right order and gets re-shaped and re-clocked it should not be noticeable....?

Could there be some form of dither effect that's related to changes in noise spectrums and levels?

[fmak]

Originally posted by A 8
I've got a cd player fitted with a asrc that includes a FIFO and separate reclocking before spdif out. All voltage supplies are individually supplied ,regulated and decoupled.
Spdif then goes through toslink on to the dac that again has a FIFO and asrc (complete reclocking) and guess what.......I can still hear changing a decoupling cap in the transports rf circuitry?

Could there be some form of dither effect that's related to changes in noise spectrums and levels?

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Relocking isn't everything. PS noise is a factor too and the LDO used may not be very good. I have found that insitu measurement and decoupling are important in ensuring genuine low noise. The output impedance may be inportant too. The list of factors go on and on as theretically well matched and relocked dacs should not be that sensitive to cabling. They are!!