Wednesday, December 23, 2009

Only transport clocked

Only managed to install the clock for the transport. SPDIF reclock was not possible as the circuit that does the digital out conversion on my cd pro2 kit is somehow defective. I recalled that it does not work even prior to me doing the reclock as then, I tried to route the EBU signal from my transport to the pcb, but there is just no signal at the digital output.

So, only the transport is using the new 1PPM TCXO clock. Nick Tan helped me during the troubleshooting. Some tips to determine if the new clock works is when the TOC on the cd is read and playback is possible by the transport. This is exactly what I experienced, but the DAC does not seem to latch onto the digital signal. I had to tap the signal from the EBU right to the BNC connector for my DAC.

While I was searching the web for more articles on reclocking, it seems that the majority of the solutions out there reclock the DAC portion while totally ignoring the transport. There is also another school of thought that sticks with the DAC as non-oversampled and without reclocking. Well, this is audio. Lots of debate, sometimes heated, but still, the ear is the final arbitrator.

The comments I heard so far is that SPDIF reclocking sounds "hard and stiff". I'm not able to do an A/B for the 1PPM clock. There's just no easy way to do this. But I can be contented with the knowledge that even the best out there reclocks the transport. ;)

More pics here.

Edit: I suspect I know why the digital output section seems defective. It's a fundamental wiring error. Will confirm this tomorrow or so.

Further edit: My suspicions were confirmed. Last night, I looked at the circuit diagrams of the digital out section on the cd pro kit, trying to figure out where could have gone wrong. At the input connector, I noticed pin 1 is grounded, which corresponds to pin 1 of the EBU out on the cd pro transport. The only thing wrong was the wiring... I wired it with the connectors facing the same side up and pin to pin with a coaxial wire as in a mirror reflection. This resulted in pins being swapped. Signal from EBU would be effectively grounded upon input at the digital section on the pcb, thus resulting in no signal output. I overlooked this minor detail which proved to be the major screw up. I'm not listening to the cd pro2 clocked at the transport and also has the SPDIF reclocked. Can't really tell if it is better with or without the SPDIF reclock. My DAC should be slaved to the timing of the digital signal since it does not have an onboard crystal. That means it is using the new clock signals.

Even when audio reviewers A/B changes that are hair splitting, they would do extended listening before making a switch. That way, it may be easier to pick up slight changes. I'm not an audio critic, but would live with a reclocked SPDIF for now, before I do more comparisons... Or I can leave it as it is, and if I do have a DAC that has it's own master clock signal, it would still be compatible.

PS. It's difficult to A/B especially since I am using tubes. Need at least 30mins to warm up the gear. And my RCA 83 mercury rectifiers on my pre and power would need around 3 mins to be preheated.

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