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In Reply to: RE: What's the Best CD/DVD player from the past to be used as CD transport? posted by zacster on February 04, 2017 at 18:39:13
I still buy CDs! The reason is that CDs are becoming quite cheap now in second hand stores - they are being virtually thrown out at record stores now and I can pick up bargains again. It's funny having lived through the throw out of vinyl (which benefitted my collection enormously!) to the throw out of CDs and the rising price of vinyl (even second hand).
Back to your first sentence though...
Jitter is the main reason. However, it is only a problem at the final decode stage to analogue unless the engineer has implemented additional strategies to clean up (or ensure) a clean bitclock. Up to that point (as long as it wasn't imprinted on the data at the ADC stage), it really doesn't matter what happens in between as long as the jitter is within the receiver tolerance range.
The problem comes when you try and transmit data using the SPDIF format since the "clock" is embedded as part of the bitstream which is recovered by the receiver when the preamble data frame is detected.
However, the technology you refer to with DAC input buffering, reclocking and the like only came long after the initial attempts at 2 box systems highlighted surprising differences between transports and careful matching of DAC and transport became mandatory. Without these strategies, the source can be very audible.
In the "early" days (late 80s, early 90s) when the "2 boxes were better than one" idea was being touted as the "best", there was a genuine problem with jitter. In fact the single box players would better the 2 box approach in many cases. It took a fair amount of time before even the cheapest DAC had all the technical fundamentals sorted and single chip solutions are readily available. Reclocking, upsampling etc are comparatively recent (late 90s early 2000s). The transport "source impedance" and DAC "termination" impedance often weren't consistent with frequency and didn't match the 75 ohm standard. This sets up reflections in the transmission line which then leads to a jittery recovered clock since the clock is embedded in the SPDIF datastream and if the receiver doesn't pick up the preamble data at a consistent rate, you end up with jitter on the recovered clock. The interface receivers were also not very robust and the clock signal were also jittery due to injected noise from power supplies. Of course these days, reclocking is de rigeur. Also, these days upsampling is a standard "trick" to reduce the effect of jitter on the recovered data.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Follow Ups:
Jitter may be a problem, but like you say, only at the final stage. Read a CD at 10x or more, store it on a memory chip that costs pennies these days, and read and reclock it from there. I guess that's what we do now, but it took too long to get there. They were trying to solve for imperfect streams, when the stream could be eliminated entirely.
I had an original Magnavox CD player, the FD1000 I think it was, it came out at the same time as the first Sony as Philips and Sony developed it jointly. I never should have given that away. This was the player that Meridian took and modified and sold for a small fortune. I never heard the Meridian version though. It was the coolest component that I had at the time. I had to drive for an hour to buy CDs for it. I still have some of those early CDs and they just sound awful. It is amazing that anybody went along with CD, it was like fingernails on a blackboard with classical, rock albums without any bass, jazz sounded like it was being played behind a screen.
"Perfect Sound Forever". Forever lasted 30 years.
Don't bother with the standard Sony/Philips transport mechanisms.A ROM drive is infinitely better.The PS Audio and MSB transports that "read" until you obtain a "bit-perfect" copy,prior to transference to the DAC.
Made a huge difference in tonal saturation.With the standard transports,you will probably be trying to add this characteristic through cabling.This "buggers" the sound and it never recovers.
There are a few MSBs with the full power supply, being offered at competitive prices.
Tom:cat
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