audioengr
Member of the Trade: Empirical Audio
- Joined
- Aug 15, 2004
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- 17
Quote:
Mark,
I will have to differ with Mr. Lavry, who I have met and discussed many things with. I consider him a peer, as I do Mr. Siau. There is significant spectra approaching GHz in a proper S/PDIF signal (one that generates low-jitter at the receiver). Just display the spectra on a RF spectrum analyzer and you will see it.
Many DAC's have significant filtering to slow the S/PDIF edges which does reduce this spectra. This is a bad idea IMO. Faster edges result in less jitter at the receiving device, so this is more desirable. You do have to take more care in terminating the transmission-line properly and impedance matching, but this is not rocket-science, at least for me. I have 30 years experience with high-speed digital interfaces, from IBM peripheral buses to massively parallel supercomputers. Rise-times of 2 nsec on cables are not unusual in these systems.
What you must understand is that no one designer has infinite knowledge of all aspects of these designs. Some are strong in digital, some in analog. Few have much experience in power delivery, ESD, grounding and shielding and even less have much experience in HF digital transmission line effects and termination techniques. I am strong in certain areas and these designers may be strong in other areas. I would not try to compete with John Curl for instance to design a power amplifier circuit. However, I can improve the current paths and power delivery to his amp and make it sound even better. This is why I have found a niche in the modding business.
I find all kinds of crazy things in some DAC's that I have modded. Some designers have limited experience and therefore just copy other designs which also may be non-ideal. I have found poor implementations of USB interfaces and S/PDIF interfaces in lots of products, even from large companies like Sony. I'm not your typical modder that swaps parts. I have extensive experience in design, so I reverse-engineer most designs to expose the weaknesses.
The point is: there are no experts in everything. We are each experts in certain areas. This is why collaborations often lead to superior products.
Steve N.
Originally Posted by Rivendell61 /img/forum/go_quote.gif Dan Lavry tried to explain that to you last year on his forum. Here are some Lavry quotes: "....RCA or just about anything out there....is somewhere between say 25 Ohms and 180 Ohms....that one inch discontinuity at the middle of a line with a signal of say 5 nsec rise time is virtually a non issue." And more Dan lavry: "I agree that an RCA connector, (if it is far from 75 Ohms impedance), would be a disaster for 10GHz digital signal transmission. It is certainly NOT a problem for say audio signals because they are too slow. .....AES and SPDIF signals are still way too slow to care about the impedance of an RCA connector." "An SPDIF signal DOES NOT have spectra to GHZ." Also--Here on HeadFi Mr Siau has addressed the question in this post: http://www.head-fi.org/forums/showpo...68&postcount=3 Mark |
Mark,
I will have to differ with Mr. Lavry, who I have met and discussed many things with. I consider him a peer, as I do Mr. Siau. There is significant spectra approaching GHz in a proper S/PDIF signal (one that generates low-jitter at the receiver). Just display the spectra on a RF spectrum analyzer and you will see it.
Many DAC's have significant filtering to slow the S/PDIF edges which does reduce this spectra. This is a bad idea IMO. Faster edges result in less jitter at the receiving device, so this is more desirable. You do have to take more care in terminating the transmission-line properly and impedance matching, but this is not rocket-science, at least for me. I have 30 years experience with high-speed digital interfaces, from IBM peripheral buses to massively parallel supercomputers. Rise-times of 2 nsec on cables are not unusual in these systems.
What you must understand is that no one designer has infinite knowledge of all aspects of these designs. Some are strong in digital, some in analog. Few have much experience in power delivery, ESD, grounding and shielding and even less have much experience in HF digital transmission line effects and termination techniques. I am strong in certain areas and these designers may be strong in other areas. I would not try to compete with John Curl for instance to design a power amplifier circuit. However, I can improve the current paths and power delivery to his amp and make it sound even better. This is why I have found a niche in the modding business.
I find all kinds of crazy things in some DAC's that I have modded. Some designers have limited experience and therefore just copy other designs which also may be non-ideal. I have found poor implementations of USB interfaces and S/PDIF interfaces in lots of products, even from large companies like Sony. I'm not your typical modder that swaps parts. I have extensive experience in design, so I reverse-engineer most designs to expose the weaknesses.
The point is: there are no experts in everything. We are each experts in certain areas. This is why collaborations often lead to superior products.
Steve N.