Most of you were arguing that what was wrong with RCA spdiff was not serious, but wrong none the less, impossible to be the ok 75 ohms in fact. i tried some wrong RCA cables I had, and a as far as I know brandless cable with goldplated rcas was selected instead off a vandenhull coaxial and a monster video coax because I repeatedly imagined(???) low frequencies were more pleasant lol. Seriously. But maybe I ask someone to switch cables for me while I only listen sometime.
I am inclined to look for BNC or Fcon chasis-parts that will fit my system, reading they can be more perfect more easily. But then bappa shows he knows much more about it, having tested/measured and replaced circuitry around or spdifftransmitters and receivers. Is there a way to recognize good or bad circuitry/parts in my transports or powerdac spdiff transmitters and receivers? How cheap and easy are those modifications? I never read about changing transmitters/receivers befor, are there dac-builts discribing these here? or transport-treads???
I am inclined to look for BNC or Fcon chasis-parts that will fit my system, reading they can be more perfect more easily. But then bappa shows he knows much more about it, having tested/measured and replaced circuitry around or spdifftransmitters and receivers. Is there a way to recognize good or bad circuitry/parts in my transports or powerdac spdiff transmitters and receivers? How cheap and easy are those modifications? I never read about changing transmitters/receivers befor, are there dac-builts discribing these here? or transport-treads???
I would agree RCA is acceptable for consumer grade equipment (where timing uncertainty in the ns is perfectly fine) . But its a bit discomforting that even with the premium being paid for "high end" most devices don't feature proper 75ohm interfacing or any secondary PLL to clean up the recovered clock.
Edit: How to implement S/Pdif have been beaten to death several times no need to discuss it in this thread just look up almost any old post by "jocko homo"
Edit: How to implement S/Pdif have been beaten to death several times no need to discuss it in this thread just look up almost any old post by "jocko homo"
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If the added complexity is justifiable or not is of course dependent of what levels of performance one expects, or designs for. Certainly the cost of a secondary PLL is much more justifiable and the improvements much more tangible than any fancy cable.
I find the VCO's and the PLL filters in monolithic S/Pdif receivers tend to be designed for convenience (wide VCO pullrange) and fast locking rather than clock purity.
I find the VCO's and the PLL filters in monolithic S/Pdif receivers tend to be designed for convenience (wide VCO pullrange) and fast locking rather than clock purity.
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F connectors use a screw thread so take longer to attach than BNC. They often use the coax inner as centre pin so can be fragile.
As digital coax can use the same cable as video it makes sense to use the same connectors: BNC. In the UK F connectors generally only appear on satellite TV boxes and DAB receivers. Elsewhere we use Belling-Lee for domestic RF.
As digital coax can use the same cable as video it makes sense to use the same connectors: BNC. In the UK F connectors generally only appear on satellite TV boxes and DAB receivers. Elsewhere we use Belling-Lee for domestic RF.
Yesterday I swapped the braided audio cable I was using to reach the DAC to 50 ohm coaxial. It's a 27ft stretch. Made no difference to the audio whatsoever. Perfect as before.
Anyway, I may keep on and make one more test.
The 740C has input/output optic fiber ports. What do you think about installing this coax to optic converter and reaching the DAC optically?
Bi Directional Optical s PDIF Coaxial Audio Converter | eBay
Anyway, I may keep on and make one more test.
The 740C has input/output optic fiber ports. What do you think about installing this coax to optic converter and reaching the DAC optically?
Bi Directional Optical s PDIF Coaxial Audio Converter | eBay
Since I don't plan on removing/installing the cable often, I may go with F since I have both cable connectors and bulkhead mount connectors.
I suspect my BNCs are all 50 Ohm (UG-290/U).
Stephen Lampen of Belden Cable wrote a note on maximum cable lengths with mis-matched cables and the AES?EBU interconnect system.
Over on the Ampex list, we were having a discussion about how long a crummy cable one can get away with using to carry AES/EBU audio date. Thanks to Larry Miller for reminding us that the critical number is the rise time and gave an empirical rule of thumb (1/6 wavelength) for when the cable goes into the transmission line mode and needs to be the correct impedance to avoid getting into trouble.
So I'll bet the AES/EBU (IEC-60958) standard specifies the maximum and minimum rise time for the data waveform. Does anyone have a copy of that standard or know what the rise time is? I'm looking for a simple answer based on real facts to the ever popular question: "Can I use a plain old (not made from special 110 ohm cable) for AES/EBU connections?" - the answer being "Yes, if it's shorter than X feet."
Friends- Only just saw this ancient email before it fell off my list and I had to comment.
I normally tell people that the critical distance is 1/4 wavelength which then varies depending on the sampling rate (and resultant bandwidth) of a cable. I also have some eye-opening graphs (no pun intended) of 48 kHz audio running on 110 ohm cable and Belden 8451 (both 22 AWG, so we're comparing apples to apples). The result is 50 ft. is probably do-able for 8451. At 100 ft. literally half of the signal is reflected because of the impedance mismatch (8451 =~38 ohms) and it screws up the risetime (clock) because the capacitance is about 3 times as much as the 110 ohm cable (Belden 1696A).
If you go by the 1/4-wave numbers the critical distance (after which the impedance is important to match) is:
44.1 kHz = 5.6448 MHz= 44 ft.
48 kHz = 6.144 MHz = 40 ft.
96 kHz = 12.288 MHz = 20 ft.
192 kHz = 24.576 MHz = 10 ft.
Hope this helps set a limit!
Steve Lampen
Belden
04/06/2007
Thanks. Your explanation makes sense to me. Besides gives some background as to why I'm not experiencing any trouble at 27ft away from the DAC. The sound card in my pc outputs at 48khz so I'm well below the 40ft safety lenght.
I still would like some input about the coaxial to optical converter. Is it worth or a waste or money?
I still would like some input about the coaxial to optical converter. Is it worth or a waste or money?
Theory vs reality.
For example:
Beolab5 introduction some years ago: Manufacturers recomandation: use analog inputs NOT digital spdiff input to demo this speaker. Some reviews after introduction also noted SQ from analog input superior. (analog signal converted internally Beolab5 to digital for DSP)
So even when price is not really an issue the resulting SQ from spdiff can even be worse than anlog. Can anyone suggest a source to read more about spdiff transmitters/receivers or circuitry?
For example:
Beolab5 introduction some years ago: Manufacturers recomandation: use analog inputs NOT digital spdiff input to demo this speaker. Some reviews after introduction also noted SQ from analog input superior. (analog signal converted internally Beolab5 to digital for DSP)
So even when price is not really an issue the resulting SQ from spdiff can even be worse than anlog. Can anyone suggest a source to read more about spdiff transmitters/receivers or circuitry?
complete and utter anecdote, it is not a theory, or reality
perhaps they knew their spdif receiver stage was sh1t … perhaps its just a story, but it doesnt rise to the definition of theory, or fact.
marce will probably have some links, you can also use the forum search feature, its not an unusual topic. spdif can be bad if improperly applied, but its not the fault of spdif and spdif isnt the last word.
sextaafondo: adding another conversion? what for?
perhaps they knew their spdif receiver stage was sh1t … perhaps its just a story, but it doesnt rise to the definition of theory, or fact.
marce will probably have some links, you can also use the forum search feature, its not an unusual topic. spdif can be bad if improperly applied, but its not the fault of spdif and spdif isnt the last word.
sextaafondo: adding another conversion? what for?
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It is fact and reality that Beolab5 had better performance with analog input. The recommendation not to use spdiff prior to reception of first shipment is a fact, and german hifimagazins also noted in reviews analog input was superior. Yes it is an anecdote too, an example of problems with spdiff electrical connection. If you see a digital spdiff rca input or output on audio equipment, you can not be sure it got the same amount of attention in design stage as rest of circuitry. i just read how to add a digitall out to PS1 CXD2510Q,. Nothing to it, fool proof??? I really do not know.
I think thats a poor generalisation, the market deems spdif RCA as being more popular, so you can see it on otherwise well designed circuits. the anecdote speaks only of beolabs making a bad mistake and still selling something they knew was below par (especially as you say it was converted to spdif internally for the DAC and that was good, so something went terribly wrong with termination I guess), nothing at all about spdif. spdif foolproof? no and unfortunately there are lots of fools designing audio
fools are rather industrious sometimes
my point being its not theory vs reality, they obviously did not apply theory all that well.
fools are rather industrious sometimes
my point being its not theory vs reality, they obviously did not apply theory all that well.
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