That does sound impressive 🙂emuman100 said:
My cable is ~5m long(~15ft). I think it is ok, but for longer distances your implementation could be better. Never tried it tho, but if I'll need to run longer distances, I'll give it a try.
Could you post the link of that website?
roibm,
I forget where I found the site, but all it suggested was to use RS422 tranceivers for long distance transmission. I ordered some samples of the MAX3443 from Maxim and am quite satisfied with the circuit. Read the datasheet so you know the pinout and know how to hook it up. It's a simple 8 pin device. Just connect the TTL level signal to it's receive output or transmit input and you will be good to go.
I forget where I found the site, but all it suggested was to use RS422 tranceivers for long distance transmission. I ordered some samples of the MAX3443 from Maxim and am quite satisfied with the circuit. Read the datasheet so you know the pinout and know how to hook it up. It's a simple 8 pin device. Just connect the TTL level signal to it's receive output or transmit input and you will be good to go.
Maybe ADM1485 is a good choice for that purpose. Those were the ones I had in mind once for this purpose but I never used them as the project was cancelled.
They will all perform just as well. You can wait two weeks to get samples of MAX3443's, or order SN75176's from digikey, or get samples of SP1485's or SP1481's or ADM1485's. Just make sure it can operate at a minimum of 10Mbps, and is compatible with TTL levels of your circuit. I have everything powered with 5V and I have it operating for hours on end with no problems at all. I really suggest you all try it. In my opinion, it should be a 3rd option of transmission.
What is the mechanism by which a coupling capacitor in this kind of application would have any impact on the final sound?
I could accept that it might somehow increases jitter. By temporal smearing of the transients due to various capacitor related imperfections, like dissipation factor. Or perhaps creating an impedance gradient and thus reflections, also smearing the transients.
But other than that, what could it possibly do? It's a digital signal. Change the bits? As far as I am aware, there are only two issues. Is the data stream coming out the spdif receiver correct or not. And the quality of the clock. What else is there?
If the capacitor is so crappy as to actually corrupt the data stream, I imagine you are well past the PLL being able to lock onto the clock anyways.
I could accept that it might somehow increases jitter. By temporal smearing of the transients due to various capacitor related imperfections, like dissipation factor. Or perhaps creating an impedance gradient and thus reflections, also smearing the transients.
But other than that, what could it possibly do? It's a digital signal. Change the bits? As far as I am aware, there are only two issues. Is the data stream coming out the spdif receiver correct or not. And the quality of the clock. What else is there?
If the capacitor is so crappy as to actually corrupt the data stream, I imagine you are well past the PLL being able to lock onto the clock anyways.
Jocko Homo said:
What can one do to reduce radiation. I have a Theta Data 2 transport connected to a Theta DS Pro Basic 2 DAC. The transport has a transformer on the SPDIF and the AES EBU outputs, the DAC is straight in (no transformer). The transport creates terrible interference on TVs in the house, even when not connected to the DAC. As soon as the coax out cable is plugged in to the transport it seems to work as a transmitter aerial and causes diagonal lines on my TV.
Any suggestions on how to kill this. Cable used is either Monster MV1000 silver or Belden 1695.
Would like to keep my CD gear warm when the soon to be wife wishes to watch soaps and other drivel.
Thanks
Hi there,
I recall when I made my coax to optical converter the amplitude of the
SPDIF was something like 1Vpp. Dunno if the TTL level may be a problem though.
/ Mattias
I recall when I made my coax to optical converter the amplitude of the
SPDIF was something like 1Vpp. Dunno if the TTL level may be a problem though.
/ Mattias
Tubenut:
In your case, I would try a 0.1 uF cap from the shield on the TX end to ground, unless it is already grounded by the connector. The chassis will need to have a good earth ground.
A ferrite bead, right at the TX end, may help. Putting inside the chassis where it exits is where I would try.
The SPDIF level is 0.5 V_pp, terminated into 75 ohms. It will be 1.0 V_pp if it is not properly terminated.
Jocko
In your case, I would try a 0.1 uF cap from the shield on the TX end to ground, unless it is already grounded by the connector. The chassis will need to have a good earth ground.
A ferrite bead, right at the TX end, may help. Putting inside the chassis where it exits is where I would try.
The SPDIF level is 0.5 V_pp, terminated into 75 ohms. It will be 1.0 V_pp if it is not properly terminated.
Jocko
1) make sure that you TX out is not connected to circuit ground of the player. If it's AC couple to ground, cut one lead of that cap. These caps or suppose to help however many time they make thing worst.
2) With the DAC disconnected check the noise of the shield. If that is high can be a problems.
3) Check to see what logic family is used in the Transport, some families can cause severe noise problems.
4) Purchase a Transformer receiver interface assembly from Jocko Homo, this will isolated at both ends and sound better.
5) Purchase a TX card from Jocko-Homo and a timing card.
6) Check the ground of both systems.
7) or 1) Call Theta and complain about the problems. They should not be selling equipment that interferes with communications and TV. This equipment would never pass the FCC tests.
🙂
Yap,
Jocko you are right about that. I was measuring on an opened output. I also remember it was centered around ground.
/ Mattias
Jocko you are right about that. I was measuring on an opened output. I also remember it was centered around ground.
/ Mattias
Cameron,
Regards the cap; you need a good cap that designed for hf applications. Much has been written about the different mechanism and non linear effects of capacitor so I don’t fell like repeating it, however it can be found by searching the web. In addition, caps like electrolytic suck at high frequency and be come inductors so they should not be used. Caps like Mica and NPO ceramic work well in high frequency applications.
Dielectric absorption, inductance leakage, or just a few problems there are caps. Dielectric Absorption is one of the biggest offending and a enemy of the audio signals, however, since we in the digital domain and DA it not the critical since we only care about the using the change of the signal going zero to a positive state and from a positive to a negative state. So, Mica very good application, ceramic can be also if the correct material is use like an NPO or even a X7R not a Z5U. ALso, you can use some film cap here too.
🙂
I am quite familiar with how various capacitors and their properties affect analog signals. But were not talking about analog. At least in the traditional sense. It is analog if you consider the infinite fourier expansion of sin waves which create the square wave. And transmission line theory.
So my questions stand unanswered. An electrolytic would clearly trash the datastream and the receiver pll would not even lock. I agree a silver mica or ceramic should work well. The datastream should come through nicely. Though they were described as sounding bright and harsh respectively. How is that possible? What are they doing to the data which could change it's sound?
This same question applies to the sound quality of digital transports. Why would one sound any different than another? I assume they all output exactly the same bits. Otherwise you have either a crappy transport or damaged source media. The only thing left of which I am aware is clock quality/jitter. Consider a DAC with an asynchronous resampler. The jitter attenuation is massive. So that possible source of "sounding different" should be virtually gone. What else is there?
So my questions stand unanswered. An electrolytic would clearly trash the datastream and the receiver pll would not even lock. I agree a silver mica or ceramic should work well. The datastream should come through nicely. Though they were described as sounding bright and harsh respectively. How is that possible? What are they doing to the data which could change it's sound?
This same question applies to the sound quality of digital transports. Why would one sound any different than another? I assume they all output exactly the same bits. Otherwise you have either a crappy transport or damaged source media. The only thing left of which I am aware is clock quality/jitter. Consider a DAC with an asynchronous resampler. The jitter attenuation is massive. So that possible source of "sounding different" should be virtually gone. What else is there?
So my questions stand unanswered
Come on people ........there must be someone who can help this guy out......
Come on people ........there must be someone who can help this guy out......
Anytime a digital signal goes though a capacitor it enters the world of non linear effects, that’s the analog world. So it seems that you have answered your own question.
He asked about EMI......
To reduce the EMI, the shield should be grounded. Maybe it will muck up the sound, as it did for you. But leaving the shield "hot", as it will be in a transformer coupled output, will radiate.
Thanks for the kind words, but none of my boards will reduce EMI. That is not their purpose. Yes, going to a slower logic family may cut it down, but then too many harmonics are chopped off.
The Philips based CDPs that I have worked on did that. While EMI was low, they sounded awful.
As for why a cap can muck up the sound..........
If it is too inductive, it will cause reflections. And reflections make stuff sound bright. Sometimes. Always awful, just the type and degree vary from case to case.
Jocko
To reduce the EMI, the shield should be grounded. Maybe it will muck up the sound, as it did for you. But leaving the shield "hot", as it will be in a transformer coupled output, will radiate.
Thanks for the kind words, but none of my boards will reduce EMI. That is not their purpose. Yes, going to a slower logic family may cut it down, but then too many harmonics are chopped off.
The Philips based CDPs that I have worked on did that. While EMI was low, they sounded awful.
As for why a cap can muck up the sound..........
If it is too inductive, it will cause reflections. And reflections make stuff sound bright. Sometimes. Always awful, just the type and degree vary from case to case.
Jocko
Jewilson: You are thinking superficially. And I definitely did not answer my own question. How do these non linearities impact the sound? They are JUST BITS at that point. Way down the digital chain at the last stage of the DAC chips are some switching transistors creating the analog audio current output. There is no analog audio before that. How is the way those transistors are switching influenced by slight distortion in the analog characteristics of the data stream way back there? You say there are numberous articles on capacitors and their effects. Refer me to just one that discusses how coupling capacitors effect DIGITAL signals. I have not been able to find any.
Jocko: How do reflections make it sound bright? I can easily see how reflections can smear the transients and thus increase jitter. So does this all boil down to recovered clock jitter? If so, I am very unclear as how increased jitter will lead to sounding bright. It can definitely trash signal to noise ratio at high frequencies. Hum. That could end up sounding very harsh on the high end. Bright sorta implies too much high end but still relatively clean.
My moto: Suspect any statement which can not be explained.
Jocko: How do reflections make it sound bright? I can easily see how reflections can smear the transients and thus increase jitter. So does this all boil down to recovered clock jitter? If so, I am very unclear as how increased jitter will lead to sounding bright. It can definitely trash signal to noise ratio at high frequencies. Hum. That could end up sounding very harsh on the high end. Bright sorta implies too much high end but still relatively clean.
My moto: Suspect any statement which can not be explained.
Cameron,
When I talk about capacitors and their performance it’s in regards to an electrical signal. The facts here or obvious; the cap does not care if it digital or analog, it’s an electrical signal with certain electrical properties and capacitors has their own electrical characteristics and electrical properties. It obvious here that you have some understanding of what I am talking about but you want to force us to respond to something so you can argue , well enough.
So go to the data books and check out these components, most of the manufactures provide the performances specifications and frequency curves necessary for to select the right caps for the correct application. Ok, no more arguments now your empowered, I have put some links which contain the some of the best capacitor performance stuff you can find.
http://www.capacitors.com/picking_capacitors/consider.htm
http://home.comcast.net/~wjungieee/wsb/Picking_Capacitors_2.pdf
http://home.comcast.net/~wjungieee/wsb/Picking_Capacitors_2.pdf
http://home.comcast.net/~walt-jung/wsb/PDFs/A_RealTime_Signal_Test_For_Capacitor_Quality.pdf
http://www.capacitors.com/catalogs/note_6.html
http://www.capacitors.com/catalogs/note_6.html
http://www.vishay.com/docs/26033/gentecin.pdf
http://www.vishay.com/docs/45168/mkelepar.pdf
When I talk about capacitors and their performance it’s in regards to an electrical signal. The facts here or obvious; the cap does not care if it digital or analog, it’s an electrical signal with certain electrical properties and capacitors has their own electrical characteristics and electrical properties. It obvious here that you have some understanding of what I am talking about but you want to force us to respond to something so you can argue , well enough.
So go to the data books and check out these components, most of the manufactures provide the performances specifications and frequency curves necessary for to select the right caps for the correct application. Ok, no more arguments now your empowered, I have put some links which contain the some of the best capacitor performance stuff you can find.
http://www.capacitors.com/picking_capacitors/consider.htm
http://home.comcast.net/~wjungieee/wsb/Picking_Capacitors_2.pdf
http://home.comcast.net/~wjungieee/wsb/Picking_Capacitors_2.pdf
http://home.comcast.net/~walt-jung/wsb/PDFs/A_RealTime_Signal_Test_For_Capacitor_Quality.pdf
http://www.capacitors.com/catalogs/note_6.html
http://www.capacitors.com/catalogs/note_6.html
http://www.vishay.com/docs/26033/gentecin.pdf
http://www.vishay.com/docs/45168/mkelepar.pdf
You need to change you motto to suspect any statements that are not explained to your liking. To the rest of us, that sound like your demanding we debate you till your happy with the answer or you succeed in starting an argument
Jocko, your right you can't remove the ground if you not couple at both ends. However, you can determine if the CD ground is adding to the noise of you converter, by scoping out power on or output the dac while disconnecting the SPDIF cable.
As for my application the CDP, AC ground cap to the SPDIF was a major source noise for the DAC. Removing that cap caused the noise in the dac dropped, to bad a did run a S/N measurement. 🙂
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