Simplified and further improved Interface
Hi,
Finally made a interface with balanced drive to the CS8412, after listening to many hints. It is quite a improvement to the sound!
The FET in the CDP is omitted as it proved it worked just as well without it.
How to make a balanced 110 Ohm interface is left to the creativity of the interested reader.
Hi,
Finally made a interface with balanced drive to the CS8412, after listening to many hints. It is quite a improvement to the sound!
The FET in the CDP is omitted as it proved it worked just as well without it.
How to make a balanced 110 Ohm interface is left to the creativity of the interested reader.
Attachments
Nice circuit Elso. But, suppose I haven't modified the output of the CD player, and has V<sub>L</sub> 0.7V and V<sub>H</sub> 4.3V, which are the values from the output transmitter of the CS8420. In this condition, with the - input of the comparator grounded, the differential input voltage is always at least 700mV, and the comparator's output will be constantly on.
The problem is that the differential input must swing to -2mV for the output to switch, and in this case that would be 2mV below ground, which isn't going to happen With your transmitter on the left, the voltage will swing all the way down to -1.8V, which is great, but if I don't control the other end I have a problem.
Any ideas on how to adapt this reciever to general purpose use? I guess you could move the whole shooting match over to the right hand side of the cable ...
Sorry for my ignorance. I'm just trying to find a good way to interface single-ended coax transmission into the CS8420's reciever. A pulse transformer probably works fine, but that couples reciever glitches onto the cable. Perhaps a pulse transformer followed by some logic?
The problem is that the differential input must swing to -2mV for the output to switch, and in this case that would be 2mV below ground, which isn't going to happen
With your transmitter on the left, the voltage will swing all the way down to -1.8V, which is great, but if I don't control the other end I have a problem.Any ideas on how to adapt this reciever to general purpose use? I guess you could move the whole shooting match over to the right hand side of the cable ...
Sorry for my ignorance. I'm just trying to find a good way to interface single-ended coax transmission into the CS8420's reciever. A pulse transformer probably works fine, but that couples reciever glitches onto the cable. Perhaps a pulse transformer followed by some logic?
The right pulse transformer will work great
But about glitches....
If the '8420 is like the '8412/4, with a Schmitt trigger input, you will need to isolate it from the line with or without a transformer. If you do use a transformer, you can get differential operation, and employ a few chips to get the level up.
Seriously.....I've used ECL style inputs, which could mean a decent high-speed op-amp optimised for differential lines. Or even discrete circuits. That way, you wil have a circuit that will not couple anything back onto the line. The logic chips can then serve an additional isolation stage.
Jocko
But about glitches....
If the '8420 is like the '8412/4, with a Schmitt trigger input, you will need to isolate it from the line with or without a transformer. If you do use a transformer, you can get differential operation, and employ a few chips to get the level up.
Seriously.....I've used ECL style inputs, which could mean a decent high-speed op-amp optimised for differential lines. Or even discrete circuits. That way, you wil have a circuit that will not couple anything back onto the line. The logic chips can then serve an additional isolation stage.
Jocko
Since I don't run simulations....
I had to try numerous types and/or brands of logic stuff until I found something that would NOT couple energy back into the line. Too bad I didn't write it down.
One thing that I found, that I found amusing (oh, hell, I find everything amusing.....) was that the much maligned Yamaha receiver chip coupled less stuff backwards that most logic gates. No idea why.
Jocko
I had to try numerous types and/or brands of logic stuff until I found something that would NOT couple energy back into the line. Too bad I didn't write it down.
One thing that I found, that I found amusing (oh, hell, I find everything amusing.....) was that the much maligned Yamaha receiver chip coupled less stuff backwards that most logic gates. No idea why.
Jocko
Digital Interface
I hope you don't drive directly the coax cable from the CS8420 The datasheets suggests using a transformer connected to TXP with a 374 Ohm resistor and a 90.9 resistor across the primary. (fig. 33) You can also connect the TXP to a 74HCU04 as in my circuit. With the transformer installed I thrust the signal at the receivers end is up to the SPDIF standard; 0.5V p-p. In theory this should work with the AD8561 comparatoras long no DC component is present. The comparator only needs a few mV above zero to give a high outputstate.
Hi JWB,jwb said:Nice circuit Elso. But, suppose I haven't modified the output of the CD player, and has V<sub>L</sub> 0.7V and V<sub>H</sub> 4.3V, which are the values from the output transmitter of the CS8420. In this condition, with the - input of the comparator grounded, the differential input voltage is always at least 700mV, and the comparator's output will be constantly on.
The problem is that the differential input must swing to -2mV for the output to switch, and in this case that would be 2mV below ground, which isn't going to happen
Any ideas on how to adapt this reciever to general purpose use? I guess you could move the whole shooting match over to the right hand side of the cable ...
Sorry for my ignorance. I'm just trying to find a good way to interface single-ended coax transmission into the CS8420's reciever. A pulse transformer probably works fine, but that couples reciever glitches onto the cable. Perhaps a pulse transformer followed by some logic?
I hope you don't drive directly the coax cable from the CS8420 The datasheets suggests using a transformer connected to TXP with a 374 Ohm resistor and a 90.9 resistor across the primary. (fig. 33) You can also connect the TXP to a 74HCU04 as in my circuit. With the transformer installed I thrust the signal at the receivers end is up to the SPDIF standard; 0.5V p-p. In theory this should work with the AD8561 comparatoras long no DC component is present. The comparator only needs a few mV above zero to give a high outputstate.
Re: Digital Interface
I tried it with a standard Sony CDPXA30ES and got no sound output. Dead silence!
The comparator produces a series of glitches but not a real SPDIF signal. Somewhere I must have made a fault in my line of reasoning.
But the complete interface works as in the picture, provided the digital ground is connected to the chassis of the CDP.
Wel in real world it does not work!Elso Kwak said:
With the transformer installed I thrust the signal at the receivers end is up to the SPDIF standard; 0.5V p-p. In theory this should work with the AD8561 comparator as long no DC component is present. The comparator only needs a few mV above zero to give a high outputstate.
I tried it with a standard Sony CDPXA30ES and got no sound output. Dead silence!
The comparator produces a series of glitches but not a real SPDIF signal. Somewhere I must have made a fault in my line of reasoning.
But the complete interface works as in the picture, provided the digital ground is connected to the chassis of the CDP.
Re: Re: Digital Interface
Hi all,
I feel deeply ashamed as a broken ground lead to the comparator board lead to the wrong conclusion!
The interface <B>does</B> work with the standard SPDIF output from the Sony CDP.
It also does work with the TORX173 receiver provided that a 10nF coupling cap is installed and a 100k resistor to ground from the comparator input to ground, having a path for the input bias current.
Sidenote:
It should almost go without saying that for a 75 coax cable connectors and chassis parts of 75 Ohm characteristic impedance should be used. The RCA connectors as prescribed by the AES/EBU are a completely wrong set standard!. They deteriorate the sound! 75 Ohm BNC or F-connector parts can be used. Or the quite expensive Lemo [Size 1 part# 275; suitable for the RG-59 coaxcable] I will not elaborate further on this as on the AudioAsylum hundreds of posts can be found on the subject.
Hint:
Replace the 74HCU04 by 74<B>V</B>HC04. I have idea why it makes such a big difference but VHC logic sounds a awfull lot better than HC (and AC).
Elso Kwak said:
Wel in real world it does not work!
Hi all,
I feel deeply ashamed as a broken ground lead to the comparator board lead to the wrong conclusion!
The interface <B>does</B> work with the standard SPDIF output from the Sony CDP.
It also does work with the TORX173 receiver provided that a 10nF coupling cap is installed and a 100k resistor to ground from the comparator input to ground, having a path for the input bias current.
Sidenote:
It should almost go without saying that for a 75 coax cable connectors and chassis parts of 75 Ohm characteristic impedance should be used. The RCA connectors as prescribed by the AES/EBU are a completely wrong set standard!. They deteriorate the sound! 75 Ohm BNC or F-connector parts can be used. Or the quite expensive Lemo [Size 1 part# 275; suitable for the RG-59 coaxcable] I will not elaborate further on this as on the AudioAsylum hundreds of posts can be found on the subject.
Hint:
Replace the 74HCU04 by 74<B>V</B>HC04. I have idea why it makes such a big difference but VHC logic sounds a awfull lot better than HC (and AC).
One Box CD-player Solution vs. Separate DAC Component
Hi,
Yesterday I made my latest move by bypassing the digital interface pictured above and the digital input receiver (CS8412) and directly connecting DATA, WCK and BCK from the DSP (SAA7210) in the CDP to the Asynchronous Reclocker in my DAC. I just acquired a Philips CD-650 with that purpose in mind.
Sound is improved tremendously. Much more smooth and less digital. All arguments for a one box player!!!
Later I will place the ASR and the TDA1543 in the player and take out only the current outputs of the DAC-chip.
More depth and analog like! I like the sound very much.
Simplified schematic:
[SAA7210]->[ASR]->[TDA1543]->[IV-converter]->[Outputbuffer]
Hi,
Yesterday I made my latest move by bypassing the digital interface pictured above and the digital input receiver (CS8412) and directly connecting DATA, WCK and BCK from the DSP (SAA7210) in the CDP to the Asynchronous Reclocker in my DAC. I just acquired a Philips CD-650 with that purpose in mind.
Sound is improved tremendously. Much more smooth and less digital. All arguments for a one box player!!!
Later I will place the ASR and the TDA1543 in the player and take out only the current outputs of the DAC-chip.
More depth and analog like! I like the sound very much.
Simplified schematic:
[SAA7210]->[ASR]->[TDA1543]->[IV-converter]->[Outputbuffer]
Re: Re: One Box CD-player Solution vs. Separate DAC Component
Hi massimo,
I am a bit puzzled by your post. I don't see any difference between the TDA1543 and the TDA1545A regarding the IV-converter. Both use a opamp and connect the non-inverting input to Vref. I-out of the DAC connected to the inverting input.
massimo said:
Iout from TDA 1543???
From TDA 1545A maybe.....
Hi massimo,
I am a bit puzzled by your post. I don't see any difference between the TDA1543 and the TDA1545A regarding the IV-converter. Both use a opamp and connect the non-inverting input to Vref. I-out of the DAC connected to the inverting input.
I'm getting older....
SPDIF Interface
Hi,
Forced by circumstances, both my Philips CD-650's broke down, I had to use the SPDIF interface again now with a Philips CD931. I did not find the I2S signals yet, waiting for the manual.
I followed Freds suggestion removing the inputcoupling caps to the DIR.
Now I have much more bass and much less glare! How is this possible? Thanks for the hint Fred!
I added some 1N4148 diodes to the digital input limiting the voltage between +3 and -0.6V, hopefully protecting the comparator.
I also experimented with a Scientific Conversions transformer in the CD-output and also with 74VHC86 directly driven by the opamp. The opamp was configured for a gain of 2x for this configuration producing 5V at the 74VHC86 's inputs. The transformer did not improve the sound, nor did detoriate it. I noted less slam with the 74VHC86 but did not get one of the outputs right....
Hi,
Forced by circumstances, both my Philips CD-650's broke down, I had to use the SPDIF interface again now with a Philips CD931. I did not find the I2S signals yet, waiting for the manual.
I followed Freds suggestion removing the inputcoupling caps to the DIR.
Now I have much more bass and much less glare! How is this possible? Thanks for the hint Fred!
I added some 1N4148 diodes to the digital input limiting the voltage between +3 and -0.6V, hopefully protecting the comparator.
I also experimented with a Scientific Conversions transformer in the CD-output and also with 74VHC86 directly driven by the opamp. The opamp was configured for a gain of 2x for this configuration producing 5V at the 74VHC86 's inputs. The transformer did not improve the sound, nor did detoriate it. I noted less slam with the 74VHC86 but did not get one of the outputs right....
Attachments
Stupid Mistake/0.5V p-p Out
Hi,
Jocko let me know he dislikes the diodes, as they are conducting and he wants a 0.5V p-p out as SPDIF norm prescribes.
Well I can't plaese everyone
Hopefully I have learnt to count to 5 now
Sonically this circuit is not different from the previous one.....
Hi,
Jocko let me know he dislikes the diodes, as they are conducting and he wants a 0.5V p-p out as SPDIF norm prescribes.
Well I can't plaese everyone
Hopefully I have learnt to count to 5 now Sonically this circuit is not different from the previous one.....
Attachments
This circuit is taken from Digital One V. 1.1 documentation. Digital One is from NET-Labs and is designed by by Enland Unruh.
S/PDIF output
IC1 0.1 uF 0.1 uF
|\ || ||
---| +-750R--+-- ||--+ +--||--- pin
|/ | || | | ||
| )||(
| )||(
| )||(
| )||(
499R | |
| | +------- ground
+----+----+ T1
|
---
T1 is a HF-transformer which has 2:1 turns ratio. Transformer type used in example circuit is SC944-05. IC1 in this circuit consists of 8 parallel connected buffer ports from 74ACQ244 IC.
So anybody tested this circuit?... I think I will put it to the test in a Nec 6xE player, while it does not requier -12v witch makes things easier
/ Micke
S/PDIF output
IC1 0.1 uF 0.1 uF
|\ || ||
---| +-750R--+-- ||--+ +--||--- pin
|/ | || | | ||
| )||(
| )||(
| )||(
| )||(
499R | |
| | +------- ground
+----+----+ T1
|
---
T1 is a HF-transformer which has 2:1 turns ratio. Transformer type used in example circuit is SC944-05. IC1 in this circuit consists of 8 parallel connected buffer ports from 74ACQ244 IC.
So anybody tested this circuit?... I think I will put it to the test in a Nec 6xE player, while it does not requier -12v witch makes things easier
/ Micke
Re: SPDIF
Sorry, heven't got time to read to the end of the thread.
So has anyone measured the detrimental affect of the schmitt trigger input of the CS8412? Maybe it is already buffered internally. Even if it dumps energy back into the transmision line will this effect the switching transitions? Will there be reflections if the transmission line is properly termintated?
HarryHaller said:
Sorry, heven't got time to read to the end of the thread.
So has anyone measured the detrimental affect of the schmitt trigger input of the CS8412? Maybe it is already buffered internally. Even if it dumps energy back into the transmision line will this effect the switching transitions? Will there be reflections if the transmission line is properly termintated?
Hi,
Finally made a interface with balanced drive to the CS8412, after listening to many hints. It is quite a improvement to the sound!
The FET in the CDP is omitted as it proved it worked just as well without it.
How to make a balanced 110 Ohm interface is left to the creativity of the interested reader.
Hi gents,
any good candidate for OPA603 replacement? (NLA)
Thanks
http://www.diyaudio.com/forums/digital-source/3282-digital-transformer-11.html#post44053
Last edited:
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