Singxer SU-2

[joenetic]

This would be worse than the first option, LVDS are digital signals, a sinewave is an analog signal.
The FIN1002 outputs a LVTTL digital signal, in effect this is the sine to square converter.

To make matters worse, the coax clock input is single ended / unbalanced not diffrential. LVDS works best with a differential input

I think it is fine, the negative input is tight to certain voltage, need to check again, if the negative input voltage is stable, the jitter is not increase, unless the output skew time is keep changing.

 

[b0bb]

I think it is fine, the negative input is tight to certain voltage, need to check again, if the negative input voltage is stable, the jitter is not increase, unless the output skew time is keep changing.

I disagree

 

[joenetic]

I disagree

Why? Want to get your comments

 

[b0bb]

Why? Want to get your comments

In order to meet the LVDS jitter performance targets, the datasheet lays out the risetimes of the input signal, A sinewave rise time is much slower than a square wave.

 

[b0bb]

LVDS expect a squareware at its input not a sinewave. Fairchild made this explicitly clear in the rise time requirements the put in the datasheet.

There should have been a proper sine to square conversion stage instead of relying on the receiver, this is a function it was never designed for.

 

[joenetic]

In order to meet the LVDS jitter performance targets, the datasheet lays out the risetimes of the input signal, A sinewave rise time is much slower than a square wave.

I get your point, it is how good is the sin waveform reach this IC input, do you have idea of good sin to square wave converter?

 

[b0bb]

I get your point, it is how good is the sin waveform reach this IC input, do you have idea of good sin to square wave converter?

The hard part here is to have a converter that does not significantly degrade the -100dBc/Hz performance of your external clock.

The link below is an example of a part that can to this, note it comes with jitter performance numbers.
The part was designed to convert the output of precision oscillators.

https://www.ti.com/lit/ds/symlink/c...https%3A%2F%2Fwww.ti.com%2Fproduct%2FCDC3RL02

This is a 1.8V part, you will need to spend some time on the TI catalog to see if can find a more compatible 3.3V part.
If you do find one, check if you can buy an engineering demo board, it will be quite expensive but its performance is guaranteed.
The last point is important if you do not have sufficient expertise and equipment to validate the circuit.

 

[b0bb]

Another option is to try SU-2 with a different external clock with square wave output.
The clock must be capable of delivering at least the same phase noise performance as your existing clock with its square wave input.

If you see a marked improvement in sound quality compared to your original clock, then it is likely the device is a LVDS receiver.
The improvement would be due partly to the LVDS receiver being fed a digital signal and no longer operate with an out-of-spec input and no longer forced to do sine to square conversion.


If not, the device is likely the ROHM comparator.

 

[joenetic]

The hard part here is to have a converter that does not significantly degrade the -100dBc/Hz performance of your external clock.

The link below is an example of a part that can to this, note it comes with jitter performance numbers.
The part was designed to convert the output of precision oscillators.

https://www.ti.com/lit/ds/symlink/cdc3rl02.pdf?ts=1682659171865&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FCDC3RL02

This is a 1.8V part, you will need to spend some time on the TI catalog to see if can find a more compatible 3.3V part.
If you do find one, check if you can buy an engineering demo board, it will be quite expensive but its performance is guaranteed.
The last point is important if you do not have sufficient expertise and equipment to validate the circuit.

I also checked this IC, but output level is a concern.

 

[joenetic]

Another option is to try SU-2 with a different external clock with square wave output.
The clock must be capable of delivering at least the same phase noise performance as your existing clock with its square wave input.

If you see a marked improvement in sound quality compared to your original clock, then it is likely the device is a LVDS receiver.
The improvement would be due partly to the LVDS receiver being fed a digital signal and no longer operate with an out-of-spec input and no longer forced to do sine to square conversion.


If not, the device is likely the ROHM comparator.

Unless the clock is natively output square wave otherwise there has chance to suffer from sin to square tolerance, I found a Canada company has a solution SinePi, but it is quite expensive about EUR150, I may try to work on this part to improve existing differential buffer, hope I have good news to this group

 

[joenetic]

Actually I am discussing about clock cable in another group, learned that square wave 10Mhz signal need a high standard and good matching cable, otherwise the square wave rising edge in the cable is also easy be alter to cause PM noise, not easy to handle external clock in good condition, but it is fun to keep twisting

 

[joenetic]

Unless the clock is natively output square wave otherwise there has chance to suffer from sin to square tolerance, I found a Canada company has a solution SinePi, but it is quite expensive about EUR150, I may try to work on this part to improve existing differential buffer, hope I have good news to this group

I found it is common to use LVDS buffer as comparator to convert sin to square, LTC6754 has very low jitter, it may better choice to replace FIN1002M5X

 

[b0bb]

Unless the clock is natively output square wave otherwise there has chance to suffer from sin to square tolerance, I found a Canada company has a solution SinePi, but it is quite expensive about EUR150, I may try to work on this part to improve existing differential buffer, hope I have good news to this group

Why bother ?
You already have the CCHD957 low phase noise clocks, replace the stock Accusilicons and bypass all this conversion complexity in trying to use a 10MHz external input.
SU2 is in the middle of the audio chain, at the end of the day the jitter performance is limited by the I2S and SPDIF outputs, going overboard with mods is just throwing away time and money.

If you absolutely must have the 10MHz external clock, pay IanCanada the asking price, he did the validaton work and has been doing mods for 15years.
Unless you have access to a lab with the right equipment, the cost of validation is more than the cost of the SU2 just to rent the equipment.

 

[b0bb]

I found it is common to use LVDS buffer as comparator to convert sin to square, LTC6754 has very low jitter, it may better choice to replace FIN1002M5X

This is a LVDS transmitter, you have to connect this to the FIN1002 which is a LVDS receiver, assuming the chip is even a FIN1002.
This cannot replace the FIN1002

This is what SinePi from IanCanada does, just buy the thing from IanCanada and be done with it.

 

[joenetic]

Why bother ?
You already have the CCHD957 low phase noise clocks, replace the stock Accusilicons and bypass all this conversion complexity in trying to use a 10MHz external input.
SU2 is in the middle of the audio chain, at the end of the day the jitter performance is limited by the I2S and SPDIF outputs, going overboard with mods is just throwing away time and money.

If you absolutely must have the 10MHz external clock, pay IanCanada the asking price, he did the validaton work and has been doing mods for 15years.
Unless you have access to a lab with the right equipment, the cost of validation is more than the cost of the SU2 just to rent the equipment.

Yes, to do so may fix it, but everything settled, no more fun! Really want to know if I can make it better, that's why I bought this used SU2 with low price to mod. I amy also try to put Crystek back to SU2 to compare the sound with external clock, as I remember now 10M clock the sound is better.