Which sound card has an SPDIF output comparable to an expensive CD Player?

[andy_c]

Is the BNC S/PDIF output of the SndScape card transformer coupled?

 

[Franz Gysi]

No transformer

So TG-link seems the way to go, hopefully we'll see more from this new technology in the future

This could be the problem:

Technological development is not a real evolution.

Why?

Because the consumer is not as clear in his "mind" as the nature is...

It's not always a marketeers fault!

So, may be there is no big (consumer) market for TG-Link.

At the moment I just know about the Zhaolu D3 DAC with a TG Link input (and I love this solution) and no other device.

Franz

 

[Hezz]

You are right about the DAC side. However, the coax shield is NOT connected to PC chassis on the source side, only to the coax transformer output winding. Therefore the two chassis are not connected via the shield. They may be connected via the ground plug in the socket but that is a different story

Momitko,

I know it sounds obvious and you have probably already done this, but make sure there is good isolation between the PC and the DAC on the AC mains. The DAC will need a good power conditioner that reduces digital grunge in the power line and the PC also needs some kind of isolation. Ideally the power for each is from a separate circuit and the PC is transformer isolated.

 

[NeoY2k]

Hi,
If you don't want to go to RME or Motu stuff, you'd better make your own usb-spdif or maybe firewire-spdif interface, with a good clock.

For FireWire, you may try a Dice Mini from TC Electronics. (122 pins package, around 30$). You'll have to implement it, add a microcontroler... hard work. Best solution if you want firewire.

USB would be way simpler as there are ready made chips. For power supply, you'd better find a 3.3V powered chip so you can use the USB's 5V and then put your reg on it. Good clock is the way.

Be aware when using several power supplies: computers PS really do MESS the power line, and it's common using sound cards with external supply that if you plug them on the same power line, you'll have a messed up sound. Try isolator transformers then and/or change your power supply to a good one (ie Antec).

You could also use usb-i2s or firewire-i2s. Even better, same rules apply. Use LVDS line drivers.

 

[momitko]

Today I closely inspected my DAC and the optical ro coaxial converter which I use to get signal from the Toslink output on the card to the external DAC and it turned out that the power supply for the converter is of poor quality. So, I connected the converter to the PS inside the DAC and I immediately heard improvement in SPDIF output of the card.
I must tell that now the difference in SPDIF quality between my card and the Rega Saturn is not as huge as it was a few days ago.
Another thing that I did, I opened up my DAC and removed the connection between digital ground on the DAC and the shield of the cable that brings SPDIF stream to my DAC. There's an SPDIF transformer which is used to isolate the DAC from the source.
Now that I have achieved complete galvanic isolation I want to implement a DIY SPDIF electric coaxial output on my card in order to get rid of the TTL - optical - coaxial conversion.
I will be following the instructions on this page: http://www.hardwarebook.info/S/PDIF_output#Isolation_transformer_for_S.2FPDIF_output
Can anyone tell me whether I can use the Simplest TTL to S/PDIF coax interface shown there without any IC's if I connect it to the input pin of the TOTX optical transmitter on the card?
Which would be better for the highest quality of SPDIF?

 

[analog_sa]

I doubt if the TOTX output is suitable for driving a 75R cable. It's probably a good idea to build a buffer on a little board and try comparing the direct and buffered outputs. PS to the buffer is extremely critical.

 

[NeoY2k]

analog sa: +1

 

[momitko]

There's one more thing that I can't understand.
When I read a datasheet for an IC I see the following sentence:
"The transparent mode of the CS8402A is selected by by setting TRNPT, pin 24 high."
What is the meaning of setting a pin low or high?
Does it mean that if it's low then I should connect it to the gound plane and if it's high then I should connect it to +5V supply?

 

[analog_sa]

A slightly surprising question, but yes, that's right.

 

[momitko]

It's just that currently I am soldering a synchronisation board which I will put in my external DAC. THis board contains divider by 2, CS8402 and TOTX173.
I want to synchronize my card with a clock in my external DAC whereby a clock signal (11.2986) will be divided by 2 and fed to 8402 and then to the card via optical cable.
My be I will get my audio nirvana by this method.

 

[momitko]

One more thing.
Today I was inspecting my external NOS DAC (CS8412 + AD1851 + OPA627) and I noticed that the digital ground was connected to the analag groud via BNC and RCA connectors on the chassi.
As far as I understand this is wrong.
So I removed the ground connection from the input wiring (SPDIF transformer to CS8412) and now these two grounds are not connected except on the DAC board where they are islolated in some way.
I am sitting now and listening to music and it seems to me that the quality has improved. I am not sure that it improved. May be this is placebo but digital and analog grounds should not be connected, should they?

 

[analog_sa]

They should. At a single point, usually underneath the dac chip.

 

[momitko]

They should. At a single point, usually underneath the dac chip.

I didn't tell you that the analog ground is isolated from the digital ground in my DAC by ISO150U.
How can these both grounds connect at a single point beneath the DAC chip when the chip itself (AD1851) has separate contacts for the analog and the digital ground (pins 12 & 2)?
The only point where the grounds should be connected is at the ISO150U.
When I was fixing the DAC board on the shassi I overlooked this requirement and digital and analog ground were connected on the chassi through RCA and BNC connectors.

 

[khundude]

The best S/PDIF out from a cheaper soundcard is the ESI Julia at around $140. It will only do two channel, but it will do it at 192khz. Also, this TG-link is just a way of encoding a trigger to turn on a direct I2S link. You must have a receiver as well and only the Zhaolu D3 has one. Easier is to mod the ESI Julia and tap the I2S leads and send directly to your DAC on very short leads. This will skip all conversions and added errors. Be careful though, you may not be ready for this kind of detail and imaging!

 

[analog_sa]

How can these both grounds connect at a single point beneath the DAC chip when the chip itself (AD1851) has separate contacts for the analog and the digital ground (pins 12 & 2)?

I said usually. And no, you didn't mention the isolators. It's probably fine if the two grounds are connected at the ISO as long as they are connected. I am not entirely sure if the isolators don't do more harm than good but they certainly break ground loops and ground noise.

It is also possible we are talking about different things. Your dac chip requires that both digital and analogue ground are tied together. The ISOs break the galvanic connection between input ground and the dac ground. These are completely different issues.

If there was a connection between the incoming ground and the output analogue ground then this rendered any ground isolation from the ISOs useless. What you've done is certainly an improvement.

 

[momitko]

The best S/PDIF out from a cheaper soundcard is the ESI Julia at around $140. It will only do two channel, but it will do it at 192khz. Also, this TG-link is just a way of encoding a trigger to turn on a direct I2S link. You must have a receiver as well and only the Zhaolu D3 has one. Easier is to mod the ESI Julia and tap the I2S leads and send directly to your DAC on very short leads. This will skip all conversions and added errors. Be careful though, you may not be ready for this kind of detail and imaging!

I guess that since ESI Julia and that new card Audiotrak Progidy H2 Gold have only two output channels the quality of SPDIF on these cards should be better.
However, recently I have accidentally come across the datasheet for the Envy chip http://xkodi.svobodno.com/xkodi/space71.html that is inside my Terratec card. The same chip is inside the Audiotrak card as well. I don't know what chip is inside Julia. Could it be the same one?
Now I know that this chip contains I2S output and I know the location of pins on the chip. This chip contains a built in SPDIF transmitter.
So I guess the quality of SPDIF is the same on my Terratec as well as on the Audiotrak Progidy H2 Gold.
Another idea that I've got is that I can isolate this chip from the +3.3V supply and instead provide my own high quality suppy.
Since SPDIF is transmitted by this chip then I guess theoretically by improving the quality of supply I might greatly improve the quality of SPDIF out and reduce the jitter. Any ideas, comments?

 

[momitko]

I have just found out that ESI JUlia contains the same Envy-24HT chip. So theoretically the SPDIF quality on Julia should not differ form that of any other card with the same chip be it a newly released or an old card. It doesn't matter IMO.

 

[phofman]

SPDIF output of Juli does not differ from any other Envy24-HT based card, e.g. Chaintec AV710 or the inexpensive digital interface SndScape Odeum. The only difference is that Juli is not using internal clock dividers of Envy24 but a custom-programmed FPGA instead. As a result it supports real 176.4kHz SPDIF output, unlike most other Envy24HT cards which switch to 88.2kHz (likely a bug in the chip). Plus it can detect incoming SPDIF sample rate correctly. It has no impact on SPDIF output quality though.

 

[momitko]

The only difference is that Juli is not using internal clock dividers of Envy24 but a custom-programmed FPGA instead.

I wonder if Audiotrak Progidy H2 Gold (which is on Envy-24 as well) uses external or internal clock dividers.

In case I decide to go ahead with Tentlab clock do you think that the thing that my Terratec Aureon Sky has internal clock divider could be a limiting factor in improving SPDIF out in a Terratec card?

 

[phofman]

It uses internal dividers as there is no FPGA on the board

http://www.audiotrak.co.kr/audiotrak/image2/prodigyhd2Big2.jpg

However, there is no reason the external dividers should provide a better quality sound than the internal ones. Using the external clock divided to a required frequency the card circumvents the bug with 176.4kHz and prepares independent clock which allows the SPDIF receiver AK4114 to properly recognize incoming SPDIF sample rate. When working on the Juli driver for Linux alsa I could not identify any other advantage of producing the clock signal externally, instead of using Envy24 circuits.