Mr White's "Opus", designing a simple balanced DAC

[gil-garcia]

thanks j am going to try tonight.

As the shipping, the response is very quick.

The kit is nice, each composant is identificate with the value paste on it. About 20 minutes in order to make it for a beginner like me wich understand nothing to electronic...
Philippe

[gil-garcia]

it does not work, but as j do not know what is pll j haven't tried.
No sound at all

[Russ White]

Originally posted by gil-garcia
it does not work, but as j do not know what is pll j haven't tried.
No sound at all

Do you have a digital camera? Perhaps you could email me a high resolution picture or two off the forum and I will see if things look OK.

If we are at a total loss you can send back the DAC and we can test it and be sure the DAC is fine. Very sorry to hear this is not working yet, it may be there is just something we are missing.

I would need to use a scope and see exactly what is coming out of your CDPro, but if the MISC pin is really a clock at 2 x SCK then it should work as a master clock. The DAC would just be working at 128fs. But I have no way to know for sure.

Cheers
Russ

[gil-garcia]

Ok thanks a lot

J check the opus tonight and make photos.

j have an oscillo if you tell me what j have to test.

j have also the opportunity to order the spdif module in order to test , as the spdif is working with my yamaha AV.

In the standard mode on the cd pro j shoud have I2S 1 FS outpout. Perharps a matter on the transport....

For information j test with car battery and the configuration connectors found on the opus manual

[Russ White]

Great I am glad you have a scope.

Check the frequency of signals on these three pins from the CDPRO

SCK
MISC
WCLK

That will tell me a lot.

Thanks!

[Russ White]

Originally posted by gil-garcia

For information j test with car battery and the configuration connectors found on the opus manual

What is the unloaded voltage of the battery? It should not exceed 15V. I know it probably does not just wanted to be sure.

[maxlorenz]

Hi Russ and Gil-García,
I too failed to connect CD PRO to Opus a while ago...(shame)

I used the pads named CLK16, as Master Clock 16.93Mhz (page 12 from manual; see diagram on page 8), but no success.
I lack a scope so I am waiting for a USB decoder instead

I am very interested in your success

Good luck,
M

[Russ White]

Ok I knew there were benefits a fully balanced signal path.

I just tested Opus DC coupled into TXD/TXO, it works just fine! No issues at all. In fact it sounds excellent! I am leaving mine this way. Just one note. I use the TXD right after the DAC, like this:

DAC --> TXD --> Joshua Tree --> TXO-2

Also tried omitting the TXD before the Joshua Tree, and that works great too, but you will get a very very slight pop at the higher volume level transitions as the relays switch because of the DC bias.

The TXD module can tolerate common mode voltage of aroound +/- 4V so the +2.5 from the DAC is nothing at all to worry about. And at the output there are just a couple millivolts offset to GND identical on both outputs. This is actually the same as AC coupled!

The only thing really different I noted is that there is a very very faint "chirp" when DC coupled when you turn the DAC off as the PS caps slowly discharge. Nothing that will harm anything, but that chirp is not there when the caps are in place.

To do the modification you simply use a wire jumper in place of C5, C6, C7, and C8.

Very nice to get those caps out of the signal path.

Cheers!
Russ

[Painkiller]

Originally posted by Russ White
Ok I knew there were benefits a fully balanced signal path.

I just tested Opus DC coupled into TXD/TXO, it works just fine! No issues at all. In fact it sounds excellent! I am leaving mine this way. Just one note. I use the TXD right after the DAC, like this:

DAC --> TXD --> Joshua Tree --> TXO-2

How's bass performance with this setup? Does the WM8740 handle the load from the TXD? What about analog filtering?

I tried this type of thing with a PCM1732, but it was hopeless. Muddy bass and very fatiguing sound.

[Russ White]

Originally posted by Painkiller


How's bass performance with this setup? Does the WM8740 handle the load from the TXD? What about analog filtering?

I tried this type of thing with a PCM1732, but it was hopeless. Muddy bass and very fatiguing sound.

It sounds excellent. I am leaving mine this way. The bass is a bit tighter as can be expected when you remove the cap from the path. The TXD load is very very easy at 100K. Even the worst case Joshua Tree load of 2.5K is absolutely no problem for the DAC, especially with no cap to form a high pass.

Whats a little unexpected for me is the biggest difference I hear (and I have two Opus built right now so I can A/B pretty easy) seems to be in the low midrange, things like cello and slap bass seem to have better imaging.

Opus sounds excellent with the caps, but it sound even better without if you have gear that can handle the common mode 2.5V.

Cheers!
Russ