ESS Sabre Reference DAC (8-channel)

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#89
hirez69 said:
Hi Ross
Can you explain the differences between the various versions?

Stereo Reference Board
8 Ch Reference Board - Current Mode
8 Ch Reference Board - Voltage Mode
Have you set up your 8ch version to "stereo quad-differential" mode?

Thank you
Click to expand...

Hi hirez69,
I don't have the 8 channel demo board. It has 8 op-amp sections and connectors for all 8 channels.

Each of the 8 channels is differential with a + and - output pin from the Sabre 8.

The stereo board I have is configured to sum 4 channels for each of the left and right. I have the stereo I2S signal input on all 4 inputs. Since the channels are differential, the 4 + outputs for each channel are summed as are the 4 - outputs for each channel. Those drive the + and - inputs to the transformer primary for that channel.

If you do a search I'm sure you will find many articles on the benefits on summing the outputs of multiple DACs.

You probably shouldn't try using transformers if you are doing an 8 channel version. The output impedance of an individual channel isn't low enough. The cost would be very high. 😱

Current mode with an op-amp configured for I-V conversion would be ideal for 8 channel mode. 8-channel voltage mode with the op-amp configured as a diff amp would save some parts cost in the output stage.
 
#90
#95
Maybe the sudden change in what was posted as open to the public before, but became subject to confidentiality agreements later has to do with the ESS Technology company just having been acquired by a private investment company. ESS Technologies has been a publicly traded stock company, but this has come to an end.

Just take a look at these links (copy-paste each link into your browser if needed):

http://today.reuters.com/news/artic...01_RTRIDST_0_ESS-IMPERIUM-TAKEOVER-URGENT.XML

http://fr.sys-con.com/read/505544.htm

http://imperiumpartners.com/

How this will affect the Sabre DAC chip is anyone's guess.

Cheers!
 
#96
Hi Ross,

thank you for the explanation.

I have some questions:
Is it possible to see the schematics of modification?
Why haven't you used the native Spdif input of Demo Board?
Are PCBs (Wolfons, AVCC, and Clock) custom or commercial products?
In the latter case might you indicate what they are?
How did you replaced the 40 MHz crystal osc?
Could you provide the schematic of the new analog output stage?

Thanks
 
#97
Hi hirez69,

I don't have a schematic of the modification other than some notes on paper. I am still working on a schematic for a new circuit board.

The small add-on PCBs are things that I have designed for other projects. The Wolfson WM8804 SPDIF board is very similar to the one that Russ White has for sale at Twisted Pear. I made my own to do some things a little differently. None of my boards are for sale right now.

The SPDIF board and the Wolfson part are not absolutely necessary, but I installed it to do some testing. On the Sabre8 part, SPDIF input to the Sabre8 part requires a faster master clock rate than I2S input. The low jitter from the Wolfson part offers the opportunity to experiment with the DPLL register settings and to see if there is a sonic difference.

Before I installed the Wolfson board, I had used a 110 ohm AES/EBU cable input into the demo board comparator circuit, and also a TOSLINK TORX142L input directly into the Sabre8 part. Both sounded exactly the same and worked flawlessly.

I am still testing things at this point. I am making changes and listening to see if the changes make a difference.

Thanks, Ross
 
#98
Hi Ross,

I just noticed earlier in the thread you asked about PIC stuff.

Yes, I am pretty confident in my PIC programming abilities, though certainly no master.

I2C or SPI should be cake.

I will actually probably use a PIC24 type device on my board simply because I am most familiar with it, and it has built in I2C and SPI peripherals.

I will be glad to share information with you, and anyone else who is interested.

All of my projects are pretty "open". 🙂

Cheers!
Russ
 
#99
Dustin,

A quick question for you if I may. 🙂

What mechanism is used for volume control on this device?

It appear from the datasheet that the volume control is analog, and not done in the digital domain. Is this correct?

The reason I ask, is that noticed in the datasheet a blurb about 64 intermediate steps between .5db steps, so I am suspecting there must be some switching involved. Does this mean its an analog attenuation?

Thanks!
Russ
 
#100
dusfor99 said:
Hi All,


I just talked with our distributor, and he tells me anyone should be able to get parts from him. His website is

http://www.shawelectronics.com/contact.html

Please talk to him and he can get you the parts you needs.


Thanks

Dustin
Click to expand...

Hi Dustin,

Very impressive work.

Can you divulge what the OP impedance of each DAC is?

This is important, for example, when choosing a suitable I-V opamp
or discrete architecture as lower Z means higher effective gain,
especially in 2 ch mode where all the OP Z's will be in parallel. The
I-V 'virtual' gain can end up being significant. This will also affect
the linearity of the I-V.

Thanks,

Terry
 
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