Simple SPDIF-D/A-Converter needed

[kooma]

Hello,

i racked up an old NTP peakmeter, but i can't use in on my main out of my interface, because it is regulated by remote-control.
Because i integrated a bunch of Outboard, i am low on alalog-outputs. i don't want to spend two for the meter.  Now i decided to use my SPDIF out, because i don't use it very often. Is there any cheap D/A-Converter-Chip to do it?
i found this one, which fit my needs, but i think there could be a cheaper solution:

http://www.reichelt.de/A-V-Kabel-Toslink-LWL-/WANDLER-D-A/3//index.html?ACTION=3&GROUPID=3614&ARTICLE=115282&SHOW=1&START=0&OFFSET=16&&SID=33T7SnVX8AAAIAAG7o5Ak978e8b58c9298c43c182c1158be75094&LANGUAGE=EN

I needed one for my tv.
ordered something similiar for 18$
http://www.ebay.com/itm/Digital-Optical-Coaxial-Coax-S-PDIF-TOSLINK-to-Analog-RCA-R-L-Audio-Converter-US-/300747876832?pt=US_Audio_Cables_Adapters&hash=item4605f869e0

 

[kooma]

Got it.
it's small and seem to work ok
it has CS8416 receiver and cs4344 D/A chips inside.

 

[strangeandbouncy]

  dum, de dum,



    whistle, whistle, whistle



    La, La, La, . . . .




      Hi guys,



    not wannin' to be hassley, but hows it gwanin'?


    ANdyP

 

[strangeandbouncy]

  cough cough,



    . . . .



    PCM4222 ADC . . . .cough . . . .cough . . . . splutter . . choke . . . . ?




       

 

[Rochey]

Andy,

The board in my pick and place video is the dac board.
First rev have finished design and is waiting to be debugged.

Once the Eden Mic pre is running, my dac based on the pcm5102 will release.

As for an adc on the 4202, yeah - that needs a complete rehaul I think!

/R

 

[strangeandbouncy]

Hi Rochey,


  yay!


  I am very interested in the Eden. Why name it after Anthony Eden btw? Is he a personal hero?


    PCM4202 . . . . . mmmmm!



    ANdyP

 

[Rochey]

All expat audio products are nicknamed after british prime ministers.
The 4202 adc was called churchill, and the motherboard for it called lloyd-george. The front panel was nicknamed "prestatyn" after a welsh town, and because... You "press that in" (typical example of Keith's humour)

We actually had some other projects that neverwent anywhere.
keith nicknamed Eden after Anthony Eden. It's the first module that we've developed... I guess there's a funny link there too.

Anyway, enough thread theft for one night. I plan to debug the dac board over Christmas... Release in Jan/Feb, depending on my workload in real life!

 

[mhelin]

Anyway, enough thread theft for one night. I plan to debug the dac board over Christmas... Release in Jan/Feb, depending on my workload in real life!

You are late, the PCM5102 is already NRND (Not Recommended for New Design):

http://www.ti.com/product/pcm5102&lpos=See_Also_Container&lid=Alternative_Devices

;D

 

[Rochey]

I'll switch to the A rev.

 

[mhelin]

There were some problems with clipping output, maybe it's corrected in rev A?

Btw. played some night with the Purepath Studio GDE (Home ) version and noticed that PCM5142 is actually quite powerful device. In addition to it's analog outputs you can route the output from biquads via GPIO pins to other I2S DACs (didn't test limit but at one time I had two I2S outputs on the graph), so you could implement the crossover in PCM5142 part and use additional PCM5102A's (or other DAC's) as output DAC's (without DSP) for the other channels.

 

[Rochey]

There were some problems with clipping output, maybe it's corrected in rev A?

Btw. played some night with the Purepath Studio GDE (Home ) version and noticed that PCM5142 is actually quite powerful device. In addition to it's analog outputs you can route the output from biquads via GPIO pins to other I2S DACs (didn't test limit but at one time I had two I2S outputs on the graph), so you could implement the crossover in PCM5142 part and use additional PCM5102A's (or other DAC's) as output DAC's (without DSP) for the other channels.

I love it when folks find the "easter eggs".

For the clipping output, try switching the I2C programmable parts to use VCOM instead of VBandgap. We use a bandgap reference on the PCM5102 to generate the reference voltage, instead of the usual resistor divider with an external cap. That gives it great Power supply noise rejection, at the cost of requiring a relatively steady 3.3V or higher. If your power supply sags too much, then the bandgap reference continues to stay steady at 1.65V (and is no longer necessarily half of the rails).

PCM512x and PCM514x (and newer derivatives) have the option to switch between both. My personal preference is to use the bandgap, but then, I usually have a nice 3V3 regulator to look after the device.

 

[mhelin]

Related to the PCM51xx chips there are now some boards with I2S input available like these:

Hifiberry DAC for Rasberry Pi:
http://www.hifiberry.com/dac

This is simple PCM5102A DAC as you can see. However, Hifiberry have also a PCM5142 based DSP for Raspberry Pi in develoment, together with software that uses HTTP interface (Javascript based, RPi server running in Python, guess with AJAX support) to configure the chip(s, don't know how many they will put on the board yet).

There's also PCM5102 DAC by DIYINHK:
http://www.diyinhk.com/shop/audio-kits/31-384khz32bit-pcm5102a-dac-i2s-input-ultra-low-noise-regulator.html

Both ones are quite inexpensive but look promising.

However, some folks at diyaudio (forums) seem to think there's a bug in PCM5102 filter, they claim it it will digitally overload with near 0 dB mastered audio material, so they claim it's not related to badcap reference design but moore like result of Gibbs problem.

Anyway, both above kits have only the I2S so you must get the SPDIF part separately, from ebay you'll find these:

http://www.ebay.com/itm/WM8804-S-PDIF-TOSLINK-IIS-Converter-I2S-Codec-Project-integration-DIY-/350855232077?pt=DE_TV_Video_Audio_Verst%C3%A4rker_Teile&hash=item51b099fa4d

 

[madriaanse]

Why 51xx? Why not go for the PCM1794? ... And add AES?

M.

 

[Rochey]

Thats a great question.

PCM1794, whilst offering incredible performance, requires an extensive signal chain post-DAC. opamps, caps, resistors and others. It also requires multiple power rails, each of which must be generated and filtered.

PCM51xx offers similar audio performance (in tone and sound signature), offers pretty good performance (112dB at the connector), runs on a single supply and is *really* easy to design with. (feed it 2 clocks and data, and your off!). It also offers an extention to the PCM514x family that can do a LOT of very clever things. (using miniDSP).

AES support is not complex. You simply add an RS-422 front end to the S/PDIF receiver.

there are no technical issues in this solution... just a Time one.

/Dafydd

 

[madriaanse]

Either way it sounds like a great project. It would be neat if RS-422 was integrated on the PCB though, as well as a level control (so you don't have to buy an expensive monitor controller or stepped attenuator).

M.