Oversampling: "Internal" vs. "External"

[hollowman]

Originally posted by hollowman

I've ordered a couple of the chips noted in this thread. Upon testing them in various DAC "back-ends", I'll report back.

I've now got a handful of DAC chips (PCM1796, 1798, 1704) and a DF1706 OS filter to play with. But I have two "problems" now (both stemming from my lack of knowledge/expereince no doubt!) :

-- how (where) to obtain inexpensive ($USD) SSOP prototyping boards

-- determining whether SSOP soldering is worth the trouble (IOW, would I be better off using SOIC chips that are not as well rated/reviewed?)

Any advice from well-seasoned DAC builders is welcome.

P.S. I have searched/read thru myriad posts on SOP soldering issues. I'm still unclear as to whether or not to proceed with the project.

Thx again!

[ACTIVA]

Hi Hollowman,

Take note the PCM1796 needs to work with a micro-controller for internal register configuration, where the PCM1798 is straight external hardware setting, does not require programming. Both offer identical audio performance according to their respective Specs.

You also need SSOP28 to DIP adapters, try some Goggle search.

Regards
Max

[hollowman]

Originally posted by ACTIVA
Take note the PCM1796 needs to work with a micro-controller for internal register configuration, where the PCM1798 is straight external hardware setting, does not require programming. Both offer identical audio performance according to their respective Specs.

Apologies for my ignorance, but exactly how does one configure a PCM1796's internal register(s) with a micro-controller? Can you (anyone) provide a source for such a micro controller?

You also need SSOP28 to DIP adapters

futurlec.com seems to be a decent resource for inexpensive adapters. The low cost is a refreshing change of pace since many places selling SSOP adapters are quite pricey.

[ACTIVA]

Hi,

Any general purpose 8 / 16 bits micro-controllers with I2C / SPI bus interface are OK, but you need to develop your own codes and sort out the timing issues.

If not, skip the PCM1796 and go straight for the PCM1798, no coding needed. The PCM1798 / PCM1794 are external hardware configurable, much more user friendly for DIYers.

Regards
Max

[hollowman]

Originally posted by ACTIVA
Any general purpose 8 / 16 bits micro-controllers with I2C / SPI bus interface are OK, but you need to develop your own codes and sort out the timing issues.

If not, skip the PCM1796 and go straight for the PCM1798, no coding needed. The PCM1798 / PCM1794 are external hardware configurable, much more user friendly for DIYers.

Thx for your reply.

Does this mean the PCM1796 is ultimately the better choice -- i.e. since timing can be tweaked (and, hence, jitter minimized)?

Your comments re PCM1798 / PCM1794 being "more user friendly for DIYers" is interesting. Earlier I noted what seems to be a popular trend in the DIY audio community: use of Philips TDA DAC chips. I wonder how much of this is actually due to their innate simplicity/ease-of-use -- DIP, only 8 pins -- rather than purely sound quality? My (albeit limited) experience with TDA chips have not been favorable.

[ezkcdude]

Are you going to use the DAC for SACD? If not, then there is no need for the PCM1796. Go with PCM1794(8), which are pin-compatible. If you want to see one way to do it, take a look at my website. It's obviously more difficult to prototype and build with SSOP, but depending on your design, you may have no choice. If you want DIP and SOIC, stick with CS8412->TDA154X (NOS). If you're going to upsample using an ASRC (AD1896 or SRC4192, for example), then you cannot avoid SSOP. I do think one of the reasons the NOS approach is so favored is because it is simply easier to build, and less prone to producing duds, due simply to soldering errors.

[hollowman]

Originally posted by ezkcdude
Are you going to use the DAC for SACD? If not, then there is no need for the PCM1796. Go with PCM1794(8), which are pin-compatible. If you want to see one way to do it, take a look at my website. It's obviously more difficult to prototype and build with SSOP, but depending on your design, you may have no choice. If you want DIP and SOIC, stick with CS8412->TDA154X (NOS). If you're going to upsample using an ASRC (AD1896 or SRC4192, for example), then you cannot avoid SSOP. I do think one of the reasons the NOS approach is so favored is because it is simply easier to build, and less prone to producing duds, due simply to soldering errors.

Thx for your reply.

Yes, I was aware of your design via your web site. And it is one of several designs I'm considering for my next DAC project. I am a bit curious as to why you chose UPsampling rather than OVERsampling? The former was, perhaps, a "fad" a few years back but I've, more recently, read some not-as-glowing remarks as to its efficacy.

You asked whether I will use the DAC for SACD? No. But being the owner of several SACDs/DVD-A's -- and a modded combi Pioneer DV-59 player; yes, I *really* do feel that these high-rez formats are *way* better than Red Book, all else being equal -- I would like to sink my teeth into such a project. If it was do'able. AFAIK, there seem to be a lack of DIY SACD/DVD-A *DAC-only* projects. There are very few (if any?) commercial stand-alone DACs that do either or both. Please correct me if I'm wrong!

[ezkcdude]

Originally posted by hollowman


Thx for your reply.

Yes, I was aware of your design via your web site. And it is one of several designs I'm considering for my next DAC project. I am a bit curious as to why you chose UPsampling rather than OVERsampling? The former was, perhaps, a "fad" a few years back but I've, more recently, read some not-as-glowing remarks as to its efficacy.

Upsampling goes along with the ASRC, which I have converting 44.1 to 96 before the DAC (PCM1794 or 98). The DAC then does oversampling, which is basically undefeatable (except in mono mode). So, I actually am using upsampling and oversampling. It would help if you read the data sheets. That will explain a lot.