[gavinbirss]

Hello,

Does anyone deem it feasable to DIY a USB DAC.

tangent :

I recall from reading a past post that you have used the Stereolink USB DAC. I guess from the specs of that unit that it uses the Phillips UDA1321 chip. Stereolink did not want to confirm this.

I have purchased a pair of SUNG FORN USB speakers that I found the UDA1321PS/N101 IC in. The board it not very high quality and I had to rape it to remove the TDA7499 amp chip in order to tap into the input pins to get a line level output, since it had none.

The output was very low however and thus needs to be amplified.

Phillips UDA132x

The specs for the UDA132X series is not bad however.

* 16,20,24 bit playback if I recall correctly
* very respectable S/N and dynamic range


Dallas DS1802

I may have the model number wrong but I also purchased three USB DAC's that were based on this IC but they produced rubish not sound. It may be contributed to the fact that they were PC powered.

The specs for this IC is not that good. 80 db S/N if I recall correctly.


BB PCM2702

This chip has very respectable specs, produces 16 bit only and is available only in SSOP. I have 3 of these IC's and I can't do anything with them since I do not have converters or SMT board capability.

There is however a EVM from TI for $ 149.01.

Has anyone purchased this EVM ?

It uses the OPA2353 rail to rail opamp for 2nd low pass filter and can be used in PC power mode for tests other wise self power mode. (5V for analog, 3.3V digital from USB bus)

I guess that I would only be feasable if a DIY unit can be produced for less that $ 149.

There are also some other USB streaming devices from TI.

Does anyone has some comments or other possible IC's.

Gavin

 

[tangent]

This is an intriguing project, Gavin.

Before I would start on it, here's the criteria I would use to find a suitable chip:

1) The chip has to have the USB interface logic and the DAC all on one chip. I'm not about to go trying to glue a USB chip and a DAC chip together, since I don't have the equipment to debug it if it doesn't work from the start.

2) It has to implement the "USB Audio" spec, so we don't have to write a device driver. We shouldn't even have to write a UI for it -- the OS's default UI should suffice. This will also make it OS-independent. (Windows 98 SE+, MacOS 9+ and Linux 2.4+, at least.)

3) High sound quality, and a plain line output is a must. We'll add our own headphone amp circuit to it.

4) Some kind of DIL pin format. Quad packages are beyond at least this DIYer's ability to solder by hand. If we have to go surface mount, I'd personally only tolerate pins down to about SO-x size. If we can get a thru-hole package, so much the better.

5) It has to be available in relatively small quantities. If we con someone into buying a bunch, I think the maximum outlay you can ask is about $1000, no matter how much profit we build into the deal. So, if the chip cost is $6, the minimum order has to be 166 pcs. or less. If the chip cost is $20, the minimum has to be 50 or less. You see how this works.


Okay, what have we eliminated?

- The Philips chips are out -- minimum order quantity is too high. Other than that, they look ideal.

- That Dallas chip is some kind of digital pot. I searched Maxim/Dallas' web site and couldn't find anything suitable.

- The BB PCM2702E looks nearly ideal, except for the package size. Can _you_ solder SSOP-28? Dunno if I can....

Not lookin' too good so far. Wanna chase down some more chips for us, Gavin?

 

[gavinbirss]

Hello,

Dallas :
I am not at home at the moment so I have to recheck the model number, but the specs of the chip was not very good and it is quite old. It was a dip package though.

I agree that the PCM2702 is the best choice since it is USB
Audio V 0.9 spec and it very good in specs but costs is
indeed a consideration for DIY so the next best thing would be to rather buy the EVM.

Has someone out there tested this unit. With our weak currency and my low budget I would not be able to buy the EVM.

Does anyone have some info on the Wheatfield USB DAC Valve Amp. What USB + DAC circuitry does it use ?

Gavin

 

[gavinbirss]

Hello,

Dallas : DS4201

Gavin

 

[gavinbirss]

Hello,

Here is a link to the Dallas USB DAC datasheet for those who are
interested.

DS4201 datasheet

Gavin

 

[gavinbirss]

Dead link

Try this one

Sorry for the quick posts but I have been jumping around from a Wyse VT100 terminal with Links and Lynx to another Windows NT PC.

Gavin

 

[tangent]

A search for it at maxim-ic.com and findchips.com turns up nothing. The datasheet's four years old, and is still marked "preliminary". I'd say the part has been obsoleted.

 

[Joobu]

I don't think SO or (T)SSOP packages should be ruled out. Practically nothing comes out in through hole nowadays. There are many reasons for this but smaller surface mount packages have less inductance and more ground capacitance, a must for high performance mixed-signal chips.

I've soldered SSOP-16 several times. Any DIY ought to have most of the required equipment:
- thin iron tip
- thin diameter solder
- flux
- solder wick
- loupe

It can be frustrating but with practice aos can do it in 10 minutes.

To acheive the advertised S/N a wire-wrap board is utterly insufficient. It can even be difficult for a two-sided PCB to acheive the required performance. Among other things, a continuous ground plane is absolutely required.

 

[Phloodpants]

There is an eval board available for that BB chip! Too easy! (I hope)

http://www-s.ti.com/sc/psheets/sbau025/sbau025.pdf

 

[aos]

Eval board is what I'd suggest. If money is an issue don't even *think* of trying to pull off a project like this in DIY. I don't think $150 is too much to ask for an eval board. They're not making money on that, probably quite the opposite.

 

[Dusty Chalk]

Sorry, don't mean to crap on this thread, but...

Can I just bemoan the loss of Wheatfield, and, specifically, their USB->DAC->Headphone amp? Dagnabit, I was really looking forward to that! Anyone know where I can get my hands on one of the prototypes?

Please carry on your DIY discussions.

 

[Nezer]

Quote:

Originally posted by Dusty Chalk Sorry, don't mean to crap on this thread, but... Can I just bemoan the loss of Wheatfield, and, specifically, their USB->DAC->Headphone amp? Dagnabit, I was really looking forward to that! Anyone know where I can get my hands on one of the prototypes? Please carry on your DIY discussions.

Perhaps if Tyll can be convinced a market exists for this he can be convinced to start production? Until then the stereolink it is at least until someone does a DIY project and has it posted on headwize... oh wait... that isn't gonna happen...