[Clutz]

Jambo, I need another project like I need a hole in the head - but I would be interested in a kit if you put this together. The only thing that would hold me back is the power supply, but I think I would probably use a Sigma22 and then an LDO.

Brad

 

[Jambo]

The ideas about someone helping me in the US are good - not quite sure how I'd work it, but it's a good idea.

Really sorry but I'm afraid this is going to have to go on the back burner a bit again as I have a project to do. It's due in ten days so the delay won't be too long.

Things are looking good though - I've pretty much got the thing to stop making the horrendous noises when changing sources, and I have a couple of ideas for things to add.

The output amplifiers are definitely going to be changed to DIPs - the main advantage being that people can then socket them if they want. And also I have realised through a comment on diyaudio that I forgot to add support for deemphasis - that's easily done.

I've also been playing with an LCD and reading up on power supply design.

 

[TimmyMac]

Quote:

Originally Posted by Jambo /img/forum/go_quote.gif The ideas about someone helping me in the US are good - not quite sure how I'd work it, but it's a good idea.

What about Glass Jar? He's been selling kits for a while now.

Anyways, if you're looking for numbers, I'd be down for a kit (or two) for sure.

 

[Marzie]

Quote:

Originally Posted by TimmyMac /img/forum/go_quote.gif What about Glass Jar? He's been selling kits for a while now.

x2

I believe he even offers alien DACs with the "difficult" chip soldered down, so that might be an idea as well, to save you some time/effort.

 

[Jambo]

Thanks for the suggestions.

Currently looking at changing to the PCM2706 so that I can add switches for play/pause, next track, previous track etc when playing over USB, I think that would be pretty neat. The other thing is that I can easily get the 2706 in the UK, the 2707 is a struggle.

 

[lordmozilla]

hey, good to hear some progress, some added control features would be really cool!

 

[sid_]

Surely it'd be best to control playback on the transport, keeping the whole thing modular? Would playback controls not be better to be implemented via some kind of control panel that plugs into the PC's USB port and controls Foobar, or similar?

I believe that some USB DACs use the PCM2706 to send I2S to an upsampler like the AD1896 before sending it into the 8740, but you're already using the TI PCM2707 and WM8805 eliminating a need for the PCM2706 - an upsampler could be cool but I have no idea how much it affects sound quality.

If you were to go for playback controls on the DAC, I'd be slightly concerned about the sound quality of the PCM2706 vs. the WM8740.

 

[Jambo]

I should have made myself clearer

The PCM2706 is pretty much the same as the PCM2707, it is that that I am looking to replace. The DACs will still be the 8740s.

The 2706 and 2707 are pin for pin compatible, but the 2706 makes access to the HID endpoints easy (ie they are available in hardware), the 2707 requires you to talk to it by I2C to access the HIDs.

I have just put 7 headers on the board that connect to the 2706 and send the control signals over USB to the PC as you suggest. Totally up to the user whether they are used or not, the rest of the design is unchanged

 

[sid_]

Ah OK, gotcha! Giving the board headers for playback control so that users have the option is certainly a good idea. I was concerned that you were intending to use the PCM2706 for the actual D/A conversion!

Out of interest, what is your opinion on adding upsampling before the DAC stage?

 

[Jambo]

Also... firmware and hardware for deemphasis handling is done, though the support for this is probably limited to 44.1kHz. And it seems to have stopped making the nasty noises when changing sources.

The user manual is coming together.

I've got a quote for some good quality Scottish made PCBs - the last cheap Malaysian prototype I got had a track attached to the ground plane, was a disaster! Will place an order for 20 PCBs by the end of the week

 

[Jambo]

I should have said that I have sorted the software to get it to stop making nasty noises, rather than implying that it happened by chance.

Quote:

Originally Posted by imported_sid_ /img/forum/go_quote.gif Ah OK, gotcha! Giving the board headers for playback control so that users have the option is certainly a good idea. I was concerned that you were intending to use the PCM2706 for the actual D/A conversion! Out of interest, what is your opinion on adding upsampling before the DAC stage?

Hehe, good good.

On the subject of upsampling, I have never tried it or (knowingly) heard it, and I don't know much about it, so it would be unreasonable of me to have a strong opinion on the matter!

 

[Jambo]

20 PCBs ordered yesterday

I also have a tube of AD797s sitting beside a tube of WM8805s. I hope there's still plenty of interest in this as it is getting a bit expensive for me!!

 

[pistolpete111]

Excellent news!

When do you think the kits will be available? I'm really looking forward to this now!

 

[TheRobbStory]

Ooh, exciting news! How soon can we order boards? I'm chomping at the bit here.

 

[Jambo]

Well, I made some small changes to the boards, so I'll need to build one up and make sure it all still works. I guess I can take orders then

I will have the boards by the end of the month.

I just ordered the PCM2706s from Digikey, they're on back order and should ship on the 20th, I'm not sure if I trust that though. They're the only component that will be tricky to source that I haven't already got.

I finished my degree this week so I've got plenty of time to spend on the manual and tidying up a few other things. I'm quite conscious of the fact that releasing 20 of these into the wild without adequate documentation could cause some real headaches!

The only other thing that I'm not entirely sure of is how I'm going to package the kits. Lots of little SMDs, many different cap values and they're all unmarked so can't be mixed up. And the ICs need ESD protection as well as protection from having their legs bent. To do this in a way that is affordable both in terms of money and time will be a challenge!