DIYHiFi.org

Thanks Carlos for splitting the thread and for your appreciation of our work. The apodizing discussion is interesting and deserves a thread of it's own.

Back in business (I wasn't able to login properly the last week or so, the IT guys are migrating some servers and ...no surprise here...things aren't really working well)...Here is how the signal looks like after adjusting the Xover distorsion; pretty nice I would say:

And the same for a -80dB signal
Pretty good combination DF+DAC+IV isn't it?

Just for comparison I have somewhere a 4xOS TDA1541 at -70 dB screenshot (taken in the same conditions, same 'tools' etc...) I'll post it right away if I'm lucky to find it on one of my USB keys.

OK, got it! Shows signs of digititis at -70dB already.

why does the -80dB signal show 5.5mV and the -70dB shows 682uV?

Hi Andrew,
That means that for the -80dB I used the little AD797 preamp (with about 32dB gain)

For the TDA1541 based CDP used to compare I didn't use it; also this CDP had an unusually high output (2.7-2.8Vrms full scale) which helped a bit.

Anyway I don't fully trust those numbers as they use to 'jiggle' quite a bit while playing the very low level test tracks.

Side note: a few posts back I mentioned 40dB of gain for the preamp...scratch that, my bad!

The most difficult part of the case design will likely be the top.

It doesn't look promising that we have the skills to emulate the Rega or ML top-loading designs.

In an effort to do something more interesting than a sliding drawer but without springs, angles, struts...this is what I came up with. -Surely stolen from something I've seen someplace else...but I'll cite that reference when somebody tells me who / where it is.

I've got access to a glass guy who claims to be able to machine (drill holes, make nice circular shapes, etc) glass. There's a lot of great work from sidiy in there, so I was thinking of glass panels as much as we can... Glass does have a tendency to break...so it may be short-lived. However, I'm hoping that with 10mm thick or more, we might be OK.

Also, the CD-Pro2 wants to be coupled to 7 Kg of mass. I think we'll get there in the end.

I guess the most complicated part will be incorporating the rack & pinion assembly to the end of the arm. Was thinking the arm would be .75 inch x 9.25 inch x 1.25 inch (sorry to keep switching from metric to imperial...welcome to Canada, eh)

I knocked this quickly together in Visio...as concept for discussion. Please keep this in mind when flaming it!

We're having our first meeting with our mechanic tomorrow. Can't wait to get some concrete chassis action!

The ISO/IEC CD-Player symbols were rather straight-forward.

However, finding a symbol for 'DITHER' was...fruitless. So I made one up...thinking about what we're working with.

Any comments / suggestions are welcome.

For Guido,
Here is how our system is working with a -100dB signal recorded with dither (which is used at playback as well)). I know it seems a little strange because it is beyond the 16b dynamic range of redbook CD.
Anyway the little zzzz thingies represent what my oscilloscope is able to capture while the signal is being interpolated from 16b to 20b. Therefore I tend to think that whatever is inside works as a 20b DAC. (huh!)

PS. Ignore that spike, I'm not sure yet what was causing it.

sidiy...thx for keeping this important thread alive!
A few "simple" questions -- FYI, I haven't searched the thread carefully so if answers are there, just yell

The PCB(s) ... how many layers is your latest version? Recall the orig. was 2-layer and 'kitchen-made'. Also, any specific guidelines/practical advice on PCB(s) design/implementation for this project?

All the pcbs are 2-layer, the bulk of them is pictured here.


Yes, that was only for the PIC controller board that sets the dither levels for the PMD100 and the two little servos. Since then we changed the user interface (and this implies a new board for the buttons) so I decided to use the opportunity and rework 'professionally' the PIC board.

Anyway, back to your question, when everything will be boxed and ready I will post the updated schematics together with all tips and tricks (read 'patches' ) concerning the implementation. Right now I'm not sure if it makes sense to make the gerbers available....that's because I didn't print the part IDs on the silkscreen(s) which renders them pretty much useless for other potential builders.

All right, significant progress to report:
After some serious design effort my partner in crime managed to talk the people at Front Panel Express into making our enclosures:
- The first case has arrived...the beast will literally reign on top of our equipment racks with a 'modest' WxDxH of 19x15x4 inches...
- At my end of things I made the front panel board which includes the uC for the PMD100 and will accommodate the new user interface (you may recall that the original one we had from Dantimax has some bugs...)

Apart from a few minor mistakes (easy to correct) everything else seems to fit nicely:

The pcb's and the top panel

And another view

Not all the stuff is in yet...things like buttons, 'cookie jar', pillars for the CDPro plate are still in the making...we'll keep you posted.

All right, the deeds are done... .
Right now I'm trying to sort out the photos so stay tuned!