Return-to-zero shift register FIRDAC

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#202
nautibuoy said:
Add your name to the list and I'll advise of the cost after I get some quotes when Marcel finalises the PCBs.
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Add me to the list 🙂

I need to put in an order for other projects in the next week or so, so i may backorder some of the components for this too.

I suspect my little stm32f7 (216Mhz) will be too slow for DDS, so i may have to look at faster options.
 
#205
I've just been making a mouser BOM projects so I can add the projects to the main order at the weekend. I have two questions:

1. I see there's a filter BOM, I assume a BOM per filter (and the set of boards has two filter PCBs)? (Sorry but the schematics doesn't load in my version of KiCad)
2. 595-OPA210IDR int the filter BOM seems to be in multiples of 3000 😱🤣 It recommends OPA210IDT (which is back ordering).

So in short there's a number of backordering opamps, some of the SMT resistors are backordering but they should be substitutable.

Rough UK prices seem to be approx GBP63 for the DAC and GBP80 per channel filter for the BOM (there's a few connectors that need adding but that rough price seems good.

I see nautibouy has gone for a tube output which is interesting.
 
#206
NickKUK said:
I've just been making a mouser BOM projects so I can add the projects to the main order at the weekend. I have two questions:

1. I see there's a filter BOM, I assume a BOM per filter (and the set of boards has two filter PCBs)? (Sorry but the schematics doesn't load in my version of KiCad)
2. 595-OPA210IDR int the filter BOM seems to be in multiples of 3000 😱🤣 It recommends OPA210IDT (which is back ordering).

So in short there's a number of backordering opamps, some of the SMT resistors are backordering but they should be substitutable.

Rough UK prices seem to be approx GBP63 for the DAC and GBP80 per channel filter for the BOM (there's a few connectors that need adding but that rough price seems good.

I see nautibouy has gone for a tube output which is interesting.
Click to expand...
Apart from back-ordering the OPA2210D devices I'm waiting to order parts until Marcel has finalised the PCBs.

There's one filter board and one DAC board for a functioning DAC

I haven't gone for a tube output stage per se; I have Marcel's prototype build (which sounds fantastic with its op-amp filter stage) and I'm just trying a tube filter stage to see how it performs. Marcel was cautious that it might compromise the performance of the DAC so it's not a forgone conclusion. We'll see (hear!).
 
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#209
A few have asked about possible group buy costs so to get an idea I got a quote for the extant gerber files. Assuming 20 sets of unpopulated DAC and filter boards, the fabrication costs might be in the region of $10 (US) per set, plus shipping costs. Because of economy of scale factors there's no price advantage in getting fewer sets and a few spares are always useful. The numbers are just to give an idea and might change depending on design changes and when things like the required layer stack for the DAC board are factored in - please don't hold me to them!

Of course, sourcing the parts and assembly will be down to group buyers but then this is DIY Audio.
 
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#212
randytsuch said:
At that price, I can afford another set. May want to build a 2nd set with a different op amp.

Randy
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That's a total of 16 so far, and I guess we'll provide one or two set's to Marcel FOC, so 20 is a reasonable quantity at this point in time. Of course, should my estimates be overly optimistic, there will be no problem amending requirements once we actually get the GB rolling.
 
#216
Could those of you who have experience with U.FL connectors tell me if this placement is acceptable? A grid point is 0.5 mm. Looking at pictures of U.FL cables, I get the impression that you should be able to find space for the cables even though the connectors on the board are rather close, is that correct?

UFL.png
 
#217
If the U.FL placement is acceptable, then the attachments are the Gerber files and schematics for the final version.

Updates:
A. I have not placed the requested extra connectors and sockets on the filter board.
B. One extra mounting hole has been added which is aligned between the DAC and filter boards, bringing the total number of aligned holes to three.
C. I added an option to invert MUTE and DSDON by placing 0 ohm-resistors.
D. The transmission line widths are now adjusted for 0.2104 mm PR7628 prepreg, the default at Ray's favourite PCB manufacturer.
E. 0 ohm resistors that were meant for experiments have been replaced with wires and opens and the NST45011 footprints have been removed.
F. The thermal reliefs in inner layers of the DAC board have been made longer (in fact that was already the case in the previous version, but not in the prototype). Hopefully this makes soldering headers easier.
 

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#219
I want to have some sort of coaxial connector there to keep the clock well-shielded from the data. I chose U.FL because Ray (nautibuoy) wanted to have those on the raw DSD version of the valve DAC, and because they are small and needed to be added to an existing layout.

You can also not mount them, place three 0 ohm resistors to connect the inputs to an Amanero-style header and take the resulting crosstalk for granted. I know from measurements on the prototype that the connection to the source then has to be kept very short, a piece of flatcable between the circuit that drives the DAC input and the DAC will degrade the noise floor.

Would you prefer SMA or SMB over U.FL and if so, why?
 
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