Ebay parallel PCM1794 DAC any good

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#4
They are cheap, and actually pretty well made. caps and opamps could stand to be replaced with genuine and high quality units.

It's also available as a "barebones" board, that lets you populate the I/V stage with your own parts, might be a better buy and less overall work. A buddy from work built one and it works well.

HiFi parallel PCM1794A decoder board DAC core board 24Bit 192kHz PCB 831230325287 | eBay

I have one, and it's a good starting point, but the chips will need to be provided and installed yourself. I have a handful of samples that I intend to use 🙂
 
#5
Hi guys,


Thanks for the information.



Regarding the bare pcbs, I've been eyeing these up but I don't have confidence in my ability to solder on the dac chip.



Any suggestions in this regard?

Would it be plausible to goo a bit of solder onto the board then put the dac chip on and give some heat from a heatgun?
 
#6
Probably to get the completed board and modify from there would be the best approach.

I see a lot of dac boards around here and there, some expensive, some cheap, that use ceramic smd parts in the output filters.
I will expect that kind of thing In devices like phones, and other consumer level stuff, is just not so welcome in dedicated hobby equipment that I like to listen to.
Gives an appearance of having been well engineered and vibration proof that way though.

Just wondering why this is acceptable now?
 
#7
As much as many hate to admit, sometimes for our applications "standard" types of parts work just fine. Ceramic type parts are fine in certain areas (bypassing opamps, psu, etc) when done right. Some ceramic stuff measures pretty well, actually... regardless of what the snake oil pandering golden-ears may have you believe. I wouldn't use them as active filter components but some do.
 
#8
I agree, when done right and tested for resonant behavior, should be fine in certain instances/small quantities. Just am surprised at the $ being spent for certain diy products that will be impossible to improve.
Maybe some of the pps parts will save the day? I wish they could find their way into some of these newer diy boards. The lower inductance is a real bonus.

The ceramic caps are pretty hissy sounding in numbers from what I have heard anyways, whether that’s good or not idk. So audiophile or military radar or whatever, I guess I just prefer quiet parts.

Anyways, I agree that on this board, that there needs to be a lot more bulk capacitance close to the op amps, and it may be possible to add some 22uf under the board, onto the existing film caps(?)
 
#9
C0G and NPO ceramics are very good. They just don't make them in large values because they would be physically too large. When you can find them in needed values, they are very suitable for filters and for use in the analog sound path. They are the types of caps people use to make -160dB distortion audio filters. No reason not to use them. They also happen to be good up to pretty high frequencies if it matters for a particular application.

However, one shouldn't get the above caps confused with high k ceramics such as X7R, Z5U, or any other similar types we typically use for bypassing power rails. Those are not appropriate for use in the audio signal path or in filters.

As a sometimes closely related matter, it may also be useful to know that film caps are not suitable for all the purposes people sometimes want to use them for. They typically don't act like very good capacitors above 100kHz or so (or maybe a few hundred kHz for smaller ones), certainly far too low to bypass power rails for an opamp with a gain-bandwidth product of 55MHz. Far better to do as the manufacturer suggests and use 10uf tantalum in parallel with .1uf ceramic in order to help prevent very high frequency oscillations. With those in place right at IC power pins, film caps could be added in parallel nearby if they are found to improve PSRR in the audio band or something like that.
 
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#16
I'd not recommend these boards. The analog portion is not well layed out and opamps are oscillating(?) running extremely hot. Tested with various low-high grade opamp derivatives. You might use the board with passive I/V the like as DDDAC1794 but I've not gone this route.
 
#17
weissi said:
I'd not recommend these boards. The analog portion is not well layed out and opamps are oscillating(?) running extremely hot. Tested with various low-high grade opamp derivatives. You might use the board with passive I/V the like as DDDAC1794 but I've not gone this route.
Click to expand...

You mean the pictured (attached image) board is not recommended? And that one is oscillating? (Even after the X5R caps were added on the bottom side?)

Did you ever solve the oscillation problem or did you have to scrap it?
 

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#19
weissi said:
I'd not recommend these boards. The analog portion is not well layed out and opamps are oscillating(?) running extremely hot. Tested with various low-high grade opamp derivatives. You might use the board with passive I/V the like as DDDAC1794 but I've not gone this route.
Click to expand...

Ok. But was that board (that I pictured) actually oscillating? Or were you referring to a different board?
 
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