Electronics > Projects, Designs, and Technical Stuff
Headphones DAC
SiliconWizard:
--- Quote from: Kasper on December 11, 2019, 10:59:26 pm ---aside from spending a few extra bucks and potentially looking like audiophool, are there other downsides to going with 32-bit?
--- End quote ---
Well, aside from probably not being useful, one of the downsides, if you take a look at datasheets, is that affordable 32-bit DACs (eg: PCM1795) have actually worse specs than the good 24-bit ones (eg: PCM1794A) for similar prices. And as I mentioned, better 32-bit DACs are pretty expensive.
Another point related to what Bud asked you: what will be the typical sources? Most common input sources do not support 32-bit anyway, so you'd be using a 32-bit DAC with only 24-bit (at best) samples, with again usually worse specs. What would be the gain? ???
As to be future-proof, I dunno. No one can predict the future, but I kind of doubt 32-bit is going to be standard any time soon. One reason is that we're getting very close to what's reasonable on a physical level here when it comes to audio. You'll probably have ample time to make a rev. 2 of your device if you ever see signs that it's going to happen.
One reason to use a 32-bit DAC would be to avoid having to reduce quantization if your input source is natively 32-bit - because no matter how good the reduction is done (with proper dithering), it's never going to be as good as the original. But as I said, I don't know of any source currently that is *natively* 32-bit, at least from the standard ones.
Anyway as I said, if you do things really really right, you may be able to get something like 110/120dB SNR with a *good* 24-bit DAC, but only up to its output stage. The power amp stage - that's another story, and something you should definitely work on to get any benefit from using a DAC with better than 100dB SNR (or even 90dB...!)
--- Quote from: Kasper on December 11, 2019, 10:59:26 pm ---Can you recommend any good resources for learning more about layout practices for good SNR?
--- End quote ---
Hmm not really, but I'm sure some other people here can point you to some books or something.
--- Quote from: Kasper on December 11, 2019, 10:59:26 pm ---I've been learning about EMC lately and seeing conflicting advice from EMC people saying never separate ground planes even when datasheets recommend separating analog and digital.
--- End quote ---
Ah yeah. What I can tell you is that most often the better way is to simply use a single solid ground plane and NOT split ground planes. The latter should be used sparingly, only for very specific cases, rarely when there is high speed digital stuff involved (which is the case with DACs). Just don't do it here. But you should definitely route your signals so there is minimal crosstalk between the analog and digital ones.
hamster_nz:
I'm quite interested in hearing about what you do. I've been playing around with line-level 24-bit I2S ADCs and DACs lately, but without any serious aims in mind.
Sadly I lack the T+M gear needed to do most useful measurements of the performance difference that PCB layout and component selection offer...
magic:
I don't want to be a demotivational ass, or maybe don't want you to know that I am an ass, or whatever, but...
The DAC/amp market is a thing, and there is plenty of stuff already there. From single-chip junk I mentioned before, which starts at $1 apiece, through all the FiiOs, Dragonflies and Schiits, up to the ludicrously "high end" with 768kHz sampling at 32bits or special snowflake DACs made of discrete resistors matched by nude virgins or FPGAs running custom delta-sigma modulators.
There is surely no hope for one chip solution, because the Chinese would already be selling reference boards of that chip on Ali and you would stand no chance against them. And for many chip solution, you really need to go to places like head-fi or ASR and get some idea of what's out there and come up with good reasons why anyone would buy yet another DAC/amp instead of something already out there. Some of which is "cheap enough I might buy it for shit and giggles", some of which is "good enough for audio per NwAvGuy", some of which is "higher spec than the competition" - all is covered.
edit
Maybe you should just figure out a way of mounting the Khadas Tone Board inside the JDS Atom, or whatever are the latest cheap and well-measuring toys that guys over at ASR are going crazy about :P
Oh, and I forgot. Make sure you have an idea how to power that gadget (USB 2.0 gives you only 2.5W, not really enough for 10WPC class A into 4Ω :P) and I hope you know what jitter is because you will be asked about it whether you know or not.
Kasper:
SiliconWizard:
Thank you for the info. I will keep it in mind as I continue my search.
hamster_nz:
that is a nice looking board, thank you for sharing. I too lack T+M gear, aside from the EEVBLOG fan package: ds1054z and a 121GW DMM. I think I'll try to send a beta unit to someone with good gear to write up specs for me.
magic:
I appreciate the feedback. If you really wanna be an ass you should use fallacies instead of details ;) All I see there is a well laid out descripion of warnings I should consider and directions to where I can find more info and I appreciate all of that. I understand the audio market has a ton of competition (and consumers). Normally I avoid that type of stuff and focus on unique products because I can't compete with big players except for my very low cost of R&D. But in this case I think I have a unique idea. I tried buying the product I want but could not find it so now I am trying to fill this void. I understand if it does well I'll probably get copied and squashed by much bigger players but that seems to be the case with everything and maybe less so in audio. Really not sure about this part but it seems there is some appreciation for high end products from small companies in audio.
David Hess:
I would use separate ICs for reasons given earlier and because it gives more flexibility to produce a good circuit layout. And there are many good audio operational amplifiers suitable for driving headphones directly now if you want to keep things simple.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version