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lingDAC - cost effective RBCD multibit DAC design
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Old 16th February 2019, 02:27 AM   #271
wintermute is offline wintermute  Australia
just another
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lingDAC - cost effective RBCD multibit DAC design
post deleted. Hollowman if you don't have something constructive to say then best to say nothing at all.
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Old 16th February 2019, 03:08 AM   #272
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post deleted. Hollowman if you don't have something constructive to say then best to say nothing at all.
Thank you. Pretty irritating, to be sure.
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Old 21st February 2019, 01:24 AM   #273
abraxalito is offline abraxalito  United Kingdom
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Default Progress update

Still working on completing the Mouser BOM. The extra time taken to do this is down to the fact that one of the critical components (the multilayer chip inductors) don't have the same characteristics when sourced from Taobao compared to when sourced from Mouser. How do I know this? I just received an order of similar inductors from Mouser and electrically they're different.

TDK's datasheet says that the typical ESR of its 27uH inductors is 0.5ohm but from measurements I determined that those from Taobao (more than one source) read 0.8ohm typically. Meaning the Q is significantly lower. Not beyond the datasheet maximum though, which is 1ohm.

The inductors (33uH) which recently arrived from Mouser show a typical ESR about 0.6ohm (better Q than Taobao sourced ones) however their measured inductances are all over the place, well beyond the 10% tolerance for the part (MLF2012C330KT000). This makes me wonder whether Mouser sent me the 20% parts (which are cheaper) in place of those I actually ordered (and paid for).

I chose 33uH over 27uH for the Mouser inductors as there's a chance to save a few cents - since they're all in series in the filter we need fewer Ls if we use a higher value. When I tried sourcing 33uH on Taobao I found worse Q than the 27uHs.

The upshot of all this is - I'm building a sample PhiDAC with the Mouser parts to see if the performance is close enough to the DACs I've characterized with Taobao parts. The BOM's going to be slightly different between the two to accommodate the different characteristics of the inductors.

Kits of the Taobao parts are coming together, likely be wrapped up by the end of this week. Those who indicated an interest do please let me know your shipment details by PM in the next couple of days and I'll respond with payment info. For those who've not yet indicated an interest there are a couple of kit sets spare - first come, first served.
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Old 21st February 2019, 09:34 AM   #274
eljoantonyn is offline eljoantonyn  India
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Offtopic:


How do you compare the possible SQ vs the cheap WM8740 and ES9038 DACs ?
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Old 21st February 2019, 10:22 AM   #275
abraxalito is offline abraxalito  United Kingdom
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I've not done a side-by-side comparison with a WM8740 but I've modded one or two based on that chip and found, even after modding they couldn't compete with earlier incarnations of my TDA1387 designs. In particular the HF was 'mushy' (a common characteristic I've found of S-D DACs) and the bass lacked dynamics. Modding them helped, most obviously with the bass but I couldn't find a mod to fix the HF.

As for ES9038 I've not heard a board using that chip yet but I do hope to get a comparison from a local DIYA member who is in possession of both a 'Khadas' (ES9038 based, $99) and a v0 edition of PhiDAC. Stay tuned and he might be persuaded to post some subjective comments up when he's had a listen.
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Old 21st February 2019, 10:37 AM   #276
eljoantonyn is offline eljoantonyn  India
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Ok, That would be cool !
That Khadas DAC is all the rage at audiosciencereview forum !
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Old 21st February 2019, 10:44 AM   #277
zgtc is offline zgtc  Europe
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Quote:
Originally Posted by abraxalito View Post
I've not done a side-by-side comparison with a WM8740 but I've modded one or two based on that chip and found, even after modding they couldn't compete with earlier incarnations of my TDA1387 designs. In particular the HF was 'mushy' (a common characteristic I've found of S-D DACs) and the bass lacked dynamics. Modding them helped, most obviously with the bass but I couldn't find a mod to fix the HF.
WM8740 is voltage out, to start with, so comparisons here are impossible because all the I/V and filters is done inside the chip, no way to change that, AFAIK. I have a CD player with that chip I'd probably/eventually like to mod or use as an external DAC, so if what I said is wrong please let me know, I might be interested in ways to mod the WM8740. TY
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Old 21st February 2019, 10:58 AM   #278
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What makes comparisons impossible when the DAC chip's got a different mode of output? Even though ICs have differing architectures, all DACs end up putting out of the box voltage (2VRMS is the standard).
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Old 21st February 2019, 11:08 AM   #279
zgtc is offline zgtc  Europe
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What makes comparisons impossible when the DAC chip's got a different mode of output? Even though ICs have differing architectures, all DACs end up putting out of the box voltage (2VRMS is the standard).
Yes yes, that's true. But what I mean is that if you compare Iout DACs you can have the same I/V, filters, etc to compare "the DACs". Obviously you can use different I/V and filters in each and compare the end sound, which is actually what we're interested in. Sorry for the confusion.
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Old 21st February 2019, 11:17 AM   #280
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Not all Iout DACs have the same max output current or the same output impedance or output compliance range. Also they vary by whether they give out a bipolar current or are unipolar. So there are quite a few reasons why direct comparisons between Iout chips aren't likely to be possible.
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