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lingDAC - cost effective RBCD multibit DAC design
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Old 5th September 2018, 11:12 AM   #111
koldby is offline koldby  Denmark
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Quote:
Originally Posted by Alexandre View Post
Interesting.

About transformers: they can slightly soften the sound in a way that is similar to analog tape (which is a pretty much a transformer isnīt it?). So it isnīt the last word in resolution, but to my sensitive ears they are the ticket as of lately. And the low pass function is useful.

I am curious about the differences between your I/V (with current mirror) and the more typical ones which usually have a CCS at the top. Did you try any other IVs?

I have seen the mirror before, in Eric Juanedaīs schematics for example.

Thanks,
Alex
I like current mirrors, they are pretty easy get to perform well.
Current mirrors are used very often in power amplifiers at the bottom of the VAS stage (goldmund as example). The trick in the I/V stage is it acts a little like a cascode, in reducing the Miller effect in the input transistor (not that important in a common base circuit) and the voltage gain is performed by the second transistor in the mirror, depending on the impedance it looks into.

I have tried a lot of opamp based I/V and passive solutions with high gain stages after. The 1543 IMHO sounds better with minimal voltage swing at the output of the DAC chip.
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Old 5th September 2018, 04:44 PM   #112
Alexandre is offline Alexandre
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Originally Posted by koldby View Post
I have tried a lot of opamp based I/V and passive solutions with high gain stages after. The 1543 IMHO sounds better with minimal voltage swing at the output of the DAC chip.
Thanks for explaining. I have tried a few different IVs myself, but didnīt try the current mirror yet.

My preference depends on what Iīm listening to! Some things work very well with passive I/V. It is a sort of distortion that can "disappear", you hear it at first (it thickens the sound a bit; 2nd harmonic I suppose) but then forget about it and I can definitely enjoy the sound this way.

I would agree that active I/V with minimal voltage swing at the DAC sounds cleaner. More definition too. It can sound thin depending on what Iīm listening to. My amp and speakers are fairly clean sounding.

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Alex
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Old 5th September 2018, 10:01 PM   #113
koldby is offline koldby  Denmark
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Originally Posted by Alexandre View Post
Thanks for explaining. I have tried a few different IVs myself, but didnīt try the current mirror yet.

My preference depends on what Iīm listening to! Some things work very well with passive I/V. It is a sort of distortion that can "disappear", you hear it at first (it thickens the sound a bit; 2nd harmonic I suppose) but then forget about it and I can definitely enjoy the sound this way.

I would agree that active I/V with minimal voltage swing at the DAC sounds cleaner. More definition too. It can sound thin depending on what Iīm listening to. My amp and speakers are fairly clean sounding.

Thanks
Alex
This is becoming a bit OT. You got PM with my mail adress.
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Old 5th September 2018, 11:35 PM   #114
Alexandre is offline Alexandre
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I donīt think itīs off topic, but in any case. BTW what I wrote below is about Abraxalito (Richard) and the interesting I/V he presented here for the tda1387.

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Richard recently used something similar, but his circuit (Richardīs) is unique in that the filtering takes place before the active stage.
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Old 9th November 2018, 08:13 AM   #115
nlgbo1 is offline nlgbo1  United Kingdom
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I was just wondering what to do with some spare TDA1387 chips, and stumbled across this

Is there a parts list/BoM available?
Also, are there any recommendations for the power supply?

Thanks,
geoff.
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Old 9th November 2018, 08:29 AM   #116
abraxalito is offline abraxalito  United Kingdom
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Ha, welcome to the thread and thanks for the bump. BOMs are just awaiting final revisions with last-minute circuit changes, I'll endeavour to put them up before the weekend's out as I have a little unexpected free time

For the power supply I do have a 5*5 PCB with just one error on the gerbers. This is using an array of LM2662s as voltage doublers to create the rails necessary for the 3 boards from a single 5V supply at 250mA. I will go on a hunt for its schematic, the BOM will take a little bit longer.
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Old 9th November 2018, 08:42 AM   #117
nlgbo1 is offline nlgbo1  United Kingdom
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Thanks abraxalito .
I'll order the pcbs in the meantime, as that always takes a while.
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Old 9th November 2018, 01:41 PM   #118
abraxalito is offline abraxalito  United Kingdom
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Default BOMs for lingDAC 3 PCB set (not including PSU)

Thanks to @bartb for doing sterling work on getting parts, quantities, codes etc. correct. Any mistakes though are down to me
Attached Files
File Type: zip BOMx3Nov9.zip (19.2 KB, 14 views)
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Old 9th November 2018, 05:31 PM   #119
nlgbo1 is offline nlgbo1  United Kingdom
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Thanks, the list works fine with Digikey, some parts are out of stock though, so will look for some alternatives.
Dumb question, what is the difference between a TDA1387 and TDA1387T ?


geoff.
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Old 10th November 2018, 12:50 AM   #120
abraxalito is offline abraxalito  United Kingdom
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There isn't any difference. The -T suffix indicates the package style(SO-8), for TDA1387 there's only one choice available but for various other chips in the Philips family they have options like DIL8 or SO-16W.

Which parts did you find OOS?
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