lingDAC - cost effective RBCD multibit DAC design

@Luke - Rdc only matters in the hypothetical case that the DAC output current is converted into voltage on the primary. Since that clearly doesn't happen, its not really important. Where did you get your estimate for the primary impedance? 800mH gives j100k @20kHz but none of my primaries are anywhere near that.
 
Hi Abraxalito, I read one of your posts in this thread that said your primary inductance is 800mH, that explains it I got old data:)

It wasn't old in fact very up to date. But I was talking about the secondary when I mentioned the figure of 800mH. With GrossDAC I'm using passive I/V so that calls for much higher inductances, up to 250H or so. The primary inductances are in the range of a few mH but these don't determine the voltage on the DAC's output as the L is shunted by the resistor on the secondary (typically 5-10k with passive I/V).
 
BOM and schematic for PhiDAC SE

It's been a while but finally here are two documents relating to PhiDAC SE (that's the version which drives some headphones direct) - the schematic and the BOM.

PhiDAC SE consists of 4 PCBs in total - the main board plus 3 'pants' boards which each hold 8 low ESR capacitors and are wired beneath the PCB on thick wire 'legs'.
 

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It's been a while but finally here are two documents relating to PhiDAC SE (that's the version which drives some headphones direct) - the schematic and the BOM.

PhiDAC SE consists of 4 PCBs in total - the main board plus 3 'pants' boards which each hold 8 low ESR capacitors and are wired beneath the PCB on thick wire 'legs'.
Ooooooooooooooooooooooooooohhhhhhhhhhh .... you lil' tease, you!!!
But I'm a bit too backed up to read or build at the moment.
How about some free samples?
I give fair reviews. Promise, toots ;)
 
Review of the Phidac.


matt_garman kindly sent a kit and I must admit, this was my first smd soldering, aside from opamps. Gnat butts and sugar ants. As a noob smd solderer this took the better part of a day and a half.



All the parts were supplied including electrolytic caps. I first put it together with the provided caps (except on the output, which I just could not bring myself to put bad caps there) and gave it a listen.



Years ago I spent some time building cmoy headphone amps because they are so simple and fun. What is best about cmoys is that they teach you to hear each component that goes into them, simply because there are so few components. This is especially true for capacitors. This is why I cannot love Panasonic FM, because they actually have a brittle top end that is fatiguing. SEPF polymer caps are dull with weak bass. Other caps can have sonic holes in the spectrum. etc..


So listening to the phidac with the given caps, it is obvious that the frequency range has dead spots and other problems in it. Out with the old caps and in with quality audio caps.
My favorite combo is Elna Silmics and Nichicon Muse. Those two married together produce a beautiful, clear and rich sound.



After replacing all caps and giving it a listen, it is astonishing! This phidac is absolutely addicting in its presentation. Incredible separation and isolation of each instrument. Great decay on sounds like Markw4 noticed. It almost sounds like a bit of reverb but its not. It does present a real depth to the sound. The detail is better than my es9018 and also shows the 9018 to have a more 2d presentation that has a plastic sheen to it. The details are also less harsh than with the 9018. This betters the 9018 in every way.

Another nice difference from the 9018 which always has an "edge" to sharp sounds is that the phidac can do edge and also do soft.



Abraxalito, you said you are using capacitor banks to try to fix shortcomings in the higher frequencies. (evident in choral works) I think this is just chasing bad sounding capacitors with more capacitance.

The supplied caps are in the 1500uf range and I am using 2x 470uf instead in the given positions. If anything I am wondering if this might be too much. There is a sweet spot for capacitance where too much is also not better. I want to try going as low as 100uf and see if that still works. However, the dac sounds so good right now, my motivation to mess with it any more is pretty low. The bass is deeper, fuller and more textured and the highs more sweetly presented than with the es9018. Intimate voices are spectacular and present in a way that you can place them at the exact distance from you. Every genre of music is played with authority and clarity and stunning 3d, including choral works. (currently listening to Bach, Mass in B minor, nothing confused or muddy about it).
I am feeding the signal to my dc coupled headphone amp and listening on Sennheiser 650.



To everyone who has a phidac, put some good caps in there. Try the Silmic and Muse combo with the bipolar muse on the output. This dac is better than any other I have heard under $300.



So, to sum up, this is my first experience with a NOS dac and I am sold. If this little, inexpensive diy dac sounds this good compared to my other SD dacs then I have caught the NOS bug.