ProtoDAC TDA1387 X8 project

[hifinet]

An anecdote to pass along regarding C3/C4 caps. A DIYer emailed me that he had just built a ProtoDAC with parts he sourced himself. He was disappointed with the sound quality, "doesn't seem much better than my old Justboom dac-hat". Should he get a reclocker?

He used two 2200uF Panasonic for C3/C4. The C3 and C4 caps are in parallel, and the total capacitance is 4400uF, which is too high. I recommended removing one of them, which would get the capacitance close to the target of 2000uF. Response: "Fantastic, more bass and a deeper soundstage."

There is a sweet spot for the C3/C4 capacitance based on the I/V resistor (lower the I/V resistance the higher the C3/C4 capacitance). If the C3/C4 capacitance is too high, the soundstage gets thin (lacks depth, becomes flat, etc.).

I also recommended that he try a lower capacitance coupling capacitor, down to 4.7uF (he was using a 10uF PP). In my experience, the Jantzen 10uF Standard Z tends to smear a bit. A lower value capacitor can tighten up the image. The high pass frequency cutoff is 3.386 Hz with the 4.7uF and 1.59Hz with the 10uF, so that isn't much of a factor.

[michaelagiles]

So I'm new to the CamillaDSP and other signal processing part of moode, does it effect all playback? will the polarity inversion effect Airplay and Spotify also? I just want to make sure the polarity is correct, but honestly I'm not really sure if my system has anything else inverting.

Is there a good way to test this at the speakers?

Polarity inversion will affect all playback. Polarity inversion can also be done in MPD.

Most equipment does not invert polarity. If it does, it should be stated in the manual.

The only way to know is to display the input and output on an oscilloscope. Or the input could be mixed with the output in a mixer. If the output of a stage is inverting, the sum of the input and output will be zero (complete cancellation if the amplitudes are the same).

When the polarity is correct, the sound quality is better in comparison to inverted.

My experience is that the "inverted" setting is generally for SQ. However there seem to be certain recordings that benefit from "normal" polarity! I think(assume?) that it is a matter of either lack of care or ignorance or some post processing that ended up "inverting" the polarity on the recording. It often presents as the record "just not sounding right". Often, the difference is subtle but sometimes it makes an unlistenable record bearable.
Or maybe its all in my head! But thats where the listening happens anyway.
Enjoy the music!
MG

[Gaspar74]

HI, So I decided to dress up the Protodac some. I picked up a case for it, and installed the Pi which is  a PI2 inside and then i placed the Dac Hat seperately and connected it via the GPIO pins needed. The case is a Mini Thin ITX fanless case all aluminum. I had to come up with a back plate as the one it cae with wasnt going to work out. I modified a back panel from another projects and wired up some gold plated RCA's and ran shielded wire from inderneaqth the Protodac board to each RCA. The RCA that were originally were not coming off without a fight and seeing how many times Ive had to solder resolder things on the board I didint wanna temp fate. For power I added a DC barrel jacl and then on insde stripped down Micro USb cable and wired it that way, I may change that. Im powering it with a Linear power supply. Today I fired it all up and after a few tweaks she sounds fabulous. I plan on integrating the power on off on front case but for now its not wired.




https://i.imgur.com/JmbnCap.jpg

[Gaspar74]

[hifinet]

Very nice looking case. It fits in with the rest of your gear.

[Gaspar74]

Very nice looking case. It fits in with the rest of your gear.

THank you, yes that was by Design. Top shelf is Tube Dac/ Premap I modified Xiang Sheng using Sparkos OP AMps and NOS GE 5670 or Soviet era tube depending and running at as a preamp at moment. Has two RCA outs variable and fixed as well as 2 Analog inputs. Then I have the XTZ Edge A2-300 based on Icepower modules CLass D @300 w and on top of the Amp is the beloved Protodac. Runing through some Quad 77-11L speakers and a few others depending on mood lol.

[Gaspar74]

Huuuuge Thank you to @hifinet for ALWAYS responding to my MANY inquiries both during the build and after. His valuable feedback was above and beyond what I expected. Truly a valuable resource to this forum. TY again.

[Ludomaniac]

Good evening great people

Has anyone tried to make an 'all-out' ProtoDAC with the best components available? And if so, which components did you choose?

[Tim Curtis]

Good evening great people

Has anyone tried to make an 'all-out' ProtoDAC with the best components available? And if so, which components did you choose?

Have you built and listened to a PtotoDAC yet?

[DRONE7]

Good evening great people

Has anyone tried to make an 'all-out' ProtoDAC with the best components available? And if so, which components did you choose?

Have you built and listened to a PtotoDAC yet?

My Potato dac