I've been inspired by watching Gabster's YouTube videos using IanCanada designs and have quite a few parts to play with.
1. I see people replacing the ProtoDAC output coupling capacitors, but with values different than the recommendation of 10uF. Is that a concern?
2. Gabster seems to ultimately recommend running the ProtoDAC completely separated from the GPIO stack, using U.FL connections to a FifoPi Q7 instead. He corrects himself during a video about the pin order. My interpretation of his video: R1 WS / R3 DATA / R2 BCK / I toned the closest U7 connection to R2 to GND (U7 on my ProtoDAC PCB, R4 on github).
The github manual shows an order of Pin 1 WS (LRCK) / Pin 2 BCK / Pin 3 DATA / Pin 5 GND
Has anyone here tried direct U.FL, and which pins are correct for BCK and for DATA?
3. I'm also toying with the idea of using an I/V STD MkII standard OPA for Op-Amp Rolling. Has anyone tried stacking that with a ProtoDAC?
tyia
1. I see people replacing the ProtoDAC output coupling capacitors, but with values different than the recommendation of 10uF. Is that a concern?
2. Gabster seems to ultimately recommend running the ProtoDAC completely separated from the GPIO stack, using U.FL connections to a FifoPi Q7 instead. He corrects himself during a video about the pin order. My interpretation of his video: R1 WS / R3 DATA / R2 BCK / I toned the closest U7 connection to R2 to GND (U7 on my ProtoDAC PCB, R4 on github).
The github manual shows an order of Pin 1 WS (LRCK) / Pin 2 BCK / Pin 3 DATA / Pin 5 GND
Has anyone here tried direct U.FL, and which pins are correct for BCK and for DATA?
3. I'm also toying with the idea of using an I/V STD MkII standard OPA for Op-Amp Rolling. Has anyone tried stacking that with a ProtoDAC?
tyia
I’ve got caps of 5.6uF on one and 3.2uF on another, both work fine, but I’ve no preamp with a potentiometer less than 25K, and I’m not using it as a HAT.
The ProtoDAC build guide talks abut cap values.
The ProtoDAC build guide talks abut cap values.
Hi @soundsgood2me ,
Just wondering exactly what parts, modules, power supplies, clocks, etc., you are planning to use for your protodac project? (I don't watch gabster videos so I don't know what he suggests.)
Also, just curious what that stuff adds up to cost-wise?
Not planning to build a protodac myself, but do have a couple of TDA1387 dacs here which sound pretty decent given their low-ish cost. Also, I found it helped to improve the power supply to make it lower impedance as seen by the dac chip.
Thx,
Mark
Just wondering exactly what parts, modules, power supplies, clocks, etc., you are planning to use for your protodac project? (I don't watch gabster videos so I don't know what he suggests.)
Also, just curious what that stuff adds up to cost-wise?
Not planning to build a protodac myself, but do have a couple of TDA1387 dacs here which sound pretty decent given their low-ish cost. Also, I found it helped to improve the power supply to make it lower impedance as seen by the dac chip.
Thx,
Mark
Hi @Markw4,
I went a little overboard buying things, but here's my shopping list:
Core
(stack bottom to top)
#48B PurePi II 5V+3.3V ultracapacitor/LifePO4 battery power supply combo $97.00
#2G 2x 1800mAH 3.2V 18650 LifePO4 battery cell $15.00
Raspberry Pi 3B+ (kit) $100?
#1D FifoPi Q7II Flagship I2S/DSD/DoP FIFO with isolator, re-clocker and ultra-low-phase noise XOs × 1 $199.00
#49B MonitorPi Pro Integrated control center and signal analyzer × 1 $76.00
2x ProtoDAC kits $118.00 (just need one)
Raspberry Pi stack parts & pieces, copper sheet to make RF shield, low jitter power supply approx $160
SD card reader (writer) $12?
subtotal $718
Extras
Replacement capacitors approx $65 (bought 2 each x three different manufacturers)
#80B SC-Pure Extremely-low Phase Noise Audio Clock × 1 49.1520MHz $179.00
#80A SC-Pure Extremely-low Phase Noise Audio Clock × 1 45.1584MHz $179.00
#50A Universal RaspberryPi GPIO extension KIT, with 6" & 12" FFC cables × 1 $29.00
#4B ES9038Q2M Dual Mono II DAC HAT × 1 $105.00
#6A I/V STD MkII standard OPA I/V stage × 1 $39.30
#14 3 x 6” double-ended silver plated U.FL coaxial cable $12.00
Mad scientist budget all in $1,412
Would it be bad form to post YouTube links here? If so I can dm you directly. lmk
Always open to suggestions/ideas.
I went a little overboard buying things, but here's my shopping list:
Core
(stack bottom to top)
#48B PurePi II 5V+3.3V ultracapacitor/LifePO4 battery power supply combo $97.00
#2G 2x 1800mAH 3.2V 18650 LifePO4 battery cell $15.00
Raspberry Pi 3B+ (kit) $100?
#1D FifoPi Q7II Flagship I2S/DSD/DoP FIFO with isolator, re-clocker and ultra-low-phase noise XOs × 1 $199.00
#49B MonitorPi Pro Integrated control center and signal analyzer × 1 $76.00
2x ProtoDAC kits $118.00 (just need one)
Raspberry Pi stack parts & pieces, copper sheet to make RF shield, low jitter power supply approx $160
SD card reader (writer) $12?
subtotal $718
Extras
Replacement capacitors approx $65 (bought 2 each x three different manufacturers)
#80B SC-Pure Extremely-low Phase Noise Audio Clock × 1 49.1520MHz $179.00
#80A SC-Pure Extremely-low Phase Noise Audio Clock × 1 45.1584MHz $179.00
#50A Universal RaspberryPi GPIO extension KIT, with 6" & 12" FFC cables × 1 $29.00
#4B ES9038Q2M Dual Mono II DAC HAT × 1 $105.00
#6A I/V STD MkII standard OPA I/V stage × 1 $39.30
#14 3 x 6” double-ended silver plated U.FL coaxial cable $12.00
Mad scientist budget all in $1,412
Would it be bad form to post YouTube links here? If so I can dm you directly. lmk
Always open to suggestions/ideas.
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Not that I know of. Just try to keep it organized, I would suggest. Most people might not want to watch every video, but they might watch some subset if they know what the focus of each video is.
In regard to the shopping list, I like the SC Pure clocks as a 2nd best option for the dacs I like to use. I would certainly take them any day over Crystek or similar. IME they do need almost a week of continuous, around-the-clock operation to settle into their final sound.
However, if you knew how to solder small, fine-pitch surface mount devices then I might recommend a different approach to dac building for likely a little less cost. That said, if mostly plugging things together is where you are at in the present stage of your hobby then the Protodac could turn out to give a pretty satisfying result.
Regarding the FIFO_Pi, I have a fellow forum member I have been helping with a dac project in which he is using a older (I think) FIFO_Pi. He said he liked Crystek clocks more than SC Pure, so I suspected something was wrong somewhere. I think he is probably going to move the clocks off of FIFO_Pi and send copies of the clock output signals to FIFO_Pi from another board that is dedicated just for clocks. Also, I think he is using a modified version of my reclocker board just before his dac, which he said made the sound better once he switched to running it from a cleaner external power supply (not surprising since power supplies can make a real difference). Just some general information that may be of interest at some later point.
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I'm at the plugging and soldering stage of my hobby, willing to experiment. 🙂
The ProtoDAC kit does require some fine soldering for which I'm equipped, but I haven't done any surface mount components yet like resistors, LEDs or U.FL connectors.
Here are the reference videos with some brief notes:
Jul 14, 2023
ProtoDac Amazing HIFI Audio DAC HAT using eight parallel vintage Philips TDA1387 chips.
Aug 6, 2023
Protodac How to Make a $250 DIY HiFi DAC with amazing sound (Gabster Mini I/P)
- Grounded RF shield for Raspberry Pi using Altoids Spearmint lid - I'm may use Wintergreen for a "cooler" sound 🙂 or copper sheet metal
- clock options, clock rolling
Apr 26, 2024
Protodac sound Comparison and how to add a Fifo Q7 / PurePi from IanCanada
- multiple configurations, price points
- switch I2S from GPIO to U.FL wiring
- RF shield above both Raspberry Pi and FifoPi Q7
Its good that there is realization there should be some shielding between the dac board and digital boards lower in the stack that emit radiated EMI/RFI noise.
Regarding the dac itself, is this the version with digital isolators or without?
Also, we have a forum member here who has been building TDA1387 dac projects for a long time. @abraxalito has also developed fairly sophisticated output filters for that type of dac, which I would expect could improve SQ over not using any filtering. Maybe he would be willing to chime in and say a few words about that.
On the subject of soldering skills, to build the type of projects I would recommend would require being able to solder what may be referred to fine pitch, such as an FPGA chip with 144 or so pins, with each pin centered at .5mm from adjacent pins. It can be done by hand but learning how, getting the right equipment, and practicing enough would be needed before undertaking a real project of that type. An example project might be the one at: https://www.diyaudio.com/community/threads/simple-dsd-modulator-for-dsc2.370177/
Regarding the dac itself, is this the version with digital isolators or without?
Also, we have a forum member here who has been building TDA1387 dac projects for a long time. @abraxalito has also developed fairly sophisticated output filters for that type of dac, which I would expect could improve SQ over not using any filtering. Maybe he would be willing to chime in and say a few words about that.
On the subject of soldering skills, to build the type of projects I would recommend would require being able to solder what may be referred to fine pitch, such as an FPGA chip with 144 or so pins, with each pin centered at .5mm from adjacent pins. It can be done by hand but learning how, getting the right equipment, and practicing enough would be needed before undertaking a real project of that type. An example project might be the one at: https://www.diyaudio.com/community/threads/simple-dsd-modulator-for-dsc2.370177/
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Hi Mark,
How could I determine that? I don't see any mention on https://moodeaudio.org/ > ProtoDAC or the project github: https://github.com/moode-player/protodac/blob/main/docs/protodac_tda1387_x8.md
tyia
It would show up on the schematic, which it does not on the schematic you posted.
If capacitors are on a power pin of an IC and if they are approximately in the range of .1uf to .01uf then they are virtually always bypass caps.
The problem with the analog outputs on the schematic you posted is that there will be stair-step distortion on output signals that are supposed to be smoother, such as a sine wave.
As shown below, if the original analog signal is smooth like the "sampled signal" part of the pic below, then what comes out of the dac can look like the square stair-step signal as shown in the "reconstructed signal" part of the pic below, as it comes out of a dac. What an output filter is supposed to do is make the reconstructed dac output look like the original sampled signal (the red line in the reconstructed signal part of the pic below.
For reasons not really explained some people claim a dac can sound better with the output star-steps left unfiltered. In that case I would suspect the dac and or the rest of the system has serious problems that are not being addressed. Extra distortion like that can be used to cut through otherwise muddy sound from bad amplifiers, bad speakers and crossovers, bad listening room, bad input signals to the dac, and or bad dac board layout or bad dac board power supply and or bad dac output filter design.
Also, in some cases some dac architectures may sound subjectively best at a particular sample rate.
There is also an effect called "NOS droop" to consider: https://www.diyaudio.com/archive/blogs/abraxalito/862-flattening-nos-droop.html
As shown below, if the original analog signal is smooth like the "sampled signal" part of the pic below, then what comes out of the dac can look like the square stair-step signal as shown in the "reconstructed signal" part of the pic below, as it comes out of a dac. What an output filter is supposed to do is make the reconstructed dac output look like the original sampled signal (the red line in the reconstructed signal part of the pic below.
For reasons not really explained some people claim a dac can sound better with the output star-steps left unfiltered. In that case I would suspect the dac and or the rest of the system has serious problems that are not being addressed. Extra distortion like that can be used to cut through otherwise muddy sound from bad amplifiers, bad speakers and crossovers, bad listening room, bad input signals to the dac, and or bad dac board layout or bad dac board power supply and or bad dac output filter design.
Also, in some cases some dac architectures may sound subjectively best at a particular sample rate.
There is also an effect called "NOS droop" to consider: https://www.diyaudio.com/archive/blogs/abraxalito/862-flattening-nos-droop.html
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