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+--- Thread: ProtoDAC TDA1387 X8 project (/showthread.php?tid=5531)
RE: ProtoDAC TDA1387 X8 project - OnkelPH - 04-01-2024
Hi
Question regarding the I2S resistors;
I found a schismatic inspired by this ProtoDAC. It’s not very different, but the i2s resistors are only 24R, that’s a huge difference. I’ve also read that rule of thumb is between 22R to 47R.
https://youtu.be/RyGhTj5r3Gg?si=MpK5xX7QrC5QLsPk
RE: ProtoDAC TDA1387 X8 project - hifinet - 04-01-2024
I really don't think it matters much. I copied the values from another design (which actually used 470R). I left them at 430R so that someone could buy a bunch of resistors, all the same value, and use 430R for the I2S and the I/V resistors. Their purpose is to reduce noise on the lines from reflections. CANBUS uses 120R. I2S are voltage signals without any significant current, so there isn't a significant voltage drop. ProtoDAC will work up to 384kHz sampling with the 430R I2S resistors, so I didn't see a need to change them.
Looking at the TDA1387 datasheet page 7, the max leakage current is 10 microamps. So with a 24R I2S resistor, the maximum voltage drop is 0.24mV. With 430R it's 4.3mV. Digital 1 of 5V would be 4.99976V with 24R and 4.9957V with 430R.
RE: ProtoDAC TDA1387 X8 project - hifinet - 04-01-2024
Correction: Since there are eight chips in the module, max voltage drop with the 24R is 1.92mV and with 430R it's 34.4mV. It still doesn't really matter.
RE: ProtoDAC TDA1387 X8 project - OnkelPH - 04-02-2024
(04-01-2024, 09:57 PM)hifinet Wrote: Correction: Since there are eight chips in the module, max voltage drop with the 24R is 1.92mV and with 430R it's 34.4mV. It still doesn't really matter.
Ok, probably not, but I’ll try some other values. With an oscilloscope it could be possible to find the right value, but I don’t got one. So if anyone has one it would be interesting to see the results.
RE: ProtoDAC TDA1387 X8 project - DRONE7 - 04-02-2024
As Mark posted " It still doesn't really matter." +++
You would be better to experiment with the output cap value related to the input impedance of the following stage and once set then adjust the value of the supply electrolytic for best balance (or preference) of sound-stage, depth, and bass response.
The ProtoDac has such few (such few..is that even proper English ? so few !) components that it is easy to mix and match.
The module itself is cheap..buy several and and some perf-boards, Pi-Headers, and resistors and different value caps then play :-)
No need for ultra-uber-audiophile parts at this stage...once settled on the best match for your equipment then buy the fancy component values as found and be happy.
RE: ProtoDAC TDA1387 X8 project - OnkelPH - 04-02-2024
(04-02-2024, 05:35 AM)DRONE7 Wrote: As Mark posted " It still doesn't really matter." +++
You would be better to experiment with the output cap value related to the input impedance of the following stage and once set then adjust the value of the supply electrolytic for best balance (or preference) of sound-stage, depth, and bass response.
The ProtoDac has such few (such few..is that even proper English ? so few !) components that it is easy to mix and match.
The module itself is cheap..buy several and and some perf-boards, Pi-Headers, and resistors and different value caps then play :-)
No need for ultra-uber-audiophile parts at this stage...once settled on the best match for your equipment then buy the fancy component values as found and be happy.
Good point. Luckily I got some second hand VCap ODAM 0.47uf that seems to be a perfect match with my Decware amp (100K impedance) On the input I’ve been using one Auduio Note Kaisei 2200uf for some months.
The only place left to play with is the i2s….
RE: ProtoDAC TDA1387 X8 project - DRONE7 - 04-02-2024
"second hand VCap ODAM 0.47uf" Nice! :-)
RE: ProtoDAC TDA1387 X8 project - v12nut - 04-02-2024
(03-19-2024, 08:24 PM)hifinet Wrote: ProtoDAC can only handle 5V (5.5V max). You can use an LT1963 module to regulate down to 5V. The one problem with the LiPO is the higher ESR (internal resistance) compared to LifePO4 batteries. The LiPO don't sound as dynamic.
The Soviet K77-1 polycarbonate caps sound excellent. Just trying them now. Great value. Sound better than the used CRC 10uF 30V.
I use the LiitoKala Lii-202 .
Hi, I have just picked up a pair of those Soviet caps, do they take awhile to break in?
cheers
RE: ProtoDAC TDA1387 X8 project - Skip Pack - 04-02-2024
(04-02-2024, 10:21 AM)v12nut Wrote:(03-19-2024, 08:24 PM)hifinet Wrote: ProtoDAC can only handle 5V (5.5V max). You can use an LT1963 module to regulate down to 5V. The one problem with the LiPO is the higher ESR (internal resistance) compared to LifePO4 batteries. The LiPO don't sound as dynamic.
The Soviet K77-1 polycarbonate caps sound excellent. Just trying them now. Great value. Sound better than the used CRC 10uF 30V.
I use the LiitoKala Lii-202 .
Hi, I have just picked up a pair of those Soviet caps, do they take awhile to break in?
cheers
Longtime general Soviet cap reputation says yes. These are the first Soviet polycarbonate caps I've used. I just use MoOde's repeat play with a huge directory of album subdirectories, and the amplification chain off.
RE: ProtoDAC TDA1387 X8 project - v12nut - 04-02-2024
(04-02-2024, 02:58 PM)Skip Pack Wrote:Thanks, I suppose leaving a radio station running would do the same job?(04-02-2024, 10:21 AM)v12nut Wrote:(03-19-2024, 08:24 PM)hifinet Wrote: ProtoDAC can only handle 5V (5.5V max). You can use an LT1963 module to regulate down to 5V. The one problem with the LiPO is the higher ESR (internal resistance) compared to LifePO4 batteries. The LiPO don't sound as dynamic.
The Soviet K77-1 polycarbonate caps sound excellent. Just trying them now. Great value. Sound better than the used CRC 10uF 30V.
I use the LiitoKala Lii-202 .
Hi, I have just picked up a pair of those Soviet caps, do they take awhile to break in?
cheers
Longtime general Soviet cap reputation says yes. These are the first Soviet polycarbonate caps I've used. I just use MoOde's repeat play with a huge directory of album subdirectories, and the amplification chain off.