ProtoDAC TDA1387 X8 project

[OnkelPH]

Since the LM317 are cheap and easy to get a fixed 5v, that’s the first I’ll try. I also have a second one that I’m going to try, jung super power design I found on Ali. But I’m still open for suggestions and ideas. I still learning about this and are enjoying the process. I also got some second hand electrolytes that I going to test. Muse, Jovial, Audio Note Kaisei og Cerafine, looking forward to that.

[hifinet]

These LT1963 to LT7805 modules are handy. Note in the picture, the GOI pins are mislabeled. Connect as indicated in the connection diagram: input, ground, output (IGO, left to right). Just like a 7805. They need a general purpose 10uF electrolytic (you don't want too low an ESR) on the output. More info on output caps on page 14 of the datasheet .

I think these sound very close to the Chinese Jung super regulator board I tried.

[hifinet]

Since the LM317 are cheap and easy to get a fixed 5v, that’s the first I’ll try. I also have a second one that I’m going to try, jung super power design I found on Ali. But I’m still open for suggestions and ideas. I still learning about this and are enjoying the process. I also got some second hand electrolytes that I going to test. Muse, Jovial, Audio Note Kaisei og Cerafine, looking forward to that.

I ordered a lm317/lm337.  Is that going to work, or do I need a plain lm317?

Also, I have a bunch of old laptop PS laying around.  That should work to feed the lm317/lm337, shouldn't it?

Please forgive the noob questions, still learning.

Thanks!

The LM337 is the negative voltage regulator. So you don't need that. Just the LM317. ProtoDAC needs very little current. A laptop supply is overkill. The heat generated by the regulator in watts is voltage drop times current in amps. You can drop 7 volts (12-5V) without much heat at all.

[OnkelPH]

Since the LM317 are cheap and easy to get a fixed 5v, that’s the first I’ll try. I also have a second one that I’m going to try, jung super power design I found on Ali. But I’m still open for suggestions and ideas. I still learning about this and are enjoying the process. I also got some second hand electrolytes that I going to test. Muse, Jovial, Audio Note Kaisei og Cerafine, looking forward to that.

I ordered a lm317/lm337.  Is that going to work, or do I need a plain lm317?

Also, I have a bunch of old laptop PS laying around.  That should work to feed the lm317/lm337, shouldn't it?

Please forgive the noob questions, still learning.

Thanks!

I’m still learning to and regarding the LM314 I’m copying Gabsters approach. As for 3.3v you’ll need 9v PS, it will probably be okay for 5v output as well. 

Do anyone know how much current the ProtoDAC draws? A single 1387 draws 6.5mA I guess?!?

[hifinet]

6.5mA max current for one times 8 is 0.052A. The LM317 is not considered an LDO. It needs 3V minimum difference between voltage in and voltage out.

The LT1963 is an LDO, and can operate with 350mV differential (or even less at low current).

[hifinet]

The LM317 was designed in 1976. It is incredibly versatile, and over the years there have been scores of different circuits developed with the LM317. It can even regulate voltages in the hundreds for tube circuits. I used the Maida regulator in my tube amps.

[hifinet]

Yes, it will work. It's more than you need for this project. You can use it in the future for other projects. It's very versatile. It is an unassembled kit. You can use a transformer (for example, a center tapped power transformer) for a linear supply, since it has a full wave bridge rectifier, or input from the laptop SMPS to pin 3 (positive voltage) and pin 2 ground. You will use the LM317 side (pins 1 and 2 of P1), and leave the LM337 side idle.

Note that the diodes in the full wave bridge rectifier will drop 1.2V on the front end. If you want a lower voltage drop and quieter supply with a transformer input, use a Schottky full wave bride rectifier in place of the silicon rectifier supplied with the kit. The silicon diodes won't add switching noise with the SMPS input, because they are always on.

If you plan to use it only with a DC SMPS, you could bypass the full wave bridge rectifier and caps in the front end, and feed the positive supply directly to pin 3 of the LM317.

[OnkelPH]

6.5mA max current for one times 8 is 0.052A. The LM317 is not considered an LDO. It needs 3V minimum difference between voltage in and voltage out.

The LT1963 is an LDO, and can operate with 350mV differential (or even less at low current).

Do you think It can be a good idea to try a breakout GPIO in between the rpi and the IC Q7 too bypass the 5v to the ProtoDAC? and add a LT1963 filter??? If you understand my idea???

[hifinet]

Do you mean getting the 5V from the pin 2 and/or 4 of the RPi GPIO? I don't think the voltage differential will be enough. The voltages are usually less than 5.1V, and that is right on the margin of the dropout voltage of the LT1963 to get 5.0V with the current draw of ProtoDAC. You will need at least a 100mV differential. If the voltage differential is less than indicated in the chart on page 1 of the datasheet, the LT1963 won't regulate.

[OnkelPH]

Do you mean getting the 5V from the pin 2 and/or 4 of the RPi GPIO? I don't think the voltage differential will be enough. The voltages are usually less than 5.1V, and that is right on the margin of the dropout voltage of the LT1963 to get 5.0V with the current draw of ProtoDAC. You will need at least a 100mV differential. If the voltage differential is less than indicated in the chart on page 1 of the datasheet, the LT1963 won't regulate.

Thanks, so I can get 5v from pin 2/4, but LT1963 will most likely not work. Understand.