ProtoDAC TDA1387 X8 project

[eculcea]

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hifinet pid='59029' dateline='1731363529'][attachment=4241][attachment=4240][attachment=4239]

It looks the more TDA1387 the better. I think physically I could solder another 8 chips adapter on top of each other to make it 16 chips, from electronics standpoint would this work?
I am a hobbyist learning about audio electronics and maybe this is a dumb question.

Yes, it works. I removed all of the pins from two modules, and then soldered 7 wires (pins 1, 2, 3, 5, 6, 25, 28) connecting the two boards to the PCB. The IV resistor needs to be reduced in half to about 210R (or less than 215R), since the current will be doubled. This will reduce noise by another 3dB, and also reduce the output impedence. I think the power supply decoupling capacitors will need to be doubled.

I did not hear much of a difference in sound quality, but there were some limitations in that I used standard metal film IV resistors, and I didn't double the decoupling capacitors.

I got this working. I used tantalum SMD resistors in serial to make it 200R. I changed the capacitors to 2200uF. Listening between the 2 I think the 16 chips TDA1387 has a better and more detailed sound at the lower frequencies. It could be just a placebo effect since this is all subjective

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[Onionhead]

Starting second Protodac build and want it to be an upgrade from first. I want to be very clear in no way am I disappointed by the standard component, just like to use other compents to hear for myself. From reading this thread seems best place to upgrade is to start with I/V resistors.I would like to try the Caddock TF020 but concerned with width of pins. I am sure this has been documented just can't find it so I'll ask what is the pin spacing for R4/5?

[hifinet]

Starting second Protodac build and want it to be an upgrade from first. I want to be very clear in no way am I disappointed by the standard component, just like to use other compents to hear for myself. From reading this thread seems best place to upgrade is to start with I/V resistors.I would like to try the Caddock TF020 but concerned with width of pins. I am sure this has been documented just can't find it so I'll ask what is the pin spacing for R4/5?

According to the datasheet, lead spacing is 0.150 inches or 3.81mm.

My brother has two shunt-type passive volume controls, a "premium" one using the TF020 and the other using the MP series, and the discontinued TF020 sounds much better.

As an aside, a shunt volume control is not a good idea, because it creates a variable frequency high pass filter (due to the variable resistance of the shunt design) with the output coupling cap of the prior stage. A standard potentiometer has a fixed resistance presenting to the prior stage, a variable resistance to the following stage.

[hifinet]

@eculcea Nice work! How do you think the SMD tantalum resistors sound compared to the TX2575 metal foil? Which brand did you use? You are using two 2200uF caps (total 4400uF capacitance), right?

I found out about the thin film tantalum resistors in this diyA post. Different application.

[fdealexa]

Hi all,
The link to the datasheet point, for me, to a transformer family.
I found some specs and it seems that the minimal value is 1k.

The TF020 series from Caddock are low TCR ultra-precision film resistors, with a resistance range from 1kΩ to 2MΩ. These resistors have a tolerance range from ±0.25% to ±1.0%. The TCR values available are ±5 ppm/°C (between -15°C and +105°C), ±10 ppm/°C (between -15°C and +105°C) and ±15 ppm/°C (between -15°C and +105°C). The Caddock TF020 series is available with either radial or axial tinned copper leads, it offers long term stability and is constructed using the Tetrinox® resistance technology.

Ultra precision film through-hole resistors
Radial or axial leaded variants available
Resistance values available between 1kΩ and 2MΩ
TCR of ±5 ppm/°C (between -15°C and +105°C), ±10 ppm/°C (between -15°C and +105°C) and ±15 ppm/°C (between -15°C and +105°C)
Tolerance of ±0.01%, ±0.025%, ±0.05%, ±0.1% and ±1.0%
Maximum power rating of 0.33W (at +70°C)
Long term stability to 0.01% per 1,000 hours
Storage temperature range from -55°C up to +105°C
Maximum working voltage of 300V
Utilises Caddock’s Tetrinox® resistance technology

Best regards and thanks,
Francesco

[hifinet]

Percy Audio has them listed in the catalog (page 11) from 50R and up.

[eculcea]

@eculcea Nice work! How do you think the SMD tantalum resistors sound compared to the TX2575 metal foil? Which brand did you use? You are using two 2200uF caps (total 4400uF capacitance), right?

I found out about the thin film tantalum resistors in this diyA post. Different application.

Thank you. First I build one ProtoDac using the standard configuration with TX2575 metal foil as you recommended.
Then I build this second one. I doubled the capacitors to a total of 4400uF as recommended.
For the SMD tantalum I used Yageo 100R in serial from Mouser. NT1206BRD07100RL
Listening between the 2 versions, I think the second version with 16 DAC chips in parallel, has a better lower frequencies sound. It sounds to me  more full and more defined. Since is all subjective, it could be a placebo due to me thinking more is better.

[hifinet]

@eculcea Nice work! How do you think the SMD tantalum resistors sound compared to the TX2575 metal foil? Which brand did you use? You are using two 2200uF caps (total 4400uF capacitance), right?

I found out about the thin film tantalum resistors in this diyA post. Different application.

Thank you. First I build one ProtoDac using the standard configuration with TX2575 metal foil as you recommended.
Then I build this second one. I doubled the capacitors to a total of 4400uF as recommended.
For the SMD tantalum I used Yageo 100R in serial from Mouser. NT1206BRD07100RL
Listening between the 2 versions, I think the second version with 16 DAC chips in parallel, has a better lower frequencies sound. It sounds to me  more full and more defined. Since is all subjective, it could be a placebo due to me thinking more is better.

Thank you for your review. The DAC with two modules should sound fuller in the bass, due to the lower output impedence. If the tantalum resistors sound equal to the metal foil, that is a significant cost savings. Listen to the 16 chip DAC for a week, and then go back. The differences should become more obvious. Also, listen for soundstage depth, in comparison to the 8 chip version. Increasing the decoupling caps too much can improve bass at the expense of soundstage depth.

[eculcea]

Those SMD resistors are certainly way cheaper option than the Z-foil resistors.
for sure I will do some more listening between the 2 versions during the next few weeks. I will also try those SMD resistor on the standard version of ProtoDAC I build.
Once I figured out my impression I will report back.

[hifinet]

Unfortunately, only 100R in 1206 is available (Stackpole RTAN, Vishay PTN and Yageo NT at DK). 200R Vishay, but only 0402 and 0805. I don't think I can solder parts that small. I hope they will expand the stocked values. These adapter boards might help (stand on end).