ProtoDAC TDA1387 X8 project

[hifinet]

One test to try is to put some tracks in the Queue, start the first track playing and then let MPD automatically transition to each subsequent track. AFAIK MPD keeps the audio output open continuously under these circumstances and there should not be any glitches.

Tim - I did try your  queuing suggestion for which thanks . . . but I'm still get a varying selection of clicks occurring  (some pronounced, others quieter) across the queue listing, but not in any noticeable pattern

Mark - new module purchased and installed - still getting the  fairly frequently occurring click on track start  either (i) as per Tim's queuing suggestion above, or  (ii) playing tracks straight from an album.  Continuation of the issue with new module tends to suggests the module is not the cause.  Anything else on the DAC board - component-wise -  I should be looking at or testing?

Let me know

Best, Simon P

The click/pop problem is an infrequent complaint with ProtoDAC. I am still not sure what is causing it. Here is another mention of it in this thread. If changing modules didn't help, try adding resistors (250K to 1M) across each RCA jack (signal to ground). This can help with popping when switching the preamp input to ProtoDAC.

[varunach]

@hifinet quick question. What’s the output VRMS voltage the ProtoDac puts out?

[hifinet]

It is about 1.3 VRMS.

[thomaschan]

Anybody an idea? I am missing the trebles on my ProtoDac, have Rpi3, pure pi, FifoQ7 installed, especially on spotify i am missing the trebles, with airplay it is better. Proto DAC becomes the 5V directly from the pure Pi.

The first thing I will check is the output capacitor. What value are you using? Brand and type?

[thomaschan]

Recently, I have successfully modified the ProtoDAC to a standalone DAC. With the addition of CS8412 receiver chip and Russian made 6N16B miniature tube output, this DAC now takes coaxial, optical and USB as input. Very good performance.

https://www.youtube.com/watch?v=RobjsdBUZCI

[hifinet]

Anybody an idea? I am missing the trebles on my ProtoDac, have Rpi3, pure pi, FifoQ7 installed, especially on spotify i am missing the trebles, with airplay it is better. Proto DAC becomes the 5V directly from the pure Pi.

The first thing I will check is the output capacitor. What value are you using? Brand and type?

Output capacitor could affect all highs from all sources. His problem seems to be selective with Spotify.

[hifinet]

Recently, I have successfully modified the ProtoDAC to a standalone DAC. With the addition of CS8412 receiver chip and Russian made 6N16B miniature tube output, this DAC now takes coaxial, optical and USB as input. Very good performance.

https://www.youtube.com/watch?v=RobjsdBUZCI

I don't recognize the CS8412 board you are using. Any details? Maybe a closeup view of your rig?

[thomaschan]

Recently, I have successfully modified the ProtoDAC to a standalone DAC. With the addition of CS8412 receiver chip and Russian made 6N16B miniature tube output, this DAC now takes coaxial, optical and USB as input. Very good performance.

https://www.youtube.com/watch?v=RobjsdBUZCI

I don't recognize the CS8412 board you are using. Any details? Maybe a closeup view of your rig?

I bought this board on Taobao.

[hifinet]

POPPING ISSUE UPDATE

I built a ProtoDAC using older Obligatto Copper Series 3.3uF/630V (NOS or new old stock). The first time I have used these caps other than unsoldered in the test rig. I don't remember if they popped the first time in the test rig. If they did, I probably attributed it up to the fact they were unsoldered. In this newly soldered ProtoDAC with the Obligattos, there was a loud pop at the beginning of the very first track played. This subsequently reduced to very minor tics at the beginning of many subsequent tracks. This suggests the output capacitor as the source of the pop problem. 

The worst pop is always at the beginning of the very first track in a cold system that has just been connected to RCAs. The pop was not as pronounced when the system was repowered while still remaining connected by RCAs to the preamp. 

Resistors (installed between the RCA signal lead and ground) as low as 100K did not change the loudness or character of this "cold" pop. There are tics with some track changes, all fairly minor.

[hlucas]

I also experienced a very loud popping sound at the start of the first track when using NOS 6.8uF 5% 30V Sprague HI-REL capacitors. After that, everything seemed fine until I powered off the DAC for a few hours.

Recently, I replaced the Sprague capacitors with 0.22uF Miflex ones, and the popping issue has completely disappeared. I'm not certain whether the change in capacitance value, age, or the quality of the capacitors is responsible for the improvement.