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Hi Eboz,

S&B 102mk3, yes. Manufacturer confirmed that 120mV or so would be the upper limit, I measure just a few mV with one of Elibs S2 chips and a decent heatsink.

I did find the offset to surge when the unit was powered up and/or down, and decided that I need to make sure the transformer is decoupled from the DAC at these times, which is easy if you have a selector switch on your control unit.


Regards,
Shane

Michael,

Manufacturer's suggestions on this matter are often made the way it is simplest to them. This notice doesn't apply to the Bent / S&B only, similar recommendation comes from Jensen too, they suggest no more than 0.1mA through the primary, so 4mV across 40 Ohm winding. In reality I have managed to increase the DC to ten times higher value with no measurably deteriorated performance.

I did had Bent here in my system for some days but I've never checked its actual ability to handle the DC, so I can not give you my own advice. But what Shane says means that you will never had to worry about this issue.

Dear all,

last weekend I finally managed to fit the last parts into the aya dac pcb; Voltages etc. are as they should be.

Listening test did not succeed ... am I right that the green LED must be on when spdif signal is OK? Green LED is off so I guess I have a problem on the signal input ... Am I right?

Christian.

New AYA DAC completed for another forum member. This one uses a CS8412-IS for the receiver chip and a double-crown TDA!

Christian,

That is correct. Please check the installation of your CS8414 chip and its power supplies. Make sure that the input transformer is oriented correctly as well. You should get a green light regardless of any problems after the receiver section.

Thanks eboz, i will try ...

Hello Christian,

I hope you can verify that your source actually works in the first place. As for the green LED, some S/PDIF sources will light up that LED as soon as they are powered up, whereas some need to playback to do so.

Do you have a scope? If not, here are some DC voltages to check... TDA pins 1 and 2, these will tell you whether the TDA receives the clock signals or not, i.e. whether CS outputs anything or it is dead. You can also try checking if error flag is high (once this flag goes low, the green LED will turn on), it is CS pin 28.

BTW, to synchronize the watches, what a version of AYA is it? Sorry for asking, I did tried checking through my archives and found two Christians so far, but apparently none of them is you.

Hello Pedja,

thanks for your reply; my board is rev 2.0b; i got it from a kind of small group buy (a fried ordered at least 4 pcbs).

The source is OK, my other DAC works with it. I will have to check frequency, there is a small chance that the drive is delivering 96kHz which wil not be what CS8414 is waiting for ...

Best,
Christian

CS8414 should normally work with 96kHz fS. So, it would be good if you make sure that the CS8414 works at all.

One method: even if it doesn't lock, CS8414 normally outputs some clock signals, and frequencies are 11-12kHz at FSYNC (pin 11), and some 750kHz at SCK pin (pin 12). You can probe these signals also at R107 and R108.

As I said, not using a scope, a DC meter can be useful too, since it will show clock signals as about half supply voltage, so some 2.5V. If there is nothing, it will show 0V.

As for the error flag, you can probe CS8414 pin 28 also at the top board side, at right side of R14. If all is well with CS8414 and it really only doesn't lock onto the incoming stream, you should measure here 5V (or somewhat less than that).

If you can report back these results, they will give us somewhat clearer picture on what's happening with CS8414.

Hello Pedja,

thank you for the detailled instructions. My old 30 year old scope recently broke so I will have to buy a new (used) one ... I will ask all my friends around here if they have something for me ... I will measure the CS8414 on weekend using whatever I have then, be it a scope or a dc/ac meter.

BTW, do you have some suggestions what technical date a new scope should have for diy hifi purposes?

best regards
Christian

Hi Christian,

Bandwidth comes first, and I wouldn't go below 50-60 MHz. Fortunately, these days this is not really high demand. For regular troubleshooting you most usually don't need any special features. So the number of channels and the all the rest is less important, of course unless you want something particular, say FFT.

You still don't have to invest too much if you settle on something second hand.

Hi,

i will get an old 10 MHz scope in exchange for a used soldering station ... so this will have to work for the next few years At the moment I am afraidf I can not afford 50 MHz ...

I guess i will check the CS8414 using the multimeter this weekend as the arrival of the scope will be somewhat later on.

Cheers
Christian

Hello,

i now managed to let the green LED shine .... now Pin 28 of the CS is low, before it was high.
There was some SMD soldering problem on the data input pin. Your description helped a lot for finding the faulty spot.

Unfortunately there are problems left as there is no output voltage of the dac. As far as I could measure using the cd/ac-meter there is no output from the TDA but some input (no idea whether this input signal is OK) ...

How could i trace the signal in order to find where it is left?

How can I check of the clock signals are OK?

BTW, I am waiting for a used 10 MHz scope ... maybe this will help findig the error then. Unfortunaltely, it is not clear yet wheter the scope does work at all ...

Best,
Christian

Hello Christian,

So, does the error flag generally work well, going up when you stop the source (please note that some sources must be completely turned off), and going down when you start it? If error flag works this way, the chances are good that the CS works fine.

Then, looking downstream... Using Voltmeter only, I'd put it to DC, and firstly probe R107 and R108. The DC meter will integrate clock signals so, if CS8414 outputs the clocks, your DC meter will integrate these waveforms as their middle value, which is about 2.5V.

Now if it is fine at this point, you should check if reclocker works too, and whether these clock signals arrive to the TDA or not. So you should repeat the DC check at TDA pins 1 and 2.

Hello Pedja,

thanks for your reply.

Yes, error flag goes down & up (LED on & off) when connecting & disconnecting the source.

If I remember correctly, there was some DC on TDA pins 1 & 2 yesterday. I will repeat measurements and follow your instructions this evening.

Best,
Christian