Kubelik NOS DAC kits

[nautibuoy]

I guess I'll await the opamp pin voltage measurements to shed some light.

Hi Richard. I finally found some spare time. I reflowed all the pins on the op-amp U7 first off and here are my latest measurements:

Firstly, the test points;

• TP1 = 10.1V
• TP2 = 2.5V
• TP3 = 2.9V
• TP4 = 10.8V
• TP5 = 10.2V
• TP6 = 9.7V
• TP7 = 10V
• TP8 = 4.5V
• TP9 = 18.8V
• TP10 = 10V

Next the pins of the op-amp U7 (Right channel)

• P1 = 8.5V
• P2 = 10.1V
• P3 = 10.1V
• P4 = 0V
• P5 = 9.7V
• P6 = 18.8V
• P7 = 17.7V
• P8 = 20.0V

then R14/15 (right channel)

• Voltage between R14 & R15 = 9.4V
• Voltage across R14 = 0V
• Voltage across R15 = 0V

and op-amp U8 (left channel)

• P1 = 8.5V
• P2 = 10.1V
• P3 = 10.1V
• P4 = 0V
• P5 = 10.1V
• P6 = 10.0V
• P7 = 8.8VV
• P8 = 20.0V

Finally R31/44 (left channel)

• Voltage between R31 & R44 = 8.7V
• Voltage across R31 = 0V
• Voltage across R44 = 0V

 

[abraxalito]

Those voltages are making sense now Ray and seems your second half U7 opamp isn't functioning correctly. You could check if sound comes out from bypassing the opamp. To do that you need to lift pin7 of U7 (or if its easier, lift R22 opamp side and wire to that) and connect from the pad of pin7 (maybe easier from R22) to pin5. This mod will turn the filter into a copy of the Dorati's output filter which runs without an opamp.

 

[nautibuoy]

Thanks Richard. I'll have a look as you suggest.

 

[Joel Wesseling]

Kubelik really is a good sounding dac.

Is there Distortion measurements posted anywhere? Nice to see what that looks like

 

[gpapag]

Hi Joel
I have posted some at posts: #163, #166, #185.
https://www.diyaudio.com/community/threads/kubelik-nos-dac-kits.375955/post-6889623
https://www.diyaudio.com/community/threads/kubelik-nos-dac-kits.375955/post-6889855
https://www.diyaudio.com/community/threads/kubelik-nos-dac-kits.375955/post-6905246
I have some more, not shown.
If there is anything specific that you want to see, just ask, I may have it in my HD.
George

 

[wootwootman]

Hi Richard, I'm new to the forums so I'm unable to pm you, but if you could contact me I'd be interested in ordering 2-3 of these kits from you.

 

[abraxalito]

@wootwootman - a warm welcome to the forum! PM sent.

 

[nautibuoy]

Those voltages are making sense now Ray and seems your second half U7 opamp isn't functioning correctly. You could check if sound comes out from bypassing the opamp. To do that you need to lift pin7 of U7 (or if its easier, lift R22 opamp side and wire to that) and connect from the pad of pin7 (maybe easier from R22) to pin5. This mod will turn the filter into a copy of the Dorati's output filter which runs without an opamp.

Hi Richard, I really ought to try and get this working so I'm thinking I'll just swap out the op-amp(s) - as OPA2209s seem to be out of stock any thoughts on using different op-amps. I have some spare NE5532 op-amps?

Incidentally, are you still supplying Kubelik kits?

 

[nautibuoy]

Those voltages are making sense now Ray and seems your second half U7 opamp isn't functioning correctly. You could check if sound comes out from bypassing the opamp. To do that you need to lift pin7 of U7 (or if its easier, lift R22 opamp side and wire to that) and connect from the pad of pin7 (maybe easier from R22) to pin5. This mod will turn the filter into a copy of the Dorati's output filter which runs without an opamp.

Just a thought Richard, but if I remove R23 and just bridge pins 5.6 &7 of U7 that should give me the same result with regard to to isolating the fault I have? If I'm going to need to swap out U7 anyway to fix the Kubelik it seems like an easier temporary fix.

 

[abraxalito]

Ray - I think NE5532 would probably work even though noisier than OPA2209.

As regards the mod, with hindsight I look to have assumed that the manner of failure of U7 wouldn't load the circuit, but this may not be correct. My mistake. The ideal solution would be to isolate (lift) pin5 and pin7 and wire pad5 to pad7. Your method would work as well as my original suggestion I think which has the possibility of introducing distortion due to pin5 not being high impedance.

 

[nautibuoy]

Thanks Richard, I'll try my fix and see if it sorts out the fault - it feels simpler to implement without stressing the PCB with too much repeated heating. If it works and sounds good maybe I'll modify the good channel in the same - would that be a Kubelati DAC?

 

[nautibuoy]

Hi Richard. Thanks for sending the spare OPA2209 with my Dorati kit - I managed to replace the faulty OPA and have just tested the Kubelik - it is now working properly and I have music in both channels so all's will that ends well.

I've only had a quick 'test listen' and it sounds good.

Ray

 

[ghitus]

Hi guys, I just started soldering my Kubelik and it's my first attempt at SMD. I began with the tda1387 chips. To be honest, I chose to entirely solder them immediately, cause I felt more confident doing that than solder just two pins. So I of course hope that they are all working chips. I forgot just one thing: as per guide, it's suggested not to solder pin 7, but I did it, I soldered all pin 7. As far as you know, is it a big mistake? Does it compromise tda1387 functionality?

Thank you,

Gaetano.

 

[abraxalito]

Soldering pin7 doesn't matter at all since the pad beneath that pin doesn't connect to anything at all.

 

[ghitus]

Hi Richard, just out of curiosity, what should I do with yellow pads which on the guide are marked as "yelled"?

Thank you.

 

[abraxalito]

That 'yelled' is actually YEL LED - shorthand for yellow LED. Its a power indicator.

 

[ghitus]

Ah, ok!

Thanks.

 

[ghitus]

Hi Richard, I just finished my Step 1. All's good but TP1. It reads about 3.98V, while other TPs are ok. LED doesn't turn on and I tested all tda1387s pin 7 and they read all about 0.745V. Then what could be the issue?

Many thanks,

Gaetano.

Don't blame me for the poor SMD soldering skills, I'm at the first attempt, if something went wrong it's quite normal!

 

[Grarea]

Fiddly little buggers aren't they?
Fired any across the room yet?

 

[ghitus]

No, not yet!! Anyway I tried reflowing some solderings here and there and the magic happened: LED turned on and TP1 read 10.1V, being all other tests correct. Fiuuuu...I suspect Q2 wasn't working properly.

Gaetano.