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Kubelik NOS DAC kits

It's a tough job to please a woman :rofl:

Indeed so! After finding not enough distortion I turned to power supplies and realized I now had two TL431s in series with this design to get lower noise. So I wondered if there was some kind of interaction between those two shunts and added a damping 220uF capacitor across each and invited wifey for another listen. This time she didn't notice the imbalanced sound/distortion on piano. Hmm, that's progress :p

The last step is - remove those capacitors and see if anything changes. What do y'all think the result will be?
 

gpapag

Moderator
Paid Member
2002-11-17 6:42 pm
Athens-Greece
Indeed so! After finding not enough distortion I turned to power supplies and realized I now had two TL431s in series with this design to get lower noise. So I wondered if there was some kind of interaction between those two shunts and added a damping 220uF capacitor across each and invited wifey for another listen. This time she didn't notice the imbalanced sound/distortion on piano. Hmm, that's progress :p

The last step is - remove those capacitors and see if anything changes. What do y'all think the result will be?
TL431 can oscillate. See oscillation reference in the datasheet https://www.ti.com/lit/ds/symlink/tl431.pdf?ts=1653450587539&ref_url=https%3A%2F%2Fwww.google.com%2F

and in the much more explanatory https://www.ti.com/lit/an/slva482a/slva482a.pdf?ts=1653463187100

This means depending on the Vak and the Iak, a capacitor -or better a resistor in series with a capacitor- may need to be placed across anode and cathode.

George
edit: They may not oscillate in static condition but require some form of load step change (e.g. percussion instrument playing)
 
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As usual, the incredible packaging from Abraxalito. Very nice looking Dorati Dac, right at my door step today. Thanks to Abraxalito.
 

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i will be using the same psu regulation, same usb interface and also the same output caps (they are off the dac board) to compare between the op amp and discrete boards. But i need to use a different power transformer to avoid overheating my psu regulators. Good thing that the mechanical mounting footprint for both boards are the same.
 
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Any updates on your new 12V Dorati power supply @commstech?
Hi Abraxalito, I have completed it on Monday evening after the transformer reached me last week on Friday. There was a delay in the delivery at the customs because i have opted for the wrong method of shipping. Should have chosen Sensitive Air instead of Economy Air shipping. Package was rejected and then reshipped. I have listened to it for 2 days to form an impression. I shall post this evening (my local time) when i get home from work.
 
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Sorry for the delay and thanks to Abraxalito for his patience. Finally settled down from some life and work matters and have some free time to write. As a background, I have Kubelik with opamp in the IV/output stage. Abraxalito, please correct me if i am wrong -- Kubelik has discrete transistors biased in class A at the outputs, in combination of Op amp stages. Recently, i received a new version with full discrete IV/output stage, which is now called Dorati. Kubelik works on 20Vdc and Dorati works on 15Vdc max, which prompted me to get a new transformer.

Upon firing up Dorati, the immediate impression is a more quieter and dark background. This is a very obvious difference from the Kubelik. This could be due to a less demanding power supply? I am using the same psu regulation on both dac. The Dorati presented a more solid imaging when i played Chinese orchestra music. More pin-point positions of the various instruments. I can feel that there is more depth in the soundstaging presented by Dorati as compared to Kubelik. To be more specific, there is more depth and space.

I played female vocals and listened. Again, the above observations. However, i feel that the singer actually took a couple steps back as compared to Kubelik. Instruments are more widely spaced apart, more resolution for Dorati - which sometimes i feel the Kubelik may slightly lack in when i compare it to my Soekris r2r dac. The Dorati does sound more extended in the frequencies when strings are played, better decay than Kubelik.

At this point of time, one may think the Dorati is a clear cut above the Kubelik. I will say no. The Kubelik has a quality that i like very much. It has more ambience to the music. It adds warmth and bloom especially in the mid and low regions. When complex passages like the Chinese Orchestra is playing, the Kubelik may not produce the bigger soundstage and separation of Dorati but let me say that the Kubelik has a very good control of the music - unfazed, there is no nervousness. The Dorati has a certain small degree of strain whenever i really push up the volume playing the orchestra, while the Kubelik has no sweat at all. This is something that the Kubelik impressed me since day one.

In general, the Kubelik has a more upfront and forward presentation versus the more backward and bigger presentation of the Dorati. the Dorati plays with more finesse, finer resolution , more hi-fi style. Kubelik is about warmth and control, good grip and bite on complex passages. I do believe the different output stages work done by Abraxalito attribute to a strong influence on the sonic outcome on the same dac implementation. I do believe both designs can work well on different systems and the individual's taste.

I hope this helps.
 
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That's all very interesting - thanks for such a detailed review @commstech . I wonder whether the 'small amount of strain' of Dorati could be due to having a lower power supply voltage so the signal's closer to the rails. I will have a look into this - I specifically designed Kubelik to have lots of headroom, which is why it needs 20V. What supply voltage are you using on Dorati?

As regards the darker background of Dorati, I think this comes from deleting the opamp, I figure the transistors give it a lower noise floor.
 
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