The VOCM mod makes a large improvement as does adding an external power supply with the Jkrichards power supply board. If you are in the US then Jkrichards can do the mods if he is still doing that. I sent my dac to Jeff for the work and I could not be happier. Highly recommended.
One of the listings is mine. The JKRichards power adaptor. It uses and LPS to power one side of the dac for better isolation
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I think we figured out one of the reasons why the new nickel transformers clarify and makes the staging more detailed and real sounding without adding any treble or sibilance. The distortion between 1k and 20k is only 0.00097% and the super flat frequency response goes beyond 50k with little to no roll off.
The LL1948 has a 1k distortion of 0.03% and a 20k of 0.0016% and starts rolling off well before 25k
The XS4400 is no better. As a matter of fact the big Jensen does not measure as well ether.
Iām not trying to disparage your work, Iām only clarifying something that might not be obvious:
The data sheet for the JT-11SSP-8MA specify an RC that flattens the FR and takes it to a Bessel response. With them it should be flat up to way over 20k and only down by 1 dB at 120kHz in a 600 Ohms to 600 Ohms configuration which is what it was designed for.
The DS is pretty rude on this account: it drives the primaries at a lower impedance and doesnāt load the secondaries. This, of course requires a different transformer design.
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Thanks Ted. That makes total sense. I still would have thought it would have better distortion measurements. The new transformers do sound better then the Jensens in this application. Our new transformers are only down 1dB at 200k with no filter.
I enjoy and learn from everything you comment on here.
Yes this is a good upgrade and a very good price.
ā¦but only with the 15nF cap. It is flat up to 20 kHz with -3dB@50kHz with 7800pF and -1,5dB@50kHz with 6800pF by the charts you provided (although not comparable with the flatness from 50 kHz on as well as with other measurements of yours and the RCāed Jensen)
RC for the Jensenās flat response as Ted mentioned means, it also needs a cap?
Then a transformer designed for a DAC seems really special compared to cirquits adjusted for transformers.
Would be interesting not only how much better but also how much different, compared to all the other options many of us went through, your new transformer sounds.
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Sorry you are correct. It starts rolling off at 25K. I fixed this above.
No filter is needed with the Jensenās as itās input is way under 600 ohms and the output impedance is over 600 ohms (~20k).
Here is the actual output of my DAC with the big Jensenās
the 0.1 dB down at 20k is Teds designed filter in the opamp circuit. (not the transformer)
Also with no filter we get a near perfect phase response from the transformer.
The DAC is so good now. Unbelievably holographic, open, focused, enveloping and firm/contoured in bass!
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I truly believe the modified DS is one of the best sounding DAC on the market.
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Yes, the potential to show this in setups far over its price point is immense. I also think that with the better linearity of FR at the top end with the right C704 and the Lundahl or your transformer, the improvements by those transformers stand out much more than in the initial setting. All this now is 1000 miles ahead of just the ext. power supply with the XS4400.
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@tedsmith
Thank you Ted for making one of the best DACās on the planet.
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I hope to find someone in Melbourne Australia does the transformer update for my MKI 
This one looks promising.
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Yep Jim does a great job - highly recommended and a quality job
Thank you Jeff for researching and making these mods available and accessible!
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Your welcome. How do you like the sound?
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Does anyone know someone in the Denver area that can do the transformer mod?
Bass is amazing, super clean top end. Still breaking in I think but itās already amazing. Iām experimenting with DAC levels vs (Ref 6) preamp levels. I keep reading about the ā92ā setting, but that requires running the preamp at a very low level. Seems to close in and get harsh at that. Trying 60 DAC and 30 preamp and seems to sound more relaxed.
Overall the sound is very transparent and organic.
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Yesā¦ Some playing with the gain structure always helps. Thanks to Ted we have a lot of adjustments in the DS and can lock it down when we find the magic combination for our setup.
Enjoy the new sound.
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