A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) - Page 73 - diyAudio
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Old 12th December 2013, 05:42 PM   #721
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Why not use the balanced output without transformer or capacitor?
When you do not measure DC on the output of the balanced connection it would not be a problem, and I expect he sound quality would go up. It did in my case, but as I am using an input transformer in my amps my experience may not be compairable to other cases..
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Old 12th December 2013, 07:20 PM   #722
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Default Clivem - good to see you back

Quote:
Originally Posted by clivem View Post
I'm not suggesting anyone should rush out and buy a pair of these, only that I had them spare in the parts box, tried them in several configurations and this configuration proved one of the best sounding and something I put top of the list as being one to return to and have another play with, but as per usual I never seem to find the time to go back. (I can see most of you guys discussing transformers, are following the Doede doctrine of passive output, and seem to be looking at 10k:10k line driver parts, but anyway.....)

A pair of Sowter 9545's, primaries in series, (join brown and orange but don't ground, grey/blue to +/- on the DDAC mainboard), secondaries in parallel, so 2:5 == 1:2.5 step-up. 1R2 I/V resistors with a single deck, and a triode gain stage (x45) connected to the 9545 secondaries, for ~2V RMS single-ended output.
Missed reading your thoughts and of your trials with output configurations.

Does this mean you have dismissed the active approach and that you have found transformers the best you have found, so far?

Please, let us know your current thoughts.
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Old 13th December 2013, 01:19 PM   #723
clivem is offline clivem  United Kingdom
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Quote:
Originally Posted by rickmcinnis View Post
Missed reading your thoughts and of your trials with output configurations.
LOL. You haven't missed anything. I don't post very often, but when I do check-in with the forum I always see if there have been any updates to this thread.

Quote:
Originally Posted by rickmcinnis View Post
Does this mean you have dismissed the active approach and that you have found transformers the best you have found, so far?
I spent quite some time with a simple Broskie cathode follower as the output from the DDDAC. Active, but not active in terms of gain. (I still think there is a benefit to be had from combining both phases into a single ended output, whether you do it via a transformer or an active device, like the BCF.) I really do need a 2V output to drive my very low gain headphone amp, so I went back to the Broskie unbalancer circuit, differential driver in front of the BCF providing gain. Nothing really interesting there.... 4xECC88, 200V B+, long-tail CCS set for 10mA for the input tubes, so 5mA each, something like a 25k plate resistor, so ~75V on the plates. 200R cathode resistors for the BCF portion sets Ia to roughly 10mA for the output tubes. Can't remember what value I/V resistor, but it was chosen for 2V RMS out of the unbalancer. Sounds good. You could spend a lot more $$$'s and end up with worse. I stopped tinkering some time ago. In this configuration, it's been to a few listening sessions with other audiophools. One hosted at a hi-fi dealership where it was put up against a very high-end, (translation: very, very, very expensive and shall remain nameless), DAC and resulted in two people, there and then, asking where they could buy one. (Hi-Fi dealer trying to sell his many 1000 $$$$ DAC, which was the main reason for hosting the evening, really not amused at this point. Another place I'll never get invited back to. LOL.) Anyway, I digress. Passive transformer output or active output, I'd recommend either in preference to the passive cap output.

Forgetting the NOS and DF thing for a moment, the beauty of one of the things Doede picked-up on with the PCM1794 is that it is a recent generation, current output DAC which tolerates a decent size I/V resistor, which you'll never get away with elsewhere, like with the 1704 where you'll pay a heavy sonic penalty if you try. Which means that yes, passive cap out is an option, but that passive transformer is an option as well as more traditional gain stages, whether tube, or perish the thought, the traditional virtual ground op-amp. Which makes it great for tinkering with various output stages, even if that wasn't really what Doede intended.

Last edited by clivem; 13th December 2013 at 01:25 PM. Reason: typo
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Old 13th December 2013, 03:55 PM   #724
dddac is offline dddac  Germany
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Quote:
Originally Posted by clivem View Post
Which makes it great for tinkering with various output stages, even if that wasn't really what Doede intended.
LOL, now I could say, I yes that is exactly what I intended

Seriously, I always like people to experiment with my KITs.... and this time this really happens. I am very pleased with that

FRESH NEWS: today the PCBs with SMD assembled parts arrived, so I can start with the new prototypes with SPDIF Input...

to be cont'd
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Old 13th December 2013, 09:26 PM   #725
carlsor is offline carlsor  United States
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My DDDAC1794 is running after about 6 hours of assembly time. Initial upgrade included Tantalum IV resistors and Cinemag 15/15B output transformers. I downloaded the WaveIO Windows driver which magically found its way to the JRiver music playing software on my Windows 8 core i7 computer. No problems getting the computer to communicate with the WaveIO board through the DDDAC1794.

After 20 hours of music playing time the sound quality already surpasses my Sony SCD-XA5400ES with CD's. This is amazing because new wires, caps, resistors usually take about 300 hours to break in which means the best is yet to come.

I bought 8 270ohm tantalum 1% 1/2 watt resistors from Parts Connection so that I could find pairs at 135ohms that matched within .1% at the balanced outputs for each channel. The DC offset for the 2 channels is 1.3mv and 0.4mv which doesn't seem to present any problems for the Cinemags. The Cinemags have a 10K load. I paid less than $120USD for the pair of Cinemags which is much less than what high-end capacitors cost.

My next upgrade will be a DIY upgraded USB cable with an external 5VDC premium power supply for the WaveIO.

Like many others I feel compelled to share pictures of my DDDAC1794 on a wooden board.
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Old 14th December 2013, 04:20 AM   #726
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Would anyone in the states like to build me a DDDAC?
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Old 14th December 2013, 11:41 AM   #727
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" The Cinemags have a 10K load. I paid less than $120USD for the pair of Cinemags which is much less than what high-end capacitors cost."

That proves that capacitors are ridiculously overpriced by the high-end maffia!

You can also see this with Jensen paper in oils; when they discovered that the aluminium housing on the caps sound worse than a paper housing they started making paper housings and overpricing them shamelessly!

I just buy the aluminium housings and saw off the housing, this is the best free upgrade you can do

But transformers are almost always better than a cap.........................
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Old 15th December 2013, 11:54 AM   #728
Undarra is offline Undarra  United Kingdom
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I've recently installed a pair of cinemag 15/15B transformers and they have improved the clarity and vocal texture immensely, but i've noticed the bass has reduced considerably, the really low frequencies mainly. This is compared to the Mundorf caps i had in there, which i swapped back in to make sure i was imagining it. Id this an expected result of Tx coupled outputs? i have tried loading them with 10K and 15K resistors(in place if the 100k originally), but this didn't affect bass performance. Maybe the clarity i'm hearing in the upper frequencies is because of the reduction in lower frequenct not muddying them? Anyway just wanted some thoughts from people that use Cinemags.

Many thanks, Si
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Old 15th December 2013, 12:06 PM   #729
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I agree. Miss bass a lot with the Cinemags.

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Old 15th December 2013, 12:09 PM   #730
Undarra is offline Undarra  United Kingdom
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Thanks for the reply Bas, i'm glad i'm not imagining it!! Shame really because everything else they do is great.
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