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DCX2496 Upgrade Board - Objectively Tackling the Improvement of a Stock DCX2496
DCX2496 Upgrade Board - Objectively Tackling the Improvement of a Stock DCX2496
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Old 18th June 2013, 09:54 AM   #21
jan.didden is offline jan.didden  Europe
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Not according to the data sheet.

jan
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Old 18th June 2013, 10:02 AM   #22
Julf is offline Julf  Europe
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Originally Posted by tomtom View Post
Linear supply will be nice.
The subject of this thread is "objectively tackling the improvement of a stock dcx2496". To me that implies first mapping out what needs to be improved, then making a change, and then verifying if it actually improved the situation.

Things that need to be improved could include things like SNR, THD and gain structure / output voltage. I don't really see "lack of linear supply" as an issue. There has to be some problem that the linear supply supposedly solves, and it has to be verified that the supply actually solves that problem. Otherwise it belongs in the "has to be coloured pink" category.

So, what specific issue do you want to solve with a linear supply?
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Old 18th June 2013, 10:07 AM   #23
hochopeper is offline hochopeper  Australia
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I was going off this ...
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Originally Posted by opc View Post

The DAC itself also has a rather low differential output of 0.85VRMS at 0dBFS, so I think I would opt for a single OPA1632 per channel with a gain of 2.4 to get the differential output up to 2VRMS and the SE output up to 1VRMS.

Are you using balanced or SE outputs? If you're using SE then you're giving up the CMRR needed to maximize the DAC performance and you're only getting 0.425VRMS at 0dBFS

Last edited by hochopeper; 18th June 2013 at 10:19 AM.
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Old 18th June 2013, 10:33 AM   #24
SY is offline SY  United States
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DCX2496 Upgrade Board - Objectively Tackling the Improvement of a Stock DCX2496
Quote:
Originally Posted by jan.didden View Post
Stuart,

Assuming that the output R-C is part of the reconstruction filter, the load influences the filter characteristics. You's only use the opamp as buffer.
Putting aside that, unless you're an inveterate equipment swapper, the values can just be set for your preamp or passive control, how much difference is there between loading your circuit with (say) 10k and 100k using "normal" cables (say, 75pF)?

Output voltage from the DAC is +/-2.4V.
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Old 18th June 2013, 11:23 AM   #25
Pano is offline Pano  United States
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DCX2496 Upgrade Board - Objectively Tackling the Improvement of a Stock DCX2496
Transformer outputs work best for me in blind listening tests. There is enough output level for almost any amp.

On one unit I modified the Spdif was routed to an RCA input over by the multipin connector in the back. In fact it was 2 RCA with a switch. Worked very well.
Cleaning up the PSU helps, so does replacing the electrolytic caps that decouple the DAC chips. A larger value and lower ESR cap seems to work well.

Looking forward to seeing what you do with the jitter.
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Old 18th June 2013, 11:25 AM   #26
qusp is offline qusp  Australia
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there are those that take the opportunity provided by DSP to do away with the preamp altogether, which can only be a source of noise, as the interconnecting line level cables are. makes for pretty large output impedance too, not so hot for some amps.

@ Pano, large electros of any type for decoupling a DAC? not much chop for any HF or RFI. SMD X7R FTW

Last edited by qusp; 18th June 2013 at 11:31 AM.
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Old 18th June 2013, 03:33 PM   #27
tomtom is offline tomtom  Slovakia
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Quote:
Originally Posted by Julf View Post

So, what specific issue do you want to solve with a linear supply?

Nothing specific - DCX is nice hardware but PS is unreliable joke. Thats all
I dont have false hope in PS.
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Old 18th June 2013, 03:40 PM   #28
Julf is offline Julf  Europe
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Originally Posted by tomtom View Post
Nothing specific - DCX is nice hardware but PS is unreliable joke.
I guess the right description would be "cost-optimized"

Reliability is definitely a valid concern.

Quote:
I dont have false hope in PS.
In my experience the PS is something to think about when everything else has been taken care of - and even then a linear supply is not necessarily better than a switcher from a sound quality point of view.
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Old 18th June 2013, 05:40 PM   #29
qusp is offline qusp  Australia
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I reckon a cheapo linear will win out against a cheapo switcher though. switchers can indeed be excellent if done well, with keeping residue/sidebands out of the audio band part of the design spec, but if its careless application, or simply designed without any of that in mind, it can be horrid and completely unsuitable for audio.
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Old 18th June 2013, 05:43 PM   #30
Julf is offline Julf  Europe
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f its careless application, or simply designed without any of that in mind, it can be horrid and completely unsuitable for audio.
I am afraid that can apply to a cheap linear supply too.
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