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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: RE: Dacs powered by batteries - any successful story ? posted by Thorsten on June 15, 2015 at 10:25:28:
Good morning Mr. Thorsten
" But this regulator makes so much noise, batteries or even our "next generation" plugtop supplies would be wasted, just as the pure water in my rather graphic example "
actually i saw the datasheet and was surprised to see a poor performance on the higher Hz.
Clearly some kind of additional filtering is mandatory to keep noise down.
" This is possible. It is almost impossible to say without suitble test ger "
and this is my main regret because i understand that good testing rig are both complex and very very expensive. And this also normal.
" Of course. All electronic circuits generate noise. The specific one you mentioned is specified as adding this much noise under ideal conditions "
unfortunately i have no chance to test it but i trust you completely
In the end is a cheap product.
" Well, 40uV of noise might be expressed as 93dB (forgive if I am a little out) below 2V. If driving a clock, this may matter. On a single gate it will likely add around 1pS of jitter. Many modern circuits have 100's of gates. SO these 40uV can very quickly become several 100 times 1ps jitter... "
I see. However i see also very expensive master clock generators powered by what look like off-the-shelf SMPS.
Maybe there is also some kind of filterin, actually i am sure of that.
" It will, especially in this case. The regulator you mention does not do much to reduce noise past appx 1kHz. So giving it a passive filter in front will add the passive filters effect to the regulator "
and this exactly one of the reason to replace the toroidal.
I understand that a same effect of a split bobbin transformer (that i see used on high end units) can be achieved with passive filtering before the toroidal, but if space were not a constraint that toroidal will fly in the garbage bin immediately.
My approach is simple. Look what is inside the best unit and try to use it. Unfortunately schematics are not that common.
" Of course, you cannot go lower than the regulators self noise, but you can minimise the noise that gets to the regulator and past. Just there is a point where further improvements no longer help, due to build in limitations.
For fun, I can routinely make something that offers around 0.4uV of self-noise using less than one USD in parts for two channels (in 1KU), if all we need is 3.3...5V at 0.5...1A per channel and using quite generic parts. We can go as low as 0.15uV if we spend more money. Walt Jung is a good source "
wow ... that is very low indeed.
I understand that in order to suppress the noise generated by the regulator additional filtering after it would be extremely beneficial.
But i have no access to the schema and it is difficult to extract it from the pcb.
But i still could clean up a little the feed to the regulator.
Especially the HF noise that tends to pass through the regulator unsuppressed.
Even just a different transformer could be a good change.
" And if you are unlucky, they produce 400uV of noise... ;-)
Ciao T "
Yes. But as i said i cannot do anything for this.
Thinking about this a little more the idea to use an external decent SMPS or linear and put in the box just an additional filtering stage before the regulator caps is interesting.
I have just to place a new DC panel socket on the box and the filter inside.
I will look for some suitable schematic.
I see that many dvd/br player have passive mains filters.
I should be able to copy them.
Just some inductors and caps. Nothing out of this world.
I understand that the performance will be determined by the pcb design anyway.
But i can only try to feed the regulator as well as possible.
If i touch the pcb the unit i destroy everything.
And i do not like the idea to increase further the noise already generated by the regulators.
To end i have a strong feeling that the war to noise is a decisive one for sound. In the future i would like to be able to understand more on how the noise generates and how it can be suppressed.
I watched a very simple but also very interesting demo on Youtube.
The speaker compared the noise to a carpet. The more the noise the thicker the carpet.
If some objects of different sizes are then thrown on the carpet we can still see the bigger one but the smaller ones will be down in the carpet.
These small objects are like details in music.
A higher noise hides them. There is so much noise already in like.
So i think this is a very interesting field of study.
Thanks a lot again for the very kind and precious help.
Have a nice day.
Kind regards,
bg
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