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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz

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#5,642
Hi,

Soren, as I understand the board is optimized for -/+4V on Vref for 74LVC595A shift registers which is already bit more than the -/+3.6V specified as max recommended in datasheet. However datasheet states 6.5V for Vcc as absolute maximum rating.

I want to try "hot rod" mosfet shunt regulator (Zout 1mohm) for direct Vref powering, however cannot go as low as 4V due to mosfet Vgs. It works above 4.6V.

So, do you see any dangerous or disadvantages running Vref at ~ +/-5V? Should this work theoretically without problems?

Thanks,
 
#5,645
dear Rick

thx for answer. i think this answer was pretty close but doesn't work.

i tried a bit an it seems to be:

set mode = normal
set mode = invert

if i just enter set i get a feedback for all set commands 😉

but i am not sure, if it realy works. if i enter for eg set volume = -50 or set volume = 0 there is no change in volume but if i enter just set i get the feedback, that volume is changed ;(

is it maybe not changing during playback?

greetz

christian
 
#5,646
chriss0212 said:
dear Rick

thx for answer. i think this answer was pretty close but doesn't work.

i tried a bit an it seems to be:

set mode = normal
set mode = invert

if i just enter set i get a feedback for all set commands 😉

but i am not sure, if it realy works. if i enter for eg set volume = -50 or set volume = 0 there is no change in volume but if i enter just set i get the feedback, that volume is changed ;(

is it maybe not changing during playback?

greetz

christian
Click to expand...

I was writing from work and relying on my memory (yikes!)

I typed it that way initially and then I thought the "extra" spaces were wrong so I removed the spaces.

I am using a free hotkey program so I do not have to type all of that and since I do not have to type it regularly it was not remembered. One of the downsides of convenience!

Good thing: umanager's "?" key shows all the possibilities, though I was a little hesitant at first to experiment. Fear of screwing it up. Don't worry, it ignores what it doesn't recognize.

I hear a difference when I change the polarity. I am absolutely sure it works on my DAC and should on yours, also.

Unless I have completely fooled myself, which is something I worry about all of the time!

I, too, have noticed nothing changing with the volume control. I thought it might be a good idea to set the volume a little lower since so many new recordings are at such a high average level. Wondered if there was the possibility of overloading the DAC. I am using 3.3 volts on the shift registers and thought: maybe this is a good idea. So I did.

Then a few days later I was playing a recording with very low levels so I thought I would return it to zero and there was no difference at all.

I use an autoformer after the DAC output to set volume levels not the internal. Maybe there needs to be a pot attached for this to work? I do not know. I have left it at zero ever since.

But to reassure on the polarity - it does work and is a good addition to a great device.
 
#5,648
Hi I have Soekris dam dac v2 with lot of mods, work great! but I still wondering what to do more. I have heard that i can disolder analog opa's. Im working on raw out put. This mode give me better sound? I have looked on board and I have see that from 2R2 ladder is connected to raw out and to a analog opa's , mayby just cut connection from ladder to opa?
 
#5,656
So you are saying it is impossible that the polarity change can occur during playback?

I have long maintained that a placebo audio tweak is as good as any as long as the illusion lasts!

I sure thought I heard a difference. Hope I can maintain the illusion ...

Well, that's a little more than a little embarrassing.

I guess this applies to the filters, also?

I know there is only so much that can be done but not being able to switch during playback makes it close to useless since this is something that can change between tracks, let alone, albums. Oh, well ...
 
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#5,657
rickmcinnis said:
So you are saying it is impossible that the polarity change can occur during playback?

I have long maintained that a placebo audio tweak is as good as any as long as the illusion lasts!

I sure thought I heard a difference. Hope I can maintain the illusion ...

Well, that's a little more than a little embarrassing.

I guess this applies to the filters, also?

I know there is only so much that can be done but not being able to switch during playback makes it close to useless since this is something that can change between tracks, let alone, albums. Oh, well ...
Click to expand...

I said "undefined", some of the "set mode=" commands might work during playback, but I have done no effort for it to, I don't test it, and it might change in the future....
 
#5,658
Dear zfe,

You are able to measure things.

Could you see if the polarity switch works during playback?

I would hope I would be among many grateful to you if you could.

Edit: Just thinking - could one feed the SOEKRIS say a 100 hz sine wave "file" and simply use an AC voltmeter to see if the polarity changes?

Thanks and take care,
 
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#5,659
rickmcinnis said:
So you are saying it is impossible that the polarity change can occur during playback?

I have long maintained that a placebo audio tweak is as good as any as long as the illusion lasts!

I sure thought I heard a difference. Hope I can maintain the illusion ...

Well, that's a little more than a little embarrassing.

I guess this applies to the filters, also?

I know there is only so much that can be done but not being able to switch during playback makes it close to useless since this is something that can change between tracks, let alone, albums. Oh, well ...
Click to expand...

Perhaps after all you do change the polarity as even Soren cannot confirm what exactly happens during runtime when you activate the command. I guess if you change the polarity now same way you did before, but now after your confidence is shaken, I guess you will hear the difference if it is real, meaning polarity can be changed during playback.

Did you also investigate if polarity can be changed in SDTrans? I am going to check now if I can change the polarity in my cd transport signal processor. It would be cool and elegant if one could change the polarity this way by just applying H or L to a corresponding IC pin.
 
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#5,660
rickmcinnis said:
Dear zfe,

You are able to measure things.

Could you see if the polarity switch works during playback?

I would hope I would be among many grateful to you if you could.

Edit: Just thinking - could one feed the SOEKRIS say a 100 hz sine wave "file" and simply use an AC voltmeter to see if the polarity changes?

Thanks and take care,
Click to expand...

I was only able to trigger the invert/normal change (after set mode =...) with a power cycle.
Exiting back from the "+++" level does not change invert/normal.
Things that work with loading new filters during playback (switching inputs and/or sample rate) did not change the invert/normal state.

By the way, BOTH channels get inverted. Invert will be of no use for correcting recording where one channel was accidentally inverted.
 
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