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

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A

arf

Member
Joined 2006
TNT said:
So you change the OP amps for a better one?

//
Click to expand...

OPA365 should be the same as OAVQ ? and this is not point of my mod.
My mod is to replicate original Søren buffer x 16 (12 in reality) and place this new boards on the top of each LVC595A. Then lift pin 1 of LVC (cut board trace) and connect it to OPA365 buffer. Only two wires will connect each OPA buffer to original Søren buffer on the board; Vref and 5v.
Søren what is your opinion about this mod? and also do I need to lower Cx in Vreff line?

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Cheers
Danny
 

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A

arf

Member
Joined 2006
zfe said:
Perhaps helpful also for others until we (hopefully) get the schematics:
I photoshoped the traces and vias that are on the backside of the DAM (rev1) as transparent red on the front side. What is missing are the traces on the front beneath the components or covered by the white paint and on the back the ones that are under the sticker.
Click to expand...

Wow man, this is insane, how you did it? thank's it helps heaps!
cheers
Danny
 
W

wineds

Member
Joined 2006
arf said:
OPA365 should be the same as OAVQ ? and this is not point of my mod.
My mod is to replicate original Søren buffer x 16 (12 in reality) and place this new boards on the top of each LVC595A. Then lift pin 1 of LVC (cut board trace) and connect it to OPA365 buffer. Only two wires will connect each OPA buffer to original Søren buffer on the board; Vref and 5v.
Søren what is your opinion about this mod? and also do I need to lower Cx in Vreff line?

attachment.php


Cheers
Danny
Click to expand...

Will there actually be any benefit given that surely the greatest step load is likely coming from the MSBs (ie : only four LV shift registers for the whole DAM)? I think additional capacitors will still be required?
 
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R

rhythmsandy

Member
Joined 2012
soekris said:
Sorry, this is beyond where I will even comment on it, you're on your own....

I can only say to everybody else: Don't try it, the chances are pretty high that you ruin the board.
Click to expand...

I feel the same the mod levels are going too deep I think soren its better that you add a LDO for each Shift register. That would solve the problem where everybody is worried about.
 
W

wineds

Member
Joined 2006
zfe said:
Perhaps helpful also for others until we (hopefully) get the schematics:
I photoshoped the traces and vias that are on the backside of the DAM (rev1) as transparent red on the front side. What is missing are the traces on the front beneath the components or covered by the white paint and on the back the ones that are under the sticker.
Click to expand...

Nice work zfe. Now based on Paul's latest work, all we need now is SMD pads to add large value Polymer caps to the back on the board. I hope this can be added in a future board revision :

Vref musings: the final frontier? | moreDAMfilters

875075155010 - WURTH ELEKTRONIK - CAP, ALU POLYMER, 1000UF, 6.3V, RAD CAN | element14 Australia
 
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B

bambadoo

Member
Joined 2003
bambadoo said:
Houston - we got sound. :D
This was the problem.

Searched the bin and found a couple of smd resistors parallelling to approx 6.5kohm. (nearest 6040r I could find).
Now it works again.

How important is the value 6040r here? Will order some in a couple of days.

Thanks guys !
Click to expand...

But I am not sure if the mod was worthwhile soundwise.

arf said:
no big 3300+uF caps (turn DAM1021 into a boombox and no ceramics
Click to expand...

I got the same feeling. The dam gets really "bass heavy". Almost a loudness effect.
I use 16*1000uf (16 cap mod) polymers in total. Total 16000/4 = 4000uf each vref.

Has anyone experimented with different cap values for the vref. Testing by ear and not with scope ?
I might try to reduce the capacitance and test?
 
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A

arf

Member
Joined 2006
bambadoo said:
But I am not sure if the mod was worthwhile soundwise.



I got the same feeling. The dam gets really "bass heavy". Almost a loudness effect.
I use 16*1000uf (16 cap mod) polymers in total. Total 16000/4 = 4000uf each vref.

Has anyone experimented with different cap values for the vref. Testing by ear and not with scope ?
I might try to reduce the capacitance and test?
Click to expand...

I did, replaced all ceramic shifter caps with 10uF stacked film plus 2x 10uF on OAVQ buffer = total per rail 60uF (no electrolytes any where). Also 1200pf with 470pF polystyrene caps and lifted leg of LM49710 (connected to the ground).No mod to OAVQ buffer (stock form). After low esr high caps mod plus resistors, comparing to stock DAM(my second board) I felt like "the trill is gone", all those uMcro guitar riffs, spouky notes of real sound, all turn into mushy background and boombox. So I took off all fancy mega uF ally NICHICON's And o boy what a difference, even PANDORA app now sings....not to mention HiRez flac, can't wait for DSD support......(this could be so far the best mod).....

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now next is uncharted territory of OPA365 individual Vref buffer's mod, for which I believe does have merit because serving individually each shifter with its own buffer (lets say the "loudest" one in given time) would keep balance to the rest of R-2R . Thanks Søren any way on your comment.
cheers
Danny
 

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B

bambadoo

Member
Joined 2003
To be of help...
Here is the manual on Soekris "tech" page
http://www.soekris.dk/download/dam1021/dam1021 user manual 20151005.pdf
I cannot find any reference to J9 though. f you search this thread there might be some information.

Good luck with your board. There are people here willing to help.

Pages you should visit.
moreDAMfilters
https://hifiduino.wordpress.com/
Dimdim's Blog | DIY Audio, Arduino, Computers, Music
Soekris Engineering, Inc. | Single Board Communication Computers (official site)
and of course this thread and especially the first post.

They all provide excellent information

And once again. Good luck with this great product.
 
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