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

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#3,883
nige2000 said:
its a bit worrying that these 4 13 ohm resistors would have so much influence
after further investigation approx half the msb goes through these 13r's
although these 13r's have the largest influence there is many other resistors contributing to an increasingly accumulative sq loss

it would seem from the pics from the rmaf that there's a different type of resistor on the most significant portion of the r2r ladder
and by the look of the dk website there will be a diy version and an oem version along with a newer version of the 1021 called 1121
is all the creases ironed out?

i'm doing my testing on a 0.05 v1 board so i'll likely not bother changing any resistors on this board maybe the "final" one

i removed the lpf cap for me it sounds much better without
but maybe there's a cap that will sound better
Click to expand...

Nige your PM box is full, empty it in order to receive msg's.

Hi Nige, 13R are part of the ladder and also LPF and I wouldn't recommend to short them out, it wouldn't damage anything but the R2R ladder impedance will be affected (may make signal worse off?). Taking out c135/c142 is what Søren did in order to improve speed of DAM. Now this is good only for testing purpose but in real application I have replaced them with 470pf polystyrene ones.
cheers
Danny
 
#3,885
arf said:
Nige your PM box is full, empty it in order to receive msg's.

Hi Nige, 13R are part of the ladder and also LPF and I wouldn't recommend to short them out, it wouldn't damage anything but the R2R ladder impedance will be affected (may make signal worse off?). Taking out c135/c142 is what Søren did in order to improve speed of DAM. Now this is good only for testing purpose but in real application I have replaced them with 470pf polystyrene ones.
cheers
Danny
Click to expand...

deleted a few messages so im good to go

i had another probe about with the meter since then and with other advice realised these cant be taken out only replaced
ill certainly try some polystyrene caps net time im ordering stuff
thanks for the help
 
#3,887
Trying to connect a usb->i2s interface seems that I have damaged the isolation chips (probably incorrect ISO VDD polarity or overvoltage). Measuring resistance between ISO V3.3 and ISO GND is zero. All voltages on J2 header are OK. The DAC responds to commands sent through RS-232 just fine.

There is no optical damage to the isolation chips but I guess they are fried. Is it safe to assume the only the 3 Si8620 isolation chips are damaged? Should the capacitors on the input side of the isolator be replaced as well?

If any of the other Greek members know of a facility that is able to replace the chips please chime in. As I don't have the equipment to desolder and solder SOIC8.
 
#3,888
As arf already points out, those 13R resistors are part of the R-2R resistor network. They should not be changed, they're not part of any filter as such, but remember that the total R-2R networks output impedance is the R part of the RC output filter.

It's already a high quality thin film resistor, but it's effect on the total resistor network is so tiny that I can't imagine changing it would have any effect at all, unless the value is changed....

Anybody claiming otherwise have either changed other things or are victim to the psyshoacoustic effect of wanting to hear something after spending way too much on otherwise inexpensive parts....
 
#3,890
soekris said:
As arf already points out, those 13R resistors are part of the R-2R resistor network. They should not be changed, they're not part of any filter as such, but remember that the total R-2R networks output impedance is the R part of the RC output filter.

It's already a high quality thin film resistor, but it's effect on the total resistor network is so tiny that I can't imagine changing it would have any effect at all, unless the value is changed....

Anybody claiming otherwise have either changed other things or are victim to the psyshoacoustic effect of wanting to hear something after spending way too much on otherwise inexpensive parts....
Click to expand...


Hi Søren, thanks for clarifying R2R network for us.

Could I ask if November release of DAC1101 will bring long promised DSD capability to DAM1021?
Cheers
Danny
btw
I don't believe expensive parts as per se would make "miracle" in any system, and unfortunately you are right about "psyshoacoustic" effect of expensive parts (some say that gold plated power fuses is all you need!?). However just like special lacquer coating of Stradivary make Stradivarius violin unique, I do believe that adding some of "exotic" components (silver solder, Z foil R and stacked film caps) in DAM's audio path can make for "unique life like" sound.
 

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#3,891
nkalogridis said:
Trying to connect a usb->i2s interface seems that I have damaged the isolation chips (probably incorrect ISO VDD polarity or overvoltage). Measuring resistance between ISO V3.3 and ISO GND is zero. All voltages on J2 header are OK. The DAC responds to commands sent through RS-232 just fine.

There is no optical damage to the isolation chips but I guess they are fried. Is it safe to assume the only the 3 Si8620 isolation chips are damaged? Should the capacitors on the input side of the isolator be replaced as well?

If any of the other Greek members know of a facility that is able to replace the chips please chime in. As I don't have the equipment to desolder and solder SOIC8.
Click to expand...

Look hear
???????? iPhone - Smartphones, Service ??????????? - Laptop - ired.gr
 
#3,892
After a long break, I'm resurrecting my efforts to fire up my DAC

Been reading about the mods.

So FYI, if you don't want to buy a 0.01 ohm 0603 resistor, a 1.2 inch piece of 30 gauge wire has about that much resistance.

In this application, I think it would be "close enough".

I would think it would be easier to install too, but you still have to get the 499r resistor installed.

Randy
 
#3,894
randytsuch said:
After a long break, I'm resurrecting my efforts to fire up my DAC

Been reading about the mods.

So FYI, if you don't want to buy a 0.01 ohm 0603 resistor, a 1.2 inch piece of 30 gauge wire has about that much resistance.

In this application, I think it would be "close enough".

I would think it would be easier to install too, but you still have to get the 499r resistor installed.

Randy
Click to expand...

Btw which make are these resistors?
 
#3,896
soekris said:
As arf already points out, those 13R resistors are part of the R-2R resistor network. They should not be changed, they're not part of any filter as such, but remember that the total R-2R networks output impedance is the R part of the RC output filter.

It's already a high quality thin film resistor, but it's effect on the total resistor network is so tiny that I can't imagine changing it would have any effect at all, unless the value is changed....

Anybody claiming otherwise have either changed other things or are victim to the psyshoacoustic effect of wanting to hear something after spending way too much on otherwise inexpensive parts....
Click to expand...

Came across John Curl reminiscing on capacitors in audio, maybe some of this could be applied to DAM1021 analog part?

Cheers
Danny

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#3,898
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