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

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#3,521
soundcheck said:
I guess that's not what he meant.

It'll be tricky to compare "a" DAM, since it is just a module, a part of a system.

The overall performance of the DAC - the entire system - e.g. depends on what

1. power supply
2. filter and firmware revisions
3. output stage
4. usb interface
5. onboard modifications
6. and perhaps even transport with usb-link tweaks (filter/USB-Regen etc.)
u run.

Even the attached amp might matters.

His message was. Yes the DAM has quite some potential if you've done your
homework. A pretty basic implementation of the module will probably have a hard time
competing with the top commercial DACs out there.
Click to expand...

Very well put soundcheck. That's exactly what I was inferring.
 
#3,526
27.4K Resister for pop noise

soekris said:
Finally it's here, the first major dam1021 firmware update. I have named it version 0.99, please let me know if there are any issues, small or large. The plan is then to release version 1.00 in a week or two.

Firmware update on the dam1021 is done using the RS232 serial port, either by one large file or three separate files:

http://www.soekris.dk/1021full_099.skr ----> all firmware/filters

http://www.soekris.dk/1021fpga_099.skr --> fpga firmware
http://www.soekris.dk/1021filt_099.skr ----> dac filters
http://www.soekris.dk/1021_uc_099.skr ---> uC firmware

To update the dam1021 firmware, you need to have the rs232 serial port connected and working with terminal emulator software. Enter the uManager by typing +++. You should then get the uManager prompt, then you type

# download

Start download session using Xmodem CRC protocol, when all downloaded then type command to update the uC with new firmware

# update

You can then enter uManager again and verify revision 0.99 firmware is loaded.

Revision 0.99 firmware have the following bug fixes / improvements / new functions:

* PLL Clock Sync at sample rate change cut down to less than 0.2 second
* Isolated Serial port now works, note that port is at 3.3V cmos level
* Serial Port now interrupt driven, no character loss at high speed
* Volume Control now is -80db to +10 db, and phase bug fixed
* Volume Control also now have zero crossing detect
* Power Off plop can be reduced to 1/3 by adding a single 27K4 resistors, see picture attachment
* FIR1 filters doubled in size, so max 2032 coeff @ 44K/48K, 1016 @ 88/96K, 508 @ 176/192K, 127 @ 352/384K
* You can now select four sets of filters, named Linear, Mixed, Minimum and Soft.
* FIR1 coefficients are now 1.31 format, filters should be good down to around -150 db
* Stock filter now have improved deemphasis filter
* Input Source Select bug fixed
* New mode setting: Normal, Inverted, Balanced Left, Balanced Right
* The tiny bug on signal saturation on -full scale fixed
* Should now be possible to do balanced and crossovers by parallel the inputs and connecting the isolated serial ports together, more details to follow

To do: DSD support, will add that in a couple of months.

To experiments with filters, the filter .txt file and updated mkrom utility is here, note that FIR1 coefficients now have to be < 1, but are now checked by mkrom utility.

http://www.soekris.dk/1021filt_099.txt
http://www.soekris.dk/mkrom.exe
Click to expand...

For this 27.4K resistor mod, please verify whether need to upgrade firmware to latest version 0.99?
 
#3,527
Soren, while MKROM makes old style filters (type 1/2) I do not see a possibillity to use them with firmware 0.99. Do I overlook something?

Type 1/2 filters would ease life for measurements. If it is not possible with firmware 0.99 I would downgrade to 0.9 for that ... or are there any objections versus downgrading?
 
#3,528
zfe said:
Soren, while MKROM makes old style filters (type 1/2) I do not see a possibillity to use them with firmware 0.99. Do I overlook something?

Type 1/2 filters would ease life for measurements. If it is not possible with firmware 0.99 I would downgrade to 0.9 for that ... or are there any objections versus downgrading?
Click to expand...

Type 1/2 is for firmware 0.9 only, going forward from 0.99 it's all type 4-7 & 8-11.

I do not recommend downgrading firmware as it's not tested, but it's probably possible. Keep your ST programming tools close by if something goes wrong....
 
#3,529
Today we spent sometime at another friend's home, comparing his MSB dac (an older model - Platinum Link Plus) with Soren’ s R2R.

Other equip: CEC belt drive, Audio Research, Wilson Sabrina.

We listended to a number of variety CDs, and its clear to.us that Soren’s dac had the upperarm in the overall performance, with or without the Lampizator buffer insitu. (opamps section bypassed).

The dac I have (serial #00048) is the.first version with no firmware upgrade fyi.

Congrats Soren. 🙂

BTW, I am looking forward to.upgrade the hardware.part of my dac..could someone help.to.point out where the info is? Thanks! 😀
 
#3,537
SMT soldering

Hello,
yesterday I started soldering the Vref PS mod, one hour later I finally had one resistor soldered 😱
I use a PC microscope to see what I'm doing.
Those SMT are really small, I've done some SMT soldering in 1206 package and that's still doable.
But the SMT package of the R2R is really small, many times the SMT component stick to my soldering iron instead of the PCB.
Is there some kind of trick to keep the SMT part on its place ?

Regards,
Danny
 

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#3,538
Apply solder to one solder pad, hold the iron against that pad to keep the solder melted, move one side of the resistor onto the pad with the help of a magnifying glass and forceps and then solder the other side while the first side is secure. You might have to resolder the first side if the contact isn't good enough.
 
#3,539
danny_66 said:
Hello,
yesterday I started soldering the Vref PS mod, one hour later I finally had one resistor soldered 😱
I use a PC microscope to see what I'm doing.
Those SMT are really small, I've done some SMT soldering in 1206 package and that's still doable.
But the SMT package of the R2R is really small, many times the SMT component stick to my soldering iron instead of the PCB.
Is there some kind of trick to keep the SMT part on its place ?

Regards,
Danny
Click to expand...

It's crucial to use a very fine tipped soldering iron. I used a 0.12mm and it was relatively easy.

You should start by putting a little soldering paste on the existing solder joints. Do not skip this step - it will make your job a lot easier.

Then add some solder on one of the two joints of the existing part so as to tin it. Then place the new part on top of the existing part and heat the tinned joint while holding the new part in place with some forceps. I usually just press lightly on top of it to keep it in place. Use needle-point forceps.

Upon heating, the solder should melt and stick to the new part as well. Then go to the other side of the part and solder it.

Once the new part is secured in place I usually go back to the first joint and add some more solder, just to be sure.
 
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