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

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wushuliu

wushuliu

Member
Joined 2008
And add flip flop. I preferred flip flop with all i2s connections I tried including, diyinhk and singxer usb/spdif boards. Now using potato thanks to Nige2000. Spdif -->WM8804-->potato flip flop-->soekris. I've tried regular coaxial spdif as well. The potato adds a level of refinement that the generic flipflops and other input methods don't come close to, and given how inexpensive it is to implement there's no reason not to.
 
carsten.witt

carsten.witt

Member
Joined 2006
M

matt_garman

Member
Joined 2008
paulebappie said:
I'm using a 30VA Rcore transformer 2 x 9V and same regulator. The input voltage to the regulator is 11,2V AC. I'm powering 1 board. Works fine. I tested the regulator @ 300ma and still get 9V output.
So almost same setup, but powering 1 board.

Make sure to isolate the dac, the corner holes are all connected to ground so i use plastic screws.

Try to measure the regulator outputs not connected to the dac but with a 30 ohm load (300mA), do you still get 9 Volts?

[ ... ]

You're powering 2 boards so 2 x 180mA = 360mA (positive rails). Try a load of 22,5 ohm (400mA). 5W resistor should work.
Click to expand...

OK, I finally got some power resistors and time to test this out. The regulator is the DIYINHK LT3042 power supply. Jumpers set the voltage to +/- 9, 12, or 15 volts. For this test I was using the +/- 9V setting. With no load the +9VDC output hovers around 8.99 to 9.01 volts.

Transformer is an R-Core sourced from ebay. Using the 110V primary. It has dual 9V and 15V secondaries (i.e. four total secondaries). I had the 15V secondaries taped off (unused) for this test. 9V secondaries are rated 0.8A each.


|-
| Resistance (ohms)
| Potential (Volts)
| Current (Amps)
|-
| 30.5
| 7.80
| 0.26
|-
|23.0
|7.20
|0.31
|-
|52.6
|8.90
|0.17
|-
|45.0
|8.66
|0.19
|-

In the above table, resistance and potential were measured with my (super cheap) DMM. Current was calculated by dividing resistance by voltage.

So it looks like at least with my stuff, the DIYINHK LT3042 doesn't like using a 9VAC transformer for 9VDC output.

I'm waiting to receive another one of these R-Core transformers with 12V secondaries. I'll repeat this test when I receive that.
 
Last edited:
P

paulebappie

Member
Joined 2006
matt_garman said:
OK, I finally got some power resistors and time to test this out. The regulator is the DIYINHK LT3042 power supply. Jumpers set the voltage to +/- 9, 12, or 15 volts. For this test I was using the +/- 9V setting. With no load the +9VDC output hovers around 8.99 to 9.01 volts.

Transformer is an R-Core sourced from ebay. Using the 110V primary. It has dual 9V and 15V secondaries (i.e. four total secondaries). I had the 15V secondaries taped off (unused) for this test. 9V secondaries are rated 0.8A each.


|-
| Resistance (ohms)
| Potential (Volts)
| Current (Amps)
|-
| 30.5
| 7.80
| 0.26
|-
|23.0
|7.20
|0.31
|-
|52.6
|8.90
|0.17
|-
|45.0
|8.66
|0.19
|-

In the above table, resistance and potential were measured with my (super cheap) DMM. Current was calculated by dividing resistance by voltage.

So it looks like at least with my stuff, the DIYINHK LT3042 doesn't like using a 9VAC transformer for 9VDC output.

I'm waiting to receive another one of these R-Core transformers with 12V secondaries. I'll repeat this test when I receive that.
Click to expand...


Nice measuring!

@least now you're sure where the problems originate.

Keep us posted.
 
MikeyFresh

MikeyFresh

Member
Joined 2016
carsten.witt said:
Hi all,

som pics from my build ...

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


Now just a little align the cables ... black cable ties ..... :D
Click to expand...

Simply outstanding, congratulations!
 
M

matt_garman

Member
Joined 2008
gavinb said:
You could also measure short circuit current through 9V secondary to confirm 0.8A is available.

Winding will heat up but a quick test should confirm current rating.

Hopefully a uprated transformer will also confirm.
Click to expand...

I tried to measure AC current through the 9V secondaries. I don't think my $10 DMM has the precision for this. My current-mode settings jump from 200mA to 10A. And over 200mA I have to use the no-fuse leads. I got some nice little sparks and made the transformer hum, but the DMM always read 0.0. :confused:

Anyway, I received the new transformer with two 12V/0.7A secondaries and two 9V/0.7A secondaries. For this test, the DIYINHK LT3042 regulator was again set to +/- 9 VDC mode. I used the 12V secondaries on the transformer (taped off the 9V secondaries). Using the 110V primary of course.

Unloaded, the 12V secondaries measure 15.1 or 15.2 VAC.

Here's how the voltage measured with different pure resistive loads (i.e. power resistor across + and GND terminals of the regulator):

Code: 
Xformer   Resistance  Potential  Current
          (ohms)      (Volts)    (Amps)
9V/0.8A   52.6        8.90       0.17
          45.0        8.66       0.19
          30.5        7.80       0.26
          23.0        7.20       0.31

12V/0.7A  30.5        9.00       0.30
          23.0        9.00       0.39
          20.8        9.01       0.43
          18.9        9.00       0.48
          15.7        8.35       0.53
          10.7        6.87       0.64

I copied the table from my previous post and included it with the new results. This allows for easy comparison; also, I noticed that when viewing it on my phone via Tapatalk, it doesn't render the table tags at all. So I'll try with a code block.

So, according to Soekris's documentation, a single dam1021 draws 0.18A at 10V on the positive rail. My pair should therefore draw about 0.36A. According to the results above, I ought to be able to do this comfortably while maintaining 9V.
 
G

gavinb

Member
Joined 2009
@matt_garman

So you will be using 12V secondaries and set LT3042 to 9V?

The onboard bridge if still there will lower the 9V.

How is heat on LT3042's and Soekris?

I plan to use same regulators for a dual-mono setup as soon as they arrive, transformer will be 2x 9V/in parallel (50VA).

Will be using a regular for each rail (4 in total)
 
Last edited:
M

matt_garman

Member
Joined 2008
gavinb said:
So you will be using 12V secondaries and set LT3042 to 9V?
Click to expand...

That's the plan. Currently using an xformer with 15V secondaries and setting the LT3042 to 12V. This works fine, but per Soekris's recent statement that 9VDC is ideal for the dam1021, I'm thought I could save some heat by going down to 9V for the DACs.

gavinb said:
How is heat on LT3042's and Soekris?
Click to expand...

I haven't done any formal testing of heat, other than to touch random things and see if I get burned. :) I haven't poked around on the dam1021 boards too much. But with the current 15V xformer / 12V LT3042 setup, it's actually the choke on the LT3042 positive rail that gets too hot to touch (for more than a second or so anyway). And the info on DIYINHK's webpage says that the choke is the first thing that will have thermal problems in a too-much-current situation.

Generally, I fire up the system on a Friday evening and let it run nonstop until Sunday evening. No smoke, and everything works as expected... so in that regard, I think it's OK. However, I don't have this system in an enclosed case yet (i.e. the top is open). So heat could be a problem when I close the lid, I'll just have to wait and see.

gavinb said:
I plan to use same regulators for a dual-mono setup as soon as they arrive, transformer will be 2x 9V/in parallel (50VA).

Will be using a regular for each rail (4 in total)
Click to expand...

I think a 50VA transformer is quite a bit too big, unless you're going to power other things as well.

Though I do like the idea of separate regulators for each dam1021 board. I'd go that route too, except that I'm out of space in the chassis (and don't want a bigger chassis). That's my only complaint about the dam1021, the physical size. If I ever manage to wrap up the countless other projects I have in flight right now, I'd like to take a stab at designing a board like Normunds's 1021 input/switch board, but mine would be for the dam1121 (OEM module). The 1121 is physically smaller. I'm thinking one approach would be to actually make a "motherboard" similar to what Schiit does with their DACs. That is, the motherboard has all the power supplies, and all the "glue" circuitry to connect all the other modules. In my case, I'd have two dam1121s and a Raspberry Pi (or other SBC). It's just a fantasy at this point though. :)
 
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