High Performance WM8741 Upsampling DAC New Version build thread (show 'n tell too) - Page 5 - diyAudio
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Old 27th January 2012, 02:23 PM   #41
regal is offline regal  United States
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Well here is a good start from the datasheet, we just need to find appropriate opamps and package size to fit the three spots on the board, there will be some jumpering. trace cutting but I think this would be worth the effort. Unfortunately I am not up to speed on opamps for V-out S-D dacs, So any recommendations would be appreciated. This would also give balanced and proper unbalanced outputs.

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Old 27th January 2012, 02:32 PM   #42
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Could we use something like Burr-Brown fully-differantial OPA1632?

Could also use LME49720 for bal to se?

The easy solution would be to just buy the TPA IVY III line stage

Do

Last edited by pinnocchio; 27th January 2012 at 02:37 PM.
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Old 27th January 2012, 05:18 PM   #43
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I got my boards in today! I'll need to get someone to assemble this.
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Old 27th January 2012, 08:37 PM   #44
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Quote:
Originally Posted by merlin2069er View Post
I got my boards in today! I'll need to get someone to assemble this.
Can you take some pics of the boards, especially the top and bottom of the main DAC?

I ordered late, so I am still waiting for my boards to show up.

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Old 28th January 2012, 06:24 PM   #45
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Information directly from Priyesh

Just everyone can use the data

MAIN DAC BOARD
74HCU04 IC1 SOIC14
PCM2707 IC2 32-TQFP
74HC157 IC3 SO1
SRC4192/AD1896 IC4 SSOP28
WM8741/WM8742 IC5 SSOP28
OPA2365 IC6 SO-8
SN74AHC1G08 IC7 SOT23-5
SN74AHC1G14 IC8 SOT23-5
AD8656/AD8532 IC9 SOIC8
LP2992 REG 1,2,3,4,5 SOT23-5
TPS3809K33 RST SOT-23

DIGITAL RECEIVER 1
DIR9001 IC TSSOP28

DIGITAL RECEIVER 2
WM8804 IC SSOP20


Thanks
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Old 29th January 2012, 12:15 AM   #46
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Mini dac boards....

Click the image to open in full size.

Click the image to open in full size.

Sorry they're a bit fuzzy. I'll take a few more soon (my batteries were running low on my digital camera.)
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Old 29th January 2012, 04:09 AM   #47
regal is offline regal  United States
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Its been a while since I did smd chips like these (been in tube world too long.) I used to use a low temp solder from Tangent with SSop-28 fairly easily but he no longer sells it. It makes installing these little chips a breeze for anyone.

anyone know where to get the tangent low temp solder for smd work?

(yes I know its technically not as good to use a eutectic solder for boards destined for the military, nasa, etc but for this DAC I think it will be fine)
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Old 30th January 2012, 04:47 AM   #48
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Quote:
Originally Posted by regal View Post
Its been a while since I did smd chips like these (been in tube world too long.) I used to use a low temp solder from Tangent with SSop-28 fairly easily but he no longer sells it. It makes installing these little chips a breeze for anyone.
I guess I'm dense, but I'm not sure how low temp solder helps to install SMD chips? I see people use low temp solder for removing parts.
BTW, low temp solder seems to be easy to find, not sure if there was anything special about Tangents. I would guess maybe not, and that's why he no longer sells it.

A good magnifying glass (I have a headband kind) really helps, along with a very fine tip for your iron. Also, some fine solder braid, so if you get bridges you can remove them.

Before you're done, you may find that the little regs and gates are harder to install then the bigger IC's.

BTW, general comment, you guys may want to buy spares of the little parts, it's easy to push too hard on them when you are trying to hold them down, and send these little guys flying somewhere.

Randy
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Old 30th January 2012, 04:57 AM   #49
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Default Voltage Regs

Thought I would share my thoughts on the voltage regs, and how they are used.

In the DAC, there are two 5VDC regs, and five 3.3VDC regs.

The first 5V reg powers the HC04, HC157, Oscillator and analog section of 8741. Each device has itís own ferrite bead to isolate it, but power still comes from one reg.

The 2nd 5V reg powers opamp, headphone amp and HCg14.

So, since I am planning to remove the opamp and headphone amp, the 2nd reg would just power the HCg14. This gate is used to drive one of the LEDís. I donít like having all of that stuff on the first reg, so I plan to put the oscillator on this reg.

At first, I want to use this as a USB DAC, and not use SPDIF or I2S inputs.

As such, I am not really using the HC04, and donít need to HC157. The HC04 buffers the SPDIF input, and the HC157 selects the i2S datastream. I may choose to not install the 157, or the HC04. This would leave the analog 8741 on its own regulator, and the oscillator on its own regulator, which I think is ideal. My goal is for each IC to have itís own regulator, so if I do add the HC04 and HC157 later, I would probably add a couple more regs for them too.

For the 3.3V regs, the first one powers the PCM2707 and the g08. The g08 just generates a status signal which I donít think switches state, so I think it is OK to leave both parts on this reg

The 2nd 3.3 reg powers the daughtercard.

The 3rd 3.3 reg powers the SRC4192.

The 4th 3.3 reg powers the RST chip.

The 5th 3.3 reg powers the logic part of the WM8741.

So, 3.3 power seems very well done (IMHO), one reg for every chip, except the first set, where it should be fine.

One last comment about power. I have read part of the long buffalo dac threads, and power is a big deal for that DAC. Wondering how much affect it would have on the sound if you provided separate regs different parts of the DAC?

One more last comment.
I may try a better reg, something like this
Shunt reg
I have seen the Thorsten design this was based on, and had planned to use that, but this may be an improved, albeit slightly more complicated version of Thorsten's simple shunt reg.

Randy
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Old 30th January 2012, 05:06 AM   #50
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Originally Posted by regal View Post
Shouldn't we use a dual supply opamp to combine the differential signals, get the cmrr and possibly lose the output cap? Thinking somehow using the headamp spots for a better analog stage.
I plan to start with transformers, but if those don't work out, will add an active stage.

Aikido has a balanced to SE circuit, if you want a glow in your dac.

Even if I use solid state, I would probably do the output stage on a seperate board, I think it would be easier than trying to mod the board for a different circuit, but I could be wrong.

Randy
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