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Mr White's "Opus", designing a simple balanced DAC

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K

korben69

Member
Joined 2006
Russ, I've tried as you've told me.
DIP Switch 1 on SPDIF Module shows 3 positions from left to right : + 0 1

Tested setup
AIF -> Right = 1
TXSRC -> Left & Center = 0 & + (both positions tested)
AIFCONF1 -> Left & Center = 0 & + (both positions tested)
AIFCONF0 -> Right = 1

All 4 Green Leds On when SPDIF cable connected from CDPlayers to SPDIF, tried with Marantz CD873 and CD50.
Tried with 2 other sets of XLR balanced cables.

No sound :(
 
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K

korben69

Member
Joined 2006
Hi Brian

I've set PSU voltage and wiring like this
1° - VA : 6.50v for OPUS
2° - VD : 5.00v for OPUS, S/PDIF and OTTO
3° - USB : Din/Dout + Jumper : I2S

I'm wondering about another 5v supply for OTTO and Led's.
One led is for On/Off, the other one for S/PDIF or USB.
Do you think I need another transfo or could, I use one secondary for this purpose ?

Cheers
 
eclectic2k

eclectic2k

Member
Joined 2005
korben69 said:
Do you think I need another transfo or could, I use one secondary for this purpose ?

Cheers
Click to expand...

My 2c - You're fine using the same VD supply for the otto & LED's. The opus has another set of regulators anyway, so anything else on the 5v is pretty well isolated. (and as long as there's enough power, a relay and some LED's isn't going to generate much if any noise)

If you really want to have another supply, there's no problem sharing the same transformer. Again, as long as there's enough current available (which there should be)

-CK
 
eclectic2k

eclectic2k

Member
Joined 2005
eclectic2k said:
I finally finished my Opus. (WM8741) It sounds fantastic. Squeezebox (flac) -> TP 8804 SPDIF -> Opus -> Ballsie. (using LCDPS & Placid BP)
Click to expand...

I just thought I'd post a few of notes...

Since I left the DAC in hardware mode, I found it necessary to connect GEN_FLAG (diode 'D2A') to the mute (MUTEB) signal on Opus (8741). Otherwise I got an ugly scratching noise whenever I had no signal. (8741 does not auto mute in hardware mode) This way it mutes when there's not a valid input signal.

I also connected up some toggle switches to control the 8741 samplerate and filter select settings. Haven't played with them much yet though.

In default Medium Sample rate & minimum phase 'soft knee' filter, it sounds pretty darn good.
-----------

comparisons:
with my Lavry DA10, it was difficult to pinpoint the differences in sound. It most definitely sounds at least as good as the DA10 if not better. (sound is clean and detailed, without any noticeable harshness) I've been listening primarily to the Opus now for a while and am quite happy with it. If I were to try pinpoint how it sounds different from the Lavry I'll need a lot more back to back comparison. I may not bother :D

I also compared to an "off the shelf" gigalab (teradak?) tda1543 based DAC. (borrowed from a friend) This was my first listen to a 1543 based DAC. It's an x8 version, unmodified. I think it could likely use some better output caps at the very least? :confused:
anyway, the Opus is noticeable cleaner and more detailed, without losing any musicality. The tda1543 DAC was not very bad - bass was OK, midrange was OK, but the overall sound was a bit smeared with the highs especially 'fuzzy' Maybe not a fair comparison, but I'd go for the opus any day over a 1543 DAC ;)
(maybe a better implemented 1543 could compare - though I think the 1543 is of limited potential)
 
K

korben69

Member
Joined 2006
eclectic2k said:
My 2c - You're fine using the same VD supply for the otto & LED's. The opus has another set of regulators anyway, so anything else on the 5v is pretty well isolated. (and as long as there's enough power, a relay and some LED's isn't going to generate much if any noise)

If you really want to have another supply, there's no problem sharing the same transformer. Again, as long as there's enough current available (which there should be)

-CK
Click to expand...

Many thanks to you CK for your hints, I'll let it run like this.
On LCDPS, VD rail is hottest than VA, more current consumption (Opus/Otto/SPDIF/Leds.
The transformer is 30VA rated, enough for this build I suppose.
Thanks for your input ;)
 
max426

max426

Member
Joined 2008
Paid Member
After letting my Opus DAC sit in a drawer for over a year I finally decided to put everything in a temporary chassis. I purchased it as a dual mono with Ivy, however I am currently running (trying) it in stereo mode with only 1 dac board.
OK, so I ordered transformers last week from TP and got them 2 days later.
Thanks for the quick service Brian:D
Everythig went together with no problems, I set the voltages to 15V for anolog and 7.5V for digital. Plugged it into a windoze xp machine, it was recognized right away, I thought WOW that was easy.

Not so much. I have hardly any volume, with my ear against the speaker and volume maxed out I only hear a very faint hint of the music.

I have attached a few pics.


Any ideas on what I screwed up?:confused:
 

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Russ White

Russ White

Member
Joined 2005
twistedpearaudio.com
I would look at the IVY. Make sure the relay is activating. The the voltage into the IVY is too low the relay will not activate.

Also check the that relay is not in backward.

If it is not your output will always be shunted to GND.

One other note. When using the IVY you can short the output caps on the Opus. I usually omit them and just use wire jumpers from clipped resistor leads or such. You will get better results this way. I highly recommend it.
 
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max426

max426

Member
Joined 2008
Paid Member
Russ White said:
Also you could try taking +OUT and GND from the balanced output. If this gets you sound then the issue is with the BAL/SE side of things. Very likely the relay.
Click to expand...

Russ, Thank you very much for the quick reply.:cool:
I took the signal from the balanced output on 1 channel and it has volume now, however it only had about half the volume of my cd player.
The relay is installed with the text opposite of the pcb text. I have attached a pic
I will turn the voltage up on the Ivy(1-2V) a bit to see what happens.
If I had a balanced preamp I would probably just go direct from the Opus.

Thanks again, Jim
 

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hayenc

hayenc

Member
Joined 2005
Paid Member
Russ, do you have a manual/schematic still floating around for this version of the IVY? I also have been a bit tardy in building up the old Buffalo and OPUS using it. I do notice on the picture max426 just posted in #1795 that R17-R20 are resistors. In the kit I got for the OPUS IVY, those are zero ohm jumpers.

Craig
 
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