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

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Russ White

Russ White

Member
Joined 2005
twistedpearaudio.com
_atari_ said:
Hi,

I am one (little step) further in planning for my DAC (OPUS, Metrnome, USB, prob. SPDIF).
Now I am thinking about the power supply:
Is 2*9v for the DAC sufficient? And how should it be spend?
9v for Controller, SPDIF and DAC, 9v for DAC analogue & metronome or
9v for Controller, SPDIF, DAC Metronome and 9v for DAC analogue?

The 9v will of course be regulated to something like 8v/5v respectively (The OPUS, Metronome and SPDIF have regulators for smaller voltage on board?!)
Click to expand...

It will work great!

They have 3.3V regulators. 5V input is fine. A little more gets a bit better regulation.

I would use one supply for everything but the DAC, and one supply for the DAC.

This is the way I have been running the DAC in my office.

Cheers!
Russ
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
ssmith said:


Hi Russ,
On the verge of making an order -- but wondering if the PSUs for the opus and the balsie be run off a single transformer of sufficient capacity -- just by branching the secondaries, one to the LCDPS and one to the LCBPS?
Click to expand...

No, You need separate secondaries for each, in this case 4 would be required. The LCDPS needs approximately 9V/1A x 2 and LCBPS needs approximately 18 - 20V/0.5A x 2. They must be totally separate windings. Overall rating should be in the vicinity of 50VA based on TPA recommendations.
 
BrianDonegan

BrianDonegan

Member
Joined 2004
twistedpearaudio.com
No, You need separate secondaries for each, in this case 4 would be required. The LCDPS needs approximately 9V/1A x 2 and LCBPS needs approximately 18 - 20V/0.5A x 2. They must be totally separate windings. Overall rating should be in the vicinity of 50VA based on TPA recommendations.
Click to expand...

Actually, LCBPS can use 12-18V secondaries. We have switched back to 15VA trafos, which we had originally. Last order, Avel was out of stock of the 15VAs, so we got 25VAs.
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
BrianDonegan said:


Actually, LCBPS can use 12-18V secondaries. We have switched back to 15VA trafos, which we had originally. Last order, Avel was out of stock of the 15VAs, so we got 25VAs.
Click to expand...


:D

The 15VA should be much more compact. I used a competing company's 20VA/25VA transformer and they take up more space in my dac than I originally anticipated.
 
C

culture

Member
Joined 2006
Hi All

Finally finished my opus dac today, nice project but i have to confess i expected a bit more of a difference compared to the internal dac of my harman kardon hd720 cd player. I'm using it in combination with my pass p1.7/f4 and rega r5 speakers. Both rca from the cd player and xlr from the dac are connected next to each other so i can switch instantly from one source to the other but to be honest... i couldn't tell the difference :rolleyes:

makes me wonder, am i worthy this dac.... :confused:

ok, this is only my first impression, i'm just listening to this dac for an hour now and maybe i should give it some time to burn in or what ever and do a bit more serous listening session at a later time..

cheers,

c.

ps, doesn't make me less happy with the dac, only makes me appreciate my old harman kardon cd player a bit more :)
 
O

orthoefer

Member
Joined 2006
Re: USB jack take 2.2

orthoefer said:
Ok. Let's try the USB jack again.

Here is what I have this time: Datasheet

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.
Click to expand...

I posted a description of the above USB jack days (months?) ago and am finally getting around to using it. Let me say, I don't like this jack at all. There are two major problems with it. First, the manufacturer put the text on the jack upside down. USB convention calls for the jack to be mounted in a certain orientation, yet the name and descriptor on this jack are printed opposite--no big deal. It just shows that their "designers" are not paying attention to the standard. Second, the power leads on this jack are comprised of 20 ga wire whereas the data lines are 24 ga. The 24 ga is fine and can be easily soldered into Twisted Pear's USB board. However the 20 ga wires are too big to fit through the PCB holes. The solder pads on the USB input module are very small, so drilling them out is not an option. The only option is to shear off some of the strands so that the wire can fit through the hole. This is a little messy and does not give a clean result. So there you have it. This jack stinks. I don't like the bulkhead connectors that require another USB cable either--too many connections. I'll be on the lookout for a better solution. For now, I will use what I have even though I don't like it.

I think I should have used this instead. It has only 24 ga wires.
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
Re: Re: USB jack take 2.2

orthoefer said:


I posted a description of the above USB jack days (months?) ago and am finally getting around to using it. Let me say, I don't like this jack at all. There are two major problems with it. First, the manufacturer put the text on the jack upside down. USB convention calls for the jack to be mounted in a certain orientation, yet the name and descriptor on this jack are printed opposite--no big deal. It just shows that their "designers" are not paying attention to the standard. Second, the power leads on this jack are comprised of 20 ga wire whereas the data lines are 24 ga. The 24 ga is fine and can be easily soldered into Twisted Pear's USB board. However the 20 ga wires are too big to fit through the PCB holes. The solder pads on the USB input module are very small, so drilling them out is not an option. The only option is to shear off some of the strands so that the wire can fit through the hole. This is a little messy and does not give a clean result. So there you have it. This jack stinks. I don't like the bulkhead connectors that require another USB cable either--too many connections. I'll be on the lookout for a better solution. For now, I will use what I have even though I don't like it.

I think I should have used this instead. It has only 24 ga wires.
Click to expand...

I am confused, the current usb receiver board has a terminal block and at the relatively low speeds used for usb1.1 it ought to be ok. (Heck it sort of works with sck which is much faster ;) ) Do you not have this version of board? Frankly I would be much more concerned about what is going on with the I2S end of things than the USB which is pretty robust by comparison.
 
Russ White

Russ White

Member
Joined 2005
twistedpearaudio.com
Buffalo update

PCBs will be here tomorrow, hopefully will be able to play with the circuit next week.

I have not decided which options too allow for the simple on board controller. I am willing to entertain suggestions.

Keep in mind. I only have 4 switches on the board.

My idea was to use one to select between SPDIF and PCM/DSD.

The other three could be used as a 3 bit register for 7 modes, or it could be used as 3 single option registers.

Of course the cool thing is that since there is an I2C header you are free to configure the chip however you like.

I will even make the source code for the firmware available for anyone who wants to try custom configuration.

Cheers!
Russ
 
O

ojg

Member
Joined 2003
Re: Buffalo update

Russ White said:
Of course the cool thing is that since there is an I2C header you are free to configure the chip however you like.

I will even make the source code for the firmware available for anyone who wants to try custom configuration.
Click to expand...

Excellent! I think this will be a new best seller for you guys, I know I will want one or two :)

Any idea on the pricing? How much does ESS charge for the chip?
 
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