Dorati NOS DAC kits

[jimk04]

Thanks for the input, I do have a Miro Dac, have built a couple now.... didn't I send you a PCB? Singapore?!.*edit just seen your last post above)! My latest has the EUVL discrete IV and I built a D1 IV too.

It is an enjoyable project but like you say Richard's DACs are very much 'up there'. I have a PhiDeca DAC fed from Ian's Fifo , powered by Salas Ubib. Sounds awesome. Replaced an Ian ESS DAC with it and all its awkward PSU requirements.

Looking forward to the Dorati

 

[Vunce]

Hi Richard,
If Dorati is strictly used as a source feeding a preamp only, not with headphones or driving an amplifier direct, would you omit or change values of any components in the output stage?

 

[abraxalito]

Hi Vunce - if the load is high impedance I might reduce the bias in the output stage so as to draw less power from the supply. This wouldn't make it sound any better its just a touch 'greener' to run it cooler. Increase R32 and R44 to 47ohm (from 30ohm). I might also use film caps in place of electrolytics (C11,C16) but those would have to be off-board.

 

[Vunce]

I believe 22K is the lowest input impedance preamp in my stable.
I’m not bothered by Dorati running warm, probably won’t do that mod just to lower the bias. Would R17, R50 be required at all in this scenario?

 

[abraxalito]

If you take out R17 and R50 then connecting the DAC to a preamp might give an audible 'clunk' as the output caps charge. Those resistors are an attempt to pre-charge the output caps as soon as power's applied to the DAC.

 

[Vunce]

Thanks for the info Richard. Enjoy your weekend!

 

[ClaudeG]

Thanks Abrax!

I guess the output resistor isn't a must do re tweaks, but the output cap could be worth exploring depending on the impedance to be driven.

Wonder how various PS caps could react

Need to move house and build one

 

[twocents]

Finished my psu for Dorati last night, using a MC7812CT regulator - but it only pumps out 11.5V
Will that be ok for Dorati? I was hoping for a little more than 12V rather than less.

 

[abraxalito]

Sounds a little bit marginal. Do you have a diode you could put in series with the 0V lead of the 7812? That'll push the voltage up to just above 12V. The cathode of the diode goes to GND.

 

[twocents]

Thanks. I can also use MC7815 here - would 15V rails be better?

 

[abraxalito]

I think 15V would be better than 11.5V. If its a little bit under 15V, better still.

 

[commstech]

waiting for my pair of Elna silmic 1000uf caps to use at output. curious to find out.

 

[Vunce]

Comms,
The physical size of the 1000uF Silmic is very large for that position. If you have a 220uF try that. I haven’t noticed any loss of bass using a 220uF output cap.

 

[abraxalito]

^^ 1000uF is there to allow direct drive of 300 ohm HPs. For preamps, 220uF is more than plenty.

 

[Vunce]

Thanks for the additional info Abrax, I don’t ever use HP’s and mostly ignore that part of our hobby. I should probably pay more attention there

 

[abraxalito]

With a pair of Drop HD6XX and a Dorati you've gotten yourself very simple and comfortable output to hang off a PC or tablet...

 

[twocents]

Dorati on my bench tonight. First sorted out the psu. Now pumping out 14.4V and I am happy with that. Started soldering Step 1 components and overcame my biggest anxiety - getting those dac chips soldered to the board. Should be downhill from here, but I won't relax until the measurements are ok. Getting excited to finish this DAC, but the enclosure must also be made sometime.

So, it looks like 220uF Silmics might be a good option for outputs caps? I have also read good things about Nichicon Muse UES series non-polar caps, but can non-polars be used here?

 

[abraxalito]

Non-polars would be perfectly fine.

 

[twocents]

My downhill is more rocky than I hoped. Please help - I have no idea what to do with R23. I see a couple of 0R resistors and assume they have some part to play here, but there are 3 solder pads. Do I have to choose between two pads, based on what? Sorry for the noob question.

 

[twocents]

Sorry - I recall something now. It sets the signal phase - normal or inverted, right? For a normal plane jane non inverting signal DAC do I use a 0R across the two pads on the right (0 degrees)?
Noob question - why would one want to invert the phase?