A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

Jump to Latest
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
juliobozek said:
Am I the only one who gets the best sound at 7.5V on analog side?
Click to expand...

Hard to say, if you are the only one. So far I had no complaints that the DAC would not sound well at 8 volt.

The analog voltage is not the only thing of course. It depends on the bias current. Pin 20 so to speak and the DC bias resulting of that with the Reload resistor value. And bottom line on the AC rms output at 0dBFS

So what is your bias you are playing with and what is your ac voltage at the load resistor when playing a sinus tone at 0dBFS ?

.
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
Not sure what you simulated, but the voltage is dependent on the 2 yellow LEDs and the current flowing through them. And you will likely not have the right spice models for exactly those parts I must assume. Which looks like it as the outcome is not what the real shunt on the PCB delivers.

But to be honest, for simulations it does not matter too much, as you probably look more for PSSR and output impedance over a wide frequency spectrum in your simulations ?

.
 
J

juliobozek

Member
Joined 2020
michl2604 said:
I guess you will not find that many people who have compared different analog voltage levels. I would try it, because I'm curious if I could hear any differences, but especially with the new DAC boards it's not that easy to change the voltage (because of the tent shunt part). And I think that doede with his experience has chosen the correct voltage carefully during design phase! I don't find any lack of bass with my DDDAC either. I remember that the input voltage for the shunt and the LDO in front is important and that exact 12V may be a little bit too low. There was 12,5V recommended. I'm also running it with a little bit higher input voltage. So maybe you get a better performance by decreasing the analog (output) voltage, because the working voltage for the LDO / Tent shunt is higher in that case?
Click to expand...

I don't use LDO. I have very stable 10.2V regulated power supply directly at shunt input.
 
J

juliobozek

Member
Joined 2020
dddac said:
Hard to say, if you are the only one. So far I had no complaints that the DAC would not sound well at 8 volt.

The analog voltage is not the only thing of course. It depends on the bias current. Pin 20 so to speak and the DC bias resulting of that with the Reload resistor value. And bottom line on the AC rms output at 0dBFS

So what is your bias you are playing with and what is your ac voltage at the load resistor when playing a sinus tone at 0dBFS ?

.
Click to expand...

I have 2.65V bias, 135ohm resistors, 7.5V analog supply voltage.

I also use 2SK208-R, not 2SK208-O, because it wasn't in stock. Should i use the "O" type? I have 40.2mV across 100ohm resistor on both channels. Potentiometer resistance is 110ohm.

I can measure sinus in few hours, i will post results here.

Maybe i should change jfet current in shunt supply.
 
B

bobafet

Member
Joined 2017
Hello everyone!
I would like to get some advice before making a purchase.

Currently my DAC consists of 2 boards + Cinemag Transformers + FifoPi with ReclokPi.
My plan is to upgrade 3.3V PSU FifoPi and ReclokPi to UcPure.

Would using UcPure (set to 15V) for DDDAC be a good idea? For example, using New Class D regulator set to 10V without 7810 reg on the DAC boards, or setting to 12V with 7810 reg?
 
J

juliobozek

Member
Joined 2020
Mini DDDAC

As i promised, my mini DDDAC is in an appropriate case. Pcb slides in case notches, so no screws and drills needed for pcb mounting. Screws are used only on back panel. I will add second deck and transformer in a month. There will be exactly 1mm of height space left :D
 

Attachments

  • 20211127_141236.jpg
    20211127_141236.jpg
    863 KB · Views: 296
  • 20211127_165934.jpg
    20211127_165934.jpg
    818.2 KB · Views: 281
  • 20211127_170002.jpg
    20211127_170002.jpg
    822.6 KB · Views: 314
  • 20211127_170034.jpg
    20211127_170034.jpg
    979.4 KB · Views: 306
  • 20211127_170056.jpg
    20211127_170056.jpg
    747.4 KB · Views: 301
  • 20211127_170209.jpg
    20211127_170209.jpg
    961.9 KB · Views: 185
  • 20211127_171240.jpg
    20211127_171240.jpg
    836.5 KB · Views: 186
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
bobafet said:
Hello everyone!
I would like to get some advice before making a purchase.

Currently my DAC consists of 2 boards + Cinemag Transformers + FifoPi with ReclokPi.
My plan is to upgrade 3.3V PSU FifoPi and ReclokPi to UcPure.

Would using UcPure (set to 15V) for DDDAC be a good idea? For example, using New Class D regulator set to 10V without 7810 reg on the DAC boards, or setting to 12V with 7810 reg?
Click to expand...

Hi Bobafet,

15 volt umpire and than class d 10 volt without 7810 sounds as a good plan, BUT you need to make sure dissipation of the 5volt x current consumption in the class D is taken care off
 
F

Flikoman

Member
Joined 2010
Hi,

I need some advice. I am building DDDAC with 4 boards. There are 2x Ra and 2x Rb per channel. One Ra & Rb on POS and one Ra & Rb on NEG.

For 4 boards there is recommended 68R on Ra and 68R on Rb OR 34R on Ra.

Does this mean I need 4x 68R resistors per channel? See attached image. I am confused because I received only 4x 68R resistors with the mainboard.

Regards
 

Attachments

  • DDDAC.JPG
    DDDAC.JPG
    66.9 KB · Views: 123
F

Flikoman

Member
Joined 2010
dddac said:
Please ask Audio Creative - with 4 boards you should receive 4x 33 (or 34) Ohm resistors

The 8x 68 Ohm (Also additionally populating 4x Rb) is just an alternative to have less power dissipation in the Rload resistors
Click to expand...

Ok, thanks. I will check. I have 68R resistors, but was not sure why there were only 4pcs. If I don't find 33R (34R), I will solder 4x 68R per channel.

Thanks
 
F

Flikoman

Member
Joined 2010
I have finished the build. Will post pictures when I finish wiring, but it sings and works.

Just quick question. Did anyone try more than 2uF output capacitors? Let's say 10uF or even 20uF? It is a matter of phase, yes. :)

But, for now, I will leave it with 2uF and have a listen. Long term plan are output transformers. How do the gold ones for Audio Creative sound? Does anyone have them?

Regards
 
You must log in or register to reply here.
Top Bottom