NOT QUITE NEVER AGAIN, THE GROUP BUY DAC BUILD

[nige2000]

Takes a while to charge bout 2 mins
The norm will be to be on constant charge to save time

[jrling]

Nige
Are you using regulators on the DAC board or how are you keeping the voltage steady?
From what I can understand, you are not concurrently charging supercaps while playing DAC, are you?
Have you found the sound better when not concurrently charging?

We're using the amp power supply system
Nothing completely set in stone though
This is the way i envisage it
Five supercaps
Set to 1.65,1.65,2.35,2.35,2.35
So we have 3.3v 8v and 10 odd volts
The dac has on board regs 10v for that
That manages power up then there's the direct supercap power that bypasses that as soon as the voltages are correct
We're going to use a comparator and relay system to manage that probably on the 8v rail
Supercaps are been charged constantly

There's an interesting difference with the bypass

That sounds clever.

My initial thought was that the first two UltraCaps running at 1.65V each were nearly half the nominal 2.7V voltage spec and I wondered if that was going to cause below par performance of those UltraCaps?

But looking at Maxwell's technical notes, I could find no mention that would be the case and certainly it is not frowned upon by them to have UltraCaps running at any voltage as long as it is not over voltage. I couldn't find a graph of voltage v. Internal ESR but I suspect it might be higher at lower voltage.

There is a loss of energy stored of course as per their note -

Since the energy in the capacitor is proportional to the voltage squared according to the following equation:
E = 1⁄2 C V2
It is possible to utilize approximately 75% of the available energy if the application utilizes from the rated voltage to 1⁄2 rated voltage of the capacitor.

But if they are being constantly charged, even the approx 25% of the available energy you will have stored at 1.65V, will still be 'a lot'.

Good luck with this innovative PSU arrangement.

[jkeny]

Yea, keeping caps at different voltages is not detrimental to them or affect their current delivery capabilities & is a clever way of combining voltages for various power rail requirements

[Sligolad]

Finally got to hear the first DAC board today with USB in and powered by the Supercaps and it is amazing.
Still hard to believe that for the cost involved it can put the Lampizator Big 7 with upgraded PS on the DAC board and EML 45 Globe Valves at $800 a pair a run for it money.

We listened back to back between Niges DAC and the Big 7 on Niges Class A amp and custom speakers and you would struggle on a blind test.
I would say both have strengths over the other but it is so close it is just a matter of flavour.
Niges DAC does great low end and both DACs sound great on Niges speakers, i heard detail and dynamics in familiar tracks today I have never heard before.

Looking forward to getting one of these babies home fed with the SD card and good clocks.
Another amazing piece of kit from Nige will be doing the rounds soon and be prepared to be amazed.

[jkeny]

Nige, you are probably using the same passive I/V as the DDDAC design uses?
You could probably get a good uplift in sound using Richard's filter & I/V?

[abraxalito]

...well at least a CLC filter. Using the trafo provides some filtering (at least of CM noise) but a passive filter will give a more '3D' sound, in my experience. What's the I/V resistor value? If you tell me this I can design the filter fairly quickly.

[nige2000]

133r
I've got 2 270s in atm
If I remember right anything between 100 and 150r seemed to work just fine

[nige2000]

We were talking about srpp valves in the background but my knowledge is almost zero of such things

I though when I put a transistor on the output of my batt tda1387 the difference wasn't huge

I was hoping that using a traffo to convert differential to single ended would bring us far enough

[nige2000]

Abrax if you draw up a mosfet output iv and or filter ill try set it up for sat when the lads are down

[nige2000]

https://www.diyaudio.com/forums/diyaudi ... oject.html
just thinking out aloud
abrax what you think of this?