Soekris Dam Dac

[rickmcinnis]

From what SOEKRIS has written there is nothing critical about this filter.

I am planning on removing it and if I hear the need placing a better cap on the output cables.

I had got Russian teflons for this purpose but was told by someone at DIYAudio that he had tried a Russian teflon and thought it sounded bad. Seems hard to believe but not impossible to believe. Of course, there are a bunch of Russian teflon caps which only adds to the mystery. This same person, I think I am remembering correctly, thought the stacked PP film WIMAs did a good job. Certianly would be much easier to implement than the R-teflons which are huge considering their small capacity.

Nothing wrong with keeping super high frequency garbage out of the amplifiers.

Sending my board to the SMD lady today. Will be back in the fold in a week or so. The LP setup is sounding really good. I am going to be hard to please with the digital setup but then I may get a nice surprise ...

[nige2000]

successfully killed two of the 4 op-amps for 4v
cant say im surprised with the load of charging the 5 farad caps

now i wonder would two rails of +/-4v work instead of 4 rails
if i go external supply

Edit 1.2v reg works fine at 4 v

What happens if we power the vref at say 3.3v
Would be a very simple supply +/- 3.3v

Will sleep on it

[nige2000]

ok then this was the theory test external +/-4v vref bypass direct from lifepo4
eventually the one thing i wanted to do from the start

with the antics with the supercaps and the os-con type caps i was starting to think direct lifepo4 wasnt warranted
but since i blew the opamps for the 4v vref it was a good opportunity to try the direct route

anyway the results are off the scale
noisefloor down
soundstage deeper, wider higher
increased resolution
even more agile
its a very natural, neutral sound far removed from the usual dac chip thats digitally filtered sound

[rickmcinnis]

I was wondering if the supercaps would need to be charged before installation which would add some excitement to installation!

From what I have read about the supercaps is they are extremely intolerant of overvoltage. Do you wonder if that could have caused the problem or at least added to it.

During my time of forced digital inactivity I had started to wonder if the batteries were not the best solution but I am relieved to hear this is not the case.

So are you still using the onboard regulators to charge the batteries? The shift register only needs 3.3 volts so is it the TL431 that performs the voltage reduction - does it care if it is supplied only 3.3 volts? Will it be working at all?

I am assuming the shift registers have these before each one. the things marked "104". From what I see in the datasheet I get the feeling they require some voltage drop but I am just guessing.

That do you think? Soekris wrote that the plus and minus rails must have precisely equal voltages for low distortion. Could one use one battery and connect each rail to the respective end of the battery?

Are you using the onboard regulators to charge the battery or something remote? If remote it seems it would have to be something very accurate like that TI TPS7A4700?

Am I missing this entirely?

[nige2000]

I was wondering if the supercaps would need to be charged before installation which would add some excitement to installation!

certainly would add some excitement
anyway doesnt matter as they discharge on shutdown

From what I have read about the supercaps is they are extremely intolerant of overvoltage. Do you wonder if that could have caused the problem or at least added to it.

the caps were 5.5v so 4v aint a problem

During my time of forced digital inactivity I had started to wonder if the batteries were not the best solution but I am relieved to hear this is not the case.

yea unfortunately theres no comparison but i will say the supercaps were a good improvement

So are you still using the onboard regulators to charge the batteries?

tried it didnt really work well not well anyhow

The shift register only needs 3.3 volts so is it the TL431 that performs the voltage reduction - does it care if it is supplied only 3.3 volts? Will it be working at all?

theres 4v going into the shift register
i will try 3.3v at some stage but i doubt the 1.2v reg will work

I am assuming the shift registers have these before each one. the things marked "104". From what I see in the datasheet I get the feeling they require some voltage drop but I am just guessing.

ive no idea what they are we probably should ask someone smart

That do you think? Soekris wrote that the plus and minus rails must have precisely equal voltages for low distortion. Could one use one battery and connect each rail to the respective end of the battery?

i havent got the +/-4 exactly matched i cant say i noticed any distortion actually it never sounded better

Are you using the onboard regulators to charge the battery or something remote? If remote it seems it would have to be something very accurate like that TI TPS7A4700?

no im using the audiowind regs :()
it only a practice test i did but sounds real good

Am I missing this entirely?

[nige2000]

the 1.2v switch mode reg must have been causing a bit of noise as there is better low level detail with an ldo reg bypassing the sm reg

started to build version 2

[nige2000]

version 2 3.3v







working ok except ive got some buzzy bass i think its because i was too lazy to remove the regs so ill to that tommorow

[nige2000]

the old electrolytic caps, the opamps had to go were interfering somehow
took off the diode bridge when i was at it

anyway the 3.3v version is sounding good

[gstew]

Nigel,

What regulator are you using for the 1.2v?

Greg in Mississippi

[nige2000]

Nigel,

What regulator are you using for the 1.2v?

Greg in Mississippi

sorry greg i missed your post

i didn't get all scientific on it
it was the first one i came across with a pinout that i understood

http://ie.farnell.com/torex/xc6210b122m ... dp/1057797

vref is the probably 60% of the issues on this board