Soekris Dam Dac

[randytsuch]

Randy

Was thinking that you should at least remove the 10uf caps on the shift registers
There the darker brown ones

Yeah, its on my list of things to do.

I had been making a lot of changes lately, so I had decided to slow down for a bit, and listen more.
And life is currently getting in the way, may be a little bit before I make any more changes.

I do have some surface mount panny film caps on the way, and when I have time I plan to replace all the fpga caps too.

Randy

[randytsuch]

Randy,

THANKS for your time and trouble.

I had not considered the parallel aspect. AND that makes perfect sense.

I feel assured and will go ahead and see what happens tonight.

Much gratitude is being sent your way.

Take care,

So did it work??
Sometime silence is good, and sometimes its bad

[rickmcinnis]

Got much done but not enough.

Maybe tonight.

The desire for a sip of whiskey and listening to music got the best of me and I put it aside.

I feel good about it though.

THANKS, again, for your help and re-assurance.

Sorry I did not persevere and get it done. At this point I have taken so long I figure another day won't matter.

One of the disadvantages of having another "front end" to use. If the phono was not working I would have had it done weeks ago but as it is ... One good thing with the passage of time is that I think I have the packaging as tight as it can be.

It is getting all of the regulators done that is holding me back.

Thanks for the concern!

[randytsuch]

Randy

Was thinking that you should at least remove the 10uf caps on the shift registers
There the darker brown ones

Finally got around to removing the 10uf caps, at least I think I did. I removed 8 caps that used to be around the opamps, I think 4 were the 10uf, not sure what the other 4 were.

I think it made a slight improvement in sound quality. Not huge, but little better, and it was easy enough to do this.

I'm thinking about removing some of the caps at the shift registers, maybe every other one, and replacing the remaining ones. But that is a bigger project, so has been put off until I have more time.

Randy

[nige2000]

Randy

Was thinking that you should at least remove the 10uf caps on the shift registers
There the darker brown ones

Finally got around to removing the 10uf caps, at least I think I did. I removed 8 caps that used to be around the opamps, I think 4 were the 10uf, not sure what the other 4 were.

I think it made a slight improvement in sound quality. Not huge, but little better, and it was easy enough to do this.

I'm thinking about removing some of the caps at the shift registers, maybe every other one, and replacing the remaining ones. But that is a bigger project, so has been put off until I have more time.

Randy

ive a good few bits to take off yet, think they all seem to have an effect to some extent
when i get the usb reclocking put to bed ill take the remaining stuff off

[rickmcinnis]

After all of this work that has been done on the SOEKRIS:

http://www.transient-audio.nl/EVA%20datasheet%20.pdf

Who knows how the resistances are realized? Some large scale resistance chip? Can't imagine them being of higher quality than the singles on the SOEKRIS board but they might have an advantage when it comes to tolerance? And smaller is usually better in these applications.

No FPGA based filter, I am presuming , so it would be a true NOS DAC though there is a module for this but is not available for DIY.

The first link is the only part they will sell to us, the rest is OEM.

No mention of price. One has to apply for pricing which is something I have not bothered to do.

Home page: http://www.transient-audio.nl/index.html

This the the company that makes the METRUM DACs but this is completely different from their previous products.

Saw this at 6Moons.

[gstew]

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

Nigel,

Just getting around to ordering regs... do you happen to know the current usage on the 1.2v line? I'm looking at something that's limited to 200ma, thinking it should be ok, but if you know, it would help.

TIA!

And also MANY THANKS for all your pack-leading (and occasionally DAM-killing!) mods & pix!!!!

Greg in Mississippi

[randytsuch]

Greg,
I don't know for sure, but 200 ma sounds low to me.

This is used for the FPGA, and I wouldn't go lower that the 700 ma part that Nigel used, but that's just my opinion.

Randy

[gstew]

Thanks Randy.

I was figuring that with the posted current requirement for the positive rail of .18a @ 10v, I could probably get away with a 200ma max current at 1.2v. Doesn't sound right, huh?

TIA!

Greg in Mississippi

[randytsuch]

Thanks Randy.

I was figuring that with the posted current requirement for the positive rail of .18a @ 10v, I could probably get away with a 200ma max current at 1.2v. Doesn't sound right, huh?

TIA!

Greg in Mississippi

The positive takes 180ma, the negative takes 60ma. The negative is only for the ladder, so figure the positive ladder is also 60ma, so you need 120ma for the 3.3 and 1.2v regs.

I'll make a wag that 80ma is used for the 1.2v, and 40 is for the 3.3v.

The 3.3V reg is a linear, but the 1.2V reg is a switcher, so you need to account that.
I'll assume 80% efficiency for this switcher, which should be close.

.08a x 10v = .8va
.8va * 80% efficiency = .64va
.64va / 1.2v = .53a =530 ma on the 1.2v.


I used a LT1764 because I had them, but it was really easy to do. You just need some wire, a cap, and the 1764, see my blog for the details. It is a 3a part, and maybe overkill, but it works
http://randytsuch-audio.blogspot.com/20 ... dding.html