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New PCB for shoebox size NAC preamp part IV

Thanks chilly you are fast as... a shark (aaah, those days),
but damn it if I make an order from overseas just for these caps (2 needed).
 
ramona said:
...for that position most people use silver micas...
Click to expand...

I switwched to Silver Micas originally because 22pF polys are really hard to find - and found that I actually prefer them so they have become part of my standard BOM in the 729 cards.
 
neiljadman said:
I switwched to Silver Micas originally because 22uF polys are really hard to find - and found that I actually prefer them so they have become part of my standard BOM in the 729 cards.
Click to expand...

Isnt it odd how there is space on the PCB for silver mica caps in the filter positions :D
 
neiljadman said:
I switwched to Silver Micas originally because 22uF polys are really hard to find - and found that I actually prefer them so they have become part of my standard BOM in the 729 cards.
Click to expand...

And 22uF silver micas are easy to find?

:)

That's pF, right???
 
In the process of building the Starfish to the v1.2 spec, with Traco and Nert.

I have to show my ignorance now as I am trying to find a suitable supply wallwart or similar.
My understanding is I am looking for a linear supply around 750ma and up to 20v DC.
Maplins do lots of supplies some switch mode, which I know I should avoid?
Other are described as regulated, are these then linear supplies?

If someone could help with advice of what to look for, or point me to a product which will work on the Starfish, I would be grateful.


Thanks

Hugh
 
Hi Hugh

That psu you linked to looks very much like a switch mode. I am guessing a little but it is quite slim and linear psu's need a largish transformer which usually means a chunkier box. I was having the same problem you had and decided to make my own psu as a bit of soldering practise as a preamble to building the Starfish. I used a LM317 and so could build what I wanted, just used the very simple 317 psu from the tech sheet.

DSC_8043.jpg


btw, regulated means it has a ic regulator in it such as a 7805 or 7812 possibly even an LM317. Non regulated means it is just rectified and possibly smoothed.

HTH

Cheers

Gareth
 
Hugh I run my Fish from a wall wart I got from Mapplin I will,post the details tomorow.
Geoff
 
Hi All

I finished up the main construction except the selector switch which is still AWOL and connected up to my Nap90, Monitor Audio bookshelf speakers and ipod.

Sounds came flooding out and for the first time I could get a sense of the audio signature of the Starfish. It certainly still has the Naim bounce but was a little harse on first switch on. I also noticed a mains hum so put the case back on and it disapeared which was cool. Cave it an hour of playing then set it up as my study system for and extended burn in.

Oh dear after about 2-3 hours it suddenly started to hum quite audibly. The music could easily drown it out but all is not well.

I need some advice please. The hum is from both speakers and seems to be around a 1-2Khz tone (not measured, just my opinion). It is completely independent of the volume control and does not vary at all.

I turned it off for 30 mins and then it worked fine for another 1.5 hrs before coming back. I turned off and immediately back on again and it had disapeared but came back 10 mins later. Seems to be heat/warmup dependent and the psu is getting a touch warmer than I would expect. What should the current draw be on a 1.2BOM with Nert? Can I have some suggestions as to where to look for troubleshooting please.

Cheers

Gareth
 
cutting42 said:
Hi All

I finished up the main construction except the selector switch which is still AWOL and connected up to my Nap90, Monitor Audio bookshelf speakers and ipod.

Sounds came flooding out and for the first time I could get a sense of the audio signature of the Starfish. It certainly still has the Naim bounce but was a little harse on first switch on. I also noticed a mains hum so put the case back on and it disapeared which was cool. Cave it an hour of playing then set it up as my study system for and extended burn in.

Oh dear after about 2-3 hours it suddenly started to hum quite audibly. The music could easily drown it out but all is not well.

I need some advice please. The hum is from both speakers and seems to be around a 1-2Khz tone (not measured, just my opinion). It is completely independent of the volume control and does not vary at all.

I turned it off for 30 mins and then it worked fine for another 1.5 hrs before coming back. I turned off and immediately back on again and it had disapeared but came back 10 mins later. Seems to be heat/warmup dependent and the psu is getting a touch warmer than I would expect. What should the current draw be on a 1.2BOM with Nert? Can I have some suggestions as to where to look for troubleshooting please.

Cheers

Gareth
Click to expand...


Gareth,

Could you take a photo from above and email it to me?

I'll have a look and see if anything looks amiss.

Cheers,

Jim.




Edit - just a thought - had a look at your previous photos - is there a link wire between "signal ground" and "power ground"?
It looks like there might be but it's dificult to tell. It does need to be there.
 
Yes it is certainly there, first thing fitted as I recall. Any help would be great, here are some more pics:

DSC_8069.jpg


DSC_8067.jpg


Cheers

Gareth
 
Hugh the Maplin wall wart I use is 12V at 400mA,I used a smaller one to start but it expired after about an hour so concider this as a minimum.
Geoff
 
Thanks for the help on the power supply, I will go the Maplins route, see they do a 1200ma version, which might be the better option.

Hugh
 
My Starfish is now fully populated to BOM1.2, have double checked and it all looks good so far.
Need to hook the NERT up, hook some temporary inputs/outputs up and sort the PSU out so the testing can begin.

:)

Cant wait!
 
Very cool, good luck and it should sound ace. I am listening to mine right now (bit of Saint Saens) waiting to see if the hum comes back. 3 hrs and waiting so I am hopeful!

Cheers

Gareth
 
:) Ta
Going the overkill route, Regulating/cleaning the power before it gets to the board, using an oversized toroid (300va! It was in my spares box) in an external PSU box.
Ultimate plan is a Buffalo DAC in the same chassis as the starfish, with a nice volumite controller and darwin for the source selection, lcd etc....

One step at a time though, get it working right and sounding good as is, then add the goodies one at a time!

:)
 
I'm just finishing off my second Starfish build and I have a query. The 1.2v BoM details some, but not all, components for the relay section of the PCB, eg Q27, Q28, C360, C361, etc. I assume these are not required to make the Starfish work? I've not install any of these components on my other board.

Cheers
 
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