power supply questions........(sorry)

[Mr modnaR]

i have looked though a few pages of threads, and done some searches too, if the following questions have definitely been answered before, don't hesitate to tell me, thanks!

1. i'm having trouble understanding exactly what voltages are needed to run 4xCOREs and 4xSIDs. the optimised psu pdf states 14VDC and 5VDC, yet elsewhere it's stated 15VAC is needed for the SID modules.  ??? if only 14VDC and 5VDC are needed, would it be possible to power the whole lot with a PC PSU? really i'd like just a standard 'kettle' lead going to the synth.  ;D

2. i don't understand why the audio ins must be shorted as in the optimised psu pdf. i can see they'd possibly add additional noise, but does it mean that they are useless? i would like to throw a few things through the sid, you know, just to see what happens!  ;D

thanks in advance!

[TK.]

To 1) 15V is specified to be at the secure side if somebody with no electronic background knowledge orders a PSU

14 V PSUs are very rarely available, 15 V are much easier to get and mostly much cheaper.

I wouldn't use a PC PSU, too noisy...

To 2) so long a voltage source is connected to the Audio In, you won't hear that much additional background noise. General rule: Use the Audio In whenever you want, put the jumper on it when you are not using it in order to achive best results. You can also let the audio In open of course, the jumper measure is just to achieve the optimum!

I think that you will quickly notice this, when you are doing the first experiments on your own MIDIbox SID. Maybe you won't hear any change regardless if the Audio In is shortened or not (like most people...)

Best Regards, Thorsten.

[Mr modnaR]

To 1) 15V is specified to be at the secure side if somebody with no electronic background knowledge orders a PSU

14 V PSUs are very rarely available, 15 V are much easier to get and mostly much cheaper.

I wouldn't use a PC PSU, too noisy...

ahh, i think i understand now that the SID module can take AC or DC (sorry didn't read properly!)

i though PC PSUs are designed to give very stable voltages, due to the sensitive nature of the CPU etc.?

To 2) so long a voltage source is connected to the Audio In, you won't hear that much additional background noise. General rule: Use the Audio In whenever you want, put the jumper on it when you are not using it in order to achive best results. You can also let the audio In open of course, the jumper measure is just to achieve the optimum!

I think that you will quickly notice this, when you are doing the first experiments on your own MIDIbox SID. Maybe you won't hear any change regardless if the Audio In is shortened or not (like most people...)

Best Regards, Thorsten.

ok, thanks for explaining this to me. is it possible to make a connection that's shorted when no jack is present in the socket, and open when there is one? or would it be easier to just have some shorted jacks which could be placed in the input sockets when they're not in use? or is all this speculation/brainstorming not worth it. i mean what can you actually do to inputted audio? is it just the filter, or are there other plans up your sleeve?

thank you for your replys thorsten, much appreciated!

[TK.]

PC PSUs are switching power supplies, they need a certain load to work correctly, and they intersperse some high frequency noise into the circuit, which has to be filtered out with coils and caps. There are people who tried this before, some had luck, some not... if you want it newbie friendly, then don't use a switching PSU...

ok, thanks for explaining this to me. is it possible to make a connection that's shorted when no jack is present in the socket, and open when there is one?

yes, there are jacks available which are doing this automatically - they shorten the input to ground when no plug is inside the jack.

i mean what can you actually do to inputted audio? is it just the filter, or are there other plans up your sleeve?

I never really used the Audio In...

Best Regards, Thorsten.

[Mr modnaR]

ok, thanks for your help thorsten! i think i'll venture down the newbie path with regards to the power supply and the audio in i guess. there's always the next MBSID!

[bionix]

Hiho,

oh i'm also "new" to your midibox project. my core is running and currently i start to test interconnection with sid module.

therefore another question about psu:

i found at pollin.de a nice and CHEAP psu set (http://www.pollin.de/shop/shop.php?cf=detail.php&pg=NQ==&a=Njg0OTQ2OTk= or just search for "netzteil bausatz") which delivers 12v and 5v dc (both with 500mA). Should be enough to drive one core + one sid with lcd + CS. now two simple questions:

1. is the output of that littel set enough to drive both modules, even more of them (3x sid or smth) ?

2. if i got something like noise (i wanna connect also over the normal input psu connectors which filters a lot), could anyone "design" a filter for the 12v/5v psu? because it should only be a modification of the c64 optimized psu. or isn't that possible?

best regards, jan

ps: damn, i so happy when the lcd starts to say "hello world" while mios debugging ;-)

[TK.]

It's worth a try for this small money. The 5V output is a little bit weak, but it could be enough (it mainly depends on the power consumption of the backlit LCD, and how many LEDs are connected).

Filter: maybe the Synth-DIY mailinglist could help here, there are the experts for PSU filters :)

Best Regards, Thorsten.

[bionix]

thank you TK :-)

*damn, forgot smth*

the lcd could be powered by another 5v string (2 psu 12v/5v, each 500mA within each string (das sagt zumindest das datenblatt ;-) )

currently the backlit lcd should not be the problem, and if i use the "small" led (not ultra bright) all could be fine. but i don't know - nor nearly - the real consumption of one core+cs. the sid plate will be powered through the 12v strings of another psu (2 how i said) ;-)

or is there smth bad idea? i'm definitly not an electronic enginier or guru :-(