Looks like this device turns a positive voltage into negative. ATX power supplies already have a negative -12V rail so you don't really need one of these. All you need to get -5V out of it is one LM7905 and two caps (total cost < $3). Since 79xx is a linear regulator you'll get better ripple rejection too ("~100mV typical" according to the negatron web site... vs 0.125 mV from the 79xx datasheet 😉)

I bought one of these based on the recommendation of someone here at Vogons. Works great!

http://www.ebay.com/itm/251025150787

boxpressed wrote:

I bought one of these based on the recommendation of someone here at Vogons. Works great!

http://www.ebay.com/itm/251025150787

Same here! Working great.

@jwt27
thanks for the idea, it sure looks easier and cheaper with a LM7905 , IIRC you've told me this before but I totally forgot about it...
noise is a huge issue IMHO when you deal with sound stuff...
it's that schematic from the datasheet, right?

@boxpressed
first time I see this cable, it looks really nice! do you know what's inside the -5v "shrink wrapped black thingie" ? does it feel like a classic 7805 regulator?

Yes, that's the right schematic. Doesn't get much easier than that 😉
Note that the recommended cap sizes are for tantalums only. If you use normal electrolytics they should be 10+ µF (read: as large as possible)

That cable looks like a much easier solution though, and I bet you'll find the same 7905 in that heat shrink tube 😉

awesome, thanks for the verification jwt27! I'll go the 7905 route my self, just another thing to build 😁

keropi wrote:

@jwt27
@boxpressed
first time I see this cable, it looks really nice! do you know what's inside the -5v "shrink wrapped black thingie" ? does it feel like a classic 7805 regulator?

Hmm, I'm not sure whether there is one of those in there, but it is certainly possible. Whatever is in there is about one-inch wide.

SB Pro 2? I thought that only SB 2.0 requires -5v from SB series.

bristlehog wrote:

SB Pro 2? I thought that only SB 2.0 requires -5v from SB series.

Yup that's correct.

I'm pretty sure that my Yamaha YMF719 card also requires -5v.

Just remember that the 7905 is a linear reg, and going from -12V to -5V is a 7V gap.

If you draw just 200mA of current through that reg, it's going to pump out 1.4W of heat, which is a lot in terms of a TO-220 package device, it'll get hot quickly.

I don't know what the current requirements are for these sound/MIDI cards, in terms of the -5V supply. It could be nowhere near 200mA.

boxpressed wrote:

I'm pretty sure that my Yamaha YMF719 card also requires -5v.

It doesn't require -5V. You can check this by looking on ISA slot pins and compare with contact pads on card.
http://upload.wikimedia.org/wikipedia/commons … SA_Bus_pins.png

tyuper wrote:

boxpressed wrote:

I'm pretty sure that my Yamaha YMF719 card also requires -5v.

It doesn't require -5V. You can check this by looking on ISA slot pins and compare with contact pads on card.
http://upload.wikimedia.org/wikipedia/commons … SA_Bus_pins.png

Cool, didn't know that. Thanks.

Mfr states first thing on the product page that it's an adjustable buck-boost converter, not a linear regulator. http://en.wikipedia.org/wiki/Buck_converter More efficient but potentially more noise. These are possible to build without an IC, but you need a clock.