Where did all my volts go ?

IslandPink · Post by **IslandPink** » Tue Jul 23, 2013 10:02 pm

Is this a good or a bad time to confess that I've been looking at switched-mode Dell laptop power supplies for the GM70 filament, on and off for most of today ?

I'm guessing it's a bad time to say this

JamesD · Post by **JamesD** » Tue Jul 23, 2013 10:32 pm

Tee hee hee

slowmotion · Post by **slowmotion** » Wed Jul 24, 2013 7:49 am

Why not use double EI trafos and choke input + small cheating cap?

That said, I was collecting computer power supplies for years to use as filament supplies, but chickened out in the end.

Paul Barker · Post by **Paul Barker** » Wed Jul 24, 2013 12:44 pm

IslandPink wrote:Is this a good or a bad time to confess that I've been looking at switched-mode Dell laptop power supplies for the GM70 filament, on and off for most of today ?

I'm guessing it's a bad time to say this

I use thrm on 833a. The valve itsellf is such a dominant influence on sound for good I get away with that. As does Phil.

I prefer otherwise to find a way to use ac .

Paul Barker · Post by **Paul Barker** » Wed Jul 24, 2013 12:46 pm

By them I dont mean dell supplies I mean computer. It is a very beefy one I use.

JamesD · Post by **JamesD** » Wed Jul 24, 2013 5:10 pm

10V at 10A - it would need to be a beefy supply for that

Although there are enough 120W 20V at 6A laptop supplies around so 10V at 10A is doable with a dc to dc converter as 90%+ efficiency is achievable..

J

pre65 · Post by **pre65** » Wed Jul 24, 2013 5:12 pm

My 833a PSU is 12v @ 30A

I use R & C to get down to 10v

JamesD · Post by **JamesD** » Wed Jul 24, 2013 5:41 pm

I use a fully stabilized linear 10V at 10A supply so even at switch on it only gets 10A... but each one weighs 28Ibs!

The attraction of SMPS is obvious!

IslandPink · Post by **IslandPink** » Wed Jul 24, 2013 6:02 pm

I think the attraction became obvious also when I started collecting an order on RS and realised that two of the Epcos input caps ( 10,000u/40V, 8A ripple current ) for GM70 passive supplies would cost as much alone as two recent spec 19.5v SMPS supplies !
We have a few ideas up our sleeves about how to get rid of the residual noise ( which can be as low as 60mV at ~ 60kHz nowadays ) , such as using a virtual centre-tap , but obviously there may be some fun & games ( & a roll of mu-metal ? ) in controlling radiated EMF .
Anyway, Andrew I showed how nice things could sound with SMPS's , so it's worth trying .

audio-talk

Where did all my volts go ?

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