FOverture5

For the three and more legged things
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Nick
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#31 Re: FOverture5

Post by Nick »

They can be used in both situations. Some are designed as temperature sensors, others as inrush limiters, just depends on how much current they are designed for. They are used in the g5 amp circuit to sense the heat sink temp to stabilise the thing. They are also used in the power supply to limit inrush.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
little eddy
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#32 Re: FOverture5

Post by little eddy »

Not quite as much glare as the photo suggests. Quite pleased but it takes 2 LEDs each at 50mA.
vu meters small.jpg
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.
little eddy
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#33 Re: FOverture5

Post by little eddy »

By chance I fitted fuses to each PSU rail to each channel, (4 in total). Good thing as I had made a mistake on one of the boards! Good news is that I found it but now it's making a noise, the only ones I had around were 1.25A fast blow and I am quickly running out!

Any recommendations as to fuse rating and slow/fast blow types for a 26 V per rail amp

I see none of the Pass PSUs have fuses. Might remove one proven.
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.
little eddy
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Joined: Sun Nov 09, 2008 2:06 pm
Location: Manchester

#34 Re: FOverture5

Post by little eddy »

Nearing completion - the only part I'm waiting for is a vu meter driver board, (again from China). Plus a few aesthetic bits like fitting the old control knobs where no pots or switches now exist.

Amp has been running in for 30 hours now so will give it a listening to tomorrow.

Latest schematic as attached.
FOverture5 Stereo PSU.jpg
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.
little eddy
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Joined: Sun Nov 09, 2008 2:06 pm
Location: Manchester

#35 Re: FOverture5

Post by little eddy »

So got wired up to my daughter's small Mission speakers using my phone. Thought that it came across very detail but not too harsh. Promising.

Will get some more listening once completed and can move to the living room with my dac and Zingalis. Can't wait to see the illuminated vu meters - hope they work.
Playing small.jpg
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.
little eddy
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Joined: Sun Nov 09, 2008 2:06 pm
Location: Manchester

#36 Re: FOverture5

Post by little eddy »

I measured heatsink temp while on a reasonable output level and it is between 50 and 55 C with quite a low ambient in the garage and no cover in place. I believe that this isn't too bad as the chips might be reaching 65C. The max thermal power dissipation of the current LM3886 @ 24V is quoted at 16W.

Thinking about a future F4 or F5, with a bit of rejigging I could fit 3 of the current heatsinks per channel, i.e threefold. Each heatsink is 100*69*36 and 270g but with a very fine fin arrangement.

Does anyone know what the max heat dissipation of the F4 or F5 would be with +/-24V supply rails in comparison?

I quite liked the current heatsinks because I thought that dissipation capacity might be more related to the fin surface area than just heatsink weight as many commentators simply use. Unfortunately I don't have a C/W figure.

I think 0.3 C/W is recommended per channel for the F5. The smaller 4U DIYaudio enclosures include a 300*165 per channel with 40-deep fins. If they have 30 fins, the fin area is 30*40*165= 198k mm2. 3 of my current heasinks would be 3*29*36*100= 313k mm2 so in fin surface area terms they are more than comparable.

Is fin area alone a reasonable indication of heat dissipation capacity?

Thoughts please.

If 6 are not enough, then need to look for a larger chassis and heatsinks for the F4/5. If OK I would need to do something to improve the chassis venting.
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.
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