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Old 7th May 2009, 09:03 AM   #671
cyxg is offline cyxg  Australia
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Quote:
Originally posted by mattcalf
Another question:
With the pot, I've bought an ALPS 50k. What's will be the difference between using a 10k, 25k, and 50k?

Cheers,
Matt.
50K is better.
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Old 7th May 2009, 09:12 AM   #672
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Quote:
Originally posted by mattcalf
Thanks, was hoping for a closer shot of actual wiring but this should help.

Another question:
With the pot, I've bought an ALPS 50k. What's will be the difference between using a 10k, 25k, and 50k?

Cheers,
Matt.

50k = more attenuation, more silent in full ccw rotation i think since pots are logarithmic.

Nick
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Old 7th May 2009, 01:34 PM   #673
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Peter

do you think that a copper disk d=5cm with thickness of approx 2 cm will be ok for a heat sink ?



Thanx

Nick
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Old 7th May 2009, 01:45 PM   #674
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Definitely not, but could be OK if you attach additional aluminum panels to it.
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Old 7th May 2009, 01:59 PM   #675
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Thanx Peter

You've made my day

If these are aluminum, does this change things a bit?

Nick
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Old 7th May 2009, 02:06 PM   #676
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I wouldn't think so, too much copper is not a good idea either. I like to combine: copper for heat spreadign (and weight), aluminum for dissipation, that's how it's done in Patek amp: http://audiosector.com/chassis_patek2_amp.shtml
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Old 8th May 2009, 02:16 AM   #677
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Quote:
Originally posted by Peter Daniel
It's not possible to implement itt without resistors. Just use the size and color you like the most, adjust resistor accordingly to desired brightness: http://www.diyaudio.com/forums/showt...11#post1517911
Thanks Peter
I have read that post but I still fail to understand how you are getting to the proper resistor value. For example if I am working with dual 24V rails and am trying to use a standard 3V LED. What resistor would cause the LED to operate at 3V? Is there a simple calculation for this?
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Old 8th May 2009, 07:04 AM   #678
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Quote:
Originally posted by Peter Daniel
I wouldn't think so, too much copper is not a good idea either. I like to combine: copper for heat spreadign (and weight), aluminum for dissipation, that's how it's done in Patek amp: http://audiosector.com/chassis_patek2_amp.shtml
Peter,
thanx for your responses.!

Yes i have seen the patek and its really very very neat !
But in my case the chip is mounted on a 12,8x12,8 1mm copper plate and i think i will add underneath a 12,8x12,8 4mm solid aluminum.

Will this be enough for heatsink?

And is there an online place to buy solid alimunum 12,8cm x12,8cm of lets say 1,2 cm thickness? I see you got some very good aluminum blocks.


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Old 8th May 2009, 12:57 PM   #679
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Mike-Toronto
I still fail to understand how you are getting to the proper resistor value. For example if I am working with dual 24V rails and am trying to use a standard 3V LED. What resistor would cause the LED to operate at 3V? Is there a simple calculation for this?
Hi,
3V is not a standard LED, it may be a blue one.

First subtract the LED voltage from your supply voltage. Either 24V-3V or 48V-3V.

Look up the datasheet for the LED and decide roughly what current you would like to pass through the LED. More current = brighter, less current = dimmer, too much current = overheating or .
Take the remaining voltage and your desired current and apply ohms law. I = V / R , rearranged as R = V / I

Let's use the 48V supply and 4mA as an example.
V = 48 - 3 = 45
I = 4 /1000 = 0.004
R = 45 / 0.004 = 11250ohms.
Use 11k
the actual current is given by I = V / R = 45 / 11k = 4.1mA.

Try this and see how bright it is. Then decide if you want/need more or less current.
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Old 8th May 2009, 01:34 PM   #680
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Quote:
Originally posted by tiglitosa

But in my case the chip is mounted on a 12,8x12,8 1mm copper plate and i think i will add underneath a 12,8x12,8 4mm solid aluminum.

Will this be enough for heatsink?

And is there an online place to buy solid alimunum 12,8cm x12,8cm of lets say 1,2 cm thickness? I see you got some very good aluminum blocks.


It might be a good idea to add aluminum plate underneath copper sheet (1mm is too thin to call it a plate) to reinforce it.

I can't say if it's going to be enough for heat dissipation as that will depend on type of music, volume level and type of speakers. In some cases it could be enough, but not when you really push the amp.

I would certainly consider some additional aluminum elements to increase the dissipating surface, but then agaun you can always do it later.
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