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Old 13th February 2009, 06:07 PM   #2911
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Wow! That's a very impressive 'copy'
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Old 13th February 2009, 06:13 PM   #2912
steenoe is offline steenoe  Denmark
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Kind of makes you feel humble. That is more than astonishing work, Patrick

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Old 13th February 2009, 06:36 PM   #2913
sekess is offline sekess  United States
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Default copy

How did you create the front plate? Do you have a milling machine?
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Old 13th February 2009, 06:42 PM   #2914
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Default Choke vs Resistor in the PS

I am no expert in using the DUNCAN AMP TOOLS PS designer but find it interesting that when the supply is configured per Mr. Pass with my crude implementation (not knowing xformer DCR and other such) I (think) I see a ripple figure of 8.7mV (using total 20000uF of capacitance with the .01175 ohm resistor bank).

When I plug in a 50mH/.165 ohm choke I get slightly more voltage with the same capacitor size and 14 mV of ripple.

Is this to be expected?

I have long believed that the choke made for a smoother supply. What am I missing?

Thanks,
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Old 13th February 2009, 06:51 PM   #2915
steenoe is offline steenoe  Denmark
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Default Re: Choke vs Resistor in the PS

Quote:
Originally posted by rickmcinnis
I am no expert in using the DUNCAN AMP TOOLS PS designer but find it interesting that when the supply is configured per Mr. Pass with my crude implementation (not knowing xformer DCR and other such) I (think) I see a ripple figure of 8.7mV (using total 20000uF of capacitance with the .01175 ohm resistor bank).

When I plug in a 50mH/.165 ohm choke I get slightly more voltage with the same capacitor size and 14 mV of ripple.

Is this to be expected?

I have long believed that the choke made for a smoother supply. What am I missing?

Thanks,
The 50mH choke of yours, will probably be saturating! For any practical purpose, use a 2mH aircore. It will never saturate (at least under usual poweramp conditions) as long as it is made from 2mm dia cupperthread. This should give you a picture of what you are up against!




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Old 13th February 2009, 07:50 PM   #2916
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Default "Hairy" heat sinks

Hello again, fellow geeks !! My D-988 amp case arrived from Hong Kong today , (3 days from eBay/Paypal to doorstep no less !!) via Cathay Pacific Jumbo Jet and UPS #$%^ brown truck. It is HUGE, 19" wide, 15" deep, 6.5" tall (on the inside). The thing came with four heat sinks which are 7.5" wide, 6.375" tall and each holding (18) 1" tall, hairy fins. By hairy, I mean they have (10)~ 1 mm high stubs along the length of each side of each fin, see attached. I assume these help by increasing skin area and inducing turbulence in the convected flow, but I have no idea how to adjust the thermal resistance calculation for these features, (it has to be good, though.....it just LOOKS cool).

When I calculate the thermal resistance on Aavid's excellent website, ()http://www.aavidthermalloy.com/technical/thermal.shtml, I come up with ~ 0.33 degree C / watt. Since I intend to mount two MOSFETs on each of these babies, (for a total of 8-bridged), I would expect a temperature rise of 20- 30 degrees C, (depending on the ambient temperature). Given the volume of the inside of this box - I can literally keep the rest of the amp a good 5" away from the sinks, so I think, heat-wise, I'm OK. Has anybody used one of these cases for your project - it really looks nice, (although still a poor cousin to Papa's cases - they are works of art, IMHO)
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Old 13th February 2009, 07:57 PM   #2917
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Default Hairy Heat Sinks

Oooooppps !! My jpeg was too big, (not my normal issue, heh, heh, heh !!)

Here goes again....
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File Type: jpg heat sink2.jpg (95.8 KB, 1556 views)
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Old 13th February 2009, 08:40 PM   #2918
EUVL is offline EUVL  Europe
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> Wow! That's a very impressive 'copy'

That is some complement coming from you !!

> How did you create the front plate? Do you have a milling machine?

Turned, then CNC milled, as the pocket is concave on all surfaces and hence more complex to make than the original ML33.

Also note no screws visible (not even at the back) and only very well placed joint lines and ventilation slots. They all made life sort of difficult.


Patrick
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Old 13th February 2009, 08:46 PM   #2919
steenoe is offline steenoe  Denmark
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Patrick, that amp-case is simply just too gourgious BTW what amp is it??

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Old 13th February 2009, 09:03 PM   #2920
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Quote:
Originally posted by EUVL
Also note
Puts the origin to shame, doesn't it.
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