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Old 11th September 2002, 12:27 PM   #21
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I like this HH's "star".

JH
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Old 11th September 2002, 02:56 PM   #22
HDTVman is offline HDTVman  United States
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Could the hum your talking about be caused by the changing magnetic flux in the transformer vibrating the metal of the case? I have seen that cause a buzzing sound. If so, mount the transformer on rubber washers and space it up 1/4 inch / 5mm.

Later
Bruce
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Old 12th September 2002, 04:42 PM   #23
2Bak is offline 2Bak  Denmark
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Default Scaleable zen case

I have decided to build my zen 4 using the heatsinks and the 10 kilo EI transformer shown at the top of this thread.
Here is quick drawing of my idea of cooling:

Click the image to open in full size.

Since the sinks are 220 mm long the rear of the 3 or 5 mm case sides (blue) will not have any sinks.
The sinks will be bolted to the sides, maybe using thermal grease between, and the FETS will be mounted on the sides, thus hoping for cooling through the blue sides over to the sinks...?

Would this be possible or do I have to mount the FETS directly on the sinks?

My case here would be scalable, and I can add more small sinks to the rear sides, if things get to hot, couldn't I?

If this get too warmy, I also have the option to lower BIAS.

Front will be oak wood.
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Old 20th September 2002, 08:46 PM   #24
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Default Fet mounting

I would not mount the FETs in the way you have pictured here. If the sides of the case are aluminum, it might work, but even then there will be additional thermal resistance. Using thermal compound will help, but given that your sinks are already on the small side, I think this mounting arrangement is asking for trouble. If the case is steel, it will be even worse.

You should mount the FETs directly on the heatsinks, perhaps by cutting holes in the sides of the case.

-Dan
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Old 21st September 2002, 11:31 AM   #25
2Bak is offline 2Bak  Denmark
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Thanks Sparhawk
I will mount them directly.

Click the image to open in full size.

Click the image to open in full size.

Caps
Can I have someones opinion on this issue:
If I decide to use two beer cans only the total capacitance will be 33000uF per channel. If I use all four of them on the first pic it will be 60000uF per channel.
My trafo is 800VA. Nelson recommends 25000uF per channel as minimum (?)
My case will be quite huge if I use four. Easier to build with only two of 'em.

1. Not a good thing to place the caps on top off the trafo ?
2. Do I get a better sounding amplifier using 60000uF per channel ?

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Old 21st September 2002, 01:32 PM   #26
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1.
No idea if good or bad. But, my amp has four 22000uF caps arranged in a row about 1 inch above EI tansformer (300VA). I don't catch any problem.

2.
Well known is that the bigger the caps are, the smaller ripple and that the smaller the ripple is, the better. I however suspect the caps bigger than the amp designer's calculation would improve the sound.

Hoping this will help.
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Old 21st September 2002, 02:41 PM   #27
paulb is offline paulb  Canada
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Here's a thought. If you don't mind having two boxes.
Put the transformer and one pair of caps in the first box, and the second pair and the amps and heatsinks in the second box. The first box can be ugly and hidden away, and it solves the possible problem of the transformer flux causing hum. I've also had a problem with the charging current peaks inducing hum.
You can add a small amount of resistance between the two pairs of caps (in addition to that of the wiring itself), to get a pi-filter.
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Old 21st September 2002, 04:19 PM   #28
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Default Capacitors

I'm planning to use 33,000uF per channel on my Zen v4. It might be on the small side, but given that the v4 contains a regulated supply, I think ripple won't be a problem. It should still be very quiet. Though maybe the power supply won't be quite as "stiff" as it could be?
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Old 21st September 2002, 05:29 PM   #29
jag is offline jag  United States
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I got a quote from mmmetals for mm5060s: $166 for 6 pcs - I was planning to use 3 per channel. This was bit on a high side though not bad considering that they are new (also, I found out that they are .5C/W each - not bad at all).

Subsequently I picked up two 24" (huge!) sinks from MECI - one per channel. Just a note to anyone planning to buy these - they look anodized in the pictures shown but are not actually. I am planning to put both mono-blocks in one case with huge heatsinks on both sides - 24" tall tower. Just sent in a check to passlabs for PCBs!
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