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Old 9th August 2011, 03:53 PM   #1201
Tea-Bag is offline Tea-Bag  United States
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I think the heatsinks are too small considering the resistor you want to use, and I would not use a clip, use a bolt and even a fender washer to hold the mosfet to a sink.
When hot rodded, floor mounting them is a start, and can glue heatsinks near the fets if needed as well.
I glued heatsinks to L-Channel and use that on both ends. I think my blog can show that.
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Old 9th August 2011, 07:15 PM   #1202
TerryC is offline TerryC  United States
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Quote:
Originally Posted by parodielin View Post
Thinking about my hot rod operations on my wondrfully working DCB1:

Resistors: 4.5 Ohm 12 W Mills (I have two of these laying around)
At that current you are going to need a much more substantial hunk of metal. Horizontal mounting to the floor of a metal chassis has the added advantage of moving the radiated heat further away from other components, particularly the VRef LED strings.
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Old 9th August 2011, 08:26 PM   #1203
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What if I use one 10 Ohm 12W resistor? Would the heatsink be enough?

Quote:
Originally Posted by TerryC View Post
At that current you are going to need a much more substantial hunk of metal. Horizontal mounting to the floor of a metal chassis has the added advantage of moving the radiated heat further away from other components, particularly the VRef LED strings.
Quote:
Originally Posted by Tea-Bag View Post
I think the heatsinks are too small considering the resistor you want to use, and I would not use a clip, use a bolt and even a fender washer to hold the mosfet to a sink.
When hot rodded, floor mounting them is a start, and can glue heatsinks near the fets if needed as well.
I glued heatsinks to L-Channel and use that on both ends. I think my blog can show that.
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Old 9th August 2011, 08:32 PM   #1204
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Quote:
Originally Posted by parodielin View Post
Thinking about my hot rod operations on my wondrfully working DCB1:

Resistors: 4.5 Ohm 12 W Mills (I have two of these laying around)

Heatsinks:

http://www.newark.com/jsp/search/productdetail.jsp?SKU=10WX1023
http://www.newark.com/jsp/search/productdetail.jsp?SKU=02M0324

I'll use silpads (not sure if I need Arctic Silver adhesive) to attach the clips to the heatsink. It will not be bolted to the chassis.
parodielin,

With those resistors you are going to pulling somewhere close to the magic 600mA and generating substantial heat. Small individual heatsinks won't cut it. Salas suggested something akin to a 30watt class AB amp. I am looking at the following found online, mostly eBay:

Quote:
Originally Posted by mike_mcf View Post
I am working on heat sinking for a stage 2, 600mA version.
  • Option 1) Use the case bottom as the heatsink, assuming a roughly 12x12x1/4" plate of aluminum with the MOSFETs bolted to them from the bottom of the PCB
  • Option 2) a single 140x190x32mm horizontal finned plate, mounted fins down in the case, with the PCB mounted on the back.
  • Option 3) A pair of 140x81x44mm vertical finned plates on each side of the PCB, MOSFETS mounted above board and bolted to the heatsink.
  • Option 4) As above, 250x100x55mm
Anybody successful at 600mA with any of these approaches?
Do any of you experienced DCB1 builders have some input for parodielin and I.
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Old 10th August 2011, 08:03 PM   #1205
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I’m building a balanced DCB1 hot rodded @ 600ma. I’m using a 111 x 222 10mm thick al anodized blocks to sink to the 3mm base plate 435mm x 353mm of the chassis.

This is my set-up internally:

http://www.imgplace.com/viewimg6/3936/76img5881.jpg

Click the image to open in full size.
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Old 11th August 2011, 05:02 PM   #1206
cersepn is offline cersepn  United States
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Quote:
Originally Posted by Salas View Post
I would have been worried if you had said something like 5m to the actives about it may had needed higher value interfacing resistors than 220R not to oscillate on cabling capacitance, but 1.5m is very near to what all people use with DCB1 in home systems.

Both 1 & 2 on the graph ground pin 3 fully. So you had it grounded as your speaker's manual usually expects.

I am suspicious of possible bad joints, the computer's output as a source and what it may give out erratically through a DC preamp as the operating system does stuff, possible peculiarities in the unknown Dynaudio active plate amp, its preamp, filters, on board protection and limiters. As for what it may had happened to it and is lower but still has voice...don't know, from a tripped and stack limiter to burned stuff in a Class D power circuit. Check it with a balanced source with XLR output and XLR ready made cables first.
Alright, i got down to checking all the cable joints. They are all fine.

I changed the source to a CD player. When i tried it yesterday, there was some slight buzz/hiss but nothing major. Today, i shifted the speakers a little and when i turned on the left speaker, there was a huge, huge buzz. Right speaker is silent. I suspect it is because i shifted the left side closer to the TV.

But after some rewiring and shifting of cables, that was settled. Speakers are completely silent only when there is no source hooked up to the dcb1. Once i plug in the source, the noise comes back.

Is it really not possible to run it open case for now without getting *any* hum/buzz at all?

Is anything wrong with my internal wiring? And what should be done about it?
Click the image to open in full size.
Click the image to open in full size.
I know it's dangerous leaving the power wires exposed like that.. but it's temporary and i have no children/pets in the house so it'll do for now.

I'm thinking of trying out this alternative rca->xlr cabling arrangement. Any idea how well it'll work? According to the diagram, my cable is wired 'wrongly' although most literature elsewhere states otherwise.. so im not sure who to believe
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Old 11th August 2011, 05:55 PM   #1207
AndrewT is offline AndrewT  Scotland
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I use uncased amplifiers regularly (same conditions, no kids, no wife, no pets).

While you are aware where the dangerous parts are, you are careful not to fall into them when you have been drinking (Oh I don't imbide either).

I find that the performance without a case is usually better than when inside a case particularly if the case is steel. I find steel cased two channel damned difficult to get completely quiet.

Generally I do not hear any interference coming into my gear while uncased and I rarely use any screened cable. Twisted pairs/triplets/quads are what I use.
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Old 11th August 2011, 05:59 PM   #1208
cersepn is offline cersepn  United States
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Thank you, Andrew. As always, your posts are very helpful. Is there any improvement i can make to the internal wiring?
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Old 11th August 2011, 06:03 PM   #1209
AndrewT is offline AndrewT  Scotland
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Twisted pairs are missing.

Remember for every flow there must be a return route.
Electrical/electronic circuits are approximately what it says. The electricity flows around in a loop (circular route = circuit) all the way back to the start (the source of the emf).
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Old 11th August 2011, 06:55 PM   #1210
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I've got my heatsinks bent over the sides of my board. I wanted to attached them to the bottom of the chassis, but I guess I'll need to insulate them?
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