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Old 24th June 2009, 09:26 AM   #21
Ted205 is offline Ted205  United Kingdom
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heres the regulated psu from nuuks site - http://myweb.tiscali.co.uk/nuukspot/...ub.reg.psu.png


one thing you should included is fuses. Ideally one before the transformer and one on the power rail after the PSU to protect the amp.
Personally i use a fuse on the power rail (both +ve and -ve) and the Power Gnd rails (+PGND, -PGND) coming from the PSU to protect against reverse polarity (which is easy to do when modifiying the circuit).
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Old 24th June 2009, 09:39 AM   #22
AndrewT is offline AndrewT  Scotland
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Hi,
fuse the mains side - definitely.
Keep the mains fuse as low as possible - preferable. This requires some form of soft start.

Use a bulb tester on the mains input.

The PTC of the bulb filament gives automatic protection to the downstream circuit, even wiring faults on the mains side of the transformer and reversing the PSU to amplifier connections.
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Old 24th June 2009, 10:03 AM   #23
Atilla is offline Atilla  Norway
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Quote:
Originally posted by PJPro

Do you think that my two 160VA transformers will be under powered?
I've fantastic results with 2x120VA and chipamp.com power supply modules. If you're doing dual-mono, 160VA per channel should be very solid.
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Old 24th June 2009, 10:33 AM   #24
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Atilla
I've fantastic results with 2x120VA and chipamp.com power supply modules. If you're doing dual-mono, 160VA per channel should be very solid.
agreed.
If you want 60W + 60W from a two channel amplifier, then generally one will find that a transformer rated from 120VA to 240VA will work well, i.e. VA ~ one to two times the total maximum output power.
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Old 24th June 2009, 06:42 PM   #25
PJPro is offline PJPro  England
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Quote:
Originally posted by Atilla

I've fantastic results with 2x120VA and chipamp.com power supply modules. If you're doing dual-mono, 160VA per channel should be very solid.
Result! That's good to know.

I've really been sweating over transformer selection and ended up just getting them. They arrived the other day and look pretty impressive. And they're soooo heavy so must be high quality! I went for the fully potted/encapsulated ones from RS. Cost almost as much as the dual mono kit from chipamp.com. Still....
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Old 24th June 2009, 07:29 PM   #26
PJPro is offline PJPro  England
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Quote:
Originally posted by PJPro

Gotcha. It's my schematic that's wrong. I was comparing the schematic quadtech posted with the chipamp.cpm schematic.

I'll revise mine and repost.

Thanks
Ya know, I made the changes to my schematic and spent some time looking at....feeling that something was not quite right. I finally realised that it was the schematic from chipamp.com that was incorrect. Perhaps I'm learning something?

I have swopped around C6 and R4 on my schematic and will resubmit shortly.
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Old 24th June 2009, 07:35 PM   #27
PJPro is offline PJPro  England
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Here's my revised schematic.

Click the image to open in full size.
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Old 24th June 2009, 09:14 PM   #28
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I don't think the order of C6 and R4 matters.
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Old 25th June 2009, 08:05 AM   #29
Ted205 is offline Ted205  United Kingdom
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c6 & r4 is the snubber network and is commonly put at the output of the power supply i.e after c10
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Old 25th June 2009, 10:40 AM   #30
AndrewT is offline AndrewT  Scotland
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Hi,
what does the 338 datasheet have to say about fitting capacitors close to the input and output pins of the regulator?
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