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Old 17th April 2005, 01:21 AM   #1
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Default Bleed current?

I did a search and found references to small bleeder resistors across PSU caps to discharge them at power off. Has anyone experimented with bleeding a much larger current - like 5 to 10 times the idle current of the chips? This would have some negative side effects with relation to peak current available and possibly PSU hum, but I wonder if it may provide some benefit in relation to damping PSU resonances and modulation of rail voltage with the music signal. Any thoughts?
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Old 17th April 2005, 07:49 AM   #2
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Hi,
most bleeders schematics show the resistor connected all the time, not just at power off (no relay).
Your scheme will increase the size of the whole PSU; fuse, transformer, rectifier, capacitor and finally volume & weight.
When the opamps ask for more current the PSU already has a demand and the total current is still going to modulate the PSU output. Your gain will be reduced percentage modulation.
I think this is why over-rated PSU's are reputed to work well (without the bleeder). And I agree with this philosophy.
How about a shunt regulator instead of a resistor?
If you make it really fast the modulation at any audio related frequency will be negligible. Followed by lo inductance caps to reduce vhf hash.
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Old 17th April 2005, 08:00 AM   #3
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Why was this topic moved??? It isn't a general power supply question. My query is specific to chip amps. I want responses from chip amp forum readers who may not read this forum or may not now realise that I'm referring to chip amps because it has been removed from the context of the chip amp forum. If I'd wanted this in the PSU forum, I'd have posted here in the first place. Please move it back to the chip amp forum where it belongs.
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Old 17th April 2005, 08:03 AM   #4
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Quote:
Originally posted by AndrewT
How about a shunt regulator instead of a resistor?
If you make it really fast the modulation at any audio related frequency will be negligible. Followed by lo inductance caps to reduce vhf hash.
A resistor is a lot less trouble than a shunt regulator.
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Old 17th April 2005, 08:12 AM   #5
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Quote:
Originally posted by jeff mai


A resistor is a lot less trouble than a shunt regulator.

A zener and cap? Since when?

...Oh wait, everything has to be megasupercomplicated...nevermind!

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Old 17th April 2005, 08:12 AM   #6
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Why should psu design for chip amps be any different to psu design for other Solid state amps? I moved it here because I thought you would get a better quality of reply. But if you only want replies from one selection of our community, rather than a wide range of members then I'll move it back.
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Old 17th April 2005, 08:18 AM   #7
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Hi,
I would never have seen it if you had hidden it in Chip Amps.
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Old 17th April 2005, 08:22 AM   #8
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Quote:
Originally posted by pinkmouse
Why should psu design for chip amps be any different to psu design for other Solid state amps?
Because the idle current in a chip amp is very low and most other SS development here revolves around class A. Mainly, I want to hear from people who may have actually tried it with a chip amp.

Thank you for moving it back.
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Old 17th April 2005, 08:23 AM   #9
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Quote:
Originally posted by AndrewT
Hi,
I would never have seen it if you had hidden it in Chip Amps.
No offense, but this is fine by me.
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Old 17th April 2005, 08:27 AM   #10
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Quote:
Originally posted by jeff mai
No offense, but this is fine by me.
Never mind, Andy, we tried...
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