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Very Efficient Very Low Distortion Linear+ Amp
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Old 12th November 2018, 04:25 AM   #21
Dave Zan is offline Dave Zan  Australia
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Quote:
I have some articles on LLC SMPS to study
I looked at LLC resonant conversion.
This is the current state of the art for SMPS because it permits ZCS/ZVS (Zero Current/Volt Switches to reduce losses and EMI).
Seemed like it could work for buck converters too but I am now less optimistic, I suspect there is some Non Minimum Phase behavior that will complicate feedback and probably
step response.
Whereas my intuition is that any PWM system will have hard commutation and consequent losses and EMI.
So maybe some kind of fly-back is worth a look, I believe there is "Boundary Mode" conduction that at least reduces turn-off EMI.
Otherwise it's back to linear class H, as recommended by several people.

David

Last edited by Dave Zan; 12th November 2018 at 04:32 AM.
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Old 12th November 2018, 08:17 AM   #22
astx is offline astx  Austria
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Very Efficient Very Low Distortion Linear+ Amp
Another approach would be running class ab amplifiers at reduced rail voltages during low volume levels. E.g. my av receiver switches to higher rail voltages if I select volume above -15db. Of course an amplifier only construction doesn't know when user selects high volume ...

BR, Toni
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Old 12th November 2018, 10:35 AM   #23
Dave Zan is offline Dave Zan  Australia
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Originally Posted by astx View Post
...my av receiver switches...if I select volume above -15db.
Thanks Toni, that is quite a clever idea, simple and yet I've never seen it.
What brand is the AV receiver?
Would not be too hard to send a control from the pre-amp.
Simpler than a switch mode down converter!

Best wishes
David
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Old 12th November 2018, 10:39 AM   #24
astx is offline astx  Austria
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E.g. Denon flagships AV receivers with high number of output channels.
Running in "ECO mode". If you tune the volume above a specific db number you hear a relay switch click - I assume that this changes bias and/or rail voltages.
BR, Toni
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Old 12th November 2018, 10:59 AM   #25
sajti is offline sajti  Hungary
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Quote:
Originally Posted by astx View Post
I assume that this changes bias and/or rail voltages.
BR, Toni
Rail voltage. Same in Marantz home movie amplifier, such as 7055 rails are switched between +/-38V, and +/-55V depending by the output power.

Sajti

Last edited by sajti; 12th November 2018 at 11:06 AM.
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Old 12th November 2018, 11:10 AM   #26
Dave Zan is offline Dave Zan  Australia
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Quote:
Originally Posted by astx View Post
...in "ECO mode". If you tune the volume above a specific db number you hear a relay switch click...
Kind of manual class H!
Often threads run off track with too many attempts to push alternative, "think outside the square" solutions.
But this one is actually pretty attractive, thanks.

Best wishes
David

Sajti, yes switched rails makes sense, was what I planned.

Last edited by Dave Zan; 12th November 2018 at 11:13 AM. Reason: Cross post with Sajti.
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