• Re: multi-supply audio amp

    From Phil Hobbs@21:1/5 to john larkin on Tue Jan 7 19:22:32 2025
    john larkin <jl@glen--canyon.com> wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?



    Class E through G, iirc. Class H makes the supply rail approximately track
    the output. (We use that for TEC controllers. )

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

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  • From john larkin@21:1/5 to All on Tue Jan 7 11:19:01 2025
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?

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  • From Edward Rawde@21:1/5 to john larkin on Tue Jan 7 15:55:10 2025
    "john larkin" <jl@glen--canyon.com> wrote in message news:e7uqnjlhaesulfrqc7n6q961degb556kga@4ax.com...
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?


    About ten years ago someone asked me if I could repair an audio amplifier, which I did by replacing a shorted output transistor and
    a few associated components.

    The topology was that a conventional class B circuit had the + and - halves of the output supplied initially by a few volts from a
    linear regulator followed by a regulator switching synchronously with the audio waveform to keep the collectors a few volts above
    the required audio output.

    Unfortunately I can't remember enough to find an online reference. Not sure it was called anything specific.

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  • From Lasse Langwadt@21:1/5 to john larkin on Tue Jan 7 22:27:37 2025
    On 1/7/25 20:19, john larkin wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?


    class-G (or H) depending on who you ask

    https://sound-au.com/articles/class-g.htm

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  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Tue Jan 7 13:57:26 2025
    On Tue, 7 Jan 2025 19:22:32 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    john larkin <jl@glen--canyon.com> wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?



    Class E through G, iirc. Class H makes the supply rail approximately track >the output. (We use that for TEC controllers. )

    Cheers

    Phil Hobbs

    Looks like G or H. Thanks.

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  • From john larkin@21:1/5 to Lasse Langwadt on Tue Jan 7 14:15:30 2025
    On Tue, 7 Jan 2025 22:27:37 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 1/7/25 20:19, john larkin wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?


    class-G (or H) depending on who you ask

    https://sound-au.com/articles/class-g.htm

    Cool. Thanks.

    I need a power amp that runs near ground most of the time but spikes
    to higher output voltage occasionally. And runs 4 quadrant.

    I have a switcher design that looks good, but it's slow.

    I vaguely recall the G/H topology having someone's name too.

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  • From Phil Hobbs@21:1/5 to john larkin on Wed Jan 8 00:09:51 2025
    john larkin <jl@glen--canyon.com> wrote:
    On Tue, 7 Jan 2025 22:27:37 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 1/7/25 20:19, john larkin wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?


    class-G (or H) depending on who you ask

    https://sound-au.com/articles/class-g.htm

    Cool. Thanks.

    I need a power amp that runs near ground most of the time but spikes
    to higher output voltage occasionally. And runs 4 quadrant.

    I have a switcher design that looks good, but it's slow.

    Our TEC controller is like that, 4-quadrant asymmetric bridge, but current mode. Too slow for audio, but that’s mostly parts values.
    Cheers

    Phil Hobbs
    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

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  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Tue Jan 7 16:40:36 2025
    On Wed, 8 Jan 2025 00:09:51 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    john larkin <jl@glen--canyon.com> wrote:
    On Tue, 7 Jan 2025 22:27:37 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 1/7/25 20:19, john larkin wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?


    class-G (or H) depending on who you ask

    https://sound-au.com/articles/class-g.htm

    Cool. Thanks.

    I need a power amp that runs near ground most of the time but spikes
    to higher output voltage occasionally. And runs 4 quadrant.

    I have a switcher design that looks good, but it's slow.

    Our TEC controller is like that, 4-quadrant asymmetric bridge, but current >mode. Too slow for audio, but that’s mostly parts values.
    Cheers

    Phil Hobbs

    My current design uses a TI DRV8962, which is a quad halfbridge. I'm
    using two sections to make a full-bridge bipolar class-D amp. It's a
    very cool chip, with lots of current limits and suppy lockouts and
    stuff.

    One of those chips would make a nice 200 watt stereo amp.

    But they only recommend running it at 200 KHz max. I could go a lot
    faster with a class G/H linear amp, of course at the cost of a heap of complexity.

    Why does a TEC driver run in the goofy quadrants? Does the cooler ever
    act as a generator?

    I'm designing a dummy load that looks resistive+inductive, like a
    solenoid, so it usually runs in the odd quadrants, where the user is
    pushing power into us. Sometimes we pretend that we stored some energy
    and have to return it.

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  • From Phil Hobbs@21:1/5 to john larkin on Wed Jan 8 00:55:43 2025
    john larkin <JL@gct.com> wrote:
    On Wed, 8 Jan 2025 00:09:51 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    john larkin <jl@glen--canyon.com> wrote:
    On Tue, 7 Jan 2025 22:27:37 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 1/7/25 20:19, john larkin wrote:
    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?


    class-G (or H) depending on who you ask

    https://sound-au.com/articles/class-g.htm

    Cool. Thanks.

    I need a power amp that runs near ground most of the time but spikes
    to higher output voltage occasionally. And runs 4 quadrant.

    I have a switcher design that looks good, but it's slow.

    Our TEC controller is like that, 4-quadrant asymmetric bridge, but current >> mode. Too slow for audio, but thatÂ’s mostly parts values.
    Cheers

    Phil Hobbs

    My current design uses a TI DRV8962, which is a quad halfbridge. I'm
    using two sections to make a full-bridge bipolar class-D amp. It's a
    very cool chip, with lots of current limits and suppy lockouts and
    stuff.

    One of those chips would make a nice 200 watt stereo amp.

    But they only recommend running it at 200 KHz max. I could go a lot
    faster with a class G/H linear amp, of course at the cost of a heap of complexity.

    Looks like a nice part for reasonably noise-tolerant applications. Class H allows us to use Class-A noise rejection with very good efficiency.
    Normally VDD is less than four tenths of a volt more than the differential output voltage.


    Why does a TEC driver run in the goofy quadrants? Does the cooler ever
    act as a generator?

    Yup. Not a very good one, of course—max thermodynamic efficiency of a
    couple of percent.


    I'm designing a dummy load that looks resistive+inductive, like a
    solenoid, so it usually runs in the odd quadrants, where the user is
    pushing power into us. Sometimes we pretend that we stored some energy
    and have to return it.

    Cheers

    Phil Hobbs



    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

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  • From Dave Platt@21:1/5 to jl@glen--canyon.com on Tue Jan 7 17:00:51 2025
    In article <fp8rnj5bg4rpj2ofjeunnj6l90fd6tq158@4ax.com>,
    john larkin <jl@glen--canyon.com> wrote:

    I recall that there was an audio power amp topology that used two
    transistors and two power supplies for each polarity output. Low
    voltage swings used a low voltage supply but it cut over to a HV
    supply for big swings, with diodes or something.

    What was that called?

    Class E through G, iirc. Class H makes the supply rail approximately track >>the output. (We use that for TEC controllers. )

    Looks like G or H. Thanks.

    The Proton AA-1150 is a nice example of this... 50 watts/channel
    continuous into 8 ohms, but it'll do short peaks of up to well over
    100 watts/channel without clipping.

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