Beezar Audio/ECP Audio History

Discussion in 'Beezar' started by TomB, Oct 26, 2018.

  1. gixxerwimp

    gixxerwimp Professional tricycle rider

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    That's what I thought it might be, but I've seen "DSHA" referred to like a a specific design or topology that @dsavitsk created. Anyway, I'll substitute it in my head with "Doug's Secret Sauce" when I come across it in future.
     
  2. Cspirou

    Cspirou They call me Sparky

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    I've seen it written somewhere, but DSHA generally refers to an input transformer to split the signal and a differential SS buffer of some sort which goes to a transformer output(or not for the DSHA3-F)

    He also has a super spetial Copenhagen amp which is like DSHA but with an extra stage and all sorts of over-the-top extras
     
  3. TomB

    TomB MOT: Beezar

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    You're both correct, I believe. The 3F outputs directly, without transformer-coupling. Thus, the amp cannot be used with single-ended headphones or a balanced to single-ended adapter. Or else, a direct short will result.

    The T4 uses tubes in a long-tail pair arrangement to split the signal into differential components, then the solid-state buffer is fully differential until the output transformers, effectively making the T4 a tube-based, DSHA.

    Doug will have to confirm, but I think with solid-state DSHAs, he sometimes uses input transformers to split the signal into differential components, but I think sometimes he uses FETs in a long-tail pair, too.
     
    Last edited: Jul 5, 2019
  4. TomB

    TomB MOT: Beezar

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    Reading back further in the thread, Doug discovered the usefulness of the DSHA topology with his HPDAC 5. In its simplest terms, it is a differential circuit. However, what Doug is sometimes reluctant to add are the many tweaks he has added, not the least of which is his work with transformers. Doug's designs represent the cutting edge of transformer applications in headphone audio.
     
  5. TomB

    TomB MOT: Beezar

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    Don't know if this is technically within the rules, but I thought I'd mention that I have several prototypes and a production model available at beezar.com for the Starving Student headphone amplifier. Originally designed by Pete Millett as a point-to-point design, Dsavitsk of ECP Audio designed the PCB that we used for several years in selling kits. We referred to it as the SSMH PCB, for Starving Student Millett Hybrid.

    I built three prototypes (one exactly like production) and a populated PCB. All are fully functional and extremely lightly used. The 19J6 tubes sell for around $12-$15 each these days and I'm including two pairs wtth each amplifier (only one pair for the uncased, populated PCB).

    For those not aware, the amp is a single-ended, cathode-bypass tube with a single MOSFET follower (tube hybrid). That puts very few parts in the actual signal path. What's unique is that Pete Millett designed the circuit to use the tube heaters to bias the MOSFETs. That means these little amps run Class A at 150ma current! (Hence, the gianormous heat sinks.) Also, the power supply is a surplus Cisco VoIP power supply that provides approximately 48VDC, for a Vpp potential of 24V. This means a lot of power in a very small package. The Cisco power supply also seamlessly converts between 110 and 220 (Int'l) line power.

    [​IMG]
    [​IMG]
     
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