All-tube amp with "full" MIDI control of all parameters (like Strymon Sunset)?

Discussion in 'Amps and Cabs' started by 9985, Sep 1, 2019.

  1. big mike

    big mike Plexi Loving Admin Staff Member

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  2. 9985

    9985 Member

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    To try to get discussion back on track:

    I don't think I understand how analog signal flow works with pots for gain, level, & EQ, every amp I've owned (tube or SS) had regular analog pots, only ever had digital-type pots on rack gear. What technology do each of the non-motorized full MIDI amps in question use for programmable pots?
    • Superfly
    • HK GMD40
    • HK Switchblade (same as GMD40?)
    • SD30/50 (are they the same?)

    Do those technologies alter the signal so that it isn't 100% analog tube path? What is the proper term for those that do alter it- hybrids?
     
  3. oneblackened

    oneblackened Member

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    The Switchblade for absolute certain use what are called digipots - specifically, ones from Analog Devices. They're essentially switching between different resistor values with a microcontroller. Why is this not more common? 1, they're expensive, and 2, they can't take much in the way of either voltage or current. I'd bet the GMD40 uses the same scheme.

    The SD30/SD50 are, judging by the front panel, probably using rotary encoders with a DAC to do all the adjustments. I'm not particularly up to speed on how this stuff works, so keep that in mind. They're also (apparently) out of production.

    As for the Superfly, I'm not sure - but judging by the sheer mess of a blog thread I just read about one, I wouldn't recommend picking one up.
     
  4. 9985

    9985 Member

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    Thanks! Do you or anyone else have info about if the digipots alter the signal chain? I found their website, they had pricing for a bunch of different versions, nothing over $5 each in lots of 1000, only pots I've ever purchased were for a guitar, $10-15 bucks retail, so the digipots don't seem prohibitively expensive.

    DACs on the Stone Deaf - my ignorance of the way these pots work has me unsure about the impact. Is the guitar signal itself passing through the DAC, or is the DAC doing something with a... not sure the term- some sort of control signal, telling a separate analog component a 0-127 value to apply to the actual guitar signal? Some assistance here, EE types.

    Wouldn't all the relatively common MIDI rack Pre-amps get absolutely destroyed with criticism if their pots were altering the signal?
     
  5. oneblackened

    oneblackened Member

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    Keep in mind Alpha pots (which are quite good quality, and are better and more expensive than many used in cheaper amps) are about $1.25 each in quantities of 1,000 (considerably less than that for higher quantities) on Mouser. Guitar parts sites jack up electronics prices like mad.

    As for the DACs, yup - they're essentially telling a separate analog component to do something (obviously that's not actually what's happening, but...). For example in a Mesa Triaxis they use light-dependent resistors (optoresistors) to actually do the control changes, and those are controlled by the microcontroller.
     
  6. 9985

    9985 Member

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    Thanks. So, if I'm tracking, both digipots and the DACs do not alter the analog signal & the HK /Stone Deaf amps remain a 100% analog tube tone?
     
  7. oneblackened

    oneblackened Member

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    Correct.
     
  8. vicdeluca71

    vicdeluca71 Member

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    I had one of the very last superfly’s,what a great sounding amp! ... I agree with your sentiment about trying amp first before buying, I made that mistake with the superfly, I wanted a Hiwatt at that so bad and there none around for me to try so I sold it and bought a 72’ dr103. Huge mistake!
     

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