Massdrop Cavalli Tube Hybrid Amp

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Aug 11, 2017.

  1. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Thanks for the feedback. I occasionally find even my modded Clears to be a bit too forward from MM/MCTH. So maybe NBM would work for me. Curious about the sound of a transformer coupled tube amp. In any case, I already pulled the trigger so I'll find out in a couple of weeks or so.

    Going through the glossary page to clarify the definition of "laid back", I came to the realization that I probably fall into the camp preferring the "warm [email protected]" sound.

    Even more off topic, is 650K that much more forward than 650M?

    We now return you to regularly scheduled programming.
     
  2. purr1n

    purr1n Building Magnis part time because it's peaceful.

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    The K mod brings the bass down to HD600 levels.
     
  3. msommers

    msommers High on Epipens

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    My MCTH has definitely developed the scratchy volume pot and it's getting to the point it is really bugging me, so I'd like to fix it. Any ideas on how and what to replace it with?
     
  4. Ice-man

    Ice-man Friend

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    I believe if you are the original owner that Drop will replace the unit for with a new one. Problem I think that all of these will eventually develop the issue with noise with the pot. You could use a pre-amp and bypass the issue. I'm not sure I've known anyone who has actually done a physical change of the pot though. An Alps pot would probably be just fine.
     
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  5. dBel84

    dBel84 Friend

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    The pots are custom made (iirc through alpha), not challenging to replace if you are handy with a soldering iron. An alps would likely be a good drop in.
     
  6. Biodegraded

    Biodegraded Friend

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    If you have room for it, a SYS or similar as Ice-man suggested would mean you could easily switch between your two DACs. Just leave the MCTH pot at 1.30pm (unity gain according to atomicbob's measurements).
     
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  7. ohshitgorillas

    ohshitgorillas Friend

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    That's not a bad idea, my volume knob is also very scratchy. I should also replace the switch between SDAC/external input too, it's very sensitive and if you look at it wrong or brush against it while adjusting the volume, the music can cut out entirely. I tried opening it up and cleaning it, there was also a less-than-ideal blob of solder on one of the pins which I cleaned up, but it's still having the same issue.
     
  8. msommers

    msommers High on Epipens

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    I wouldn't mind soldering, but this noob needs help picking specs for ALPS pot, impedances etc (albeit the SYS would make my life easier but a bit more expensive).

    A sys sounds like the easiest option here. Sad to hear so many have scratchy pots though.
     
    Last edited: Aug 6, 2019
  9. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I too use a SYS as it provides additional attenuation for my louder modern recordings, allowing the MCTH's pot to be set closer to the ideal "unity gain". But I would also appreciate info for a drop-in replacement pot that would get rid of the scratch. The SYS' knob is tiny and nowhere near as enjoyable to twist as the MCTH's.
     
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  10. Azimuth

    Azimuth FKA rtaylor76, Friend

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    An Alps pot would likely not fit the MCTH case. It very cramped in there. I would say there might be better Bournes conductive pastic or something. Even replacing with a brand new pot is only a few vucks and about a half hour job.

    So sad that unit is bent on that one part. Aren't these getting just over the two year mark?
     
  11. gixxerwimp

    gixxerwimp Professional tricycle rider

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  12. dBel84

    dBel84 Friend

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    I will have to measure one and compare it to the data sheet - but I am sure it will be one of these

    upload_2019-8-8_6-10-50.png

    I wish Bourns did something like this but they don't. The alpha pots stocked by mouser are not the same packaging as above

    ..dB
     
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  13. dBel84

    dBel84 Friend

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    The spacing looks to be 2.5mm between the pins and 2mm between the rows of pins with a little wiggle room. If I am reading the spec sheet correctly then this one should work. Not sure if the shaft length would work but this is the only one without a switch.

    Code 0971220 = type 097, 122= dual log volume, 0 = no switch
     
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  14. Azimuth

    Azimuth FKA rtaylor76, Friend

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    A decent replacement for $2.50. Not metalized plastic, but a decent choice none the less.
     
  15. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I haven't found a local source yet, but I figured I'd take a closer look at the stock pot. I remember searching for "SANNI A203 7A35" when I had it open to swap out the exploded cap, and not finding anything. Still can't find anything.

    The shaft is 15mm long and the flat part is 7mm. The knob is glued on and requires a bit of effort to get off.

    I can hear a scratching sound when turning the shaft, the rhythm of which sounds similar to scratch heard through the headphones. Must have been some pretty dirty conditions at the factory. Too bad for an otherwise well built amp (from what I can see).

    20190811_152501.jpg

    20190811_152445.jpg

    20190811_153147.jpg

    20190811_153339.jpg
     
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  16. dBel84

    dBel84 Friend

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    I wonder if dousing it in "DeOxit" would impact this scratching at all?
     
  17. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I think I might have tried spraying it with some cheapo contact cleaner when had it open before. Not sure, because ... dotardism.

    Edit: Would enough get in there to make a difference? I definitely tried it with the scratchy iEMatch switch on my iDSD ... didn't do squat.
     
  18. dBel84

    dBel84 Friend

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    Not sure if it would penetrate. Last I cleaned out a pot, I opened it up and cleaned it. These little sealed pot are a different matter. Might have the best chance by spraying through the control shaft.
     
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  19. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So I picked up a couple of these 10k pots, but "HA" rather than "MC" as that's all they had. Difference is the shaft is 20mm instead of 15. I cut 5mm off and everything fits fine, but I thought I'd measure the stock pot in situ before removing it. The resistance between these 2 pairs of pins is 20k when turned fully cc-wise, and 0 ohms when turned fully c-wise. Does that mean this should be a 20k pot, rather than the 10k linked to on the Mouser site?

    Should we be using the RK09712200MT instead?
    https://www.mouser.com/ProductDetai...aRhCb3c/5VdhtWiPBdqz07YwPbN8lpJ7my4wks6oGvg==

    The one I cut is toast if this is the case, but I can go back and exchange the spare I bought.
     
  20. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Forgot to upload the diagram. I marked them as viewed from the bottom side of the PCB with the front panel facing to the right. The MT also has a 20mm shaft, but I don't see another 20k pot in the series w/o a switch.

    RK09712200MC.jpg
     

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