Massdrop Cavalli Tube Hybrid Amp

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

  1. dBel84

    dBel84 Friend

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    10k will work too. The biggest thing to check is that it is a log taper for volume control application, not a linear taper.


    Looking at your original images, it should have dawned on me that this was a 20k pot, the numbering states A203 (which would be 20 000)
     
  2. gixxerwimp

    gixxerwimp Professional tricycle rider

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    OK, does that mean that "unity gain" will be in a different location on the o'clock dial? I wasn't sure how the pot resistance translated to volume control and didn't want to lose 1/2 of the granularity, or lose 1/2 the gain.

    I trust you if you say it'll work. I'll fire it in tonight and see what happens.
     
  3. dBel84

    dBel84 Friend

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    [​IMG]

    This image should help explain why

    You won't lose gain but you are right in assuming that the unity gain spot will be different.
     
  4. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So I did the swap. This is how they look side by side. The stock pot is still soldered in place.
    20190814_224249.jpg

    The ALPS pot has a tab that needs to be filed off so it can sit flush against the inside of the face plate. This is half way through the filing process when I realized I should take a photo.
    20190814_212733.jpg

    The pins of the ALPS are a few mm shorter than those on the stock pot, the body of which extends a bit below the box part. So when the ALPS is at the right height, the pins only just poke into the mounting holes. I soldered them with the pot secured to the face plate to hold it at the correct height and was just able to make electrical contact with each via (forgot to take a photo).

    End result is no scratchy noise, but the ALPS pot doesn't feel as smooth and slick as the stocker, and has a little slack so there's some slop when you turn it. Going by ear, unity gain is now at around 11 o'clock.
    20190814_223920.jpg
     
  5. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Pic of stock pot (left) and the extra ALPS pot (right) that I bought in case I fucked it up (Yay, I didn't!). You can just make out the tab that needs to be filed off sandwiched between the washer and the bottom of the front face of the pot.
    20190814_231325.jpg
     
    Last edited: Aug 15, 2019
  6. msommers

    msommers High on Epipens

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    While you were doing surgery, did you notice the output caps? Would be curious if those can be replaced/upgraded as well....
     
  7. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I think there are photos in this thread of the naked board. I couldn't tell an output cap from a baseball cap :p

    I only replaced the cap that exploded last year when I used a solder-snot covered el cheapo socket "saver". Everything looks easily accessible on the board, so I don't see why you couldn't upgrade any and every cap if you wanted to.
     
  8. dBel84

    dBel84 Friend

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    It doesn't really have output caps but the red ones in the image below are the coupling caps

    [​IMG]

    they couple the tube stage to the output buffer and are the only caps in the signal path.

    ..dB
     
  9. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Last edited: Aug 14, 2019
  10. Azimuth

    Azimuth FKA rtaylor76, Friend

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    According to the datasheet for the RK09712200...
    • MC = 10K w/15mm shaft
    • HA = 10K w/20mm shaft
    • MT = 20K w/20mm shaft
    So the RK09712200MC is probably the one you want if you can find it.

    Make sure you are measuring just one gang as well, not both gangs in series...that would add resistance. Measure both outside pins to measure the pot..don't worry measuring the wiper.
     
  11. gixxerwimp

    gixxerwimp Professional tricycle rider

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    However, the MC (which is what @dBel84 recommended originally) is 10k and the stock pot is 20k. So if you wanted unity gain at the same location you'd have to go for the MT. I couldn't find a pinout so I just measured pairs of pins until I could get a non-infinite reading. The stock pot measures 20k across the pairs of pins I marked above and the HA measures 10k. The MC will save you shortening the shaft (the knob will stick out by about 2-3mm otherwise), but still has the same problem as the HA I bought of pins being too short. If I wasn't able to get them soldered in I would have filed out the hole in the face plate so the shaft could drop by about 1 mm, but then the knob would no longer be centered in the cutout.

    I'm done, but for the next person who wants to try this, is there a way to extend the pins? Solder an extra length of wire onto the ends?
     
  12. gixxerwimp

    gixxerwimp Professional tricycle rider

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    While out getting the pot and other supplies, I picked up some 3M Scotch 1625 Contact Cleaner. I put the stock pot into a little aluminum foil bathtub and gave it a good soaking. The mechanical scratching sound that matched what I was hearing through the headphones is gone and is now replaced by a general rough feeling. I guess whatever lubricant was in there is also gone. So maybe a few soakings with contact cleaner followed by a silicone lubricant spray might fix the problem. I tried a really old can of Dow 557 silicone dry film lubricant and it helped a bit, but it still feels somewhat rough to turn. No more scratching sound, just more of a sweeping sound as the knob is turned.

    Just don't use vaseliine like one of @Zampotech's clients.
    https://www.superbestaudiofriends.o...t-jr-official-thread.5408/page-38#post-267217
     
  13. VonAtlas

    VonAtlas New

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    Thinking about going in on a Cavalli amp, either this or the Liquid Carbon... I already have a Vali 2, and the THX 789, and curious if either would really provide a different experience from what I've already got.

    Any suggestions would be helpful.
     
  14. BrokeSkoolBoi

    BrokeSkoolBoi Acquaintance

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    I'm not sure it's worth your time to get the MCTH if you have the VALI 2. It is different, but if you're going to get a another hybrid I would suggest you just upgrade to the lyr 3 rather than do a slight side grade (or be forced to buy an lps to feel a bigger improvement). Honestly I don't believe it's necessary to have two high profile amps, so in that way I would suggest the CTH just for the better looking stack haha. Maybe just get an OTL tube amp like the ZDT Jr. (if they've fixed the hum issue) instead and forgo a hybrid all together?
     
  15. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I haven't heard Vali 2, but I think it's safe to say MCTH will be a significant step up in performance, especially with LPS. But you said "different". What are you looking for? ZDT Jr (NBM) definitely has a different presentation, better in some ways, worse in others. Read the impressions in the relevant threads, and Marv's Three Affordable Tube Hybrid Headamps – Garage1217 Project Horizon Compared. Try to demo if you can.
     
  16. Azimuth

    Azimuth FKA rtaylor76, Friend

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    I have had the MCTH and now I have the Vali 2, much different IMO.

    MCTH is much better at microdynamics, slightly greyer, smoother, laid back. Vali 2 much better at overall dynamics and macrodynamics.

    Vali 2 is more aggressive, detailed, faster, and immediate (comparatively of course).

    Vali 2 also changes on type of tube. The MCTH sounds nearly the best with the 6922, albeit a bit light in the bass, however when I tried different tubs, there was TOO much bloom.

    I won't comment on width because it has been way too long since I had MCTH to compare.

    To me MCTH is ≤ Vali 2. Vali 2 to MCTH It is more of a side grade, and an LPS must be acquired to reach full potential.
     
  17. Pogo

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    Late to this party but wanted to share my LPS experience.
    I went with this one:
    https://www.ebay.com/itm/Finished-6...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
    Arrived via DHL in 6 days, easy tracking on its journey from Singapore thru Hong Kong to the US, no add on tariffs. Yet.
    Use: Tidal>Eitr>Modi Multibit v.2>Loki>MCTH>DT 1990 which was the chain for a year+ Yep, bass is tighter, better controlled. Mids are better detailed, treble is better detailed. As was descibed before many time; an LPS does make a significant difference, Im a believer now..
    Note: if you own an MCTH and are on the fence about a China sourced LPS, order befor 12/15 as they are on the 15% tariff hitlist.
     
  18. msommers

    msommers High on Epipens

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    Anyone know who makes the stock power supply for the MCTH? I can't seem to find it and looking to sell mine off but naturally it's pretty useless without a power supply!
     
  19. dBel84

    dBel84 Friend

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    It is a custom unit from China.

    What was the voltage? 24v or 30v... Or other, I have lost track.

    There is a 24v supply on us audio for about $12 if it is 24v


    Edit. I looked back in the thread and see it is 28V
     
  20. TomNC

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    Made by Xing Yuan Electronics in China. Output: 28V, 1.25A. Input: 100-240VAC, 1.0A max. Model #: XY36S-2801250Q-UW.
     

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