Massdrop Cavalli Tube Hybrid Amp

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

  1. Biodegraded

    Biodegraded Friend

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    Another report on tube rolling with this thing. When reading this, note that I’m totally new to tubes and tube amps so have no reference points...

    Amperex 6DJ8/ECC88 ‘A-frame’ with orange ‘PQ’ label, Heerlen 1972

    Amperex JAN 6922 with orange ‘globe’ label, NY 1967

    Electro-Harmonix 6922 (stock tube), Russia 2017

    Telefunken ECC88, Berlin 1972

    Short version: Telefunken or Amperex A-frame (depending on taste) > EH > Amperex 6922.

    The A-frame is smoother through the mids, particularly the upper mids, and is slightly more extended in the treble than the stock EH. Bass is stronger but more rounded at the edges. The EH seemed to me the lightest of all in the bass and has a slight peak in the mid-treble.

    The JAN Amperex lacks the A-frame’s smooth mids as well as its (and the EH’s) treble extension. It seems to have more amplitude in the bass, but doesn’t seem as coherent across the range as either of those others.

    The Telefunken is more extended and precise than the A-frame and EH at both ends, but not as smooth as the A-frame in the midrange; it comes across as more ‘analytical’, but is great at bringing out microdetail. Although the label was worn on this one it otherwise looked like it might not have been used, and did seem a trifle smoother after c. 24 hours of burn-in (the other tubes were more obviously used and I didn’t give them any burn time).

    The rest of my chain is Mimby and HD6XX. The entirety would be viewed as being on the warm side (Marv’s first impressions of the MCTH as neutral were of a pre-production version; well-known warmfolks – you know who you are ;) – later declared the production version slightly warm). I’ve decided that while I’m not one of the warmfolk, neither am I obsessively 'neutral'. I go between preferring the Telefunken and the A-frame, appreciating the former’s technicalities and extension but the latter’s smooth presentation. I suspect I’ll be switching between them depending on mood & genre. Others’ preferences will depend on chain and tastes. In the same chain, those who prefer more warmth would likely pick the A-frame every time, those who lean more neutral, the Telefunken. Personally I'd wish for a combination of the A-frame's smooth midrange and the Telefunken's highs & lows, but I like both well enough that I'd rather spend the hunting-time listening and the money on more music.

    I should say that I didn’t find the EH hugely different from the other two in either respect, so I’m not saying anybody should roll tubes; I really only did it because I hadn’t before and thought it’d be fun to see if I could hear differences (and as usual was amazed that I could). Also – I have a second A-frame, purchased as a pair with the one described above, the two having date codes within 6 weeks of each other, supposedly testing within 3%, and having a similar history (Tektronix stock). @msommers heard this second one before I did and found the highs to be noticeably truncated vs the EH. When I subsequently compared the pair, the characteristics were otherwise the same – but #2 was indeed rolled off in the treble cf. #1. #2 looks like it’s had more use, and I know it’s no news to the experienced that there are variations between used tubes of identical manufacture. Indeed it was noted in the tube rolling thread that there’s little correlation between a tube’s test results and its sound.
     
    Last edited: Jul 14, 2018
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  2. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Of the tubes I tried, I also preferred the Telefunken ECC88. But it developed an intermittent buzzing / wheezing / whistling and became very microphonic, so I guess it's reached "old age". Went back to the stock EH and I'm fine with the sound.
     
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  3. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Others may have mentioned doing this, but I can't find it. I'm using a cable with an XLR connector with my HD650s. It's a bit stiff to connect/disconnect, so it would be more convenient to leave it plugged in. That leaves the 6.5mm connector free for my Clears (which are easily unplugged when listening to the Senns). Aside from possibly hearing the sound coming out of the HD650s while listening to the Clears, will the performance of the MCTH be affected by running both phones simultaneously? I think the outputs are in parallel so the amp will see a reduced impedance compared to when only 1 pair of phones is connected. And that impedance will be frequency dependent and the combined result of each phone's impedance curve. Zout is < 0.5 ohm at 1 kHz, and presumably low from 20Hz to 20kHz, so one would think there shouldn't be any combined impedance "bass bump" effect. Using the nominal impedances of 300Ω and 55Ω, the nominal parallel impedance is 46.5Ω.

    Any ideas? For convenience, grabbed from Tyll's measurements.

    HD650 impedance curve
    Sennheiser HD650 impedance.jpg

    Clear impedance curve
    Focal Clear impedance.jpg
     
    Last edited: Sep 1, 2018
  4. Biodegraded

    Biodegraded Friend

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    Apart from having to turn the volume knob higher, no problem - unless, as @Bill-P said, you have to turn it so high that the overdrive protection kicks in.
     
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  5. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I know it'll work, but I'm interested in whether or not the audio quality will be affected. Will one or both phones be driven with less "impact" due to the amp having to drive both of them simultaneously? Will there be any difference in tonality due to interactions between the loads of both phones?

    I guess I could just listen and see if I can hear any difference. I was curious from scientific/engineering perspective. Maybe this would better addressed in the All-Purpose thread, but the use case is specific to the parallel outputs of the MCTH.
     
  6. jowls

    jowls Never shitposts (please) - Friend

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    A short male to female XLR pigtail would make more sense. That way you could leave it plugged into the amp and just connect your headphones when required.
     
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  7. likearake

    likearake Acquaintance

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    Is this amp good with LCD2s? Found a couple of short mentions in the thread but still not sure.
     
  8. udin

    udin Acquaintance

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    I personally do not like the CTH with the LCD-2C, but haven't tried it with an original LCD-2. If I get a chance, I'll borrow a friend's and check it out. I found the former pairing to just seem shouty and harsh.
     
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  9. Sqveak

    Sqveak Friend

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    I like it once the tube or amp is burnt in, or however you prefer to think of it.
    This was my main combo for around two months in place of my HD600 on the same amp.
    I did not like the pairing untill the amp settled down.

    It can be shouty or harsh but I find this to be dependent on what you are listening to.
    Industrial and questionably produced electronic music is very hit and miss in particular.
    Most other music is fine.

    With the worst offenders among my music collection I hear some of the same harshness with the HD600 on the MCTH and don't hear it in the same way with my other amps. The LCD-2C just declines to be polite about it.

    @likearake
    Try it with your own music if you can.
    It's not a bad pairing but don't buy blind on this one.
     
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