Massdrop Cavalli Tube Hybrid Amp

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

  1. monacelli

    monacelli Friend

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    Good question, most likely a combination. Pure speculation, but maybe the interstage capacitors needed some burn-in time to open up. Thanks for sharing your experience with tube rolling. Using the magic 8-ball, I don't think tube rolling will change my overall opinion much. I rolled the stock tube, a NOS 6N23P-EV, and a GE 5670 with adapter. The differences were subtle, an order of magnitude smaller than the sonic changes I observed rolling tubes in Vali 2. If no one buys my combo unit, I will turn it into a little project. My hunch is that rolling interstage capacitors would make a much bigger difference than rolling tubes. To my eye, it looks like they used some cheapo knockoff WIMA caps. (Edit: They're WIMA, see dBel's post.) I wouldn't spend more than a few bucks, but I'm curious if those green Russian PIO caps would sound any better.
     
    Last edited: Jun 24, 2020
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  2. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I always have to go back and check my posts to remember what my impressions were (because early onset Alzheimer's). I'm not one to hear subtle differences, so if I really think I heard something, it's gotta be pretty significant. Not saying you should be hearing things that you aren't.

    My initial tube rolling impressions from a random selection of tubes (maybe they were crappy, so who knows):
    https://www.superbestaudiofriends.o...alli-tube-hybrid-amp.4866/page-39#post-208403

    Would be very interested in what the results are. Already replaced a cap that exploded due to a solder bukkake (trademark @schiit) tube saver, so that could be something fun to try. I've been kind of sitting on the fence as to whether to sell mine. It's a decent amp overall, but SW51+ kicks its butt to the curb and back.

    @dBel84 Do you think upgrading the caps would make any difference?
     
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  3. dBel84

    dBel84 Friend

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    Caps are such subjective things. I recall reading a cap comparison recently and wima faired very well from a pure measurement perspective. The stock caps are wima, not some copy.

    A personal experience story. When I built the first stacker, I just tossed in whatever parts I had in my bin. When it sounded as good as it did I bought some audiophool PIO to upgrade. It sounded off, constricted, serious move in the wrong direction. I figured it might need time. Finally gave up and put the cheap polyester caps back in and the amp sprang back to life.

    What this tells me is that caps do make a difference, which cap will work best for you (in this amp) might take some trial and error.

    If you are up to living with a Frankenstein for a while, use clips on a lead wire and roll through a bunch.

    .. dB
     
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  4. magicscreen

    magicscreen Rando

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    Can I use 6N1P-EV and 6N6P russian tubes in the MCTH?
    Tube rolling.
     
  5. Zampotech

    Zampotech Friend

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    Most likely, it is undesirable to do this. These are very different tubes. Match only by pin.
     
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  6. purr1n

    purr1n Finding his inner redneck

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    Don’t be dumb. Just because it fits doesn’t mean you should stick anything you can find into it. If you want a 6SN7 hybrid amp, buy one. Don’t be like that guy on HF with the x-mas tree Feliks. Different type tubes have different electrical properties. Most of these assholes rolling in random tubes are probably loving the sound of distortion and have probably already ruined the filament voltage regulator.

    The amp designer designs the amp around the tubes used, the voltage, the bias, the rest of the circuit. Don’t put beans into Wolfgang Puck’s corn and bacon soup unless you know what you are doing, like exactly what you are doing at the chef’s recipe level.

    P.S. if you want to roll tubes and be pretend amp-designer, the Garage 1217 Project Sunrise or Horizon will serve as a better platform. It has through hole components which allow you to change resistors for bias, etc.

    The MCTH is a great amp for the price. Enjoy listening to music with it, not tubes.
     
    Last edited: Aug 29, 2020
  7. insidious meme

    insidious meme Ambivalent Kumquat

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    Nope, not an urban myth.

    [​IMG]
     
  8. mk801

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    Forgive me for my tube-rolling sinning ways. I feel that I let my brothers here down with the vertical photo compounding the sin. What penance must I perform to get back in everyone's good graces?

    [​IMG]
     
  9. CEE TEE

    CEE TEE Free Agent

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    ^Erm, share how it sounds before the beatings begin?
     
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  10. mk801

    mk801 Facebook Friend

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    The Tung-Sol's (pictured, could be a rebrand) throws the widest soundstage, great depth and imaging (very holographic), and a touch of warmth. For me, it is best paired with my HD6XX and HE-500 (also pictured with a modded headband) and is probably my favorite 6C8G . I never seen a Tung-Sol 6C8G without its characteristic black glass. It sounds unlike my other 6C8G's on the CTH, RCA meatball logo (kind of dry), Ken-Rad (well-balanced, but a smaller soundstage), and National Union (somewhat boring sounding with what seems to be some treble roll-off and a soundstage similar in size to the Ken-Rads).

    All of the above are more "tube-y" than the stock EH 6922's. I already had most of them prior my CTH purchase from rolling them with my Darkvoice.
     
    Last edited: Sep 3, 2020
  11. CEE TEE

    CEE TEE Free Agent

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    Ah, looks like others have been using that combo and like it as well. I don't recall that tube being compatible. I love old Tung Sols.
     
  12. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So is that a legit compatible* swap using an adapter like this? Oh noes ... I thought I was done with tubes for this amp :confused:

    *calling @dBel84
     
  13. mk801

    mk801 Facebook Friend

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  14. Cspirou

    Cspirou They call me Sparky

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    At first I thought this was the Apex audio Peak
     
  15. CEE TEE

    CEE TEE Free Agent

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  16. CEE TEE

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    I liked that amp.
    SneakPeak.JPG
     
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  17. CEE TEE

    CEE TEE Free Agent

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  18. mk801

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    Heh, luckily my two Tung-Sols are quiet. Some 6C8G's have microphonics, most of the rest are thankfully quiet, and one NU has a slight hum in the left channel. With these tubes and how cheap I got them (~$15-25 a pop), it was the luck of the draw.
     
  19. Phantaminum

    Phantaminum Friend

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    That particular tube isn’t a Tung-Sol but a RCA 6c8g. All the TS for this particular tube family have a black glass. Though I do agree with you, old NOS TS are some of my favorite sounding tubes.
     
  20. dBel84

    dBel84 Friend

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    I know I have said not to roll tubes in the CTH ( for many good reasons ) but if you track the history of the CTH , it was a spin off from the SOHA / Stacker early development. It originally evolved out of a modular amp that was being tossed about where you essentially had 3 sections - power supply // Voltage Gain stage // Current Buffer stage - the idea being that you could use a psu board that offered dual rail, heater and B+ voltages and you could use any parts of it you wanted, gain stage was typically tubed but there was a solid state option and buffer was always solid state but took many different forms : diamond, CLP, etc. I forget who the person was back then but they specifically wanted a hybrid amp that could fit into a tiny off the shelf extruded chassis but it needed to have all the elements for good tube amp sound - hence the desire to get a real B+ from a relatively low "wallwart" - for those keen enough, the web is full of discovery.

    Back to the current CTH

    this is how it started :
    [​IMG]

    and for those with keen eyes ....

    [​IMG]

    yep, the prototype could switch heater voltages which should be a tell that the amp can accept other tubes - the 12AU7 was the primary other consideration

    The key things to consider - autobias, the idea was that the amp could adjust to a small subset of tubes and maintain its operating points, this also allowed for tube variability as a fixed bias relies on fairly dependable operating characteristics and anyone who has been around tubes for long enough knows that tubes are typically highly variable and even dual triodes vary between their sections.

    The heater is now limited to 6.3V operation and I forget where the current taps out but it is not very high. B+ is targeted at 100V.

    If you run a tube at lower B+ and with 2mA of current ( which if memory serves me is where the CTH runs ) you increase distortion characteristics - this is not necessarily a bad thing unless you bow to the flat trace , fortunately for us it is mostly 2nd harmonic which if you read more about the impact of H2 on sound perception, you may become a believer. If the tube is way out of spec and it doesn't kill the amp , the effect will be your great/grandparents tube radio - lots of bloom, everything sounds sweet and mushy.

    I was looking for an online tutorial I used to send people to to learn how to read tube graphs - if you know what you are doing, you can have a lot of fun with the CTH. If you don't , you could still have fun and possibly get lucky . The amp is hard to kill but you could burn out its heater supply by trying something like the 6H30 .

    Back to the reason I advocate for the 6DJ8 / 6922 in this amp - there are so many to choose from, the B+ and bias are well suited to this tube and it will be operating in its sweet spot. I know it costs a lot more but the Liquid Glass was designed to be the tube rollers amp ( again not all tubes but a lot more with a switchable B+ of 200 and 300V , heaters of either 6.3/12.6 ..iirc current limit here is 2A ) not to get off topic, the amp was designed to be cheap enough to be accessible, allow, imho, excellent performance value and more than enough flavours of the optimal tube to allow experimentation.

    ..dB
     

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