Massdrop Cavalli Tube Hybrid Amp

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

  1. TomNC

    TomNC Almost "Made"

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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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  2. ohshitgorillas

    ohshitgorillas Friend

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    I am still rocking this excellent amp for my office rig, now paired with a pair of ZMF Blackwoods (Padauk) I scored off of eBay. It pairs so freaking well with the ZMF Classic and Blackwoods that I really don't feel any need to upgrade the amp or headphones, although I'll eventually pick up an Airist R2RDAC and a linear power supply to "complete" the setup. Honestly, I love the way this thing sounds, but I've been having some issues with the input switch since day one (mine is the version with the SDAC).

    The input switch has always been very sensitive and jiggling it around even while in the same position could cause the SDAC signal to cut out entirely. Using an external DAC (xDuoo X10T II > Chord Mojo), I can hear the signal from the external DAC even when the input switch is in the SDAC position if I jiggle it around right. Also, the static/scratching on the volume knob is more persistent and annoying than any other scratchy pot I've ever heard (but is only audible when adjusting the pot).

    I've actually opened the unit up before to look for bad solder joints around the volume knob and the input switch before. One post on the input switch had less than ideal looking solder, so I re-did it to look identical to the other joints, but the problem has persisted. Before anyone says I should have just contacted Massdrop about this instead of voiding the warranty... the unit was purchased second-hand, and I wasn't able to get the purchase information from the eBay seller. Although CEE TEE, working for Massdrop at the time, was kind enough to push a warranty request through when the internal SDAC died (I am so, so grateful to him for this <3), he's no longer there and so I would have a much harder time convincing Massdrop to fix the unit out of warranty without him on my side. Besides, if I do the work myself, I don't have to ship it off and go a week or so without it.

    I'd like to repair this before the issue potentially becomes catastrophic, but I'm not sure exactly what to look for. I assume that the solder joints around the switch and pot will be suspect, but I'm not an engineer and I may be overlooking something obvious here. I'm thinking about maybe replacing the input switch altogether, although I'm not sure exactly which part I would need to get the job done. I also need to replace the RCA jacks in the back, since I once used the female jacks to hold a male connector in place while I soldered some wires onto it... and it melted the teflon a little bit. Not a major issue, but annoying to me.
     
  3. Type35

    Type35 Rando

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    I have the same issue with the volume pot on my MCTH+SDAC: there is a low level static noise that gets louder as I turn the volume up. The noise disappear when I don't touch the pot or when I put my other hand on the chassis. The noise is the same in both left and right channels. It looks like some sort of grounding issue. A quick search on Google and I found a bunch of similar cases where Massdrop would just replace the unit under warranty. Unfortunately for me I bought my unit second hand and I am in the UK so no free repair for me. I was just thinking of running an additional wire to the star ground inside the chassis (I haven't taken the amp apart yet). Anybody else dealt with this issue? What's the best solution?
     
  4. Ksaurav402

    Ksaurav402 Friend

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    First check if your Power socket is fine and doesn't have any grounding issue. Sometime the ground is missing from power socket.
     
  5. CEE TEE

    CEE TEE Free Agent

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    CTH shares ground with source- check to make sure source is grounded well...

    Inside, anodization should be stripped at the place where the PCB grounds to chassis.
     
  6. msommers

    msommers High on Epipens

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    I have a JAN Tung-Sol 6C8G and metal adapter for sale that I used with the MCTH that I'm no longer needing.
     
  7. ohshitgorillas

    ohshitgorillas Friend

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    I finally solved the issue of the scratchy pot and inconsistent input switch... all it took was a little deoxit and some movement across the pot and switch, and now the pot is dead silent across the whole range. That one issue was my major gripe with the CTH, so it's really satisfying to have it put to bed.

    I finally just acquired an Airist R-2R DAC to pair with the CTH, at last. It's been on for about 26 hours now and I'm thoroughly impressed. Usually this would be my office headphone rig but, with everything shut down, it's now sitting at my home desk with my computer. Using xDuoo X10T II as a coax source. Damn, this is a really enjoyable combo, it's hard to imagine that people have so much angst about this DAC's existence, given how competent it is. I am especially into the way the R-2R DAC renders space/staging/placement. Instruments have a very full, discrete, and well-placed image with good timbre. The presentation and staging almost reminds me of a good vinyl rig... vinyl is superior, imho, but this is a positive step in that direction. It's said that this DAC sounds similar to NOS, and if this is a taste of what R2R NOS DACs offer, I think I'm already sold. (I also got to hear the Metrum Onyx + Glenn OTL + ZMF Verite at CanJam NYC, and the presentation in that setup was similar in that sense).

    My only gripe with the combo is that, in stacking them, they are two different materials. I prefer the black brushed metal of the DAC to the literally-anything-will-leave-a-mark black matte of the CTH.
     
  8. CEE TEE

    CEE TEE Free Agent

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    ^Ah, must be from the first build...revised the finish after feedback. If you have a spare lens cleaning cloth around, I keep a couple in my desk drawer. One for laptop screen and one for wiping off gear.

    Would you mind sharing your process with deoxit in case someone else has a similar issue?
     
  9. ohshitgorillas

    ohshitgorillas Friend

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    Ah, dang, there's a different finish available? Man, now I am tempted to trade my unit with the SDAC for a newer one without . SDAC is very good for a built-in unit but it does leave something to be desired in terms of soundstage and microdetail, and doesn't really compete with the Airist DAC. Not in any hurry though, I do have some of those microfiber cloths.

    Of course I'll share the deoxit process!

    1. Unplug the unit. Loosen the screws on the bottom and back plate. Note that there are three different lengths: the bottom are shortest, the backplate are medium length, and the single screw right above the RCA jacks is the longest. This will almost certainly void your warranty, but if you do it right, no one will ever know you were inside.

    2. Put on gloves. Make sure you've got somewhere clean, soft, well ventilated, and well lit to set the circuit board down. Be gentle with the unit and don't do anything stupid like drop it. Yes, I know that's the company's name, but that's not what they meant.

    3. Remove the backplate and gently slide the circuit board out by holding the back of the chassis in one hand and the front plate in the other, and slowly pull. The PCB is sitting on sliders inside the chassis, so don't pull in any direction that isn't directly opposite and parallel to the length of the chassis. Set the circuit board down, and set the chassis aside.

    4. Locate your can of deoxit or similar electronic contact cleaner. Now locate the potentiometer (and, if you have a CTH+SDAC combo unit, the input switch... in my case both were scratchy).

    5. It really does not take a ton of this stuff. Pressing down on the spray nozzle all the way is way too much. Get in a few practice sprays so you're not overdoing it. That said, you at least want to thoroughly coat the switch and volume pot. You want to get the liquid *inside* the target. The excess will quickly evaporate, but will leave a thin film on the PCB that should be cleaned up.

    6. Turn the potentiometer across its full range, and/or push the switch in and out for several minutes. Leave the unit in a well ventilated area for 30 minutes to let the cleaner completely evaporate.

    7. Make sure the PCB is clean with no traces of deoxit or finger prints, and reassemble the unit. It should be good to go now and scratch-free (unless you have the unit with my finish, in which case it will be hella scratched all over and will need wiped down with a microfiber cloth).
     
    Last edited: Mar 25, 2020
  10. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I sprayed the shit out of my pot with a standard contact cleaner and it didn't help much. After I swapped it for a new one, I tried soaking it contact cleaner and could still hear the physical scratchiness, though it sounded different (I didn't solder it back in to see if the scratch could still be heard through the phones, as the new pot was already iin). Maybe actual Deoxit has some magic that plain ol' contact cleaner doesn't. Glad it worked for you!
     
  11. ohshitgorillas

    ohshitgorillas Friend

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    Actually, I was also using the cheap shit that you can get at O'Reilly's, that comes in a red can. I have been meaning to order some actual Deoxit since there's apparently nowhere in town that actually sells the stuff, but haven't gotten around to it as this stuff seems to work pretty well for me. I assume you didn't just spray it, but also moved the pot back and forth for a while after soaking it? Then again, if the pot was actually physically scratchy... there might not have been any chance of saving it in the first place.
     
  12. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Yeah, I hosed it down very thoroughly, turning it back and forth multiple times. I could hear the scratch while the original pot was still mounted on the board. And I soaked it in contact cleaner using an aluminum foil boat after I removed it from the board, turned it a lot, then soaked it again. Still sounded scratchy, but different.

    Anyway, it's good now with the replacement pot I mentioned earlier in this thread.
     
  13. ohshitgorillas

    ohshitgorillas Friend

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    I am seriously considering removing the RCA jacks from the Airist DAC and CTH, and hardwiring both together once I have to return them to my campus office. It would be a reversible process... someone convince me this is very stupid so I don't actually do it, please. It feels stupid, but also like it could be awesome.
     
  14. Pogo

    Pogo Friend

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    Uncertain what you expect to gain, but I'll definitely have some of what you're smoking.
    Looking forward to another "hold my beer and watch this" moment.
     
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  15. rtaylor76

    rtaylor76 Can't wipe his tag

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    You likely will not notice a difference. Not worth it mate.
     
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  16. BrokeSkoolBoi

    BrokeSkoolBoi Acquaintance

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    Built a pc and I was finally able to fix the reverse polarity issue through foobar2000. It honestly bothered my ears more than I thought it would, and was quite noticeable after using my FDx1 through an ES100.

    You need to download the following plugins and extract them to Program Files x86>foobar2000>components

    https://hydrogenaud.io/index.php/topic,84947.0.html

    https://my.pcloud.com/publink/show?code=XZEbP8kZhDjkfdqtH5Jc3Rlq5BFjPul7nfqy

    After that, reopen foobar2000 and go to File, preferences> DSP Manager. Press the '+' next to the 'Polarity' column to add it to the left then press the '...' to toggle.

    Apologies if links are frowned upon, I glanced through the rules but I've been staring at a screen all day.

    I also wanted to let everyone know about a 6922 tube that might be the best thing you can put in this amp at the risk it might sell out from me posting about it.

    https://www.thetubestore.com/6h23n-eb-6922

    Last time i put an EH 6922 in the CTH+LPS it blew in a couple months (might have been a power outlet issue). The Reflector 6H23N-EB tube has lasted me a few hundred hours of listening already since black friday (they were $40!). I've rolled an Amperex Orange Globe, Mullards, a Tesla (JJ and NOS E88CC '32' production). This Reflector tube sounds like it was made for this amp.

    The disconnected sensation between treble, mid, and bass with the stock tube is gone. There is no harshness anywhere in the spectrum (bad recordings aside), the trade off is that the treble is not as sparkly as it should be and attack is a little softer than SS, but all the detail comes through as well as I think this amp can manage which was not the case with the stock tube or any of the others I rolled (amperex was orgasmic with an Elex though ;] ). Bass is a bit bloomy but I'm using a D70 dac so it is appreciated. Easy listening for all hours of the day, but still involving!

    Edit: I sold my Elex but I still have the Amperex if anybody wants to hear it with their Focals.

    @gixxerwimp I've been reading about the SW51 tonight and it sounds spectacular. Are you keeping your CTH Gixxerwimp?
     
    Last edited: Apr 13, 2020
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  17. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Mine is stored in a cupboard for now. The SW51+ kinda makes the the MCTH redundant for me.
     
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  18. dBel84

    dBel84 Friend

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    I use that tube a lot too - have a set running in my platinum/crimson and use it in my "Bootstrapped" unity gain pre-amp , it does a lot of things right.

    ..dB
     
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  19. bigant

    bigant Acquaintance

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    Hi There,
    I think this is the right place to ask this, a couple months ago my CTH stopped powering on. As I'm in Australia and its over 2 years old I figured its not worth following up with Drop.

    Due to the current lockdown I thought I'd have a bit of a poke around, in a previous life, in a country far far away I was an electronics bench tech so I have a fairly good idea what to look/sniff/measure for. First thing I did was measure the resistance across the power input socket and found it to be 52 Ohms. Hmmmm.

    Poked around a bit more and found that the capacitor marked C1 on the board also has a resistance of 52 Ohms. Hmmmm Hmmmm.

    From what I can see by looking at the PCB traces that particular cap appears to just be some sort of bypass across the power input I assume to dump HF noise coming from the PSU maybe?

    So Just for shits & giggles I desoldered it and wonder of wonders the thing powered up, red LED, relay click white LED etc. I haven't tried putting a signal through it yet, nor have I plugged in the tube, however, the Capacitor is just a small brown SMD blob with nothing printed on it. I have no idea what it's value should be.

    Don't really want to go any further until I can replace so it is there any chance anyone with a working unit could measure, or knows whats the value should be.

    I'm making the huge assumption that there isn't anything else in parallel with it.
    [​IMG]
     
  20. gixxerwimp

    gixxerwimp Professional tricycle rider

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