Massdrop Cavalli Tube Hybrid Amp

The acetone solvent covered up the scent so I didn't notice until after it dried <insert my avatar here>.

The bottle was almost finished so she gave it to me, shaking her head as I explained why I wanted it.

 

heh I had a similar thing with my goldmund clone speaker amp, the EI core transformer was painted with shellac or some other varnish which had a scent that it released when the amp got hot.. fortunately it was rather pleasant and I appreciated the old school anti vibration technique of painting the transformer with shellac

 

So I've had my MCTH since 5/3, and have probably put around 60 or so hours on it so far. There has definitely been a change in the tonality, especially with the bass. I've went from thinking the TH-X00s were unusable, to thinking they are a fantastic pairing. The HD800S were always good, but I do miss that initial warmth just a bit.

Unfortunately my enjoyment is on hold for a bit. I came home yesterday, flipped on the amp and nada. No familiar whine noise as the relay clicked, but the power led was white. Then I noticed the tube wasn't glowing at all, and thought "hmph, was the tube always white?" (it was a long day).

Went to pull the tube and reseat it, heard a concerning crunching/grinding sound and saw this:


Anybody know how this could have happened? I've already emailed MD support, I'm just a bit surprised that this happened with it off. I live in Florida and have a nest which has learned to not really run much when nobody is home, meaning the house has some decent temperature swings. Is this an issue?

 

No, the tube can handle any temp you can tolerate. Did you tube roll often? I am starting to think the newer generation tubes don't handle the rigor of change very well. It must have had a small crack which slowly let the faeries out..dB

 

Nope, never removed the tube once it was put in. It wasn't the most reassuring thing putting it in, so I left it.

 

That is odd. Assuming you don't have another tube to test the amp..dB

 

I can only imagine that the glass was already cracked/weak/chipped for that to have happened. I assume MD is sending you a new one?

I wonder a bit about your statement about a familiar whine... My cth is dead quiet, I can't even say I hear a relay click (although I'm going to listen closer tomorrow when I flip it on tomorrow)

 

Mine is dead quiet as well, except for the quiet click when it finishes it's power-up cycle and the LED changes from red to white.

 

Nope. I'm going to stop by a vintage audio repair shop and see if they have any 6922s there. At least to hold me over till the stock one is replaced.

So when you have headphones plugged in and are listening, you don't hear a whining sound when the light changes? It fades away but its there for a second for me. Can't remember if all my sets did it, but the HD800s definitely did.

Hmm guess I'll just ask, does anyone get buzzing occasionally when touching the volume knob?

 

You mean a whining sound through the headphones as the LED changes from red to white? I've checked to see if there's a "pop" like there is on shutdown and don't remember hearing anything. Will check again. Don't hear anything from the amp itself, other than the sound of the relay.

Nope, the volume pot is dead quiet, and smooth as silk

 

Exactly what I mean. I hear it every time I start the amp, but it’s more pronounced when the amp has been sitting for a while. It still happens when turning the unit off and on when warm, just not as much.

I’m hoping that’s an indicator of a bad tube, and not an issue with the amp itself. I also hope starting the amp with that bad tube didn’t cause any damage, will definitely be more careful now.

I mentioned the whine to MD support, I’m curious what they say. Unfortunately they haven’t gotten back to me yet, I just got a auto-response about it being forwarded to a special team.


Update (to not clog with posts):

Just got home with a RCA 6ES8 (guy assured me it's a proper substitute), threw it in and there is sound. The 'whine' on start that I was referring to is gone. Seems that was the faulty EH tube.

I know folks in this thread have said tube rolling has little effect with the MCTH, but I'm certainly noticing a big difference with this tube, not sure for the better or worse yet. Perhaps it is because my original tube was faulty, who knows.

 

I have the buzzing occasionally as well, seems to be when I rotate it pass a certain point. No whine on start up though, so it seems to be your faulty tube causing the whine.

 

So I rolled in a Valvo E88CC (Hamburg 10/61) that was in a grab bag I bought. Don't know if it was brand new or not, but after 10 minutes warmup, my first impression was that vocals and strings sounded a bit more forward, and both clearer and smoother at the same time, and sibilance was a bit reduced compared to the EH. Bass was reduced and wet-noodley. I left it on overnight and had another listen after work the next day. Vocals and strings didn't sound quite as nice as the previous night, but bass seemed to be not as limp dick, but still had less impact and extension than with the EH. Differences in impressions could have been down to psychoacoustic factors.

If I listened to mostly vocal, acoustic or classical, I think this would be an improvement on the EH. But since I listen to mostly pop/rock/electronic, I'll probably only swap it in if I'm in the mood for a Bach cello suite, or a session of Female vocals that shine...

Edit: Valvo sound stage seems a bit wider, too.

 

My supplied EH tube stopped working after a day. It didn't visibly lose vacuum but the heater didn't light up. After reading the past few posts I am wondering if there is an issue with these tubes failing while cooling. Nothing puts a downer on your day like waking up to find you have a tube that has cracked while cooling off. I didn't really plan on using the EH tube anyways so I wasn't really upset.

 

I’m beginning to wonder the same. Massdrop support got back to me saying they cannot source more EH tubes (they only get fully assembled units) and do not have an ETA on when they will get them. I wound up getting a partial refund because swapping the whole amp for a tube is just excessive.

FWIW support also gave me the same line about tubes going to air if the amp is not powered indefinitely, which seems... unlikely.

They may have gotten a bad batch of tubes, and think it’s the amp blowing them.

 

I wonder if they realize they have a problem with the tubes cracking on cool-down and this is their way to avoid the problem.

Glad I like my NOS amperex orange better than the EH...

 

Anyone else having an issue when listening at really loud levels, a strong hit happens and the amp goes into protection for 5-10 seconds?

I can't tell if this is some kind of over current protection or the DC offset protection.

It only happens on my Fostex T20's, which are very inefficient. And it was happening with the SMPS and the LPS.

 

Would this amp he affected too much with a preamp connected to it? I plan on saving up for a Rogue Audio Sphinx v2 and if I could go through the integrated amp first it would make the runs a lot simpler.

 

you may overdrive your integrated but if you kept the volume lower on the integrated and used the MCTH to control volume, you should be OK. I am not sure what the start up pop in the speakers would be like, so probably better to turn on MCTH first and then shut it down last..dB

 

There is not startup pop at all on the MCTH. It has a protection that monitors DC offset on output OR input, so until the offset settles down, the relay will not click on. It is not a timed relay like other devices.