Massdrop Cavalli Tube Hybrid Power Adapter


What model are you having issues with?:
Massdrop Cavalli Tube Hybrid

Describe your issue with the most detail you can:
I’m not really having an issue with it, so far it’s been great. But in order to try and minimize the amount of travel adapters plugged into my powerboard, does anyone know if I could use a 24V DC 1.25a power adapter with this? I’ve found one where the only difference to the one supplied is the voltage, 28V vs 24V and an Australian plug. It has a 30W output and the MCTH has a max of 35W output.

I’ve asked Massdrop, they said they don’t have the technical knowledge to answer and to ask in the discussion section but there’s almost 2000 comments and looks like it’ll get missed.
How long ago was it purchased?:
Got it last week, happy to keep using the plug adapter if needed but would prefer to not need an adapter.


Sorry, I would love to be able to help you but my electrical experience only goes as far as wiring a plug. And it’s 50/50 on whether or not I will explode after. Regarding your new amp though I really like the look of it and may get one myself. I have bought a few items from Massdrop and think they’re a great source of audiophile and headphone related gear. I hope you get your question answered. I am sure you will there are some very knowledgeable people frequenting this forum. Good luck.


Trying it won’t damage it, but I doubt it’s going to work - and if it does it may not work properly (i.e. sound right).

I suspect the supplied PSU has a bit more headroom, current wise, than it claims on the sticker. Using a linear supply that was at the “required” 28v @ 1.25A resulted in the MCTH failing to power up. Moving to something that had a bit more power, specifically more current capacity fixed that.

It’s possible the unit is more tolerable of lower voltage than it is of insufficient current, but that’s not typical.

If I get a chance I’ll hook the thing up to my lab supply and see at what point it a) won’t start with less than 28v and b) how much current it actually draws on start up. Probably won’t be this weekend though.


That would be awesome, cheers.

Looking a little further into it, the power supplies over here seem to go from 24V to 48V, nothing really in between. I’m just assuming that has something to do with the different power grids.


Good idea, @Torq.

Stock tube only showed 0.55A on startup. The only way to get a faster response measurement would be running my multimeter in series with it. It sits a 0.4A at idle.

Also dropped voltage to 24V and it didn’t shut down, but that’s quite far from target and wouldn’t sound as good.

I would get something with the same rating as stock. Only thing I’d risk changing is the max amperage (only go above stock, not below).


Go to Audiokarma in the DAC/Amp thread and ask this question there are numerous tube headphone amp guru’s there. When you are there ask about “tube rolling” there should be a better choice than the 6DJ8 tube that amp uses.


Finally got to try this with my, calibrated, lab PSUs …

At 24v and 1.25A startup was unreliable with the stock tube and a no-go with the tube I’m using in practice. At 28v and 1.25A I experience no issues. This in contrast to the little LPS I was playing with earlier, which had issues on startup even with the stock tube.

However, even when the amp does initialize, at 24v it sounds like a slapped arse.

It’s a lovely little amp run properly … don’t gimp it by messing with the PSU.

While in real terms I never saw more than about 0.6A of current draw, even on start-up, I still wouldn’t under-spec the PSU based on that. Even with a full 1.25A available, I had a coupe of failures to start with non-stock PSUs. I still suspect the included PSU has a bit more current-headroom than spec would suggest.


Thanks for doing that, looks like I’ll be sticking with the plug adapter for now.