Massdrop Cavalli Tube Hybrid

[cspirou]

How is high voltage generated for the tube from a DC power brick?

[kevin gilmore]

flyback switcher on board.

another stepdown flyback switcher for the filaments

[azimuth]

On 3/18/2018 at 9:57 AM, kevin gilmore said:

the thd+N is .0075%, and although it does not specify, its likely at 1khz.

look at the schematic posted above.  about 15db of feedback around the grid of the tube. Lowering the input impedance to bipolar levels or lower and kind of negating any possible use of an input tube. Also the plate current source.

spice indicates a second harmonic distortion of -74db at 1khz (.02%) and a 3rd harmonic distortion of -109db (.0003%) at 1khz

however at 10khz the second harmonic is -60db (.1%) and the third harmonic is -96db (.002%)

you can work out the summation on your own.

plus of course the messed up soundstage due to the inverse phase. Something the plankton experts seem to ignore.

In reality, with an old school analog thd meter, the numbers are going to be much much higher.

and of course this is all measured with a 300 ohm resistor. Use a real load especially low impedance, and the numbers go way up.

This amp actually gets nowhere near these numbers in real world testing.

https://www.superbestaudiofriends.org/index.php?threads/massdrop-cavalli-tube-hybrid-amp-technical-measurements.5900/

This is for testing at both 300 ohm and 30 ohm. And testing with an LPS (spoiler: THD+N drops even more).

[Hopstretch]

[Kung]

chinese bhse from taobao jr audio。。。

[Kris0603]

Having used mine for days only, i will say it is a reasonably well-behaved amp. Quiet and easy to handle, my pot tracks well and feels smooth. The construction is unusual, usually in DIY we strive to make compact little PCBs and connect them all together, enabling us to upgrade various components as time progresses. I am very cautiously optimistic on the longevity and serviceability of my MCTH. Time will tell i guess

 

[Rhamnetin]

This is what Cavalli is up to these days (the $100 Liquid Spark)

 

 

[kevin gilmore]

Mismatched very high cacitance vishay siliconix output mosfets. And ground splitter. Otherwise identical current feedback amplifier same as liquid gold,liquid carbon,Cth, liquid platinum etc.

at least it's better assembled than schiit.

Edited October 29, 2018 by kevin gilmore

[Kattefjaes]

16 hours ago, kevin gilmore said:

Mismatched very high cacitance vishay siliconix output mosfets. And ground splitter. Otherwise identical current feedback amplifier same as liquid gold,liquid carbon,Cth, liquid platinum etc.

at least it's better assembled than schiit.

Speaking of which, seeing reports in various forums of the Lyr 3 killing headphones. Have you peeked inside one? If so, any idea what's up?

[kevin gilmore]

cavalli liquid carbon massdrop version rail splitter

cth and spark are similar

 

railsplitter.PDF

Edited November 3, 2018 by kevin gilmore

[Rhamnetin]

Closer look at the Liquid Spark

 

Underside

 

[kevin gilmore]

so it turns out this one is a bit different than the rest of them. Input is 2sk2145 dual n-channel jfet, driven by current mirror on top, and current sink on bottom. 

Definitely a voltage feedback amp, lots of feedback. liquid gold, liquid carbon,massdrop liquid carbon, massdrop cth are all current feedback amplifiers.