Massdrop Cavalli Tube Hybrid Amp

Latest in my MCTH modding & rolling saga: I rolled in a Genalex Gold Lion 6922 with gold pins. Together with the Miflex caps, they provide a full bodied sound, leaning towards the warm side at the cost of some detail. I like it as it goes more to the OTL kind of side - as always YMMV.

I had to replace my stock EH 6922 as developing noise was showing its age. Strangely, rolling in (almost) new Tesla or Philips SQ E88CCs also put out an irritating amount of noise, even though they are completely silent in my Eufonika amps. Didn't matter whether I was using the stock wall wart or Chinese LPS on my MCTH. So, I turned to new production tubes and indeed the Genalex was noise-free.

Tihs is my first Genalex and so far, I really like it. You can get more than decent NOS tubes at the same price, but I now learned that "new production" does not mean "nowhere as good production".

 

^We tried the Gold Lion during R&D, sent it out to people for feedback. (I was sweating it a little as the Gold Lion was SO much more expensive, but we wanted to know what the best new production tube was going to be.) Your Miflex caps might be making it a great balance, as in stock form people thought the Gold Lion was a little "too aggressive" with the CTH. Glad it is working for you with your cap mod!

 

I got a pair of JJ 6922 with a used Liquid Platinum amp purchase. I eventually thought they were just too aggressive in the treble. The bass was very powerful and the tube very dynamic and exciting. But eventually I found the tube fatiguing.

The tube I like in my LP amp and Sunrise 3 is the Voskhod 6N23P. Very inexpensive and you can buy matched pairs on ebay. The Voskhod seems sort of boring at first but as they break in they open and they do not do anything wrong. They just get out of the way and let the music through.

 

I would agree that the military grade versions of this tube are reliably good. I have tended to default to them despite having a small stash of NOS unobtanium.

.. dB

 

This is one of this story where a post from ages ago actually helps you. I ended up having the same issue. I have not replaced the C1 cap yet, but removing it made the amplifier starting again. I originally thought that the power transistor Q1 was faulty (since active component tends to die faster) but after unsoldering it, I stil got the issue.

From what I saw, C1 made a short circuit. My DC block made light sparkles when plugged to the amplifier and although unplugged I could verify the 28V with my multimeter, there was nothing once connected to the amplifier anymore. Icing on the cake : the bipper told me that ground and VCC (28V) were connected together, I suspect a long time deterioration and all disappeared once C1 removed. It is a filter cap straight at the entrance, so subject to most stress (since the 28V goes straight in) and maybe it was not designed to handle such a long run (I got the amplifier in March 2018 but it did not became my main amplifier at first). Some time, some voltage stress and maybe a little humidity had the best of the cap I would say. Anyway, thank you for having investigated this issue some time ago, it helped me today

Last note : I am in Europe, I do not know how well the DC block or capacitor was qualified for 230V and 50Hz. Maybe it could explain a little extra stress on the capacitor. Having to regulate a spike based on a 120V is different than 230V, especially on a long run. Just a thought.

Edit 02.29.2024 : I replaced the capacitor with a non-smd 10uF polarized 50V one and my amplifier is working again.