Also from their website ...."SYSTEMS THAT APPEAL MORE TO THE HEART THAN THE HEAD."O JoY! Here is a blurb on Mhdt.
"The gang of four founded Mhdt Lab in 2002 and are known as: ‘Music Heaven Development Team’.
They had decided to begin designing DACs to bring the feeling and fun back to digital. Motivated by the shortcomings of most DACs to faithfully convey, with spirit, varying styles of music, they have successfully created affordable great sounding and flexible little gems."
I agree. As an example, ECC82 x ECC802 in the same circuit, same test conditions. Hopefully I have put it into my archive. Please note almost 2 : 1 distortion. Please note 10dB difference in 50Hz mains line. No topology change except for tube exchange. Please note slight difference in gain (peak level).As shown by a recent post where I outlined selecting two of the lowest distortion 12AX7 tubes out of a lot of a dozen, using the preamp where the tubes would be operating, there was a range of 0.3 to 0.9% THD. I would call this significant, and certainly audible in certain circumstances!
If a product was tested here and there was that wide of a range of distortion between channels, it would be declared 'broken', yet the conclusion for this test was that the differences were not that big a deal. The range of a couple tenths of a percent distortion absolutely is significant - maybe not at 2 volts, but possibly at lower levels and depending on the program material.
I know there is a baked-in bias against vacuum tubes in parts of this forum, but glossing over and dumbing down tests results because of these biases is not a good look. Better to simply not do these kinds of tests in the first place if they cannot be performed with the rigor afforded to more mainstream components.
I never understand why it's called "rolling tubes" as opposed to "changing tubes". It seems to imply some inherent skill involved in the process.
Ok. I'll buy that, but how does one roll an op amp? I've tried. It wouldn't budge.
I lived in USA with my parents in 1966/67. I remember those testers as well.I'm old enough to remember when every store that sold TV's and radios even some corner drugstores (in NYC) had large floorstanding tube testers. You would run the testers yourself. Customers would come in with a shoebox full of tubes and test them. A waste bin was kept next to the machine for bad tubes. No one would even think of "tube rolling". Tubes were either in the "green" ranges or they were thrown away.
I second that motion, please!Please do opamps next!!!!
A couple of measurements of my iFi iTube buffer/pre, which uses the same tube as the MDHT. In the iTube's 6dB gain mode (I think). Pushing it a lot in the second to see where it clips.