Hi, I have a schiit magni heresy amp with a modi 3 DAC. I bought an FX audio tube-03 and tube swapped to GE tubes, because that's what the popular opinion to do with it was. I don't remember if I initially heard no difference, or little difference, but I decided it wasn't an improvement and set it aside.
Some amps don't necessarily add a lot of tube distortion, and not many people can hear non-placebo differences between a good, very clean amp and one that isn't but not outright crap.*
In your case that's not even a tube headphone amp, it's just a preamp.
*I mean, I have a Cantate.2, and apart from noise and more 2D soundstage, and actually being leaner despite having a tube and full Class A, the Pangea HP101 isn't that bad
I was using planar M1060c, which i was told don't react great with tubes, so i assumed that was the issue.
"Does not react well to tubes" doesn't mean "doesn't show tube distortion, at all." It means exactly the opposite: only tube distortion in the worst way possible.
To be more specific this has more to do with OTL amplifiers. They have very high output impedance, so if you start with a cheap one and put a low impedance headphone on it, you'd get even more distortion due to the drastically lowered damping factor. Their power output is also biased for high impedance loads, and chances are most lower impedance headphones actually need more power since they have lower sensitivity (save for the more recent dynamic driver designs). This is basically like having a car that understeers hard and can't be throttle-steered to point the car in the right direction.
Also that FX Audio is a hybrid amp, not a tube amp. And it's running off a power brick...a real, pure tube amp would have a transformer to run the tubes with more voltage and has preamp tubes and a tube driver stage, not a preamp tube paired with a solid state output stage. And even a hybrid amp would still have a lot of voltage for the preamp tube. (this is why there's a joke about the "Starving Student" amp being more about what the rectifier tubes are getting than what the buyer is spending).
I just got a pair of 6xx, which everyone says react real well with tubes, so I was excited to try the tubes out with them, but i still cannot hear a difference...like, at all. I bought an audio switch so I can just switch between tubes, or no tubes, with the push of a button, and I cant tell them both apart. From what I've been repeatedly hearing about the 6xx and that tube buffer, this sounds wrong. Anyone have any ideas what I might be doing wrong?
Cheap tube preamp = probably not a good circuit with brighter-sounding Shuguang preamp tubes.
If you want a relatively affordable tube amp with a lot of tube distortion, maybe try a Little Dot Mk2 on both those headphones. It'd be kind of good on the HD6XX but I wouldn't expect a lot of difference on the M1060, if not make it worse compared to the Magni Heresy, since planars don't tend to show the totally detrimental tube distortion caused by the high output impedance,
but you'd have a lot less current off that amp.
Here is am diagram of how it have it set up
The output from my DAC is split to the inputs of the tube pre, and the switch
The output from the tube pre goes into a different input on the switch
Then i can toggle which set of inputs gets output to the amp from the buttons on the switch
Your main problem with this set up is you now have two preamp circuits in the same chain.
So even if you run the signal through a tube preamp, which is essentially just a tube buffer like one of those Musical Fidelity gadgets, you're still gonna run that signal through the Magni's preamp stage again anyway.
If the tube preamp was designed specifically to have a very subtle effect ie just round out sharp edges than a badly designed one that makes the music sound like the singer and everything else has sinusitis, then you only have a very subtle effect that is less preserved than merely accounting for the amp stage distortion pattern since the Magni's preamp is still in that chain.
