Guitar pedals, Fuzz, Audio Electronics, Open Source Hardware
A/B listening and it sounds like the 12au7 has a somewhat warmer sound, is the slightly colder/linear sound just an inherent property of the NuTube or can you change it by varying the plate voltage or something?Really I just find these things very interesting.
The circuit allows adjusting grid bias and plate load resistance, but none of them seem to basically change the characteristics of the NuTube sound.Thanks for your interest.
Electronics are interesting ;) Especially new fancy stuff.Does the NuTube sound much different than a normal opamp? I know it's bound to color the sound a certain way, but it'd be interesting to know to what extent that happens.
I would say yes definitely, the "color" comes from response in saturation mode, distortion from a tube has more content of 2nd harmonics, a silicon semiconductor saturation is "harsh" and full of high harmonics. Low signal frequency response of NuTube is as flat and uncolored as an opamp.Actually definitive test would be to run a boost or overdrive in front of the tube amps and check the response under input distortion conditions.
What would be considered operating inside saturation mode in this case?
If you check the blog post on Distortion Analysis here http://rezzonics.blogspot.fr/2017/08/korg-nutube-6p1-vs-12ax7-tube-hybrid.html you will see that there is some level of distortion (saturation) for all gain levels with 2nd harmonic to 1st attenuation ranging from -20 to -11 for the NuTube and -19 to -3 dB for the 12AX7 tube, the more gain the more saturation and distortion. Most of the saturation happens on the second tube stage, adding a boost or overdrive at the input would add distortion to both tube stages, with more 2nd harmonics.