Hi BW, congrats on the new Mini!

I appreciate your observations, and that you seem happy with that particular option, except you haven't spoken about noticing sound quality tradeoffs involved when you bypass/reduce the design feedback of 6 Db for something less than that ideal.

The amp was voiced to have a special sonic signature and presumably optimized for sound quality at 6 Db negative feedback. Evidently, the dynamics are released when the feedback loop is reduced, but the tradeoff is supposed to be higher distortion. Since Beam Tetrodes (i.e. 6V6) or Pentodes, do not behave as linearly as Triodes, this feedback is much needed to avoid higher distortion levels throughout the frequency range.

My only contention is why would one buy a Class 'A' SEP if one would be willing to trade some of its inherent SQ for more dynamics? Why not choose a PP design in the first place? A little bit of 'both worlds' in the same amp, perhaps?  I'm just curious.

This is all technical and beyond our musical enjoyment objective, of course, but I'm interested to know if you have heard increased sound distortion along with the increased dynamics involved in bypassing or reducing the negative feedback during those passages.

I would be happy to learn from your inputs in this regard.  Thanks!

Thanks Fireblade, I couldn't be happier with it!

About tradeoff, it's a bit hard to answer because so far I've adjusted the feedback to give favorable results, if they aren't I simply return the setting to where it sounds best. A lot has to do with the production of the recording, some benefit from it much more than others. I suppose an example of a tradeoff that occurs sometimes would be that lowering the feedback improves the sound of the guitar but makes cymbals louder and harsher. In this case I just pick the setting that sounds best overall to me.

I struggle to make blanket statements about it because every recording and instrument is affected differently. Some a slight change will improve everything with no real tradeoff that I can notice. Others the same adjustment will be unpleasant and give a harsher in your face kind of sound. There is always the default setting though, and I have yet to come across anything that sounds bad using that.

So far I've found only small adjustments from the default to be useful. Setting it to zero feedback gives a similar sound to playing music through an instrument amplifier.

As to your question of why, I'd say to have more options. It's something that could be left alone, or it can be experimented with and you might find some recordings really benefit from just a little adjustment. Kind of like the treble shunt, or tube rolling, it's just another option. If my amp didn't have it I would want it added.

I haven't noticed any distortion occurring from simply adjusting the feedback. Also I'm just starting out building my HiFi system, the Mini is the only part worth mentioning so unfortunately I'm not the best person to ask about some of this. Though I hope what I have said is useful. It's a wonderful amp with or without mod. If you're really curious getting the mod might be the best way to answer your questions. Especially if you're sending your amp in for a different reason, at worst you'd be out $100 and have a couple knobs you don't use.