[Andrew LB]

Can someone explain the 'feedback' switch on my MG-Head OTL amp? I really have no idea what it does and would like a good explanation if someone can do that for me. Switching back and forth, the amp seems a little brighter with feedback on, maybe a little less defined though. Am I on point with this, or am I clueless? My ears aren't the best due to all the very loud club music ive listened to over the last few years when working for Nettwerk Records in LA. I really need to buy ear plugs for that crap...

Once again, I apologise for any nonsence... im pretty hammered right now due to my friends getting me completely destroyed for my birthday...

-Andrew... who is dreading his hangover tomorrow...

 

[SumB]

The switch activates negative feedback.

Feedback takes a part of the output signal and feeds it back into the input of the amplifier to cancel out errors, hence "negative feedback." It is used to control characteristics of the amplifier such as gain, frequency response, damping, output impedance, etc.

NF lowers second order distortion and increases the damping factor. The more NF applied, the less distortion, but over zealous use introduces colouration in the form of rolled off bass, smeared highs, flattened dynamics, and poor imaging. It's far from a scientific process.

Many believe it leaves its indelible mark regardless, and that the single ended triode topology without feedback is the way to go from a transparency standpoint.

Amplifiers with global negative feedback distort worse when pushed hard than those with none - and these aren't the "lush" second order harmonics of your typical SET amp, rather they're the higher order ones endemic to transistor based equipment.

As in all things in life, moderation is the key.