Hiwatt NFB circuit

[andrew]

Hello, I am going to build a Hiwatt power amp section and I see the NFB goes to the 16 ohm tap of the OT. My OT has a 2,4,and 8 ohm taps. What changes should be made to the NFB circuit? Thanks for any advise.

[martin manning]

Which circuit are you using?

[andrew]

Thanks Martin, It is the early 80's OL preamp from the Mark Huss Hiwatt site. Sorry I couldn't get my cut/paste to work.

[martin manning]

OK, it has a 10k series resistor, and then a 470 ohm that goes to ground, with the FB taken from the junction of those to the PI. You probably want to maintain about the same voltage level for the feedback, so if you use an 8-ohm speaker the voltage will be 0.707 times what it would be coming from a 16-ohm. A good start would be to just reduce the 10k feedack resistor by that factor, say use a 6k8, or 7k2.

[andrew]

Thank you, I'll try it.