Post
by VintageCharlie » Sat Aug 27, 2011 6:56 pm
One quick and really silly question. Sorry, i still don't get the nfb and various ohm tap thing correctly.
So there are 4 options - attach the violet wire that comes off the 27k nfb resistor to either 4, 8, 16 ohm tap on the impedance selector, or attactch it directly to the output jacks.
If it's directly connected to the output jacks, then the actual tap that the nfb is connected to depends on the selected impedance on the selector, is this correct? If i'd have an 8 ohm cab, i'd set the selector to 8ohm and the nfb would be connected to 8 ohm, with 16 everything would change to 16.
If i got my tech correctly, he says that connecting the nfb on, say the 16ohm tap of the impedance selector, which i suggested, would let me have negative feedback only when i am using the 16ohm tap on the impedance selector - on the other 2 settings negative feedback would be switched off entirely - i'd have negative feedback only in one position. Is this correct so far? (if i'm not mistaken, i have read the opposite on the forum - connecting the nfb resistor to one of the impedance selector tabs will give me a constant nfb setting, no matter how i set the impedance selector - for example, if the nfb resistor is connected to the 16 ohm tap and i have a speaker with 8ohms, i set the selector to 8 ohms, but the negative feedback won't be turned off - it will stay at the 16ohm setting). Which one is correct?
I want the amp to have the stock marshall nfb setting for a 45/100, which, from what i have read on the forum, is the 16ohm tap on the impedance selector (also amp archives mostly shows pics of amps connected this way, with a couple set up with the 8 ohm tap). But i sure wouldn;t want the nfb to be swithced off at either 8ohm or the 16ohm setting.