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Negative feedback options.

Posted: Sat May 05, 2012 2:30 pm
by hdahs
Just wondering if there is an appreciable difference between a 47K on the 4ohm tap, and a 100K on the 8 ohm tap? I've read that the 100k brings more gain and mids, but at the expense of some smoothness.

Any favorite combinations?

Thanks

Re: Negative feedback options.

Posted: Sat May 05, 2012 4:18 pm
by toner
I don't know how those exact values compare from experience but 100k / 8 ohms will have less NFB than 47k / 4 ohms so your description makes sense (more gain). Feedback doubles when going from 4 ohms to 16 ohms with the same resistor.

I like the stock 47k / 8 ohms in a plexi for classic rock. For me, it's a good balance of tightness and cleanness without being too clean like JTM 45 values. I can see where people wanting higher gain and sustain would prefer less NFB though.

Re: Negative feedback options.

Posted: Sat May 05, 2012 8:11 pm
by stef
toner wrote:I
I like the stock 47k / 8 ohms in a plexi for classic rock.
me too
100k/4 (stock 70's nfb) made my cranked amp unstable, prone to too much feedback and noise

Re: Negative feedback options.

Posted: Sun May 06, 2012 8:28 am
by Roe
depends on tubes, voltages, guitar, etc. best thing is to use a resistor in series with a pot. try 12k + 100k pot at 4ohms

Re: Negative feedback options.

Posted: Thu Jun 28, 2012 7:14 am
by Winslet
welcome to all,

nice forum keep up