Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on June 20, 2017, 12:00:52 pm

Title: value of feedback resistor
Post by: dude on June 20, 2017, 12:00:52 pm

To get more noticeable difference on the presence pot would one go up or down with the NFB resistor. 8 ohm spk.



al

Title: Re: value of feedback resistor
Post by: shooter on June 20, 2017, 12:51:29 pm

Quote

NFB resistor

make it a pot and see, there are a lot of examples in the NFB threads, since your presence is already a pot I would try messing with the associated cap?

Title: Re: value of feedback resistor
Post by: SILVERGUN on June 20, 2017, 12:55:50 pm

Great stuff here, dude:

http://www.aikenamps.com/index.php/what-is-negative-feedback (http://www.aikenamps.com/index.php/what-is-negative-feedback)

http://www.aikenamps.com/index.php/designing-for-global-negative-feedback (http://www.aikenamps.com/index.php/designing-for-global-negative-feedback)

Title: Re: value of feedback resistor
Post by: pompeiisneaks on June 20, 2017, 04:08:25 pm

just be sure to have some resistance always, it's often good to put some small amount like say 5k inline with the pot, I think if you do straight nfb with no attenuation it could be a bit too extreme no?  I like the idea of a pot too.  Gives you the ability to tweak it until you like it, record the value, and then replace it with something in the ballpark.

~Phil

Title: Re: value of feedback resistor
Post by: dude on June 21, 2017, 10:20:06 am

Thanks, the pot is a good idea for tasting, Ailken's site has a lot of good info.


I'm debating to take the presence pot out and replace with a switch.  Play with difference values and get the right one for my ears, pull the pots, replace with a switch. The big boost you get with NFB off is kind of nice and once you set the presence pot you don't usually fool with it too much unless you change often from humbuckers to singles. Just preference.


Thanks everybody,
Sincerely, al