software

A number of years ago I tweaked the negative feedback of my BF Pro Reverb...I raised the 820 ohm feedback resistor(Can't remember to what but probably 1k or 1.5k?)until I pull the chassis? and I installed a presence pot in place of the 100 ohm resistor to the 5k and .1 cap like on a 59 Bassman/Marshall circuit...Lately I feel like the amp is a bit too noisey(hiss)due to the changes I've made to the feedback circuit of my amp...

My question is this...
Do you guys stay with the stock 100 ohm/820 ohm values or do you increase the feedback resistor values in your own BF Fenders...I'm going to pull mine out tomorrow and probably dc the presence pot....What do you guys like in your own amps?

John

Mine is stock, but I'm thinking of wiring it with a toggle for on/off like my Two Rock is.

How old is your amp? It might not be the circuit, maybe it's time for some new caps?


Originally Posted by Scott_FMine is stock, but I'm thinking of wiring it with a toggle for on/off like my Two Rock is.

?I have the on/off thing in my '66. It's a nice mod, worth doing fo' sure, as is the on/off pot in the trem circuit.


Originally Posted by Scott_FMine is stock, but I'm thinking of wiring it with a toggle for on/off like my Two Rock is.

How old is your amp? It might not be the circuit, maybe it's time for some new caps?

I've had my 66 PR for ions and it was all recapped by your's truly about 5 years ago....Nothing has changed in the amp as far as tone,but I hadn't played through it for awhile(Other than to run it monthly)and I just thought that the feedback circuit mods were due to be put back to stock these days?

My ears have changed and maybe I'd like the feedback circuit to be stock again? I wanted to check with some of you before I experiment on mine again though..


Originally Posted by FalstaffI have the on/off thing in my '66. It's a nice mod, worth doing fo' sure, as is the on/off pot in the trem circuit.

I disconnected the vibrato on mine several years ago also,tweaked the normal channel for better tone,reverb on both channels etc...

I also added a mid pot and a presence control to mine once I took out the Vibrato circuit pots...

I was just curious as to what you guys liked with your amps as far as the feedback circuit....


Originally Posted by STRATDELUXER97I
I was just curious as to what you guys liked with your amps as far as the feedback circuit....I haven't experimented different values, but I do find that taking the NFB out does give some noticeable extra hiss. It also changes the tone quite a bit in that the amp seems to have more highs and lows. It's great for adding sizzle at low volumes but with my guitars it tends to get a bit bright at any sort of loudish volume. I really like having the ability to take the NFB in and out. Maybe you can experiment with different values and/or try the on/off thing (or even an on/somewhere in the middle/off thing) to see how you like it. At least with my amp, taking the NFB out really has a significant effect on how the amp sounds in a way that might not be everyone's cup of tea.

I liked it best when it is not completely gone, we tweaked our Fender like combo just to a sweet spot before making too much noise and still have that nice breakup that allows good chording, you know chors with more than two strings

....Just my thoughts for you SD97.....

Since I'm not sure how you wired the presence pot, I don't really know how to answer....

But decreasing negative feedback results in more low end resonse, while increasing it will reduce low end response, thus leaving more quot;high end hissquot; to be apparent...

...not even remotely sure if that helped!

Jeff Seal


Originally Posted by Jeff Seal....Just my thoughts for you SD97.....

Since I'm not sure how you wired the presence pot, I don't really know how to answer....

But decreasing negative feedback results in more low end resonse, while increasing it will reduce low end response, thus leaving more quot;high end hissquot; to be apparent...

...not even remotely sure if that helped!

Jeff Seal

Thanks Jeff.....My presence pot is wired just like on an older Marshall.....5k pot with .1 cap and a 100k feedback resistor. Maybe a pot that changes the quot;slope resistorquot; from say 33k to 100k would be cool and then I'd maybe put that where the Presence pot is now? I need to see about lowering the NFB resistor a bit because it's causing hiss....I do understand what the NFB circuit does and I was just seeing what others do with their own BF amps....I'll trust me ears though... Thanks Jeff....

Glad I went back into my amp....First I fixed a bad midrange pot...After that I went back to the 100/820 ohm NFB resistors and removed the Presence pot....I had it wired just like a Marshall using a 5K pot,.1 cap and a 100k feedback resistor....After some listening,I found I Liked the 100 ohm resistor,but a 1.5k feedback resistor in place of the 820...This gives the amp a bit more of a nice loose feel and with a bit of added harmonic content and slightly more gain...Sounds great! Most of that noise I complained about is gone after fixing the mid pot and the NFB circuit in my amp...

The normal channel is tweaked with the tone stack being .02/.02/250pf Mica and reverb on that channel and some cathode resistor and cap changes..I added a pot that now varies the quot;tone stackquot; slope resistor readings up and down...This extra mod replaced the Presence pot and it allows me to change the eq on the normal channel...Very cool mod!

Cool

Bumped for Lew,Scott,Jeff Seal,and other amp tweakers....

Bumped...Good topic