Presonance and Cut

[C Moore]

I was thinking about adding Martins Presonance Control that is in the sticky.
I have a few questions. One of which is.....
...This amp is an AC15. Is there any problem/conflict/redundancy with having a Cut and a Presonance.?
Thank You

[Gaz]

No, but you'll need to add negative feedback, which will change the amp's tone considerably.

[Stevem]

If you like the amp now adding feedback to get a presence control will change that like for less!
That cut control is there to make up for what can be had in terms of high end roll off as if the amp HAD a presence control, but without the loss of gain / touch and feel consequences !

[C Moore]

I added NFB to this amp after I built it, and That really improved the sound/performance of the amp.
The NFB resistor is 1k with a (I do not know what you call it) a 47 Ohm to ground.
The chassis has another hole available in the front panel, so I was thinking of the Presonance.
But...after talking to you guys...if the amp sounds good now, maybe I should use that hole to make the NFB switchable...maybe with 2 different values of NFB resistance.?
Thanks

[hans-jörg]

The NFB resistor is 1k with a (I do not know what you call it) a 47 Ohm to ground.

Interesting readings (1k/47 Ohm to ground). Very unusual numbers. Should I miss something in my (small) skills? Hi-Fi sizes?

Hans-Jörg

[C Moore]

The NFB resistor is 1k with a (I do not know what you call it) a 47 Ohm to ground.

Interesting readings (1k/47 Ohm to ground). Very unusual numbers. Should I miss something in my (small) skills? Hi-Fi sizes?

Hans-Jörg

Not sure if you are asking a question or not .....but I arrived at those numbers by chance.
VOX never used NFB...so I just had to guess. I am most familiar with Fender BF circuits, so I took a peek at those. Cannot remember Exactly how a settled on 1k and 47.....but it worked and made for a vast improvement.
Just dumb luck on my part. I do not have the education to figure it out on paper.

[hans-jörg]

Oh, it was a question, because never saw such numbers.
I guess it´s a ten time higher(?) feedback than the "usual" 100k/4k7 to ground.
No doubt that it works, I only would like know if its a higher feeding back (more cleaner) or lesser (less cleaner) than with 100k/4k7.

Hans-Jörg

[C Moore]

Oh, it was a question, because never saw such numbers.
I guess it´s a ten time higher(?) feedback than the "usual" 100k/4k7 to ground.
No doubt that it works, I only would like know if its a higher feeding back (more cleaner) or lesser (less cleaner) than with 100k/4k7.

Hans-Jörg

Gotcha.....no doubt (I think) I am getting quite a bit of NFB into the PI.
I do not play guitar...but it would be interesting to hear why this works at such low values, compared to most schems I see.....
All I know is that the 2 guys that test amps for me, said the NFB I used made for a big improvement in the amp.

[hans-jörg]

Thank you,

if I had more clue about voltage divider I could answer my question by myself, but so ... I just wonder

Hans-Jörg

[Stevem]

You might want to play with what's been called a resonance control in place of a presence control?
It's a 1 meg pot with the number 1and 2 lug off if the speaker jumped, and .0047 cap across the 2and 3 lug with that end feeding the feed back into the amp.

[C Moore]

You might want to play with what's been called a resonance control in place of a presence control?
It's a 1 meg pot with the number 1and 2 lug off if the speaker jumped, and .0047 cap across the 2and 3 lug with that end feeding the feed back into the amp.

Did you read the title of this thread....?