booster for bass that goes to zero

[arma61]

Hi there

i ve been asked to build a booster for bass, ok no problem here, many to choose among, but this guy is asking that the gain knob, when  turne down, bring sound to zero, is  this doable with something like AMZ mosfet booster or the MicroaAmp?

thx m8s for help
ciao

[PBE6]

You can make any booster go to zero volume by adding a log pot (say a 10kA) to the output, just connect lug 3 to the boosted signal, lug 2 to the output jack and lug 1 to ground.

[arma61]

Thx pbe6 I knew about that and forgot to mention, it has still to be a one knob booster :-) so the gain knob has to go from zero to where it's supposed to go

thanks

[PBE6]

How about using an inverting opamp gain stage? The gain is Av = -Rf/Rg, so if you dial Rf to zero you will have zero output. If you use a TL072 or similar dual opamp, you can set up the first half as an inverting opamp buffer with high value resistors (say 1M) to keep a high input impedance, then set up the second half as a gain stage with small value resistors to minimize noise. Since you've inverted the signal twice, the final signal is right-side up.

One knob and does the job!

[mth5044]

If the AMZ mosfet boost is a clean boost, you could hardwire the gain to full and tack the volume control at the end.

[Fender3D]

AMZ's gain control is just a variable resistor...
You can connect lug 1 to output, wiper to GND and lug 3 to electro.

Maybe you'll better try different pot values and, maybe again, add resistor(s) from lug 3 and wiper for a proper/better sweep...

Ciao

[Mark Hammer]

If I'm not mistaken, the gain control on my AMZ MosFET booster is at unity gain at lowest settings.  I haven't done anything special to the circuit.  I do believe the equal-value 2k7 resistors on drain and source make it unity gain when the path through the 100uf cap is greater than 2k7.  Gain is increased above 1x as the pot value goes lower than 2k7.

[PRR]

If you want a "booster", which won't overload on strong signals, AND can be turned down to zero (one knob), this widely-used opamp plan is about as simple as it gets.



knob   gain
100% = 10
90%  = 3
50%  = 1.1
10%  = 0.25
0%   = 0

[Fender3D]

Thanks for pointing it out Paul...
I've typed too much in hurry.
I meant the output capacitor in my previous post...

Sorry...

[Chugs]

PRR, that is an interesting circuit snippet. can you explain how it works?

[arma61]

+ 1 on chug and thx to everybody for replies.

I like them all!

About what seems to be the easiest, the MicroAmp with volume control added (my friend seems to like it too even with the second knob), do you think this added control will affect the tone ? and yes, I've my breadboard already on the desk!!!, just need a Masters' opinion!!

I like very much PRR's one (PRR you always have an answer for everything!!!) and due to the source it come from (PRR drawing !) will give this  a go anyway being  , and then need to digest the Mark Hone!!

So plenty of solutions to test.

Will report back

Thanks a million guys!
Armando

[arma61]

Hi these

didn't report back because..... I was left down.... i mean ... got this contact via FB, lots of question can u do you di this and that, what about a booster this way and the other, then after some testing, when I get back with the solution (uAmp with added pot ) never get a reply... I hate when this happen.

Cheers m8!

[bool]

What can I say ... "think locally, act globally", not the other way around ...