npnboostv2

[Gus]

I have not built this version but the LT spice sim looks interesting.  The different colors are different settings of the gain control R5/R10

[Ben N]

The curves look more like your Overdrive, Gus, IIRC. Why the extra part-age?

[Gus]

V2, R7, L1, R9 are a crude guitar sim.  Single pickup with no tone control and volume at max.  C4 is 10ft of 20pf a foot cable.

.8 of 5K is kind of flat in the middle.  .8 in the step pram list is 80 percent of the linear pot rotation, R10 is 4K and R5 1K.  the center node of R5 and R10 is the wiper of the pot

R8 is because of an issue Aron noted with the NPN boost.

Note at lower gains the two bumps

I posted the a screenshot of the sim so people can make their own sim I left everything on it and it uses the stock LT spice download.  I could post the file but it might be better for people to learn how to use a spice program.  If you model it change values and see what happens.

[Ben N]

Yeah, neat how it goes from a shelving response to a single peak. I recognized the pickup sim. But why is that needed?

[DougH]

When gain increases on a bootstrap ckt, Zin drops. The mid peak is probably reflecting the loading on the pickup. The original npn boost works that way and IMO it is preferred. In higher gain you generally want less bass if you want smooth distortion as opposed to "fuzz". More bass sounds good with less gain, etc.

Nice sim, Gus.

[Gus]

Just got back from a friends house.  I built ver 2 and we tried it out different guitars and even a bass, it was tested loud.  It is a very nice boost and you can hear the EQ change with gain setting.  It is for use with a tube amp so you "hit" the first preamp tube hard.

Next it will be tested in a band setting.

I adjusted the npn boost with the help of LT spice.  I think it is a cool one transistor, one gain control and different tone at different gain settings booster.  Use polyester PET or polypro films for C1, C2 and C3 and a good electro for the 22uf.  Add a 100uf or more at the 9VDC supply for the build.  Mot 2N2222

This is a nice simple good sounding circuit.

Have fun

[Gus]

R5 and R10 are a single 5k potentiometer. C5 connects to the wiper.  The step param and two resistors are a gain control in the sim.
Input  R8 and R11 node
Output C2 and R6 node

[B Tremblay]

R5 and R10 are a single 5k potentiometer. C5 connects to the wiper.  The step param and two resistors are a gain control in the sim.
Input  R8 and R11 node
Output C2 and R6 node

Very cool.

Do you have any recommendations regarding the gain pot taper based on the sim and real-world testing?  I would guess that a reverse log would be best, based on my experience.

[Gus]

I built it with a 5k lin it works OK.  A 5K reverse log makes sense.

FWIW people who tried the npnboostver2  noted even at min gain it makes the guitar, bass (need to try with a lap steel etc.) sound "bigger"

[joegagan]

gus, i breadboarded this using an old metal can 2n2222.  was trying to make it a bit of a treble boost so the input cap was a silver mica .0047u. out cap and other part values  true to your schem. i ended up liking 7.2k to ground parallel the 22 uf  E>grd. but i also was running without the output vol, so i guess that does change things a bit.

through the vibrolux with the doubleneck ( tele style pickup config) it was a very satisfying boost. hit the preamp tubes really hard but cleaned up exceedingly well when the guitar was turned down or the pick attack was backed off. like you said, it offers a pleasing range of sparkle to slight mid boost as the guitar gets turned up. to me, this is a nice way for a booster to work , integrates nicely with guitar and amp so you can play rhythm/lead and all the shades in between just with your playing dynamics or guitar vol control. i believe this would fit in nicely for Bf fender amps the same way people love the klon's boost feature. will let you now how it sounds with the jtm marshall style amp.

i will box this one up so i can take it to the store and let some more people try it with other ( righty ) guitars.

to my memory, this is even better than the original npn boost.

[Gus]

I have noted that there are not many replies to this thread.

Is it because people do not understand the schematic and what the curves show?

This is a better tuning of the NPN boost.  You do not need to have tubes and or JFETs for a nice boost IMO.  

One can even make the 100k at the output a volume control but I like it better as shown driving the first preamp tube grid (read R.G.'s TS writeup for a clue of why)

The simple guitar sim is to show what the guitar amp preamp is "seeing" as a signal.  C4 shown is for low capacitance cable. One can add a tone circuit and more and/or different pickups and look at the curves.

I really like this version of the NPN boost.

[karter2000]

I actually tried breadboarding it, and it didn't work.  I wasn't getting any sound, and I couldn't debug it.  I guess I don't understand the schematic myself  .  I'm just waiting for someone to do a layout....

[Gus]

Anyone else build this?

[kingswayguitar]

i may try in the next day or so.
anyone have sound clips?

[Ben N]

I don't have any handy 2N2222. Will any med-high gain NPN work (2N3904, MPSA-18)?

[psychedelicfish]

I don't have any handy 2N2222. Will any med-high gain NPN work (2N3904, MPSA-18)?

I don't see why it shouldn't. IIRC, the 2N2222 is reasonably noisy (it was first revealed in 1962!), so you'll probably get better performance in terms of noise using another transistor.
I wonder how it would sound with a germanium transistor? I'll have to breadboard it and find out.

[joegagan]

2n2222 is a nice part in my experience. i use them in wahs, fuzzes and boosters because the motorola batches i have here are very consistent. 180 hfe with silver leads, 220hfe with gold legs. + - 10% or so.

gus likes the way they work in these circs.

it would be hard to get the feel for the beauty of this circuit in a computer soundclip. it sort of has to be played to be appreciated. the way it interacts with player dynamics, volume control changes is really dynamic. hard to get that to come across on a soundclip.

[joegagan]

I don't have any handy 2N2222. Will any med-high gain NPN work (2N3904, MPSA-18)?

yes, i would try to find a 2n3904 with gains of around 160- 230 if you have one.

[The French connection]

Not verified, if someone can check that the schem and the vero are OK, i'll appreciate.

[Kipper4]

I've noticed the output on the vero is in the wrong place it should be at the c2 cathode/R6   Node