Please let me know if you have built this project

[acorrales]

Hello all,  This is my first post here, but my second booster. It is intended to be used to return unity gain to a passive mixer (2 ch. pot 250k R100k). 

I built a LPB1 that does not work as expected, cause is not boosting the mixer if I use it in the output (mix), and it is killing my strat highs (SSL-5 pup)  if I use it in front in one channel.

I decide to check the V2 of this one and I have it in a breadboard using a 2N2222A that I thing is working OK: it boosts, but  now I'm losing some bottom end when used strat > Mixer Ch1 dry / Mixer ch2 delay 100% wet > booster V2 > amp (the setup is more complex than that, but that's the idea).   Also, I have the bottom end loss if I set up Strat > boost > mixer ch1: Boosted dry signal / ch2: Delay 100% wet > amp. I don't really know if the cut is because the breadboard, as I also have a lot of noise that I still need to track, or if it can be solved by changing the value of some component.

Of course, no amp equalization can fix this, so, Does anybody can recommend a change in the booster, to recover that low frequencies?

[duck_arse]

hello and welcome, acorrales. we need voltages! if you go here and follow the rules, then post results, and maybe some photos of what you have built, we'll get you fixxing it.

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[acorrales]

yups... Sorry!  I found the schematic directly on Google, and haven't saw the rules.  I'm going to read them and report back.

[midwayfair]

If you like the NPN boost you might want to try ver2


R5 and R10 are one 5K gain control, 22uf to wiper,  It is drawn this way to sim the 5K control.  The sim steps though the param list and does the math "moving" the wiper, gset as .1 then .25 etc

Input is R8 and R11 node omit C4 and to the left that is a simple guitar sim

Gus (or anyone else who knows) can you explain what C1 is doing?

[Groovenut]

I could be all wet here (probably) but it looks like C1 is providing positive feedback of higher frequencies, possibly to offset the low input impedance loading on the guitar pickups. The Cornish buffer uses something similar to do the same thing but his has a slightly different config.

My 2cents

[midwayfair]

I could be all wet here (probably) but it looks like C1 is providing positive feedback of higher frequencies, possibly to offset the low input impedance loading on the guitar pickups. The Cornish buffer uses something similar to do the same thing but his has a slightly different config.

My 2cents

Ah, makes sense. Is there a benefit to that instead of just, say, having higher input impedance?

[Groovenut]

The issue with using BJTs as input amplifiers fed by guitars, is they have a low input impedance determined by the Emitter resistor. Even bootstrapping that cap only brings it up to around 300k-500k at best. The bias resistors will always be in parallel with the Emitter resistor as far as input impedance is concerned.

Again I could be wrong here, but that's how I understand it.

[midwayfair]

The issue with using BJTs as input amplifiers fed by guitars, is they have a low input impedance determined by the Emitter resistor. Even bootstrapping that cap only brings it up to around 300k-500k at best. The bias resistors will always be in parallel with the Emitter resistor as far as input impedance is concerned.

Again I could be wrong here, but that's how I understand it.

No no, you're definitely right. I just couldn't figure out that it was intentional positive feedback for the purpose of punching up the highs. Clever.

[Gus]

Bootstrapping is in "The Art of Electronics"
The Vbe drop is fairly constant
The emitter "follows" the base one Vbe drop lower in voltage
So if you have a large cap from base to emitter the emitter drives the three resistors node in phase one Vbe drop apart
The resistor from the node to base has a close to constant voltage across it

for more information
Pages 96 and 97 in the 2nd edition
C1 adjusts the "bottom bump"
the 1st ver had a greater value cap from emitter to the node

Also think about what happens as the wiper moves closer to the emitter

[jonboper]

This was the first pedal I built - took a few tries but it's working and sounding pretty good thanks to the help I've gotten on this and related forums. I had trouble with the enclosure (waterslide shrinkage) and wiring, but I learned a lot. I tried several NPN transistors, all flavored the pedal quite differently. The 2N2222a imparted almost no distortion to the pedal, a smooth warm boost. I really liked the 2N3564 “dot” from Small Bear, a mostly smooth “warm” boost until the end of the range where it distorted with and sounded slightly splattered, but it went into oscillation a little too readily and so didn’t work well with other pedals in front of it. I ended up with a 2N5088 because it held it’s tone the best, a big warm boost until it becomes a wheezy distortion.

[rutabaga bob]

@Jonboper - I really like the finish on this!  Details, please!

[duck_arse]

JonB - why haven't you (resized that yuge image and) posted this in the pictures! thread? that box looks great.

[jonboper]

Thanks! (resized pictures, not as yuge)

The finish is (homemade) alcohol inks and a waterslide decal that shrunk, which is why the odd outline and the texture. I went over it all with a lacquer I have left from finishing an instrument, but the color of the inks lost some of its brilliance while I was spraying with a clear gloss. Have to work on the finishing more, but a great first project. Learned a ton.

[aron]

Very nice!

[Sinister]

Cant see the project. Where can i find it pls?