LPB-1 / LPB-2 build

[LucifersTrip]

Just thought I'd share this since so many build this as one of their first projects and it might help someone...I never did build one, but decided to throw one together now since a friend just purchased a used one, and I could do an A - B.

Here's the first schematic I found:



Compared to my friend's, it's way louder, noisier and distorts more. For example, the volume at about 25% equaled his at 50%.

After double-checking all components, I opened up his LPB-1 and realized his was this version:



After swapping components to match that version, I tried another A - B test. It was closer, but was still louder and noisier and distorted more.
I checked voltages. With a 9.6V supply, his collector was 5V and mine was 2.8V.

In both versions, I had a 2N5088 with hfe 462.  To raise that collector voltage, I needed a lower gain transistor so I threw in a common 2N3904 with hfe 172. It nailed it!...5V with an almost identical tone.

Over the years, I think I've been burned by the "just put in a 5088, it should work" advice more than anything else.

[Kipper4]

I guess it just needed the mojo componant.
I wonder if they do mojo chips for homo sapians?
I'll Ebay it and see.
Thanks for sharing.

[davent]

Stumbled on this yesterday looking for info on the LPB-1, taught me loads.

How it Workz

http://www.beavisaudio.com/techpages/HIW/HIW.png

dave

[LucifersTrip]

that's very cool, though sadly missing transistor hfe & voltages

before I breadboarded I searched the forum for builds and other than bad voltages that were reported for troubleshooting purposes, I could barely find any good voltages, especially from originals. I was curious to know the different working voltages in those multiple original versions.  hfe & voltages on this one make a pretty big difference.

[Thecomedian]

I guess it just needed the mojo componant.
I wonder if they do mojo chips for homo sapians?
I'll Ebay it and see.
Thanks for sharing.

no mojo about it, it's all about DC gains and mathematical equivalent Transistor internal junction resistances and capacitances, in play with the surrounding resistor setup. I could almost explain how it works, but suffice to say that one COULD develop a circuit that fits the 2n5088 and grants you the same gains and sound you're receiving from your current circuit, but then you're designing circuits around transistors when it's easier to swap transistors in and out of a circuit to get the sound you want.

If a transistor has gains of 500-600 @ Vce = 10v and Ic = 2mA, provide it with that voltage and 2mA of current, and it will have those gains.
If the same transistor has gains of only 100-200 @ Vce = 5v and Ic = 500uA, provide it with that voltage and current and it will only have 100-200 gain.

You have noted that the transistor characteristic can completely change the circuit, or even make it non-functional. This is what makes up the so called "mojo" of old fuzz faces when the batches of them relied on varying gains in a circuit too simple to provide dynamic feedback adjustment to keep the desired values of currents and voltages while also preserving the unique function "the right gains" of the pedals had to offer.

it might be fun to go back and tweak the circuit with 2n5088 and just see if you can get the voltages right.

by the way, this is the second booster you posted, only with the caps switched out.

http://www.muzique.com/schem/bird.gif

you can see that what happened is that someone took the second schematic and swapped caps with the first schematic. a change in caps means more mid-lows so that'll also have an effect on the total dB level.

[PRR]

> I needed a lower gain transistor

Just reduce the base-to-ground resistor.

[candidate]

Jordan boss tone, too

[LucifersTrip]

Yes, I can re-bias and tweak with many different transistors...

But I guess my main point here is that the commonly circulating schematic which has been utilized by countless 1st builders will probably burn them.

The only reason I knew to make the change was because I was fortunate enough to have an original to compare with.


edit:
The other thing that should be noted (and probably has been many times) is that it sucks without a buffer before it. It sounds like a muddy/distorted mess straight thru, but sounds beautiful with a modern boss pedal before it in the chain (not turned on, of course)....which is why I've read so many build reports complaining that it distorts too much and/or makes it bass-y/removes high end.

[LucifersTrip]

I guess it just needed the mojo componant.

yes, the cheapest mojo component of all
http://www.taydaelectronics.com/2n3904-npn-general-propose-transistor.html

[LucifersTrip]

forgot to give all voltages

[Gus]

Have you read this thread?
http://www.diystompboxes.com/smfforum/index.php?topic=99139.0
Have you looked at the NPN boost ver 1 and ver 2 for ideas

[LucifersTrip]

No, but thanx...maybe in the future.

I really just built this as a joke to show my friend how easy it was to clone since he was too lazy to build one. I actually had more fun playing thru it with a couple clipping diodes at the output.

[deadastronaut]

ok, old thread , but relevant,

ive been on a 'simple' clean boost breadboarding extravaganza..

lpb1...great boost..

npn boost great boost..

but both don't give 'tonal unity' ...i guess i mean transparency right..

ive tinkered around with the LPB1 mostly as i like the simplicity, and also the vol is at unity
around 12 o clock position...(nice visual thing)..

without breading up the mosfet boost (which i read is best),

for space saving purposes how can i get better tonal unity from the LPB1..?

(as in second schemo lucifer posted above)

edit: (just read lucifers comment about a buffer in front) i'll try that..there goes the tiny footprint

[deadastronaut]

hmmmm..

even the buffer on its own isn't 'tonal unity'

5th down..
http://www.muzique.com/lab/buffers.htm

tried it in front of the lpb1, same issue....takes the top end off.

[deadastronaut]

simple opamp buffer nails it...