i just finished a lpb build. I've followed the ggg schematic and used http://www.generalguitargadgets.com/richardo/perfboard/booster.gif perfboard layout (i have changed it so it matches the lpb).
i couldn't find a 2n5088, so i've used a bc550c. i've made notice of the pinout difference between the 2
when i first powered it up, it didn't changed the sound, and i've found out why, look at C2 at the layout, it's connected to the base of the tranny instead of the collector!!
changed it and when i tested it, it only gave me a slight boost but it cuts all my treble away and boosts the bass response
i cant figure it out what is wrong
my voltages are:
c 5,3V (little high?)
b 646mV
e 78,6mV
Thats not an LPB layout is it? The LPB only has two caps.
it's a layout for multiple boosters from eh, you just need to drop the caps and you are there
Now you have moved C2 the layout should be right.
I notice C1 and C2 are poloarised 2n caps. I've built three LPB, on each I used unpolarised 0.1uf caps (100n).
Having said that, there are various different LPB schematics floating about the net with differing values.
Also, check your resistors are the right values in the right places.
It's always worth checking resistor values with a multimeter before using them because suppliers often get the values wrong.
i've found the problem
the perfboard wasn't etched correctly in the factory and 2 lines where connected. i've cut them and now it's ok
i only get a slight overdrive/fuzz sound from it, but will check the bias
Cool.
The LPB is a clean boost., so you shouldn't get overdrive/fuzz from it, just gain.
I have measured 15db of boost from mine.
Some people find it a little bassy, but I like that.
They are excellent from overdriving clean valve amps (what Hendrix used his for)such as the VJ.
EDIT: If you want something different from it, you could use a couple of diodes as clippers between the collector and earth/ground. Just connect them opposite polarity to each other.
im raising this thread to ask a few questions. im on the process of building an LPB and i am curious to know what the effect of changing the resistor valuesis. i already have all parts in except for the resistors. i installed a 2.2Meg for the pulldown, while i cant find the other resistor values or are hard to come by. i saw the mod sheet at GGG, and the resistor values are almost doubled. any idea what doubling the resistor values would cause?
I can tell you from experience that the two resistors that form the voltage divider can be a wide range of values as long as you observe the 1:10 ratio.
i dont know, but i used 470K, 47K, 10K, 330ohms, and 2.2meg for the pulldown. these are the only values available that are close to the specs. i saw one GGG mod sheet that had resistor values twice of that.
im planning to build another one but this time i'll be using 0.01uF caps. for more treble i think? which of the two caps by the way dictate how much treble goes into the circuit?