#1
So, I've been working on a transistor overdrive idea I had using two BJT inverters and some diodes and decided to just start with analyzing one in spice and moving from there. Now, when I setup a basic LPB1 style inverter and looked at the output waveform at, say, 90 Hz, it looks like the waveform was clipping, like the gain was set too high on the inverter and the transistor was clipping. I haven't done the math to see in what stage the transistor is in, but does the LPB technically clip the transistor, or is there something else going on here?
Epiphone Les Paul Studio w/ P90s
Epiphone Wilshire Pro Reissue w/ Pearly Gates Pickups
JCA2212c
Vox Night Train
Raven 1x12
Digitech Whammy
TC Electronic Polyphonic Tuner
Earthquaker Devices The Hoof Fuzz
Carbon Copy
BYOC BBO
TC Arena Reverb
#2
Is this what your talking about? (I found this on google): http://hotbottles.files.wordpress.com/2012/02/lpb-schematic.png?w=580

First BJT's will give you more of a fuzz sound when pushed because of the harmonics (vs a FET), but you probably already know that....

In your spice sim, what levels are you using the for the input and the battery? I would expect if you simulate the LBP with a low amplitude guitar level signal and a 9V supply, it should be pretty clean. Also note that 90hz is pretty low frequency for audio. With those series caps in the circuit, it may not pass 90hz well (I'm just guessing), so maybe do the initial check on your simulation with some mid-level audio frequency first to see if it's simulating correctly??

Lastly, you mention two inverters - I would recommend simulating the basic BJT circuit first and make sure it's all working. Start with something that you know works and get that going first, then do one mod at a time and re-simulate so you can tell if the new response is due to your circuit changes or not...
#3
Yes, that's the circuit. I've started with just the one inverter. I get an amplified waveform out, but it has much more pointed slopes, like a mix of square and triangle waveforms rather than a perfect sinusoid as I would guess. What would you suggest as mid level frequency? I thought electric guitars started around the 80Hz mark?
Epiphone Les Paul Studio w/ P90s
Epiphone Wilshire Pro Reissue w/ Pearly Gates Pickups
JCA2212c
Vox Night Train
Raven 1x12
Digitech Whammy
TC Electronic Polyphonic Tuner
Earthquaker Devices The Hoof Fuzz
Carbon Copy
BYOC BBO
TC Arena Reverb
#4
A standard-tuned guitar's low E is about 82Hz. Most audio stuff is tested with a 1kHz sine wave. Sometimes you'll also see stuff that specifies 400 or 440Hz. I've even seen as low as 300Hz.
#5
Yeah, I was thinking more like 1kHz-ish. What amplitude input are you putting in? Also, can you post a picture of the output? You might want to check that the input gets to the base of the BJT OK without any distortion there.

Also, are you using the spice parameters for the 2N5088 (or whatever transistor you're planning to use)? The biasing from the resistors really depends on the gain, etc parameters of the transistor to match.