Lpb1 distortion

[TimWaldvogel]

I have the idea to rake the lpb1 and add hard clipping/ diodes to ground after the circuit. I know this will work. But how would I control the gain of it?

[oliphaunt]

I tried this once on the breadboard, and was surprised to find that the LPB would barely drive hard clipping.  I had to add a second LPB stage to get a wide range of clipping.  I controlled the "gain" by putting a volume control in between the two stages.  It worked, but I can't say it sounded particularly good, but then I'm not a big fan of the LPB anyway.

[TimWaldvogel]

What transistor boost WOULD drive diodes hard enough?

What about a two stage boost with the 1st being on a trim pot and set internally. Then maybe it could drive it hard enough? I was think about doing this with a fet boost of some kind as well. Maybe I should just do a dual opamp distortion again and play around with it?
Has anybody made a ts808 replica circuit with hard clipping instead?

[petemoore]

  The first two stages of the BMP demonstrate a good approach to 'more', and achieves distortion. A basic 'overdrive', and probably sounds nice or better.
  Note how these stages are similar to or depart from the basic LPB stage.
  Cool experiments often result in cool OD/Distortions [as is or with tweekng].
  Add 'complimentary' stages as needed.
  Bump the boost up [two mild boosts in front of a transistor/diode clipping stage...anything else, add the 'left ~half' to complete a BMP even.
 

[Mark Hammer]

Generally, for anything that will yield audible distortion that lingers more than 100msec into any picked note, you're likely going to want a gain of at least 50x.  Even mild distortions like the TS-9 have a max gain of 213x.

[Gus]

IIRC the gain of a stock lpb is about 23.  You could try the beginner project.

[GibsonGM]

And, you can use a pot in the diode to ground branch circuit to control 'gain' in a way...something like 1M would be cool.  There are ideas for this on the AMZ site... 

[TimWaldvogel]

can someone recommend  op amp clean boost that can be modified for more output to drive silicon diodes into distortion.
heres my thoughts...
i want a distortion... not an overdrive. an overdrive is often though of smooth and transparent where as distortion is thought of as harsh.
i have breadboarded things like the mxr distortion plus and built them. i like them, but still trying to experiment. but i need a little help still.

if you listen to an opamp circuit before you put in the diodes at all, its awful trebley , and still harsh. i want very clean boost to push a 1n400x
into clipping as i send them to ground. the more transparent going in, the more transparent coming out right? can i take something like the mxr micro amp, or the simple 10db op amp boost to push out voltage needed?

[oliphaunt]

Here's a simple op amp booster with suggestions for raising and lowering the gain, you could try this.

http://www.jer00n.nl/electronics/simple-opamp-based-guitar-booster/

[TimWaldvogel]

Ok I'll have a schematic drawn up soon, if you guys could verify.
I plan in using a single op amp stage for the drive and the other for an active eq. Is there a good one knob active eq circuit you can recommend me to?

[TimWaldvogel]

heres my gain stage idea. please verify and correct.
idk if i should use a dual op amp and make the 2nd stage an active eq or it for another gain stage.
please help me create a monster lol

[TimWaldvogel]

And I don't think the cap coming into the pot needs to be electrlytic

[Mark Hammer]

You realize you are attempting to re-invent the MXR Distortion+ and DOD 250, right?

[TimWaldvogel]

The input imperence is different/biasing,  different op amp, possible active eq, different clipping diodes. What's the difference between the mxr distortion plus and any other hard clipping distortion with a single op amp in the front end? What I'm changing I the difference. This is no longer remotely the same pedal. The 741 op amp is what makes the distortion plus/dod250 what they are. Without them they are not the same pedal

[Mark Hammer]

True.  I'm just saying there is no reason to waste time on drawing anything up or doing another layout.  Just use a D+/250 schem/layout and change component values here and there to taste.

[TimWaldvogel]

Well this op amp booster is the source of the design. I want a cleanish boost to push the diodes into clipping

[TimWaldvogel]

Looked back at my response to that message and it looks as if I came off harsh and defensive. I Apologize.

[FiveseveN]

You know, there's a good reason why those designs use a rather dramatic bass rolloff. Then again, maybe you're looking for a more "muddy" or fuzzy tone.

the more transparent going in, the more transparent coming out right?

Well, that's not really true, but "transparency" is very subjective.
If you want an aggressive distortion, I'd suggest one of the 386-based circuits that are so popular now (Big Daddy, Distortus Maximus, Purple Plexi etc.).

[oliphaunt]

I spent some time with the Dist+ circuit recently and decided that 1. it sounds terrible and 2. part of the reason it sounded so bad to me is the way the tone thins out at higher gain and flubs out at lower gain.  I think a more linear boost stage could provide some very different and potentially pleasing results.  I managed to make a pretty good low gain design that used the D+ as the skeleton, but like the OP here wants to do  I heavily modified it until it is almost unrecognizable.

[Mark Hammer]

Looked back at my response to that message and it looks as if I came off harsh and defensive. I Apologize.

No apology needed.

If one has a Dist+ PCB, a sound more closely aligned with what contemporary players often want consists of:

a) Changing the op-amp from a 741 to something a little more robust.
b) Changing the resistive divider that provides Vref from 1M to 22k or so.
c) Changing the cap from the inverting input to ground from .047uf to .22uf or higher.  This will address oliphaunt's complaint about thinness.
d) Changing the diodes from Ge to Si.
e) Changing the gain pot from 500k/1M to 50k/100k.
f) Sticking a 10-22pf cap in parallel with the 1M feedback resistor.

Should a person wish to use it as clean boost, rather than distortion, I would recommend using a DPDT toggle to i) lift the ground connection for the diodes, and ii) stick a 470k resistor in parallel with the 1M feedback resistor.

This converts the unit from a clipper with a maximum of 214x gain to a non-clipping booster with a maximum gain of 69x.  The use of a lower-value gain pot means you don't have to use a reverse-log pot to get to the zone where dirt happens.