LPB-1 into Tube Reamer a strange thing happened. . . . . . .

[MartyMart]

Hello,
as you probably know I'm a "tube reamer" nut, having built three different versions !! ( R.O.G I love you and want to have your babies.....)

I plugged in the LPB-1 infront of the reamer to see how it would react to being "pushed" over the edge ! ( reamer with Ge diode/2x1N4148 )
The wierdest thing happened, the reamer went into "overdrive hell" but was sort of in the "background" while a clean and loud LPB-1 sound was in the foreground ??
The further I pushed up the LPB-1 the more "present" it was and the more "distant" the reamer was.
Answers on a postcard to "reamer/wierd" sound at the BBC. . . . . .

I work with sound/recording all the time but just dont get this one ?
Marty.

[Paul Perry (Frostwave)]

This is just a wild stab in the dark, but maybe the reamer op amp is pushed so far that it isn't acting like an op amp at all anymore, more like a (non-linear) part of a voltage divider.
Somebody with a high-impedance scope could check this out by looking at the inputs of the op amp, if there is a large signal there then the op amp isn't acting as an op amp any more.
Whether this is true or not, I think the future of analog fx is "pushing" stuff out of the normal envelope.

[MartyMart]

Thats interesting Paul, I was thinking that the "diodes" were just compressing soooo much that the signal sort of "dissapeared" into the background, but the same could be said of the op-amp I guess.
Just checked it again and it could be a cool "control" to make a pedal behave like that, "super compression" or something wierd ??
Perhaps I should place both in an enclosure and play around with some gain values......... "The LPB-Screamer-Comp"    

Marty.

[Torchy]

crp

[MartyMart]

Marty - does it distort/compress in a "non-musical" way (ie - is it a usable sound or just a novelty thing ?).

Have to try this with the Sparkler and my Tube Reamers.

Yes its "musical" just wierd !!
Like "distant" distortion mixed in with clean boost, as I back off the LPB-1 the distortion becomes more up front and clearer, as normal -- it's almost like having a "distortion balance" pot !!

Marty.

[Eric H]

opamps vary a lot in the way they handle being driven too hard at the input --look at the data sheets.
Which are you using?

-Eric

[Torchy]

crp

[stm]

The behaviour you mention is completely NORMAL and inherent to the operation of the tube**** and its derivatives.  :!:

Thisi is due to the fact the opamp is set in the non-inverting configuration.  Here the output is always composed of two components:

1) A clean signal identical to the input (i.e. gain +1)
2) A saturated or clipped signal that is more or less clipped according to the gain set by the resistors around the (-) input.

As such, if the input signal increases a lot, the clean component will increase a lot, leaving well below the clipped component.

You can also do the opposite, which is, put an attenuator at the (+) input of the op-amp (and then crank-up the gain to compensate for the attenuation).  In this case, the distortion will become even more prominent than the clean part of the signal.

In any case, the clean part of the signal is more relevant during the attack and initial period of the notes, since the input amplitude rapidly falls below the typical 0.6V clipping level of the diodes, and thus, becomes less relevant to the overall sound.

[MartyMart]

opamps vary a lot in the way they handle being driven too hard at the input --look at the data sheets.
Which are you using?

-Eric

Eric, The op-amp is an NE5532ap

stm: thats interesting, being "normal" as i've never had that effect before!
Perhaps the very high gain of the LPB-1 is such that its causing this "squashing" of the clipped signal.
Nice to know for future builds.....

Marty.

[bluesdevil]

I just built a Tube Reamer and noticed the two distinct signals (clean and clipped) when I changed one of the stock diodes with  germanium one. Having an active pickup in my guitar might have helped push it to work that way, but the clean signal seems more pronounced with the 2 different kinds of diodes together. Sounds great for smooth bluesy leads but the clean signal  really gets loud and clunky for chord work. If I could tone down the clunky chords it would be the perfect "tube" pedal for my tastes!!! Also Torchy's bass enhancer switch is a great thing to have on it as well.
     MartyMart:  did you run your 4148's in parallel or in series?

[MartyMart]

I just built a Tube Reamer and noticed the two distinct signals (clean and clipped) when I changed one of the stock diodes with  germanium one. Having an active pickup in my guitar might have helped push it to work that way, but the clean signal seems more pronounced with the 2 different kinds of diodes together.
     MartyMart:  did you run your 4148's in parallel or in series?

Hmm, thats interesting, I'll check my first reamer today which has only the stock 4148's in it....
I have the 1N34a one direction and 2x 4148's in series the other for asymetrical distortion.

Marty.