Re: JFET Doubler - A Simple Screaming Octave

Comments below -- Rich

"Charmed Snark" <snark@xxxxxxxxx> wrote in message
news:Xns9922AC09B1A43SnarkCharmedImSure@xxxxxxxxxxxxxxxx

My posts seem to be slow going out again (sigh)..

Anyway, whenever they do finally get "out there", here is a link to
something else I turned up: http://tinyurl.com/ynrdok

Its a word doc about your (Rich) Java Boost. The neat thing is that
they include a schematic for it (its only missing the values of the
two other alternate input capacitors, but it otherwise appears to be
all there). They also describe one mod (cut) for purists if they
want to eliminate the tone control (or you could just install a
switch for that).

Yup -- I read that back before I decided to buy the pedal, but had forgotten
it had the schematic when we were discussing this.

For those who want to build it for a fraction of the price, the
setup notes for voltages are a good staring point. Obviously, the
precise settings of the trim pots will differ according to the
actual transistor used in your circuit.

Distortion:

One the first page (after "congrats") they mention that:

"the rare Mullard OC44 transistor, at the heart of the Java Boost's
circuit, naturally distorts quickly, rending it unsuitable as a pure
clean boost. While the boost is extremely transparent and responsive
to pick dynamics, it's better described as an overdrive, blending
its own distortion with your amp's gain structure."

The Level Control:

The paragraph before that is obviously dumbed down - "The Level
Control boosts the range of frequencies selected by the Tone Switch.
The higher the level is set, the greater the amplification or boost
of your treble, mids or full range frequencies..."

Apart from the obvious error in Tone "switch", the "Level Control"
as shown in the schematic is nothing more than a volume control. In
other words, the booster's treble/mid/full gain is constant, but you
get to choose the signal "level" coming out of the unit. This sounds
like splitting hairs, but their description makes it sound like you
are selecting different gains-- but you're only getting to choose
how much signal you want to throw away, in essence.

By the "Tone Switch", they're referring to the three-way switch that selects
treble, treble/mid, or full boost.

What this means to the end user is this- if you want to operate your
Java Boost clean, or with less distortion, changing the Level
control won't do anything for you. Only by reducing your guitar
pickup output can you reduce the distortion coming out of the Java
Boost.

The level control will change the degree of distortion to the extent that
it's changing the amount by which the amp's tubes are overdriven. But the
best way to do that is to use the guitar's volume control -- although that
also changes the amount of OD in the pedal (at least in principle). It's
still questionable how much OD is from the pedal and how much from the amp,
but I think under conditions when you REALLY hear the OD it's mainly the
amp. It cleans up really nicely as you back off on the guitar's volume
control -- this is the mode that May uses.

So now the real question now is does the avg guitarist want:

- distorted treble boost,
- or clean treble boost?

Certainly the marketing lit that is served thru google suggests that
the Mullard OC44 is the holy grail. But is it as great as they say
it is? On a practical level, does it make sense perhaps to build a
box that includes a switch betweeen Ge and Si? It wouldn't take that
many parts to do that.

Going back to the schematic, another interesting bit is about
adjusting those trim pots (that you're not supposed to adjust), is
that they mention setting it so that the collector is -7.2V. The
interesting thing is that they say "Note: this is not a typical
measurement." Badly worded, but I take that this means the
transistor is operated in within an unusual operating range. This
leaves me wondering:

- is this for additional gain?
- or more/less distortion?
- for softer distortion?

Probably softer distortion. The thing really produces a nice sweet sound,
softer than just OD'ing an amp. Even on the "full boost" setting, although
I like that setting least of all.

You may be interested if you're into Queen. I've been recording a cover of
a song that has an organ part, and since I don't have an organ I decided to
use the Brian May multitracking/orchestration technique for the first time
(for me) using this pedal together with my Epi Valve Jr. I recorded three
separate tracks, each track having one note from the different chords being
played. It sounds really nice with this particular song, and pretty much
nails the orchestration effect heard on, for example, "God Save the Queen".
May used his so-called "Deaky amp" (which also has a Ge transistor) for
those types of effects. But the pedal/Valve Jr. combination really hits it!

Damn I love this pedal! Good luck if you're going to go ahead and make
something like it!

So many questions, so little time. I'm going to have to buy some
OC44s (or substitutes), and breadboard this thing.

Snark.

--
Posted via a free Usenet account from http://www.teranews.com



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