Is the harmonic switch the octave up? Would it be worth having a stomp switch?

[vanessa]

Is the harmonic switch the octave up on the Bass Brassmaster? Would it be worth having a stomp switch? Is it a deep octave up or faint?

Sorry for all the questions but I got my parts in and this is going to be this weekends build. Yea!!!

[petemoore]

  I can't remember what that schematic looks like.

[vanessa]

Here's what the doctor ordered;

[Mark Hammer]

I have a largely empty board (a transformer with no buddies to play with), so I can't speak from experience.  The schematic suggests, however, that there are essentially two versions of the harmonics, both being mixed in via the "Brass Volume" control (http://www.geocities.com/CollegePark/Library/1355/brassmaster.gif).  The diodes and transformer produce a basic octave-up voice (the giveaway is always the presence of a transistor with equal-value emitter and collector resistors, which makes a phase-splitter - the first step in discrete octave-up boxes), from which one of two alternate versions are derived (Brass 1/2).  The full-wave rectified signal that shows up on the non-diode side of the transformer has all sorts of harmonics in it.  What comes through the Harmonics hi/low switch would appear to be essentially everything the FWR signal consists of, set to a background level, while the Brass 1-2 voices are a derivation of the basic FWR signal with some bandpass filtering; another "upper formant", if you will.

The question from your perspective is whether the harmonics switch has enough of a meaningful impact on the sound that you would treat it as a major branch-point in sound shaping that merits a footswitch for possible mid-song change.  I honestly couldn't say.  That may well be something you have to decide after building it and wiring up a temporary toggle for comparison.

[vanessa]

It sounds like the octave is on all the time then? The switches just change the type of octave tone?

Could the octave be removed via a switch as done in the Tycobrahe Octavia octave off mod?

[Mark Hammer]

My understanding was that you removed the octave by means of the bypass switch.  This is, there is no effect to be produced *other* than the assorted octave-up combinations/formants.  What gets called "Bass volume" is essentially the clean signal, to which one adds proportions of octave voicing.  If you wanted another type of voicing, you could wire up a SPST switch to ground the link between R28 and C12.  This would still allow the harmonic Hi-Low switch to work, but would cancel the upper bandpass-type formants.    Since the cap would always have a place to drain off there would be no popping, and the 150k resistor off the Brass pot wopuld not seriously reduce level if grounded.  Of course turning off the Harmonics and grounding the upper voices would net you nothing to mix/blend in via the Brass Volume control.

[freebird1127]

You know, looking at that diode bridge, the diodes aren't in FWR orientation.  Not in any kind I've seen (such as the standard power supply - 2 in one direction, 2 in the other).  Am I losing it?  Is it a mistake or is this a bridge I haven't seen before, and if so what is the theory of operation?  Can't quite pick it out.

Ev

[vanessa]

It sounds like the octave is on all the time then? The switches just change the type of octave tone?

Could the octave be removed via a switch as done in the Tycobrahe Octavia octave off mod?

Thanks Phillip!

[vanessa]

My understanding was that you removed the octave by means of the bypass switch.  This is, there is no effect to be produced *other* than the assorted octave-up combinations/formants.  What gets called "Bass volume" is essentially the clean signal, to which one adds proportions of octave voicing.  If you wanted another type of voicing, you could wire up a SPST switch to ground the link between R28 and C12.  This would still allow the harmonic Hi-Low switch to work, but would cancel the upper bandpass-type formants.    Since the cap would always have a place to drain off there would be no popping, and the 150k resistor off the Brass pot wopuld not seriously reduce level if grounded.  Of course turning off the Harmonics and grounding the upper voices would net you nothing to mix/blend in via the Brass Volume control.

Mark, I like the idea of being able to bypass the filter section as an option. I've decided to use a DPDT on-on-on switch for the "Harmonic Hi-Lo-Hi/Filter Bypass" switch which will get me all three combos with one switch.



Thank you!

[lowstar]

the harmonics hi/lo switch works only in the brass up position. (at least in my brassmaster  )
actually, many people have reported that they can hear no difference/or their harmonics hi/lo doesn´t work.
mine does, however, and i think it´s because two of the resistor values on the upper right hand corner section of the schem don´t correspond with the geofex layout, i assumed that this was the reason for many of the builds of the other guys not having hi/lo function.
right now i can´t tell you which ones cause i have the papers in my "lab".

let us know how it goes.

i was very impressed initially with the sound (for bass), it´s a monstrous wall of distorted bass.
in real life, however, i could not find a use in a song for it yet, be it my own band´s or cover versions.

cheers,
lowstar

p.s. to answer your question, i don´t think the hi/lo function would be worth a stomp switch, but i think you made up your mind already to try it with the on/on/on 

[vanessa]

Thank you Lowstar, if you get to your "lab" or take the pedal apart let us know what those mystery values are. That would be great to get a verified working layout of this rare bird for posterity.

[vanessa]

I wonder if a bootstrapped Twin-T design would be worth putting in this?