[PICS] Mystery Envelope: cheap tricks with Ross Comp + SG-1

[Processaurus]

This was kinda an involved project...  Its a Ross clone modded to hellll, married to an SG1 clone.  Seems like the
SG-1 worked like it was supposed to only when being fed by a limiter, so that was the original impulse.  Along
the way there were a bunch of routing, mixing, and mod options that presented themselves with what was there. 
I made a deuce of them, one commissioned by a friend, one for the doctor.

The major mod to the comp was a clean blend circuit I push around here sometimes, its the little custom
made PCB in the middle.  Also there is Mr. Hammer's 3 way attack switch, and a .001 treble bleed cap across
that 10K on the output.



The routing is where it gets interesting.  The first footswitch is to bypass the whole mess.  The second
switches between the output of the clean blend mixer and the SG1 output, both of which have a volume control. 
That was important for me, that the SG-1 have extra available volume, because at unity gain it seems quieter by losing the
initial attack.  The comp always feeds the SG-1 at full volume, and the comp side of the blend circuit.  The
great happy accident I made with this pedal was when I tried switching the clean side of the blend mixer to
the output of the SG-1.  You see that input to the mixer inverts the signal, so when the swell sound gets
mixed equally, with the comp, it cancels everything but the initial attack... premature decay. The exact
opposite of the SG-1 envelope.  The fast gear?  The SG-1 swell time now controls decay time.  This was
exciting, because I'd been wanting the Dan Armstrong "Articulator" to be put into production, and this is a
good approximation of that sound.



The only mod to the SG-1 is a switch to kill the swell action only when you switch to the SG-1, you can still
get the "articulator-ish" sound from the mixer.  So the SG-1 side can be used just as a boost/100% Ross option

Parts were from small bear (including the special FET for the SG-1), PCBs from BYOC (the comp was a $5
blemished one, I forgot there was more than a pair of traces that got too close, I spent 2 hours debugging a
second problem, a missing trace, that one was tricky), the small blend PCB designed by me.  The enclosure is
the new EH 1790 box, bought from Pedal parts plus.  They specially powdercoated it "galaxy purple" for me, for
$4.25!  Thanks for that, Kirk and Connie...

Complaints? I'd like longer swells from the SG-1, and more headroom from the clean side of the blend circuit
without sacrificing the gain needed to get a equal feeling blend.

Thanks to RG for the Geo panning article, Dan Armstrong and Barber Electronics for ideas, EH for the perfect
size box, Tonepad and GGG for the nice schematics, and the people around here that have shared their
experience with these two circuits.  I kept coming back here to look stuff up, this place is the ultimate
resource, when you need to need something specific about obscure and archaic music electronics.

[Morocotopo]

Cool idea, cool pedal!
Soundclips? Any?

morocotopo

[Mark Hammer]

This schematic (http://www.generalguitargadgets.com/pdf/ggg_sgo_sc.pdf) shows what looks to be the critical elements in determining rise time as being C6 and P2.  One *could* use a higher value pot (e.g., 50k) for P2 to extend the rise time, but you run into the issue of whether greater resistances limit the current in undesirable ways.  So maybe the way to extend rise time is to use larger capacitance for C6, such as another parallel 470n unit.

[Processaurus]

This schematic (http://www.generalguitargadgets.com/pdf/ggg_sgo_sc.pdf) shows what looks to be the critical elements in determining rise time as being C6 and P2.  One *could* use a higher value pot (e.g., 50k) for P2 to extend the rise time, but you run into the issue of whether greater resistances limit the current in undesirable ways.  So maybe the way to extend rise time is to use larger capacitance for C6, such as another parallel 470n unit.

Cool, I'll try paralleling another cap with C6, I already tried a 50K pot and it seemed like all the action was on one half of the rotation, after a certain point it wouldn't get up to full volume, and would clamp down prematurely, warble, and generally act mysterious (in a basically unartistic way).

[big bustle]

AWESOME!

i put this on my gear porn blog called.... gearpron.com

check it out!

[Meanderthal]

 Awesome idea! That's the true mad scientist stuff there!

Speaking of which, the GR-700 you have it sitting on... nice! I bet you have fun with that.

[RaceDriver205]

That idea of canceling out the straight waveform with the swell waveform to make a momentary attack device is ingenious!
That box its in looks incredible as well! God knows how you make them look so prefessional.
Sound clips, sound clips, sound clips!

[Processaurus]

Thanks.  I'll see if I can record the fast decay sounds, soundcard is on the fritz.  I still haven't gotten what I feel is the ideal setting between the ross sustain, SG-1 sensitivity, SG-1 FET choice, and the SG-1 trim pot to trigger it the most reliably, when it was all apart it seemed better.  I might go back to the 2n5457 FET rather than the unusual boss one.  Might need to bring the sustain and sensitivity trimpots as real pots.

Speaking of which, the GR-700 you have it sitting on... nice! I bet you have fun with that.

Oh yeah, its... stupid.  Its my favorite pedal ever.  Chaotic, ridiculous, archaic.  I got a second one recently, at the store the clerk mentioned after the purchase that they got it from Santana, it was thrown in with the "good stuff".  Uh, Ok...

[calculating_infinity]

I know this thread is a bit old but...  Thats awesome work man!  Sounds very interesting and creative!  I'm sure this may inspire some others. 

-Jonathan