Octavia clone body mod sounds like analog synth... soundclips added.

[joelap]

EDIT:  I've fixed most of the problems in this thread, but if you go to www.joelap.com and listen to the bottom soundclip, its the sound I'm getting when I try to disengage the body mod on my tychobrahe octavia clone.  Any help is greatly appreciated.

-------------------------------------------------------

Hey all, just finished the wiring up of my octavia clone following the layout on generalguitargadgets.com.  Well, the notes are fading out rather quickly and the sound quality is overly buzzy and nothing really like the sound clip on the generalguitargadgets website.  I build this pedal with the extra bass mod, as well as another mod consisting of an SPDT switch that removes or adds one of the diodes following the transformer to eliminate or allow the octave up effect.  Both the "body" mod and the octave on/off are working fine.  I've recorded a sound clip and posted it on my website www.joelap.com.  I figure rather than sitting around explaining it all day, I can make a sound file and let some of you experts hear it for yourselves.  Ignore the crappy playing, I'm not the best player and I recently took a chunk out of my left thumb with a razor blade yesterday.

Any help appreciated.

Joe

[John Lyons]

Hey there

Most octave boxes have a similar note fade effect. The diodes and or transformer that make the octave sound and waveform gate the signal a bit. You kind of have to just live with it and taylor your playing around it. The buzzy sound is caused by the diodes clamping down and giving a square edge to the notes.

Hmmm..just listened to your sound clip.. Something is wrong, not just what I mention above. Go over all your parts with a meter and make sure everything is the correct value. (resistors mainly then orientation of caps etc)  I don't really even hear the octave. You'll eventually find something you overlooked and you'll feel stupid...as we all do.

When you get it going right try using the neck pickup and rolling off the tone control, This way you will really hear the octave. And also rolling off the guitar volume a bit can give a better octave sometimes

John

[Alex C]

Sounds like a transistor biasing issue to me.  What transistors are you using?  You might want to double-check and then fiddle with the values of the emitter resistors.  Just for reference, you're using this schematic, right?

I can hear the "true" sound in there, it's just muffled by the extra gated clipping and fizziness. 

The Rangemaster demo clips sound good too.

-Alex

[burnt fingers]

I'll second the checking of the biasing on the trannies although before you do that, do you have  fresh 9v in there.  it sounds stupid but I build my bobtavia and it didn't work the first night.  It turned out that the cheap dollar store battery i bought was almost dead.

Scott

[Pedal love]

Check the resistors, between emitter and ground. You may have a circuit amplifying improperly because of this.pl

[joelap]

Hmmm well interesting note here.  My girlfriend soldered most of the board (yes I know I have the greatest significant other in the world, she's actually interested in electronics... and she did a FANTASTIC job soldering the board too) but if the negative side of these electrolytics is the side with the giant black stripe and the sideways "-" along them, then she definately soldered one of them in backwards, and its right next to the emitter resistor (1k) of Q1. (going to the leftmost lug of the intensity knob) .  Gotta love her though.  She did all the others right.  this has to be the cause.  I'll flip this bad boy around and see if that solves it.  Either way, I'll repost within 15-20 minutes.

Joe

EDIT: also worth noting is that R3, the abse resistor of Q3, is not soldered into the board and also not in my box of parts.  This could have a lot to do with the crappy sound.

Also, since I've reversed the polarity of the first electrolytic to its proper orientation, I'm getting the most god awful squeel when I engage the "body" mod.  I gotta find an 820k somewhere, and I dont think I have one in my spare parts bag from rat shack, then see if both problems persist. 

[$uperpuma]

yeeeah, that could be it:) that is indeed the negative side...if it still sounds bad, swap that cap out for a new one...

[joelap]

yeeeah, that could be it:) that is indeed the negative side...if it still sounds bad, swap that cap out for a new one...

Well, it does sound better... but still that missing R3 is really the cause now I think... but I'm still stumped about the body switch.

[joelap]

Ok update:  didn't have an 820K resistor and mouser forgot to send me one (either that or my cat decided he'd take a bite of it).  So I rigged up 820K by putting a 1.5meg and 1meg in parallel and then a 220k resistor in series with that.  The pedal sounds great for that hendrix fuzz and octave up.  The octave up is definately working, and the octave on/off switch works great.  I noticed something however.  It's not when I turn on the body mod that it squeels, its when I turn it off.  I'm following the diagram sound here http://www.generalguitargadgets.com/diagrams/toctpl_body_mod.gif for the most part completely the same, with the exception of changing all the sleeve and ring connections on the input jack visa-versa, since usually it always appears the other way around (is that a typo having the - battery connected to the sleeve instead of ring?). 

I thought I shorted one of the caps, but I replaced it and the squeel is still there.  Any ideas?

[Pedal love]

When you have a situation like this the capacitors can really help by reducing a lot of treble hence less noise, squeal.
My advice is to check capacitors c4, c5 and c8. Also check to see if there is any build up of solder on the board in and around b+, ground, jacks, etc. This can generate noise.pl

[joelap]

When you have a situation like this the capacitors can really help by reducing a lot of treble hence less noise, squeal.
My advice is to check capacitors c4, c5 and c8. Also check to see if there is any build up of solder on the board in and around b+, ground, jacks, etc. This can generate noise.pl

Yeah, but the entire pedal is silent with the exception of when I try and remove the body mod caps from the circuit by setting the switch to cause them both to be an open circuit.  And it kind of sounds either like a giant SQUEEEEEEL that doesnt respond to the input or a really weird almost "synthesized-chainsaw-meets-really bad gas after taco night" type of sound.  I guess I could record it and repost so you can all hear.

[joelap]

Soundclips:  www.joelap.com

First Octavia clip is of the build so far, so you can hear all the settings minus when the body mod is disengaged.

Second Octavia clip is of the analog-synth like effect that its giving me now when I try and turn off the body mod.  Before, it was a loud squeel, but since I've added the 820K resistor in its been doing this instead.

[disantlor]

Second Octavia clip is of the analog-synth like effect that its giving me now when I try and turn off the body mod.  Before, it was a loud squeel, but since I've added the 820K resistor in its been doing this instead.

woah!  that sounds pretty cool actually, hopefully someone more knowledgeable than me can figure out why it's doing that and let us know so we can make a new pedal.

Uneducated guess:  Perhaps the loud squeal was a very high pitched oscillation and by adding the resistor it lowered the frequency down to a more pleasant sounding, if unintended, range

[joelap]

I know it does sound pretty cool actually, but I'd like to know why its doing it so I can correct it maybe.  I'd take voltage readings but my Fluke Multimeter hasn't arrived yet.