Followup to RoseyRay "problem"

[Mark Hammer]

I posted a schematic on my site last year for a two-headed distortion pedal that panned between a Tube-Screamer/mellower-Dist+ sound and a heavily scooped death-metal sound.  It "worked" okay, but there was an annoying motorboating sound that undermined its usability.

I finally licked the problem and the pedal is now usable.  The problem was that I had relied upon a cap before the output volume pot to block any DC proceding onto the next pedal or amp.  Unfortunately, DC and other nasties were recirculating through the second distortion stage.  So, the other day I stuck a 1uf polarized cap between the output of the second stage and the notch filter immediately after it, and a second 1uf cap between the output of the first stage (just after the diodes) and its lowpass filter.  Blocks any and all DC and hum from oscillating or reentering the second high-gain stage, and cleaned it right up.  VERY interesting pedal now and worth a try.

Carry on.

[Phorhas]

Thanx Mark... I'll give it another shot

[lenwood]

Hi Mark,

Is the Roseyray schematic on your site ok to use as is or will I need to add the two caps?

Also another thing I was wondering about was can the treble rolloff side be changed to a midboost filter?
I just keep noticing that there are alot of hard rock and metal guitarists that also used mid-boost to get heavy sounds.
So I was thinking about building the Roseyray to mix  from mid-boosted to mid-sccoped.

Do you have any ideas on a filter that would work well for that side?

[Mark Hammer]

1) The added caps are necessary to keep the circuit stable and avoid oscillation.

2) If you want to add midboost you may want to switch to a different pedal.  The "Rosey head" (output of the first stage) is simply lowpass filtered because the intent is to get a warm bluesy sound.  A mid-boost suitable for "hard rock" is probably not going to happen unless you stick in an active resonant EQ section, at which point it starts to turn into a different pedal.  On the other hand, there is nothing to stop you from swapping the .001uf bypass cap in the scoop filter with a large value to let more upper mids through.  Maybe even installing a toggle to select between caps for more and less strident scoops.

[lenwood]

Cool, Thanks I'll try that by adding a switch to go from "stock" to "mod".

Thanks for your help.

[TELEFUNKON]

ain`t it funny
how time slips away

just getting acquainted to: metal needs scoop,
now you read: metal likes boost

it`s all in the mids it seems

[Mark Hammer]

Ah, but scoop IS boost, my friend.  It's all about contrast.  You can create a heavy bass and treble sound by boosting bass and treble, or by scooping out mids afteryou've boosted everything.  Of course, there is treble, mids, and bass, and there is treble, mids, and bass.  What counts as the appropriate scoop point/amount for one player may tend to gut the sound for another, whether because of the guitar/pickups involved, the rest of the signal path, or simply taste.

The midscoop filter network I "borrowed" from the Superfuzz and its cousins for the 2ndstage of the Roseyray creates a big bottom and sizzling top of its own accord.  While the amount of bottom seemingly "created" (i.e., left over once the mids are shunted to ground) does not depend on the workings of the distortion part of the circuit, the highs do.  Keep in mind that the treble will be made of the original signal plus whatever harmonic content has been added during the clipping.  Depending on the extent of clipping produced for whatever reasons, plus the resonant peaks of the pickup itself, the amount and balance of harmonic content may seem piercing and meaty enough in some instances, yet not in others.  Allowing a little more lower treble to pass through via increasing the value of the .001uf bypass cap may simply result in what ought to have occurred in terms of balance/distribution of harmonic content.

Of course, that's the nice thing about DIY and analog circuits, isn't it.  You can say to yourself "I know what was supposed to happen, here.  I wonder how I can make it happen?"