Lumpy Ray!

[Connoisseur of Distortion]

i just finished perfing a RoseyRay. After a failed first run (very low volume) i returned to find a floating lead. So, i put it in place, and fired up again.

Tremelo! WTF?

The high gain sounds rise and fall! it happens about every 1/3 of a second, and sometimes delays longer. The lower gain section sounds great (nice one there, Mark, very refined OD sounds) but when i switch in the high gain section, i can hear the bass and treble falling on and off! Very weird!

I looked over previous posts, and decided that i placed a i uF cap in the wrong place. I thought the fix called for a cap between the clipping diodes and the next section. What he meant was put it before the Tone control!

back, must fix and try again.

[Connoisseur of Distortion]

it's behaving worse now. i don't think that was the proper fix...

now, the LEDs in the feedback loop of the second opamp are flashing on and off, and all i hear on the ouput is clicks as they do so. hmmmmm... ideas?

[Connoisseur of Distortion]

ok, an inspection and repair (once again, floating lead...) gets the distortion up and running, but now i get a low frequency oscillation, i believe it's what's called motorboating...

Mark, how did you mean for those caps to placed, and why was it causing tremelo in the first case and allowing motorboating in the second? Is there some way to make sure that the cap doesn't chagre/discharge randomly? am i missing this entirely??

Thanks in advance...

[Mark Hammer]

This one is seriously perplexing me.  I have 3 at home.  Two are well-behaved, and the third...not so much.  As near as I can tell (they are all perfed) the same fix was used on all 3.  Other folks have reported successful builds, so I know that my suggestions are not just blowing smoke, but I'm really stumped as far what makes this thing reliably behave itself.  It may well be that it is a layout issue, OR that maybe there are op-amp choices to be mindful of.  My 3 are kind of packed away, and I'm just taking a few minutes off some work I have to do, otherwise I'd say I'll check them.  Perhaps some successful builders can say what op-amps they might have used and we can begin to discount some sources of difficulty.

Sorry to present you with such a tease, bro.  Normally not my style.

[Connoisseur of Distortion]

i might go back and try switching out some opamps, then.

BTW, where is the 1 uF cap supposed to go? does it separate the opamp stages or separate the opamp from the tone control?

Thanks!

[twabelljr]

     I could be way off base here having never built a RoseyRay. I was having a very bad motorboating problem with a Hot Harmonics build recently. After reading alot of threads searching for "motorboating", one common problem was power supply decoupling. The H.H. schematic showed a small 22uF Decoupling cap. After increasing it to 220uF my concern was corrected. I see the RoseyRay Calls for a 100uF decoup. cap. In my searching I did see alot of R.R. motorboat threads but I don't recall that decoup. ever being the problem. It is something you might be able to try quite easily though. Best of luck. T.

[Connoisseur of Distortion]

my power supply is pretty well set. It has a 100 uF across the V+ to ground, and across the Vref to ground.

thanks for the suggestion, though...

[tungngruv]

I used a 4558 on my Roserays that worked. I did build 3 off of the vero board layout ( one just a week ago ). Same thing happened with mine, I can hear the volume control working, the blend control between the different sides of the op amp works but the LED's flash off and on (alternating) and I'm getting no output. I'm playing now more than ever so I don't have a lot of time to devote to this but I'm going to hand draw a layout using the Voodoo Labs OD that I perfed my first one from. Once it's drawn up, I'll post it on my site and try to verify it shortly.   

[Connoisseur of Distortion]

i'll be sure to start trying out different opamps (i used the beloved TL082).

What i REALLY want to know is where those 1 uF caps go. One goes between the notch filter and its previous stage, nd the other goes between the diodes and something else. Does it interrupt the tone control, or does it interrupt the the next stage?? or both??

that info would be immensely appreciated.

[Mark Hammer]

Like a great many op-amp based circuits operating from a 9v battery, there is a bias (Vref) voltage fed to the input of the first stage from that 47k+47k divider.  You will note that there is NO DC-blocking cap between the stages, however.  That means the bias voltage is essentially "preserved" between stages and re-used in the second stage.  That is likely the source of the problem, and a good reason to redesign the circuit with a "bias reset", and re-bias between stages.  I originally started out with a Voodoo Labs Overdrive design and perverted it.  The recycle-the-bias strategy worked for that pedal since there was only negligible gain in their second stage (to make up for what got lost due to the clipping diodes), but I suspect it was a foolish thing to attempt here, and the likely cause of hit-or-miss builds.

More importantly, if you're going to "borrow" a bias voltage from a previous stage then you better make sure the op-amp you use can do so politely and without any sort of snowball effect, which is what I suspect happened here.

In any event, as a band-aid solution, because the scoop output is unwittingly fed back to the the input of that stage via the tone/head/blend pot and the 6k8 resistor, I needed to keep any DC from feeding back.  So, I stuck 1uf NP caps (I have a batch of them, which is why I used them) on the output of each stage.  In the case of the first stage, its "output" path is the 6k8 resistor and cap to ground, just before the tone pot.  I placed the 1uf cap just *before* the 6k8 resistor.  This means that the stage 1 output doesn't pass through any cap on the way tostage 2, but DOES pass through the 1uf cap on the way to the 6k8 resistor.  The cap on the output of stage 2 is between the output pin of that op-amp and the midscoop filter formed by 10k/22k/10nf/1nf.

Clear enough?

I really need to fix the problem because when it sounds good, this is a very nice pedal that is capable of delivering some pleasingly searing tones reminiscent of Steve Vai and Satch.  Being able to get that *and* a warm Tube Screamer kind of tone in the same pedal, and blend between them is very nice, and delightfully convenient.

[Connoisseur of Distortion]

thank you for the response!

now i understand not only where that cap goes, but why it was placed there. as always, clearly explained. Fortunately, i have a pile of odd opamps that are just begging for a home, and if this does not work, i can always make another voltage divider to bias the second stage and isolate it with a DC blocking cap, right?

BTW, is that why i was getting that tremelo? when i first soldered it up, the cap was cutting DC from the second stage... Possible reason?

[Mark Hammer]

I *think* that's why you got the "tremolo", but there are many mysteries a little too deep for me.

Biasing is something that only became clear to me in the last couple of years.  It's a lot easier for me now to be able to look at a schem and think "Okay, there's a bias voltage, and it's valid up to here.".  I went for decades understanding nothing about it, though.  Don't let it get you down if it didn't click instantly.

if this does not work, i can always make another voltage divider to bias the second stage and isolate it with a DC blocking cap, right?

As near as I can tell, yes.

[Connoisseur of Distortion]

Thanks again! you really do look out for this forum!

i'll post a report as soon as this pedal is finished.

[Connoisseur of Distortion]

fixed!

the final touch was an ugly little chip i salvaged from an older amplifier, something called a 6550. it's an opamp that doesn't have the motorboating problem. I believe it is related to the 4558 family, which tungngruv confirmed to be suitable.

Perhaps a list of 'good' opamps could be compiled and attached to the schematic. I tested the TL0X2 with poor results, and the LM358 with worse results. next up was the 6550, which works fine.

VERY interesting pedal. downright weird. it gets quite a bit of distortion, if not quite enough for the highest of the high. definitely beyond the BSIAB, but not quite into the Dr. Boogey range. The tone control makes for some nifty sounds, as it has a tubescreamer-ish low gain section. at the lowest gain settings, it sounds like a very ordinary mid-hump OD, but turing the tone pot gradually adds in the treble and bass content. Beyone a certain point, the treble and bass overwhelms the mids, and a dark, powerful metal distortion takes over.

The middle areas of the tone control have some odd sounds. a death metal scoop with a touch of crunch in the mids section, a tubescreamer with its treble and bass restored, an OD with a bit more impact, whatever. This pedal has a ton of possibilities, and I recommend it to anyone.

I'll try to post pics and soundclips sometime. If anyone really wants them, lemme know, and i'll try to free some time.

[Mark Hammer]

Thanks for: a) the nod, b) the quick and thorough report, and c) confirmation of the role of op-amp.  Always happy to make the"connoisseurs" happy!      I'm looking forward to popping in another chip and reforming/boxing one when I get home tonight.

Not sure if you incorporated it, but I also stuck a 470pf cap to ground from the wiper of the tone/head/blend pot.  That has the effect of introducing differential lowpass-filtering of each side as you move the pot.  Keep in mind that each leg of the pot and the cap to ground form a LPF for each of the two channels, except that the rolloff is different for each when the pot resistance is anything other than perfectly divided in half.  This add-on doesn't create a huge difference in the overall tone, but it increases the "morphing" qualities of the tone/head control.  Small bits of rotation change the character of the sound more as you get not only different balances of the two channels but differential filtering of them as well.  You will note as well that with the multiplicative gain, the 2nd channel never really cleans up entirely, such that panning entirely to the 'Ray head' and turning the gain down can get a nice biting coloration for clucky Strat settings.  Just a ton of unexpected (for me, anyways) possibilities in there for 3 lousy knobs.

This one was a very happy accident that really started out as a desire to come up with a one knob tone control that did not force me into choosing between thin and reedy OR muffled and wooly.  Try a wah in front of it with a bit of gain turned up.  Not all pedals respond enthusiastically to wahs (e.g., my Dist+ likes them, but none of my 3 BMPs seem to take to it all that well).  With more of the "Ray" channel dialed in (I call the first stage 'Rosey' because its bluesier and funkier, while the second stage is 'Ray' because its the high-strung irritable death-metal channel....I guess you have to see the movie "Incredible Two-Headed Thing" to fully get it), it sounds very expressive with a wah.

The 6550 is an 'AN' prefix, right?  A similar device to the AN6551 and 6552.

[tungngruv]

I love the Roseyray. Don't forget Marks "Chaos" pedal. It's a very good one also. I think I used Paul Marrosy's layout and perfed it up off of that. It's different enough from the RRay that it's worthwhile to build.

[Mark Hammer]

My inspiration. 
http://www.imdb.com/title/tt0069372/usercomments
http://www.thespinningimage.co.uk/cultfilms/displaycultfilm.asp?reviewid=774
http://www.blaxploitation.com/p_96.html

Let it not be said that two heads are NOT better than one!

[Connoisseur of Distortion]

i don't think i'm going to add in the cap as is, but maybe a SPST switch to give an additional control for the pedal.

i think that this might be the way to go with a tone control. a bit large for one knob, but the idea of a mid boost mixing into a mid cut is a great one. I have noticed the BMP to go from whiny little thing to mammoth muff rock too easily, and the areas in between to be lacking in some way.

my opamp is a 6558 (sorry about the mistake earlier), with 571D underneath that. i have no clue who made it. my best guess is a japanese equivalent of the 4558, or similar.


completely off topic, i have seriously considered changing my name as of late. i never meant to be drawn into DIY so permanently, and only expected to use this name for a couple of months... hmmmm... it seems very silly, as i have built about 15 distortion pedals and seem to use maybe 3 of them. not exactly a connoisseur...

[tungngruv]

Connoisseur of Distortion , check your pm.