Tracing and modifying a Langtronics Bone Collector

[moid]

I tried two LEDs this evening and that really improved the squeal of the synth. Duck I will try your mod soon, honest! I found that the sensitivity knob is more of a bias - depending on where you set it in the sweep will give you greater or weaker results. I also tried bass guitar and had to change the setting for the pot to trigger the synth sounds.

[duck_arse]

moid - the little T handle is meant to indicate toggle, as opposed to a push.

and a correction - the ldr to the CV pin doesn't run faster OR slower, it runs faster with light, or faster with dark. one side works at a lesser rate than the other, and you probably want a good low swooping resistance ldr. also, if you look at the switch I said to ignore (SW7), the "to_osc" connection is just screaming for a cap to the lm386 output. then you have 386 cap//none//ldr modulation, and dark fast//light fast on the other switch.

as for pins 1 and 8, none of the datsheets I've seen mention shorting the two pins, although they show them thus in the "square-wave oscillator". I don't know what this means. cap, no cap, your choice.

as for the turpo supinant, it doesn't have enough switches. I couldn't keep at it because I got sick of the basic sound. it does some fab gliding up/down and faster/slower decays, at its own whim, depending on where all the divider connections are (those rotary switches, SW1 and SW2). most of that circuit has me baffled, now.

[edit :] strikethrough.

[duck_arse]

the more I think about this, the wronger I get. the CV pin is the 2/3 tap of the internal R//R//R divider between Vcc and ground, used to set internal trigger points. this is why the ldr in one direction has half the effect of the other direction. as to what it does vary ..... I give up. one day I'll BB it and then I'll know for sure, but not today.

and about that cap from the 386 to the CV pin - I don't know why the connection would cause audio noise, especially pickup dependant, but, seeing as one end is connected to 2/3 Vcc (the CV) and the lm386 output sits at 1/2 Vcc and swings wildly more and less than that, maybe connect any electro cap you fit with the (-) lead to the trimpot side of the 2u2 cap, and the (+) lead to the CV pin.

[anotherjim]

I've not played with this thing either - have an aversion to 555 circuits for some reason, though I do have some in the parts drawers.
I always assumed it's a PWM & ring mod type effect. The LDR is changing the timing of the 555. Note the "vactrol" control has no envelope cap, so it's meant to be wiggled by the input signal frequency. LDR's are slow reacting though, having some persistence of vision, so I'd have thought it would only work, if at all in ring mod fashion with deep bass notes. The output signal also resets the timer, so I guess there is an element of PWM control feedback with the LDR controlling pulse width . With the feedback from threshold to trigger the 555 ought to be free running as an oscillator. So how does it shut up when playing stops? I guess it relies on the reset level on zero input signal acting to stop the 555 timing.

[duck_arse]

today! yes, I've also concluded the reset level allows/mutes the oscillations. and I've put the basic on the bb wit der cro, and found some other things. turns out the duty cycle is only a little off 50% across an ldr range of 10k ~ 220k. with the 4k7 and the 47nF cap, ldr of 10k gives a freq of 1234.567901 Hz (astoundingly, according to my calculator), at 56k its 264 Hz and at 220k its 69 Hz.

but wait - I have a picture:


with a 4k7 and 56k (ldr) and 47nF, the middle, red trace shows the output, about 263Hz. pulling the CV pin to supply with a 47k gives the top trace, now 200Hz. the bottom trace has CV pulled to ground via 47k and a freq of 400Hz. the left of the screen shows the "t2" time doesn't vary worth bothering, and the shift is in the "t1" time. [obviously the t1 shift amount will vary with the resistance strung to +/0V as well, but I haven't mapped that.]

so now it's for moids to string it all together and tell us how it sounds.

[moid]

Thanks very much for the work you've both been doing around this circuit. I'm really sorry about my lack of replies, I'm not going to get a chance to look at things until the weekend; on Tuesday one of our management team managed to drop a bombshell on my department and has screwed us over for the next calendar year, possibly longer and so every hour of the day and night since myself and one of my colleagues have been trying to come up with disaster plans to cope with the screw up... and I've been doing that until the early hours every night since It's one of those problems that has no good solutions; only shitty ones and it's a case of trying to work out which shit solution does the least amount of long term damage to us... and I thought I was going on holiday next week le sigh...

[moid]

No news is good news? Not quite, alas... OK after last week being a giant disaster I thought, it's the weekend, I'm bound to get an hour or two to do some work on this circuit on Saturday... lo and behold the worst thunderstorm for a year meant that our sewer backed up into the garden/patio, and I had gutters / downpipes fountaining water everywhere... oh joy, I get to spend far too much time disinfecting stuff and digging crap out of drains and pipes - silver lining; at least this time it didn't go in the house! It's now about 11PM, everyone else here is finally asleep, I think I'll have a go at some of the mods... and half the circuit (the LDR / LED part) seems to have died. None of the LEDs are working, the LDR doesn't seem to respond to light (when I shine a torch on it in a dark room). I should test this, but in my current frame of mind I'm considering throwing the bloody breadboard out of the window. I've tried cursing furiously, I think I'll leave this one alone until I feel calmer...

I think Bob Dylan might have been thinking of me when he sang:

".... there's no success like failure
And failure's no success at all"

Oh and I had to cancel three days of holiday next week for more planning problems at work. Grrrrrrrr I think I will just blast my guitar through some fuzz pedals and hope the universe stops playing tricks on me next week. Watch this space!

[moid]

OK some sort of an update. I couldn't get the LEDs to light up. I tested them - they are fine. I tested the LDR, it works as well. I checked the voltage to the LEDs and they were only getting 6mV... weird. traced back to the LM386 and it's only giving out 3.4V on pin 5. That is odd. Traced to the powerjack in and it's at 3.5V What??? Then put my hand on the plug on the mains (thinking maybe it's loose and not enough power is getting through) and OWWWWW - burned my fingers! The bloody plug is red hot and the back of the case fell off! Yes, I turned off the mains socket switch before prising the plug out of the socket. Well that's dirt cheap daisy chain plugs for you I guess... time to buy a slightly less cheap one.

I switched to another (less flammable) daisy chain plug and power was restored, but still not lighting the LEDs. I had switched out the 150R resistor to a 120R as it should be and also switched the 100pF to the 82 pF on the TL072 but neither of these should've caused an issue (the 82pF sounds to me like I can hear more treble, might be me imagining things though, but it seems brighter). Using the DMM I worked out that as soon as the signal went from pin 5 of the LM386 and into the 2.2uF it dropped to only a few mV - around 6.5 of them which won't light a fart, let alone an LED. I removed the 2.2uF and the LEDs burst into light (there is an 180R resistor still between the LEDs and pin5 in case you were wondering if I was going to blow up some LEDs). Adjusting the Sensitivity knob allows for anything from no extra synth sounds to slight amounts of synth (sounds like the original pedal), to too much of the LM386 only, and after about 2/3 of the sweep there's no discernible difference in sound. So.... this works, but I have to remove something that is on the original board to do so (the 2.2uF from pin 5 of the LM386). Is this is a good thing or a bad thing?

I tried a 1K pot but the range of usable sweep was much more narrow, so I think I'll stay with 2K.

Duck, I will try your mod soon, just needed to get the circuit working first.

[duck_arse]

what was the cause of the wallwart meltdown - you need to find that and clear it before you go all fukishima again. when you were measuring the volts after the 2u2 cap, you were switched to V AC, weren't you? cause a DC voltmeter won't make a lot of sense of AC volts, and vicie versi. the cap is [blocking] at the output of the power amp (386) because the output sits at (swings about) Vcc/2 when there is no input, which will waste power if it has a DC path to ground.

put the cap back in, find out why its not werking rite.

[moid]

OK so I didn't get much chance to do much tonight. I got the 2.2uF cap back in and with a decent power supply, what do you know, it works Having said that, the sound of the pedal is more extreme without it, so I might place it on a switch to switch the circuit through it or bypass it. I also tried a blend of the final output and pin 3 of the NE555 so I could have just the synth side of the pedal if I wanted it, but I think it's fairly subtle and not worth the effort.

The insides of that wall plug are weird. There's a small PCB with through hole components with about 3 or 4 diodes on it and one of the largest capacitors I've ever seen, plus some sort of heatsink, then that lot is glued with epoxy to a slab of metal with wire coils inside it. Might be able to salvage the diodes, they've been put in vertically. The heat sink is attached to something, maybe something like a 7805? I'll have ot dismantle it to look. The inside of the plug itself is partially melted and there are some burned pieces of paper and sponge foam in it!

Hopefully tomorrow I'll try to understand your mod.

[moid]

Duck, you're some kind of genius I got your mod in and it appears to work - at present it's on two switches like your drawing, and depending on how you arrange the switches the guitar either quacks wondrously or makes arpeggiated squeals... and if I switch between neck and bridge pickups there's more variation. I had better draw this thing up before I forget what I did!

I still think I want to add a clean boost to blend with this pedal. I was wondering if I could try something like Tim Escobedo's Duende:


But because this has a single transistor, does this mean it will invert the phase of my clean signal and then when I blend that into the rest of the pedal's audio output it will go rather quiet instead of loud? Would the best be to build another Mr Black Tiger Boost which doesn't invert signal? Thanks!

[duck_arse]

ahem. and I "

Duck, you're some kind of genius .... either quacks .... or .... squeals...

excellent. glad to be of service. and yes, the single transistor with output taken from "above" (collector or drain) will invert, from "below" will follow (emitter, source). as for whether the out of phase clean will buck or boost the output is unknown for this circuit. you'll be a pathfinder.

let me draw something overnight, might replace the 386 and provide clean/boost.

[moid]

Wow, thanks, but please don't feel the need to rush this, I'm sure you have tons of your own work to be getting on with... hmmm I think I have an idea about what you're planning - are you thinking about swapping the 386 for a dual op amp IC? So that one half does what the 386 currently does and the other half is a clean boost? That sounds cool...

alternatively if you want a laugh at the current state of the circuit check out the below:


She's got a face only a mother could love; but she only works in the dark so it's not a problem for me

PS my son and I saw some of your namesakes on the river near us today, they seemed quite content with their new brood, but freaked out when a buzzard came over.

[duck_arse]

^ she looks nice, does she have a sister?

it's too late, I've done it. this is something I've sent you previous, but modified. I've used it elsewhere, Kipper 'the postman' and I messed it up a while back. it doesn't show the 555, but you just need to feed in, feed out and shine the led on the ldr, no other changes in that section. I'm not sure about how well the mix will work - if Jim or someone is looking, they might advise.

so, we chuck the LM386, and replace with an LM358 (built for the task, but most any opamp will work). the first stage has some gain, and feeds the clean mix pot and the rectifier section. the attack and decay and gain and ripple of this section are all parts/adjustable, or panel pots, or fixed, as you like them. the led now drives bright-to-dark on decay, or dark-to-bright on decay, via the switch. I think I've got enough gain to match the original, but you'll tell me either way.

it is special big, just for you. colours - just for me, let me know if they no good.

http://i.imgur.com/po4RgvW.png

[edit :] I should also point out that the Vcc/2 on my dia is the same as from the original circuit, I think it was 2 x 56k and a 10uF. connect all the Vcc/2 to that point, and note the rect sect has its own ref V.

[anotherjim]

Dry mix might be useful if you can pick it's polarity. Effect sound is (should be) so out of whack compared to dry you probably won't ever get silent phase cancellation.

We recently obtained 2 ducks. Still waiting for them to lay eggs which is what they are for. Built a nice pond for them and they won't go near it. Buggers are aquaphobic.

[moid]

^ she looks nice, does she have a sister?

I'll put in a good word for you Duck; being your wingman is the least I can do I have to warn you, she likes to get tied up with cables and can get very loud!

it's too late, I've done it. this is something I've sent you previous, but modified. I've used it elsewhere, Kipper 'the postman' and I messed it up a while back. it doesn't show the 555, but you just need to feed in, feed out and shine the led on the ldr, no other changes in that section. I'm not sure about how well the mix will work - if Jim or someone is looking, they might advise.

so, we chuck the LM386, and replace with an LM358 (built for the task, but most any opamp will work). the first stage has some gain, and feeds the clean mix pot and the rectifier section. the attack and decay and gain and ripple of this section are all parts/adjustable, or panel pots, or fixed, as you like them. the led now drives bright-to-dark on decay, or dark-to-bright on decay, via the switch. I think I've got enough gain to match the original, but you'll tell me either way.

it is special big, just for you. colours - just for me, let me know if they no good.

http://i.imgur.com/po4RgvW.png

[edit :] I should also point out that the Vcc/2 on my dia is the same as from the original circuit, I think it was 2 x 56k and a 10uF. connect all the Vcc/2 to that point, and note the rect sect has its own ref V.

Thanks very much! I have a few questions (of course). I'll need to order some parts to make this, never used an lm358 before - just out of interest does this op amp behave differently to something like a TL072? I looked at the data sheet and they seem fairly similar, but it seems to potentially provide a huge amount of dB? maybe those numbers are just theoretical, but that opamp sounds like it could make a damn loud clean boost on its own. Would this be cleaner than a JRC4558 or TL072 for example? I know you said parts could be swapped, but I get paid in a couple of days time so I can go wild and buy some parts (yes folks, just living the dream here!)

Am I right in thinking you moved the diode (yours is a BAT46 - is that an important part to get?) so that now protects power to the whole circuit whereas before the 1N4001 diode only provided protection to one IC?

If you don't mind I'll post a vero layout for this once I've drawn it (too late to start tonight and I must build the four way splitter pedal I need before my wife insists that she gets the kitchen table back and I have to clear up)

Thanks again

[moid]

Dry mix might be useful if you can pick it's polarity. Effect sound is (should be) so out of whack compared to dry you probably won't ever get silent phase cancellation.

We recently obtained 2 ducks. Still waiting for them to lay eggs which is what they are for. Built a nice pond for them and they won't go near it. Buggers are aquaphobic.

Thanks anotherjim - I was aware that a single transistor in a circuit would invert the phase of a signal, but can other components also do this?

All the ducks round here seem happy with a life aquatic, maybe yours just had a bad upbringing? It's best to blame the parents in these situations. Or maybe they think they're chickens? 

[anotherjim]

A spare op amp can invert without necessarily boosting. Either an op-amp or transistor stage an take the signal through a second inversion to give 2 opposite phases.
Duck alluded to single transistor cathodyne/concertina/phase splitter.

If R2 & R3are equal, then you have two anti-phase outputs.
The green ringer uses just that with Q2.

Put each output (after the caps) to opposite ends of a pot, then when the wiper is in the middle the signal cancels out. At each extreme of the pot it's either inverted or non-inverted signal on the wiper. Then take it to something that mixes it with the effect sound.
The effect sound might be too strong compared to dry, so some juggling of the levels will probably be needed.

[duck_arse]

alluded? deluded, more like. the BAT46 is just hanging around from the circuit dia I was recycling. it is not terribly important, any schottky will do for their low forward voltage. you could also use a 1N400* in series, or reverse parallel, if you like.

the LM358 is optimised for single supply, low voltage, so goes well w/ 9V, and also allows its inputs to go down to ground. it is a better performer as a rectifier/driver than as a clean audio part (I allays see a big step/glitch in the output w/ audio). again, it is not important, but is a better choice than the TL0** series.

I am always happy to look at pictures of people's pet ducks.

[moid]

Will be back with this one soon chaps, had a minor disaster this week with the sewer that runs behind and under my house deciding to erupt and flood the garden and garage, so have spent this week doing DIY to fix things before the next storm... we have more torrential rain predicted for tomorrow so we'll soon see whether I'm a better sanitation facilitation engineer than pedal builder... fingers crossed.

One quick thing I did build though that I have a question about (a ZVex Super Hard On). I need a boost for the buffer/splitter circuit I'm building and I was desperate to do something this week that wasn't unblocking drains / disinfecting stuff and was simple enough to do late at night, so I built this on vero board and it works (yay, a rare surprise) but... it has a fair bit of crackle to it when I play chords and some individual notes. I did have to make a couple of parts substitutions, so maybe those have cause the issue? (it's not the crackle OK thing when you turn the knob, this is when you play every note). It's not boxed yet and the offboard wiring is held together by lots of crocodile clips and jumper cables, so maybe it's that? The parts I substituted were a 5K lin pot for the 5KRev Log pot the circuit should have (I thought it's the same level of resistance, but the taper will be different, however that lack of rev on my pot is making wonder if that is important) and I had to switch the 5k1 resistor to a 5k6 because that was the nearest resistor I had to that value.

Here's the layout I used:


If this one means nothing to either of you I'll try to post this as a new thread in the forum in case anyone else has built one and had problems. I can get the part substitutions in a couple of days now I've got paid.