I had the need for a test oscillator when I was away from my signal generator, so I trotted out the Q&D oscillator, which had been broken by its storage.
So while tinkering, I did some things to it I'd intended to do for a while. I made it fake a repeated string pluck by adding an adjustment to make the oscillation decay to zero over a second or so, and a "plucker" to fire off repeated notes.
http://geofex.com/FX_images/Fake Guitar Oscillator.pdf (http://geofex.com/FX_images/Fake%20Guitar%20Oscillator.pdf)
You can flip it to a constant tone, too. I think this constitutes the world's most accurate, if boring, assistant guitarist.
One dual opamp and a few other parts.
I notice in looking at it that I still can't type. I'll fix some of the misspellings someday.
Cool!
Cool. I´m just making a circuit test "station" (well, really just a piece of wood with two jacks and a proto board...) and this is a perfect addition to it.
Thanks for sharing, R.G.
Nice one.
Oh AWESOME !!!
I've been using an Atari Punk as a tone generator for quite some time - this one would actually let you test delay pedals as well - what with the "plucking" and all.
If some could lay this out to vero or PCB - I'd be forever indebted.
Dan
thanks R.G. .... this falls under the "good to make one day when i get tired of fuzz boxes" circuits ! :icon_mrgreen:
i like it.
Great idea, I love the simplicity.
Looks real useful.
>
I still can't type.The only mechanical errors I see (
6/26/2010 11:24am version) are 2 mis-spaces and a z/x slip.
Quoteline 4: look like aguitar signal
line 10: R1...R3 and C1...C3 determinethe feedback null
last line: All rights rexerved.
Text reads well.
Circuit looks to be drawn correctly. (I assume the twin-T inverts at center frequency? Too tired to work it out.) FWIW, the OUT jack is not marked as such.
I just love this guy ;D
Quote from: PRR on June 27, 2010, 01:13:58 AM
The only mechanical errors I see (6/26/2010 11:24am version) are 2 mis-spaces and a z/x slip.
Quoteline 4: look like aguitar signal
line 10: R1...R3 and C1...C3 determinethe feedback null
last line: All rights rexerved.
Hey, thanks for nailing those down. I noticed the "rexerved" as I posted it, but didn't catch the others. I'll go fix it.
QuoteCircuit looks to be drawn correctly. (I assume the twin-T inverts at center frequency? Too tired to work it out.) FWIW, the OUT jack is not marked as such.
Again, thanks. I did this in about half an hour; I have to finish things like this before I get pulled off to other stuff I have to do. Twin T has an infinitely deep null at center (if the Rs and Cs are tuned just right, these aren't perfect values) and a dramatic phase reversal at center. The null lets the opamp go almost open loop at center and the phase change does the rest. Single transistors make OK Twin T resonators and oscillators, although you have to be very careful with loading effects if you do that. PAIA did several variations of the Twin T as a ringing oscillator (bongos simulator) and resonator (wind/surf simulator) wah ( Poptronics article, 1969 I think), and fake "Leslie", the Synthespin, which was a Twin T resonator/wah driven by an LFO. It's quite flexible.
This thing owes its heritage to the drum simulators mostly.
rg, interesting. a few weeks ago i went on a surfin safari diving deep into fifties and sixties organ schematics. the signal generator portions for drum sounds were interesting. how many ways to make white noise into a cymbal? fun stuff.
i've got a layout and a build that's working nearly 100% .... :icon_biggrin:
i'll be posting the layout and a soundclip tonight ... the tone/notes switch is incredibly handy ... with the parts that i had on hand, the frequency of the tone is somewhere between 700 and 800 Hz ...
thanks again, R.G. for providing the schematic .... it's a hassle having to plug the guitar in for testing out fuzz boxes ... ( BTW, a sine wave run through a simulated fuzz box sounds kind of nice :icon_mrgreen: )
I can't believe you guys let me get away with that. There's DC on the output. I left out a blocking cap to the output jack - which I have now corrected. :icon_biggrin:
I'll upload the corrected page.
'Course, I got the chance to put in NEW errors, too. :icon_lol:
Modified page uploaded.
Quote from: stringsthings on June 27, 2010, 12:28:01 PM
i've got a layout and a build that's working nearly 100% .... :icon_biggrin:
i'll be posting the layout and a soundclip tonight ... the tone/notes switch is incredibly handy ... with the parts that i had on hand, the frequency of the tone is somewhere between 700 and 800 Hz ...
thanks again, R.G. for providing the schematic .... it's a hassle having to plug the guitar in for testing out fuzz boxes ... ( BTW, a sine wave run through a simulated fuzz box sounds kind of nice :icon_mrgreen: )
My hero..
Thanks !
Dan
Wow! This is great. I have almost resorted to strumming with my feet so I have two hands to tweak the dials. I am certain I have all the parts on hand except perhaps the proper IC.
Thanks R. G. !!! :icon_razz:
Life is good. I found the TL072. It was a spare I bought for my Tap Tempo Tremolo build. Forgot I had it.
Quote from: KazooMan on June 27, 2010, 05:41:28 PM
Wow! This is great. I have almost resorted to strumming with my feet so I have two hands to tweak the dials. I am certain I have all the parts on hand except perhaps the proper IC.
In a pinch I'd use any dual opamp I had on the bench. It would probably work fine.
(http://i703.photobucket.com/albums/ww40/luckyfeline7/Test%20Circuits/FakeGuitarOscillator11.gif)
and a short ( but exciting ) soundclip:
http://soundclick.com/share?=songid=9330932 (http://soundclick.com/share?=songid=9330932)
at 0:54, echo and reverb are added to the "notes"
boo hoo...poor me....
pcb or vero ?
;D
Thanks, Dan
Thanks, Stringsthings. I had started doing a layout while I was BBQ'ing some chicken. The chicken won out (and was fabulous). I returned and there was a layout waiting for me.
Thanks! I will check out the layout versus the schematic and put it together. I can put my shoes back on and quit strumming my guitar with my feet while I adjust pedals.
Quote from: stringsthings on June 27, 2010, 07:32:58 PM
and a short ( but exciting ) soundclip:
Just a question. I notice the the "notes" are all quite short. Was it possible to make the notes ring for longer times, but still die out?
That looks pretty handy. I use my GEO "Down and Dirty" oscillator just to verify if something is functional when I get it done, usually when I am building a batch of pedals for one of my clients. But for stuff I build for myself, I always take the finished circuit for a test drive afterwards by playing my guitar thru it. I guess there are those times when you are tweaking stuff where the "guitar" mode might come in handy, though.
I agree with RG, it seems like the "notes" decay extremely quickly. They are very staccato...
From that sound clip stringsthings posted, it sounds like knocking on a wooden block. Is it any good for testing any pedals other than delay and reverb pedals?
Sounds exactly like the old Boss Dr Rhythm rimshot. I have to build it for that reason. :D
Quote from: mattthegamer463 on June 28, 2010, 12:56:42 PM
From that sound clip stringsthings posted, it sounds like knocking on a wooden block. Is it any good for testing any pedals other than delay and reverb pedals?
Yeah, something with a more realistic decay (like a guitar string) would be more useful.
Let's see what we get back.
Sometimes it's tricky to set a ringing oscillator to ring just the right amount. I may have to add a fine tuning knob to get it to ring for up to about half a second. I did notice that mine is very fussy about the ringing time setting.
Quote from: R.G. on June 27, 2010, 09:34:50 PM
I notice the the "notes" are all quite short. Was it possible to make the notes ring for longer times, but still die out?
http://soundclick.com/share?songid=9334230 (http://soundclick.com/share?songid=9334230)
details of soundclip:
1) turning the length control from maximum ( constant tone ) to about 1:00 ... to get the longer notes ...
2) notes into a software fuzz box
3) notes into a software phase shifter
4) notes into a hardware octave divider ( that is older than my cat :icon_mrgreen: )
Yeah, this could be quite handy,thank you.
I think I will put it in the same enclosure as my "quick and dirty" test tone generator.
Bryan
Quote from: stringsthings on June 28, 2010, 05:08:56 PM
1) turning the length control from maximum ( constant tone ) to about 1:00 ... to get the longer notes ...
Ah. That's better! I had something like that in mind, a ringing note, but which dies away in a reasonable time.
There is a slight buzz behind the note, even on the first section. Is that an artifact of the recording and playback mechanism, or does the thing actually have a slight buzz in the sound. The reason I ask is that mine didn't do that. I had a pretty much pure tone in all the decaying notes. I could turn up the gain so it would buzz, but mostly it was clean sounding.
Looks a lot like my May 2010 submission if you ask me... :D
http://www.diystompboxes.com/smfforum/index.php?topic=84323.msg711421#msg711421
Quote from: Cliff Schecht on June 28, 2010, 10:38:55 PM
Looks a lot like my May 2010 submission if you ask me... :D
Hey, neat. I hadn't seen that one, but it's another good illustration of how flexible the Twin T can be.
Quote from: R.G. on June 28, 2010, 08:12:41 PM
There is a slight buzz behind the note, even on the first section. Is that an artifact of the recording and playback mechanism, or does the thing actually have a slight buzz in the sound.....
my unit is sans volume control .... so the buzz is likely a product of taxing the recording software ....
Ah - OK, that makes sense. In any new design, I'm always aware I could have made a mistake either in the circuit or the drawing. :icon_biggrin:
Quote from: R.G. on June 28, 2010, 11:03:35 PM
Quote from: Cliff Schecht on June 28, 2010, 10:38:55 PM
Looks a lot like my May 2010 submission if you ask me... :D
Hey, neat. I hadn't seen that one, but it's another good illustration of how flexible the Twin T can be.
Agreed! I use them quite often in both personal and professional designs. Simple, cheap and it works well.
Something I really want to start playing with is LC tonestacks in guitar amps. Seems like you could get a lot more range by using three pots in conjunction with LC networks. I haven't played with this at all and it's obviously not an original thought, but it seems like it hasn't been explored much (or at least not well documented). Hrmm..
R.G. I have the perfect enclosure look for your fake guitar signal generator ;)
(http://home.comcast.net/~snmavronis/stratbox.jpg)
Um, well, duzzat come on Lake Placid Blue?
:icon_lol:
Quote from: R.G. on June 30, 2010, 11:54:18 PM
Um, well, duzzat come on Lake Placid Blue?
:icon_lol:
Actually you could do a Strat motif with one of your fabulous wooden enclosures and either paint it that color or add a pickguard with the chrome Strat jack too! It would be a Strat in a box!
8)
Better add a Muzique Pickup Simulator on the output, if you're gonna go that far.
A simple, hopefully not stupid question..is it possible to modify the circuit so the sound frequency is controlled with only one pot?
Thanks! :)
Well, there are 3 capacitors that determine the frequency. You can simulate a variable capacitor, but you're gonna needs about as many parts as the rest of the circuits, and on top of that you'll need a triple-ganged pot to control the 3 capacitors simultaneously.
This oscillator is made to be simple and easily put together - you can only go so far with it. You'll have a better chance starting off with some other circuit, for example something based on the XR2206 or perhaps the harder to obtain ICL8038.
By the way, I made a layout for this oscillator on my layout spree some weeks ago. Gonna post it when I get around to it.
My fake guitar is called an RC-20XL.
> hopefully not stupid question..is it possible to modify the circuit so the sound frequency is controlled with only one pot?
If R.G. had wanted that, with sine-wave output, he would not have used this nice simple oscillator.
It's a real problem for simple audio sources, and I'll have to work it out.
What do you want? If you just want a semi-tone of pitch and only "tone" output, change R3 to like 6K8 plus 5K pot.
Even then, because of how R4 trims the gain to 1.00000...., any change in R1 R2 R3 will want a change in R4's trimmers.
And if you take this idea further, the oscillator will get unhappy, quit or go square.
The "right" way is to change all three capacitors C1 C2 C3 in proportion. You can't get trim-caps this value. You could try switching values, but the C and R interacts so if the ratio of the capacitors changes even a little, you are back to trimming R4 every time you switch.
Not "only one pot", not with this plan.
The real "problem" is to get a Sine with one pot frequency. Most wide-range solutions use two pots on one knob plus an automatic gain trim to keep it oscillating despite minor mis-match between pots.
For many audio workbench uses, a triangle would be just as good, sometimes better,
But not here. R.G. uses self-oscillation and marginal-self-oscillation to get the "Notes" mode. The simple triangle generators don't oscillate like this, they are function generators.
Sure, it is "possible" get just what you want. Let the tone generator run steady, with whatever to control frequency. Use a variable gain scheme to make it loud/soft according to an LFO or whatever shape/rate you want.
But design thought has cost. If we pretend that R.G. worked 10 hours and is worth $10/hour that's $100. He's surely worth much more. Your ideas might take longer to think-up. Would the result save $100 in your time and labor?
A gated square is dead simple, two 555 chips. You may find plans as "555 beeper" or "2-tone siren".
nice bump on this one from 2010...
not something that i need... but i'd make one for sure if there was a pcb layout for it.... ? ;) hopefully it would annoy the neighbours slightly less prototyping...
Thanks PRR for your explanation! I'll search for something more appropriate but I'll also try this circuit on my breadboard ;D
This is cool.
When I get a few of my other projects done (Sometime in the next millennium) I'm gonna build this thing.
Hmm...build 3 to 6 of them and set their freqs. to simulate a chord :)
Wonder if this could be used for breaking in speakers?
my guitar dont sound like this?...if it did i wouldnt be playing it... :icon_mrgreen:
but seriously...this 'replicates' a guitar pluck...?...what a hard whack, with a hard pick?.....or a light finger pluck?....bridge or neck pickup?....humbuckers or single coils?....
sorry for the dumb questions. :-[
The point, I believe, is not to be a guitar synth, but to provide a somewhat controllable "distorted" signal with a simple circuit for basic testing purposes.
I haven't seen this until just now. Cool idea RG. :icon_cool:
Quote from: deadastronaut on June 30, 2011, 07:06:22 AM
my guitar dont sound like this?...if it did i wouldnt be playing it...
Yeah, I know. My guitar does sound like this; it's why I went into electronics. :icon_lol:
Quotebut seriously...this 'replicates' a guitar pluck...?...what a hard whack, with a hard pick?.....or a light finger pluck?....bridge or neck pickup?....humbuckers or single coils?....
Seriously, no. Not like any of those. It doesn't sound much like any real guitar, nor was it intended to. It's just an intermittent oscillator that makes a test signal for seeing whether a pedal/circuit is working kinda correctly without lashing up a guitar, cable, amplifier and *person to pick it*. It's a quick and dirty aid for a test bench.
When I get frustrated with a test setup, I often think "hey, I need a box that does this to help me with the test". The box usually doesn't exist, so I make one.
The problem you're talking about I solved before, in a different way. I have a friend who had a vintage guitar store. The idea was to take a laptop with a sound input into the store and make high quality recordings of vintage guitars with pickups of all kinds at various control settings and picking types. The recordings would be cleaned up and spliced together into really, really dull "songs" of repetitive notes on a CD at inter-consistent levels as a reference signal tool for making pedals. (If I had been able to get this done, I'd probably have pressed CDs and sold them, perhaps through Small Bear, although they'd be pirated instantly and the totals sales would have been about 7 discs. But that's another story.)
I have a personal problem. I can't stop inventing stuff, of all kinds. I literally woke up this morning with a solution to a problem I'm having. I have board fences on the entry way to the property. The fences have posts every ten feet and four boards running laterally between posts at about 1 foot spacing vertically. Over time, the boards split at the places where they're nailed to the posts. Takes a few years, but it eventually happens. So you gotta go nail up and replace boards every 5-6 years. It occurred to me that the problem is that the nails force the wood to split, and once it splits, it gets worse. Drilling a hole for the nail only helps until the weather makes it split there. I woke up with the image in my head of a washer with a hole for the nail, but with teeth bent down around the edges. You put the nail in the washer, then nail it in, teeth to the board side. The teeth are arranged to dig in about 1/3 of the board's depth and force the board back toward the nail. This prevents most splits, and reinforces any that do happen to prevent the board from falling off until it's really, really bad.
R.G. maybe you could use a tee-nut? Drill a clearance hole for the center part and then hammer the tee nut into the board from the front and nail the board tee nut(s) assembly to the post thought the hole.
http://en.wikipedia.org/wiki/T-nut
Quote from: R.G. on June 30, 2011, 11:06:49 AM
If I had been able to get this done, I'd probably have pressed CDs and sold them, perhaps through Small Bear, although they'd be pirated instantly and the totals sales would have been about 7 discs. But that's another story.
Yep, I'd probably burn one ;) T.
Quote from: Gus on June 30, 2011, 11:59:13 AM
R.G. maybe you could use a tee-nut? Drill a clearance hole for the center part and then hammer the tee nut into the board from the front and nail the board tee nut(s) assembly to the post thought the hole.
Yeah, a second after I visualized a spiked washer, a T-nut came to mind. T-nuts have two big issues. First, building fences in Texas heat with a drill in hand is a true PITA. Second, all the T nuts I've seen have three prongs. You really want four, two on each side of the central hole, and not one of the three reinforcing the tendency to split with the central hole. I was after the ability of the toothed washer to bite into and actually reinforce the board toward the central nail hole by slightly angling the prongs outward. Driving them in forces the wood toward the central hole.
I may have to see if there's a shop that will make a die for me.
May be more trouble than washers, but how about using bigs$$ staples above and below each nail. With a decent staple gun, it should go pretty quickly, which of course is the key in the Texas sun.
Just a little bump to this thread :icon_mrgreen:
But this is a real challenging DIY ... http://player.vimeo.com/video/36981447?title=0&byline=0&portrait=0 (http://player.vimeo.com/video/36981447?title=0&byline=0&portrait=0)
enjoy it :icon_mrgreen:
Quote from: ayayay! on June 23, 2011, 11:14:14 AM
My fake guitar is called an RC-20XL.
Mine is named Jamman delay.
CHAD
Probably deserves a PCB layout - unchecked .
(http://i492.photobucket.com/albums/rr283/DarkShadower/Fakeguitaroscillator.png)
this circuit is one of the most useful tools i've ever owned ( let alone built ) ... with the oscillator hooked up to a circuit, it frees up your hands to do testing/reading voltages/etc .... i use it just about every time i get a build ready for testing ...
What I need is not a fake guitar, but rather a fake guitarist.
Quote from: ORK on February 24, 2012, 02:45:13 AM
What I need is not a fake guitar, but rather a fake guitarist.
Kewl! I've been told many times that I'm a fake guitarist. :icon_lol:
I use my MP3 player for testing. I recorded a guitar part and looped it over and over for about 5 minutes. Works great and gives me a better idea of what the pedal sounds like. I feed the pedal into an amp. I guess I'm just re-amping...
i'm hanging out to hear a sound clip of how this sounds!
i can't imagine it having all the richness of a real guitar (harmonics, or a power chord etc.), so it might not suite me for wanting to prototype distortions/fuzzes but it sounds excellent to add to the test rig!
maybe a magician could make a few oscillators which then modulate, so there's a wider frequency range to test. not complaining, this is some awesome work which has kindly been made free (:
So, I'm lost. What does this thing do? How does it sounds?
Quote from: slideman82 on February 24, 2012, 11:32:47 PM
So, I'm lost. What does this thing do? How does it sounds?
maybe i'm wrong. it was my impression it generates a tone and then fades it away and repeats, like a guitar string being plucked over and over. it might not actually sound like it but for testing purposes it would be more useful to see how the circuit respond to a decaying signal than a simple pure sine wave.
Quote from: slideman82 on February 24, 2012, 11:32:47 PM
So, I'm lost. What does this thing do? How does it sounds?
There are sound clips on both pages one
and two of this thread......
Quote from: danielzink on February 25, 2012, 12:09:58 AM
There are sound clips on both pages one and two of this thread......
thanks. there i was hanging out. it's been a while since the thread was last bumped. sounds pretty useful in the seconds clip (page 2).
now will we make effects for the fake guitar and build them in? hehe
All this while i just use my friend's cover of my favourite song .
http://soundcloud.com/djdestiny-2/bc-cover-by-syn-humbucker-mode (http://soundcloud.com/djdestiny-2/bc-cover-by-syn-humbucker-mode)
First of Thank you R.G. for providing this info for online use, it is a great Idea and will be a great addition to my bench!
I am attempting to sandwich this idea with the beavis board. Basically take out the spst of the beavis board and add another 1/4 jack and a 2 switches. Switch one To bridge terminal in/outs if I am using an already built effects pedal instead of breadboard and the other to turn the oscillator off/on if I want to test an instrument instead. The jack would be amp out and guitar in(effect in if using oscillator) but the third jack would be oscillator out(to effect in) and lastly, turn one of the terminals into an oscillator out for the breadboard. This way I can test built pedals and breadboard projects.
Anyway, I am about 80 percent of the way done with the wiring of the box. I saw the PCB image of the wiring layout by Dave, btw thanks man! I am still perplexed about wiring this thing up. I looked at the vero layout and compared it with R.G.'s Schematic. I figured out as much as the wiper on the volume would be the output. I was confused about how to hook up the length and speed pots. At first I was thinking I had to do something from the switch sort of like Dave did. However, looking at his layout raises more questions. I see he has Tone and Note Lengths, but no speed pot? From R.G.'s Schematic I would presume that dave used a standard pot instead of a trimmer for the notes? Ok but is this the correct way to wire these pots up? or is this a good alternative?
I am not very keen at tracing a layout from a schematic, I am getting better. From RG's schematic I could gather that 3 and 2 of the Length pot would be hooked together but from the vero layout there is no specifics on how to wire the switch/pots. Sure, I see "1 a, lug 2" etc, but it left me hanging with which lugs on the pots and also whether or not the lug 1b or 3a got any attention.
I saw R.G. say he was gonna post a layout, did I read that correctly? I feel so ignorant, many people have built this it seems but I seem to be the only one confused? :icon_redface: :icon_lol:
Can someone shed some light on this? when my 3pdt toggles come In I am ready to hook this baby up.
Quote from: jwmallett on May 13, 2012, 02:19:46 PM
First of Thank you R.G. for providing this info for online use, it is a great Idea and will be a great addition to my bench!
You're welcome. Glad to help.
QuoteI figured out as much as the wiper on the volume would be the output.
Yep, correct.
QuoteI was confused about how to hook up the length and speed pots. At first I was thinking I had to do something from the switch sort of like Dave did. However, looking at his layout raises more questions. I see he has Tone and Note Lengths, but no speed pot?
I really should have explained that more I guess. It's kind of cryptic.
The section of IC1 with R1/2/3 and C1/2/3 on it is a sine wave oscillator with a fixed frequency. R1/2/3 and C1/2/3 set the frequency. It is a characteristic of this kind of oscillator that it has to have a very, very specific gain to oscillate without distortion. If the gain is too high, it distorts and is no longer a pure (-iish!) sine wave. If the gain is too low, it will start to oscillate at turn on, or at any disturbance, but it doesn't quite have enough feedback to keep itself going. If the gain is ***perfect*** it oscillates with a pure sine wave.
R4 plus either the "length" control or TR1, depending on where the switch is set, let you adjust the amount of feedback. The idea is that if you flip it to "Tone", by which I meant "steady, non varying tone" and finely adjust TR1, you can get a nearly pure sine wave out. The reason a sine wave is useful is that your ear can hear the difference between a sine wave and a few percent of distortion. TR1 lets you get a steady test tone.
If you flip the switch to "Length", you can adjust the amount of feedback so that when the circuit is disturbed by the "disturber" part of the circuit, the tone starts up, but dies away. The length pot lets you set this so it takes a goodly fraction of a second to die away, faking the sudden start, then trailing off of a guitar string being plucked. It's the electronic analog of pulling a pendulum away from rest, then letting it go, and coincidentally of plucking a taut string. You can, of course, set "Length" and TR1 both to do either always-on oscillation or dies-away notes. They do the same thing electronically. The difference is just how they're set and which one you put on the front panel.
Both pots cause longer ringing, getting into steady tones, at the biggest resistance. The little dot on the pot in the schematic is the clockwise-most terminal. When you turn the shaft full clockwise, it's closest to the dotted terminal. What that tells you is that the schematic intended for the pots to be hooked up so maximum clockwise rotation was biggest resistance. The connection from wiper to dotted/CW terminal is optional. You could leave off the connection to the dotted terminal of these pots and just connect the counterclockwise terminal and the wiper, ignoring the clockwise terminal, and the thing would work the same.
QuoteFrom R.G.'s Schematic I would presume that dave used a standard pot instead of a trimmer for the notes? Ok but is this the correct way to wire these pots up? or is this a good alternative?
"Notes" means "you get repetitive notes that die away" instead of a steady tone. "Tone" means "you get a steady tone that doesn't die away".
QuoteI saw R.G. say he was gonna post a layout, did I read that correctly? I feel so ignorant, many people have built this it seems but I seem to be the only one confused?
No more confused than I am. I had to go back and read what I wrote. By the way, you did make me find a mistake I put in there. The Speed pot is shown wired backwards. As it is, it gets slower as you turn the knob toward CW. The wire from wiper to CW/dotted terminal should go to the non-dotted/ CCW terminal instead, so the resistance goes down as you turn it clockwise.
For this one, the simple thing to do is get your pots, based on how you want the mechanics to look, and for the pots that probably means a front panel knob for speed, and maybe for length. I would use a trimmer for TR1, myself, but nothing says it can't be a front panel knob too. It's just that I didn't see adjusting it very often. When you get the pots, get out your meter, set to ohms, and connect one lead to the wiper. Hook the other lead to one of the outer lugs, then turn the shaft clockwise. If the resistance goes to nearly zero, that's the clockwise/dotted outer lug you're on. If it goes to the full nominal pot value, it's the non-dotted/CCW terminal. If it doesn't change, you guessed wrong about the wiper pin and have the meter on the CW and CCW pins.
Wow, your response was more in depth than I ever expected. I tend to want to know how things tick and why they do what they do and will spend LOTS of time trying to work it out in my mind. Although, many see this as a disadvantage and wastes precious time getting things done and just "accepting" the rules and move forward. I cannot completely disagree with them, but this is how I am. Anyway, Thank you for that!
I still struggle with all the different ways to draw schematics etc. I started to draw a vero from your schematic, but then I found "stringsnthings" vero all nice and neat, checked a few placements and thought. Why finish tracing your schematic if one is already done? So I printed his:
(http://i703.photobucket.com/albums/ww40/luckyfeline7/Test%20Circuits/FakeGuitarOscillator11.gif)
Perhaps, this was my downfall. Because the wires do not quite match up with the schematic. I have a better understanding about the dot to clockwise and will admit that the speed did look backwards to me, which being new at tracing schematics, confused me.
I assume a DPDT switch a one side b the other with 1 2 3 being the same on each side so that isn't a big deal. Looking at dave's drawing, there is no speed, but in your schematic and on this vero, there clearly is a speed knob. There is no indication on this vero that pots are hooked up to or from the switch. As I said I figured volume out by looking at your schematic. Speed is self explanatory on the vero. Length on the other hand, only shows Lug one being connected. Looking at your schematic and realizing that speed IS backwards, I now gather by connecting the Length 1 wire to the proper lug on the pot allows flow from the Length pot to the TR1 Trimmer. So the next question is where is 2 and 3 on this vero to connect from the board to the pot for continuity? Using Dave's Image:
(http://i492.photobucket.com/albums/rr283/DarkShadower/Fakeguitaroscillator.png)
At first glance clears it up, but then confuses me since clearly he is using single channel I.C's and to top it off, no speed pot. I realize there are so many different ways to wire circuits up that will achieve the same goal, but for a newb like me who likes to think things through while doing it, the lack of experience AND deciding to use 3 different methods to piece it together was not the wisest approach for me. I am not complaining or saying it SHOULD have been provided, but I was wondering if I missed a gutshot picture or wiring diagram from the vero or even the original schematic. If not, good, :icon_redface: I feel better I didn't do all this cause of haste or lack of research. I want to learn things on my own, but when I get stuck I know it is better to ask for help and I don't always explain myself thoroughly and I am sure it is so simple for some of you that you wouldn't assume a particular something is all I need. This is a learning experience for me and I appreciate you all making this available online so people like me can learn this in our own time. I want to be able to transpose a schematic into a layout. Perhaps I should have just finished my trace and went with it first, who knows, might have been the same amount of head banging ;). I also, know that creating layouts can be like fingerprints and it is that, which I have learned from this instance, what NOT to do hastily :icon_lol:. I think when I complete this one, I will build take the lessons learned and trace my own and see what I come up with. At this point, I am pretty confident that building stringsnthings vero will work, hook speed up the way it shows and where it says (Notes) attach that to lug one on my pot then lug 2 and 3 on the same pot would lead to switch 1a lug 3? Although there is a Length 1 on the vero already, which I just remembered, so just attach the wire that says (Notes) to the switch like it says, then on the Note Length pot, hook lugs 2,3 to 1a lug 3?? Thanks for any help.
Ok It was 1a lug 3 and I got it working. Thanks for all of your input! Many of the concepts I had forgotten since the last build I know have a better grasp on, and I have learned a lot on this one. I have built about five or six pedals so far and each one has given me lots of trouble! The 3 band parametric EQ actually gave me the least and was the most complex, go figure! ::) Still want to play with the Tone length and get it longer, as in before I turn speed up to the point where it sounds like a space radio dialing In to my station :icon_lol: .
A couple of things I have noticed and would like to know if this is normal, My switch is a DPDT (on off on) When I am switched to tone, it is signifigantly lower than the Notes and the decay seems a bit longer, but BARELY noticeable AND when I switch the position to off it is a solid tone like when a tv station goes offline, which seems normal. Also, the decay on notes is noticeable but it does off quick, I remember seeing something about that and I will go back and read if there was a solution to give a little more decay, but that really isn't necessary and I guess at this point the time put in would be for learning experience. My box is pretty crammed and I'm using sharpies at the moment to label stuff, but Ill post a pic of my beavis/fake oscillator smashup once I'm done tinkering, and maybe post my findings.
All in all pretty cool gadget and it is setup with a switch to allow guitar in jack to be on or switched to osc injected instead, then I have a dedicated OSC out jack (for effects already jacked up (pun intended :icon_lol: ) that would then go to my mini fender tone master amp. There is also an amp out jack. Basically if the LED is on, then that means the signal routes to the Terminal block, for breadboarding, then to the amp out socket, when it is off, it goes straight to the amp out and I can choose whether I want the FGO or guitar as an input, which means the FGO out may be redundant and I have two terminal blocks leftover since I decided against the built in switch that the beavis board layout suggests. Maybe I can make a saucer shaped box and paint it like a ufo and put FGO on it (with included space radio modulator) and submit it for the contest! or maybe not, it's probably over anyway. I'm too lazy to go look before I post. Peace
I have finished boxing up my beavis board with FGO inside. I am sure it will come in very handy. I know this is elementary to most of you, but my comment earlier on increasing the length, would not be possible, I think, by adding resistance, because less resistance means longer lengths, therefore I cannot just do this via a pot, perhaps there is another way besides using all gold/silver components :o Also, I have no idea on increasing decay, but as I said, it isn't a big deal, so I guess it is time for me to move back to my Echo Base Delay and figure out which component isn't soldered right. And Thanks to RG and BeavisAudio, this will make my troubleshooting ALOT easier!
BTW for those of you who haven't read about the Helping hand +++ instructable(instructables.com) I basically bought a black and decker workbench vise on ebay and figured out tapping the plastic holes on the brackets that hold the boards onto the table with a 3/8-24thread tap you can screw in the connector directly onto this table, a little modified micro or mini irwin quick clamp and you now have a little (and portable) Bench to use the grip to hold your box and the vise to hold boards. This makes it so much easier to remove components and works WAY better than a standard helping hand since it is much heavier and versatile.
Ok, I said I would post some pics and I know my wiring schemes aren't the tidiest, or the whole build for that matter :icon_biggrin: so here they are:
http://www.facebook.com/media/set/?set=a.3801130118388.148490.1581372303&type=3&l=9b0236078a
One day I will brush up on my gimp2.0 skills and create some stick on decals, but this will do for now.
Threw together a 2-sided PCB for this one, 2" by 2" size with on-board 16mm alpha pots, switch, LED. Works surprisingly well in virtual simulation. If there's interest I might order a batch and sell them to members.
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/th_guitaremulatorschematic.png) (http://smg.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/?action=view¤t=guitaremulatorschematic.png) (http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/th_board.png) (http://smg.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/?action=view¤t=board.png) (http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/th_3dboard.png) (http://smg.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/?action=view¤t=3dboard.png)
That's amazing, and will seriously solve my issue with cables being too heavy and making the whole board fall down, break wires and whatnot...
I've been planning in doing something like that... but I always though of building a small synth. I have the schem some where in a old book (have to look for it), if I recall it correctly it as also a vibrato option that could be changed to a slow decay.
(edit)
Here it is (http://www.diale.org/img/smallsynth.png); the text is in Portuguese and it is a translation from the French edition of "Les gadgets electroniques" by B. Fighiera 2ed.
The oscillator part uses two BC108 and the vibrato a BC109. The values of the resistances allows a range of one octave.
Hi guys - resurrecting this old thread as it is directly linked to my build of this great little circuit! Hoping you guys (especially R G Keen?!) are still around to point me in the right direction with this one!
I have pretty much finished the unit, but am having a couple of issues:
1. When on the constant (tone) setting, the disrupter part of the circuit is still audible - if I turn the speed pot I can hear the clicks speed up. I'm thinking that this shouldn't be possible since the switch should break the second half of the IC circuit?
2. The constant setting is also quieter than when on the 'note' setting....this may be related to issue 1?
I have visually checked all the veroboard connections for continuity and cleaned the gaps between the tracks to ensure there's no solder shorting out the tracks. I've also double and triple checked all switch and pot connections and tallied them up with the original schematic that R.G.Keen posted (I followed the v1.1 strip board layout when building and referred to the schematic for double checking).
If anyone could offer any advice I would be very grateful - this is one of my first builds aside from FX pedal kits and so I am on a steep learning curve at the moment!
Thanks,
Steve
Welcome.
> disrupter part of the circuit is still audible
Are your C7 C8 *good*?? Large value, proper solder, short ground path?
The oscillator is rather violent. R.G. took care to isolate power and reference so it would not bleed.
With Out Thinking: looks like the unused terminal of SW1 could be grounded to give a small added filtering. Or it may foul something? I don't see how it could smoke.
Thanks for the reply PRR.
C7 / C8 are both fine, correct values, soldered following the vero layout, checked continuity with a meter.
It just occurred to me that I have housed this in a plastic lunchbox for now (all that was to hand!) - could there be any grounding issues here? i.e does the case being physically connected to the pots provide some kind of grounding improvement? I don't know much about best practices for grounding points in circuits...!
Also I just noticed that the TR1 trimmer has to be pretty far to the end of its travel for oscillation to begin, and I don't get into audible distortion territory, something that from reading RG's posts should be possible even though undesirable?
Thanks!