Leyland Pedals Ultra Simple Tremolo layout and some questions...

[moid]

Now why didn't I think of that (no, don't tell me, I know I'm special - my teacher said so!)

the circuit in all its glory


Close up (with heavy depth of field for you cinematography fans!)


Underside


transistor 2n5089 - the circuit was plugged into a 9V DC plug from mains (no battery) and nothing was plugged into the audio jacks.
Collector 1.256V DC
Base 1.743V DC
Emitter 1.255V DC

Thanks yer duckness!

[duck_arse]

gaze, moidy, if you would, upon your last posted circuit diagram. see! the emitter of that circuit connects to ground, or a capacitor, so will show 0V at all times. no, really, stay with me ..... also see the base connected to - no DC volts, cause of old mate "cap1" and the resistors to ground. and as for the collector, the 10nF connected to blocks DC from the opamp end, and that only leaves the input resistor/s, one of which pulls to old mate ground, and the other which connects to signal, which we all know carries no DC offset.

so. something isn't wired as your circuit shows, and is loading that transistor with all sorts of DC, turning it on and eating yer signal. switch power OFF, pull the transistor from the socket, meter with yer meter set to ohms from each socket pin to places like V+, ground, signal in resistors, the opamp pin 3, etc. then work  out where the badness is. enjoy.



I think your layout has errors. the transistor appears to be one row low, the collector is connected hard-to the input, and not to the 10nF to the oppie. PERHAPS - cut that link at top of 5, and link it to D instead. I stopped looking then, there might be more.

[duck_arse]

the perils of veroboard - nobody wants to look at it, so errors go un-scruted.

we might be able to save it. lift out the 10k at 9C-9F. make a cut at 14C. add the 10k across that cut, 11C-15C. add a fly link from 16C back to 9F [pin 2]. that should correct your boost woes. you could/should also add a stop resistor for the boost pot, it could go on B [with cut!], alongside the 10k you just moved.

your speed pot lower wire showing on your layout - I think that pink wire should go to the bottom row where the 2 10uF caps join the 220k. you'll be amused to hear that the speed pot should also have a stopper R.

and if that don't get it running, whell, I dunno.

[moid]

Wow, thank you so much Duck! I've been stuck back at work this week alas, I will try to look at this tomorrow after some sleep and draw a new picture for you to cast your gaze over.

[moid]

Sorry about the slow reply, I had to cover for a colleague today at a graduation ceremony and spent the weekend learning how to pronounce a variety of complex student names so I could call them out in front of them and their parents... 800 of them... that was a very nerve wracking morning! I think I only made two slight mis-pronunciations (Lithuanian and Polish are not easy ones for surnames!)

Anyway I think I have understood all you said and made a pretty picture of it:



The new cuts are in bright yellow so I remember to make them myself later (and so you can see if I put them in the right place). I used 10K for stop resistors; is that correct? I think you said to use that on another circuit, but maybe that isn't the right value for this circuit? I've written stop 10K on them. The one on the speed pot, well unless I had it hanging off the board (which I knew would provoke rumblings of discontent from the good members of this board), the only thing I could think of was to stand it on end (yes I know you don't like that either, sorry; I reckoned that was less of a sin than hanging the resistor off the board... think of it as cordwood with a kink ) - and then attach the pink cable to the next row up (as you can see in the picture). Is that a good / bad idea? I could stick the resistor off the board or straight on the wiper of the pot and connect that to the board if you prefer?

If the above looks good, let me know and I'll start de-soldering and re-soldering.

Thanks for your noble efforts at trying to bend veroboard around your head. It might cheer you up to know that I've bought a small sheet of perfboard, if I get some time around Christmas I might try to build something simple on it and see if I can actually make that work (I've always failed at perfboard in the past), but if I screwed that up at least it might be less of a misery for people like your goodself to debug what I did wrong?

[duck_arse]

see if this makes sense. I think it correct, based on V0.6.

[later :] reading antonis has just reminded me - stop resistors. you need to pick the value to suit the app, really. in the boost section, with the pot at 0, the stop will set the gain w/ the 10k to CAP4. so unity w/ a 10k stopper, but you could have a little reduction available, just in case. maybe 5k6 or so?

as for the oscillator - sets the highest freq available with that cap value. I dunno how fast it runs, but the 10% rule can be applied, use 1k. if the osc conks out at high speed, you need a bigger stop R.

[moid]

Thanks very much Duck and Antonis. I redrew things:



Is that right? I was a little unsure which resistor was the 5K6 one (of what was two 10K ones lying horizontal above each other at the top of the board) so have I put that the wrong way round?

I think everything else is right now

Who's Al? And why is he so hungry?

[antonis]

Thanks very much Duck and Antonis.

You're welcome but I didn't have the slightest contribution in the present thread..

[duck_arse]

I was hoping antonis would point out that the boost stage is a non-inverting config, and as such never gets below unity gain. it's in the numbers. so - you can probably get away without a stop in the gain pot - or just make it 1k, keep it to cover that ugly cut you made. and yes, you picked the wrong one to make 5k6, it should be the other one.

I hope it's right - I don't want to look any more. ultra simple my screen name.

[moid]

You're welcome but I didn't have the slightest contribution in the present thread..

In that case you should see yourself as a 'spiritual advisor' to the thread

Thanks to Duck again - a new picture; this should be fine and I will try to rebuild this board this weekend - all your final suggestions should be here

[Elijah-Baley]

Good job!
I'm very interesting in a small tremolo circuit. This is not so small, anymore, but I understand that some parts are useful or necessary.
Let us to know your progress.

[duck_arse]

no sir! your 5k6 should be the "1k value doesn't really matter", and your 1k should be the 10k in the gain leg with the 10uF cap.


go the swans.

[moid]

Thanks Duck - hopefully this is all happy now

[moid]

Some success! After changing all your suggestions Duck we have a tremolo! On the normal setting (not low pass filter) this is a very hard edged square wave tremolo. It's rather fast - the slowest speed is 3hz, rising to a near ring modulation at 25Hz (which is quite interesting, I've never owned a tremolo that could go that fast!). It would be nice if it could go slower, but that's probably not possible without changing something vital I guess? I presume making this do a triangle or sine wave would require a completely different circuit?

The boost works too, at minimum setting I get unity, and maximum is louder (my guess is 6 -10dB more?). It's fine.

Where things aren't working as planned - as soon as I switch to either of the low pass filter modes the speed rate makes a constant low pitch thumping sound... and there doesn't seem to be any filtering at all, maybe very slightly less bright than the normal setting, but nothing more than that - it's subtle if it is doing anything, but it might just be hidden by the thumping sound. The boost makes the thumping much worse if I turn that up. Any guesses what to do next? If the pedal can't cope with a low pass it's not the end of the world; I haven't drilled the enclosure yet, I can just hide the switch inside! Thanks!

[duck_arse]

the one you call "cap 2" izz the timing cap. add to it in parallel, another 10uF for a start, will get you slower. also, a larger value for the speed pot = 47k or 50k or 100k, will slow proceedings and give more range.

the 10nF cap from pin 5 tp pin 7 on the oscillator is there to slow the edges of the oscillator some. you might try adding larger value there, again in parallel, but not 10uF this time. and it might lessen the squarity of the chop. at some value of added cap, the oscillator will stop.

as for your thump-a-matic switch - see Rob's comments earlier in thread.

[moid]

the one you call "cap 2" izz the timing cap. add to it in parallel, another 10uF for a start, will get you slower. also, a larger value for the speed pot = 47k or 50k or 100k, will slow proceedings and give more range.

Aha thanks Duck - I could (maybe) squeeze another cap into the board, by doing some hacky things with an SPST to bring the extra capacitor in parallel with the 10uF. If I change the Speed pot to a higher value I won't be able to get the really fast audio rate tremolo anymore though will I? I think a cap on a switch might be more what I want - I want to be able to go that fast because no tremolo I own can do that, but it's also nice if the tremolo is capable of slower speeds if I want them.

the 10nF cap from pin 5 tp pin 7 on the oscillator is there to slow the edges of the oscillator some. you might try adding larger value there, again in parallel, but not 10uF this time. and it might lessen the squarity of the chop. at some value of added cap, the oscillator will stop.

OK, this is somewhere where a SPST switch and some abuse of where a cap goes might be possible - I could try experimenting with different values and seeing what happens - I presume as the capacitor value goes up, the steep sides of the tremolo effect become more sloping, but at a certain point the slopes become too shallow and begin to remove almost all the audio?

as for your thump-a-matic switch - see Rob's comments earlier in thread.

I will try to understand Rob's comments again - I think I will need to draw something to ask if I understand them though, because I can think of two ways of interpreting what he's written, and I'm not sure which is right! I will make a schematic diagram and post it soon.

One other thought - if I was to remove the switch for the two different low pass filter options (so on my vero board G1 and J1 were just connected with a short cable) I would just have the 'normal' tremolo effect. Would it be a bad idea to make a tiny daughter board with an RC Filter on it and place it between the Audio Out of the board and the 3PDT switch? Would that remove the issue that Rob was talking about with DC going into the audio path? If it does, I got very excited to think that I could make a small vero circuit with a low pass filter and a high pass filter on it and hopefully use your ON off ON SPDT trick to cycle between normal tremolo and high pass or low pass versions. Good idea or baaaaad idea? As Lou Reed once put it, "the possiblities are endless, and for me to miss one, would seem to be groundless"... which could well be the root of my problems

[duck_arse]

If the emitter was grounded and the caps switched on the collector side I expect it would greatly reduce the ticking.  In fact for the non-low-pass case you might benefit by adding a largish cap so there's always a cap on the collector.

try this, easy peasy. [some typing follows] pull the link at 5E-5D. pull the 80nF cap at 5G-5J and fit it across 5E-5F [up, back, links and cuts, whatever]. this puts a "big" cap in the collector line.

then you need to shift your cap switch, and the 100nF, so they switch across that 80nF at the collector instead - no connections to ground on the switched parts now. I tried to suss the movements, but it did for me, no parts refs combined with vero. circuit redraw needed.


as for speed - yes sir, no sir! the fast speed corresponds to the low resistance setting allowing your timing cap to charge and discharge at a greater rate. you can make your speed pot megohms and it won't affect the fast rate, cause the low end is limited only by your famous stop resistor. so a slower rate cap on a switch is the way to go. [too big a speed pot will make fast setting very very hairy, all squashed into a little rotation.]

as for shape, you're stuck with it. it might improve with the caps shifted to the collector, but that's doubtful. as for the 10nF slow-down cap across the opamp, that's not for putting on a switch. try adding 10nF or 22nF or so, see if it makes any change to the sweep. again, probably knott, but werth a tri. somebody mentioned the phase shift oscillator early on [might have been the twin-tee instead], that's the best method of getting simple sine into a trem. but probably the transistor shunt method of trem will limit the goodness of shape, no matter what drives it.

[moid]

Edited this a bit, not sure if that makes it easier or worse for comprehension... sorry if it's gibberish, will try to get some sleep tonight and hope to be more compos mentis tomorrow!

Hi Duck Sorry about the slow reply, all my students turn up next week and things are getting very hectic... students, thousands of 'em!

Thanks for your ideas and guidance! I've tried to redraw them, I'm very confused about a couple of parts though.



The changes to the cap switch - it looks to me that I only need an SPST for this switch now? edit: I bet that's an SPDT isn't it? So there are only two modes - normal and low pass tremolo (I can live with that, I couldn't figure out where a third cap would go now or how it would attach to the board!). Will I need to make a cut somehow between the transistor Base and the 80nF cap - between 5F and 4F? And shouldn't that 80nF be attached to D5, not E5? So that it connects to the 10K from audio in?

I moved the 100nF so it is positioned diagonally (sorry!) and put a cut at 5C so it doesn't cause any problems elsewhere. I moved the cap switch cables to 1C and 1E, so that if the switch is now SPST, in one switch direction the capacitor is not added to the audio line, and in the other it runs in series with the 80nF... now that looks odd to me...I can't figure out if that works or not. Hmmm that switch should be SPDT shouldn't it?

Regarding the addition of a speed switch, does the SPST on the right side of the layout look right? I'll solder cables to the legs of the cap that is on the board and then add in an additional 10uF via the switch. Damn I just realised that SPST should be labelled SPDT... I do wish I'd had more sleep last night.

Thanks for your patience, I'm sorry to be such a drag... badly running out of time now and will soon have to give up building stuff until Christmas

[duck_arse]

like this. still centre off, spdt. as for the osc slower, you only need single pole single throw - but use a single pole double throw anyway, cause you've got those. my eyes are grinding, so I'll leave the circuit to vero translation to ..... well, anyone.

cap stays away from the base, don't be cutting there. no sleep till xmas.