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

[Eb7+9]

Wow thanks very much for all that research! I will have to admit to you now that simple person that I am, I don't understand most of what you're telling me (sorry, you are dealing with someone who went to art college... so there are vast chunks of education that would now be useful to me that I have never encountered). If you do like Duck does, and talk s l o w l y and carefully to me as if I'm a small child (and occasionally show me shiny things to keep me excited!) then sometimes I understand stuff:)

no problem - you can always ask if something is not clear

so, to recap we can look at the LFO side of things alone first ... the bipolar transistor can be ignored

namely how the resistance level on the outside (you could call it a load I guess) affects the voltage waveform appearing there

www.lynx.net/~jc/uA741-LAYLAND-LFO-LOADING.png

here we can see that loaded by 5k we get a choppy output waveform that is not strong enough to turn on the transistor later when we put it back in ... conversely, a 50k output load permits a waveform that almost makes it to one full volt - beyond what we need to turn on a bipolar transistor - hence the idea of sticking a pot in that circuit later

to be clear again, I'm lumping all resistors in the side circuit (including pot) into one total load resistor and seeing how the total affects the output ... all resistors in that branch form a voltage divider, thus scaling what's available at the top end

I do appreciate you are showing a revised version of the circuit that presumably can vary the LFO from square to triangle, and get a deeper, more choppy tremolo effect (those would both be cool). I think I would need to build this as a separate circuit; the vero of the current one is looking very battered and I'm worried it will disintegrate if I desolder anything else! If I drew a vero layout of how I interpret your schematic would you be able to see if that looks plausible and then I could try to build it? If I could add in a switch to cut high frequencies like I have on the above circuit then that would be cool (presumably that would go between R7 and the transistor?). I don't mind if I can't add the fuzz, that's for my son - he likes louder effects than me - if I get that working on the original circuit then he can have that one! Regarding your schematic, I have a few questions to make sure I understand it.

just be careful not to expect too much from this circuit ... as it is (stock) it's potentially a pretty choppy trem I would say
I just want to see if we can round things up a little

on the down-side the DEPTH control is meant to be close to full on (you'll see why when you breadboard it)
and it's meant to be placed right in front of your amp (usually)

producing an attenuating-only type of response // sort of like the Fender Blackface/Silverface photo-cell trems

Vin and Vout - this is the audio in and out of the circuit?

yup, it doesn't get any simpler than this ... a voltage divider, no caps = as close to noiseless as one could ever get in active electronics

my interest in this circuit is to see if we can keep it that way


tho, I know ... the temptation to provide make-up gain is there


the idea here is that providing back-bias will generate 100% output at its peak and a more (less choppy) rounded trem response
possibly a less choppy alternative to what it can do now

then, the idea is to afterwards compensate for overall perceived volume loss with the amp volume since it's a volume-reduce only circuit
again, the goal here is to try to get back as close to 100% output in the cycling so amp volume compensation is kept minimal

but let's see what you think ... I'm just guessing thru a circuit simulator named TINA

Cv - Not sure what this is? I've heard of Control Voltage but I thought that was for modular synths? So I presume it means something else? Sorry I don't know this one... I don't have a modular synth.

Cv in the modular world are typically buffered voltage sources designed to export control signals to other modules, etc ...

many guitar pedals have their own inner Control Voltages or Currents - not really meant to be exported outside to other pedals like synth modules might

a compressor and tremolo might use the same VCA or something but both have differently behaving inner Cv's (or Cc's)

in the case of this circuit, I'm defining the Cv  as the Control Voltage seen at the Base terminal of the bipolar transistor relative to ground
sorry, shoulda been more clear

btw, I mention it so you all can understand the time plots a little better // ie., see where the threshold needs to be broached

Are all the pots Lin or Log? I think I've got Lins of all those types, not sure about Logs though.

doesn't matter that much, Linear should do

Can I use a different Op-Amp? I don't have any TL071's. I have TL072, TL062, TL082, TL084 and TL074. I asume so, I just wouldn't be using the second op amp in those chips?

oh, yeah ... sorry

any op-amp should be good I'm guessing
try a uA741 if you have one ... OPA134 if you have expensive taste

same with the transistor and diode ... use what you got
it should work generally, no tight parameters here to observe

Thanks very much

good luck ...!

[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.

Don;t worry, I can still snatch defeat from the jaws of victory... the two settings that control which capacitor is used to remove high frequencies sound identical...  I tried a wide variety of different cap sizes in the place of C4-D4 from 1nF to 470nF and there was no change. The tremolo is different to the middle position of the switch, so there are definitely two variations in this effect, but I cannot get the third option to happen.

see, now, this is why we want to see everything, all the time. if you look the snippet above, 80nF is your main man, all the time. switch one way shorts him, and you say that possie works, as does middle. other position adds 100nF to 80nF, so if you change the 100nF for smaller, the 80 dominates. maybe put back the 100nF, and swap in 10nF or so for the 80nF instead. then your 10 is the main man, and you add-in 100, so youse gets a bigg yumpp.

with a small tremming cap, you should get something like a shimmer instead of a great deep whumping trem.


peep peep peep - you might try fitting a 1nF cap across pins 1 and 2 of the boost opamp.

[moid]

Hello chaps! Some changes / some successes / less failures

Firstly Eb7+9 - I will try to breadboard your circuit soon, but my breadboard is currently full of a problem LDR circuit that I need to post on the forum. I will get there! So regarding the CV part of the schematic that is just a trace / wire to ground from the base of the transistor (I thought it might be a component I needed to add). I will no doubt ask more questions soon.

Mister Duck! Once again your advice is manna from heaven and soothing to the deep oscillating thump that is my heart / circuit! So I made some changes based on your wisdom and have the following to report:

I soldered a 1nF across pins 1 and 2 of the op amp and that made the peep quieter.... but still pretty loud. So I thought, aha, a bigger cap will help! 2.2nF was quieter still but still quite noticeable, and the peep lowered it's pitch a fair bit. 3.3nF was much better - a faint thumping pulse now. 10nF got rid of any artefacts, but the downside was that when the fuzz mode was active it tamed it into a gentle overdrive... in the end my son and I played the circuit at different setings and we thought 3.3nF did the least damage to the fuzz whilst removing the majority of the thump noise. We also discovered that his guitar generates a lot less thump than mine does (his is a Squire strat, mine is a very cheap Cort guitar) so some of the problem is guitar based - my guitar has a dodgy volume pot that I keep meaning to fix... someday... I mean it makes sounds, what more do you need from a guitar? And everyone plays their guitar on volume 7-9, don't they? The other numbers are either too quiet to play with or in my case generate a Sonic Youth style random stutter kill switch effect... so mostly I play on 9. Loud enough to hear the sounds

Now when I say 3.3nF, that's not exactly what I have on the circuit. First of all I had to desolder a cable on the row for pin 2 and ram one leg of the 1nF in that hole with the cable and put the other leg of the cap into the same row as pin 1, and all this desoldering is causing the underside of the vero board to go black in places, which I know from long experience of screwing stuff up experimenting with circuits means that some of the copper strips will fall off soon So  I decided not to solder any other caps to the vero itself, but directly to the pins of the IC (yeah, that's the way I roll baby, danger is my middle name!). So I have a 1nF on the vero spanning the rows of pins 1 and 2, and also a 3.3nF on the pins of the IC itself. Does that mean that I actually have 4.3nF or is the smaller value ignored? Just so I can update the schematic correctly.

Other fun stuff that happened:
I switched the two tone caps (the 82 and the 100nF) out for 10nF (which gives a gentle but audible high frequency removal, sounds good) and after a a lot of testing, 330nF, which both my son and I liked for making a more extreme sound, but still with some high frequencies in it. 470nF cut too much out. So we have two great tone choices on the switch, which we are keeping, except now something weird has happened to the central switch setting which was the normal tremolo - it has now become really subtle, and also doesn't sound square wave much either! Both the 10nF and 330nF settings have a hard choppy tremolo and the normal tremolo is much more rounded, but very gentle. This may not be fixable with upsetting the other sounds, so I think we can live with it - if we want a 'normal' tremolo well I've got a TC Electronic Choka and that does normal tremolo fine - we will use that. We don't have a tremolo that can cut out frequencies, and that's what we are going to use this for.

Other fun things - on the 330nF setting with fuzz activated, if the rate is set to maximum and tone is 330nF it starts to sound like a weird broken 8 bit synth That's very cool!

To sum up; the pedal is cool and now I suspect I need to figure how to box this mess! So don't panic if there is no easy fix to bring back the 'normal' tremolo sound. Thanks very much for your patience

[duck_arse]

the added pins 1 and 2 cap will cut high freq gain, and the bigger the cap, the lower the cut freq. so your big peep peep cap may be killing the gain that produces your beloved fuzzings. making the opamp not burst into oscillations would be the ideal fix, but how?

when you say to junior I've made us a tremolo, does he roll his eyes? a trem peep peep fuzz 8 bit overdriving tone-cut synth?

[moid]

Finally managed to box this today! One of the tightest builds I've ever made... it really should've gone in a larger box. Oh and it seems I wired the Speed pot backwards, so it's got some quirky design features (I hope I never have to open it again!) Moid Jnr was most impressed with it and has already recorded a couple of tracks, so I'll try to persuade him to do a demo of it and I'll record it for everyone's amusement. It is not a happy pedal if any other pedal goes in front of it - it does increase the thumpy noise and turns it into a higher pitched squaeak... but it's much happier on it's own! It works fine with other pedals after it.

Eb7+9 - I've found an old spare breadboard so will try to breadboard your suggestion very soon.

[moid]

Hi Eb7+9

I have good news and bad news. The good news - I built your circuit design on breadboard. The bad news - it has no effect on guitar signal at all The guitar plays through it completely unaffected by the circuit... so presumably I screwed something up, although usually when I do that there is no audio at all... do you want me to break out the DMM or audio probe and look at any particular part of it?

Edit: Whoops forgot to say that I built this using a TL072 (because I don't have any TL071s). I did change the circuit to work with the different pinout (I'll draw a schematic for what I did later) and I'm only using one of the op amps.

Just checked the power and the brand new 9V battery I am using is putting 9.5V to the breadboard and the chip is getting 6.5V at the inverting input (leg 3 on this chip) and 9.5V on pin 8 (the power input). Where else should I check and what should I check for (volts, resistance, audio etc?)

Edit2: Just unplugged the battery and accidentally knocked my guitar over (still plugged into the circuit) and the audio volume level is exactly the same, so I think the audio is going straight from the in jack to the out jack and ignoring the circuit completely. So maybe I have misunderstood your schematic? Or this is the most transparent tremolo circuit ever

[Eb7+9]

... fidelity is a good sign

what's the DC voltage at the base of the DEPTH pot ?

[moid]

Measured at the Base of the Transistor it is 0V so that sounds problematic! It's always possible that the issue is my layout or the breadboard itself - I only have two breadboards and the other one is full of an LED / LDR circuit that I'm working on, so the one I'm using is old and I'm not sure how well it works.

[moid]

And here's a schematic for you. I had to substitute a 22nF cap for your 20nF (and the TL072 for the TL071). I was a bit unsure about the line that connects the base of the transistor to ground (you called it CV?) so I just connected a cable from there to ground; maybe that is the issue? Thanks!

[Eb7+9]

you're almost there mold ...

the speed pot needs to be rewired slightly and you need to remove the short at the Cv node
(a volt meter is placed at the Cv node in my TINA schematic in order to produce a waveform output in a real-time simulation)

and, btw - just in case - 20k was the simulation value I chose // use the original 10k speed pot value here ... or, maybe try 25k
you tell us what works best ...

[moid]

Thanks for the fast reply - I've made your changes (removed the short and fixed the Speed pot) and I still have clean guitar going through the circuit but no tremolo . If I remove the power from the circuit (bypass it as it were) the signal is brighter - with the circuit powered up there is a slight loss of high end signal but sadly no tremolo. Where should I probe / DMM check the circuit next? Oh and any voltages readings will be lower from now on because guess who left the damn battery attached to the circuit last night... it's lost 1V of power since yestrerday - I assume 8.5V would still be enough to power things?

Edit: I got out my audio probe and the issue is at the start of the circuit? I can hear audio at the Jack In, and the audio is fine up to the first 10K resistor - it can be heard on the side facing the In jack, but there is no audio on the leg on the other side of that resistor... which makes no sense to me, because how does the audio get to the out jack? Very weird!

Edit2: OK just realised that there were some minor issues with where that 10K resistor was placed It is now in the right place.   The audio probe now shows audio going through the 10K resistor, which connects to the Collector of the transistor. There is audio at the Collector. There is no audio at the Base or the Emitter... I think the audio is just going direct to the out jack?.  Turning the Depth pot CW lowers the high end frequencies and makes the audio more muddy. The Speed Pot doesn't do anything as far as I can tell. The Shape Pot acts as a volume on / off pot!

[Eb7+9]

The Speed Pot doesn't do anything as far as I can tell. The Shape Pot acts as a volume on / off pot!

great - confirmation that the back-bias circuit and transistor are together doing what they're supposed to ... what you're describing is exactly what would happen if the LFO wasn't running ... try another op amp perhaps and double check component values on that side of the circuit

Btw don't expect to see audio signal at base or emitter transistor terminals

[moid]

Thanks! OK I went over the whole circuit and I found one 10uF capacitor that wasn't attached to anything (the one that connects to the Speed pot) so I got very excited and attached it correctly... but still no tremolo On the plus side the circuit is now capable of picking up Dutch and German radio stations... sadly Dutch or German pop / techno is not great, although the way it fizzles in and out of audible range is quite interesting, so I guess that's something? Probably caused by all the long cables I have connecting pots to the circuits (via crocodile clips). I did wonder if it was fading in and out with a tremolo effect, but I think that is just atmospheric conditions right now because it is very random - there are two stations that fade in and out and one has German announcers and the other has Dutch ones.

Do you want me to take any measurements anywhere in the circuit?

I am guessing that this circuit works by shunting the audio to ground to make the tremolo affect? Presumably the circuit makes the connection to ground more enticing to the audio than the connection to the Out jack? But at the moment something isn't working so that the more interesting connection to ground isn't happening? So I presume there should be some sort of pulse coming out of the IC that ends up in the transistor? I am going to guess that travels through the line that goes via the shape pot - so should I check for voltage or resistance on that line? And I should see a rising / falling value?

[Eb7+9]

I am guessing that this circuit works by shunting the audio to ground to make the tremolo affect? ...

Indeed ...

In the original version it's more of a shunt ...
With the 10k resistor added it's more of a variable voltage divider

but it's nothing like a linear resistor (details omitted)

So I presume there should be some sort of pulse coming out of the IC that ends up in the transistor? I am erred to pseudogoing to guess that travels through the line that goes via the shape pot - so should I check for voltage or resistance on that line? And I should see a rising / falling value?

You got it ... the pulse that comes out of the IC is actually a square wave that is then converted to pseudo-triangle via the RC components leading to the transistor's base terminal (whose voltage to ground I call Cv)

the 33k resistor in series with 10k
Depth pot was chosen to give you a little bit of play

*BUT* the Depth control is really meant to be set full way all the time as I explained before

the fact that the Shape control works as a volume control
means you're really just one step away

so should I check for voltage or resistance on that line? And I should see a rising / falling value?

at this point you would need a scope looking at the transistor base terminal to tell anything for sure

If you want to spend another 1/2 hr on this
measure your 220k resistors to make sure, try other caps, double check power pins on op-amp...

good luck

[antonis]

>Off topic ON<

I'd short pin 3 & 5 and Pin 6 & 7..

>Off topic OFF<

[Eb7+9]

forgot to say one thing here ...

after setting the DEPTH to 100% you'd then be hunting around with the SHAPE (diode bias) pot ...
depending on the type of taper you're using you might get lucky in a very narrow range of adjust-ability

that's assuming the oscillator is doing its thing

[Ben N]

 

[moid]

Hello everyone

I will slightly cause this conversation to veer to the left for a short while - my son and I recorded a demo of the 'original' squarewave tremolo with the speed, fuzz and low pass settings, so those of you who have been on the edge of your seats ever since we finished this pedal can now breathe a sigh of relief and enjoy the below video:

I will reply to everyone else's helpful posts later tonight when it cools down a bit!

Edit: hmmm the audio sounds awful on Youtube, I will try to fix this so maybe wait until later - sorry!

Edit2:FIXED NOW! it seems our demo upset Youtube's LUFS requirements and it nuked the audio So I've spent a few hours learning more about Resolve than I thougth I would just to make this video sound reasonable - hope it works for you!

[moid]

>Off topic ON<

I'd short pin 3 & 5 and Pin 6 & 7..

>Off topic OFF<

Hi Antonis - I've done this now (thanks for the suggestion) but nothing extra happened to the circuit sadly. I've left those connctions in place because nothing went wrong when I tried them.

EDIT: Actually the volume is halved! That doesn't help much though.

[moid]

great - confirmation that the back-bias circuit and transistor are together doing what they're supposed to ... what you're describing is exactly what would happen if the LFO wasn't running ... try another op amp perhaps and double check component values on that side of the circuit

Btw don't expect to see audio signal at base or emitter transistor terminals

I just tried a TL082 chip in place of the TL072 (they seem to have the same pinout) but no joy there