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

[duck_arse]

moidy - back with us? how's?

moidy moidy moidy - observe your 5088. it has nothing attaching to the emitter. should be ground, according to the snippet I see above. and pin 4 of the IC is ground, so if you shift the transistor down by one, and shorten the 10k to base by one, you will have that bit right. also, observe that double link hole 10k and link. it shorts your pink and blue wires to things, so it is wrong. I think the bottom of the 82nF comes down one [so now spans three] and the blue off-board wire comes down one. the 10k at A3/D3 stays where it is as it connects to that 100nF at D7. so delete that link at D/E3.

yerrrssssss, I think that's right. copacetic, even. draw it up again, give us a geek at it, we'll see what is. where is the circuit diagram, pages back? I'm too scared to look.

[moid]

Thank you Duck! I'm back (at least until early September). I'm kind of like one of those migratory birds that shows up once a year and you get all excited about the little bugger because you haven't seen one in ages... and then it shits on your car! My students are all on holiday, so I am too (yay!). I hope next year won't be as crazy because I've changed jobs and am no longer in management (phew!) so hopefully that means I might get to create things even during term time... although knowing my luck something is bound to go horribly wrong, the future is rather uncertain where I work at the moment. Anyways lovely to hear / read your reply! Glad to see you're still here I'll try not to crap on your car! How is your good self? Hopefully surviving the Winter?

OK I did some scribbling and we have the below beauty:



urghhh circuit diagram... yessum, about that... (looks sideways nervously, tugs at collar), why I'm sure I kept that up to date with all those changes we've been making, yessir it would be a terrible thing if I hadn't done that, I mean that would be really amateur wouldn't it? I think I saved it in a very special secret hidden place on a back up computer in another location and it might take me a little while to find it again, so you just wait there and I'll be back faster than you can say "If practice makes perfect and perfect needs practice, I'm perfectly practiced and practically perfect"... exit, stage left

[duck_arse]

I don't own a car, and current winter is like your summer. with less rain.

well I think that looks about right - if all the other part was right, the new part at least appears to match the fragment of switch circuit I posted earlier. so why haven't you finished it yet?

[moid]

It's a good thing you don't own a car then, I'd watch out for any outdoor flat surface you do own, because guess what? The circuit did not like being fiddled with at all, and we now have a 6dB boost, but no tremolo... oh and I discovered I wired the Boost backwards, so that needs fixing too! There's no success like failure...

Flipping the switch betwen the three tremolo modes does cause a slight tonal change to the sound (I think) and on one option there is a loud pop when I switch to it... no sure if that matters. The speed switch does nothing I can perceive. I tried swapping out the 1K resistor that I had socketd that I think Rob suggested; and I tried 10K and 100K and no joy... should I try something higher? I was assuming it would be a small value above 1K to make it work if that was the issue.

I'll try to draw a schematic for this later tonight, but thought I'd post my findings so far in case they mean anything to anyone.

[moid]

Aha, was looking at the back of the board under some brighter light and I think I can see some mistakes (and one lead has popped off the board!). Will try knifing things and re soldering later, hopefully with better news.

[moid]

Well folks I bet you were on the edge of your seats after this evening's cliff hangar? Will the hero get the girl? Will the villain take over the world? Will the tremolo activate? Stay tuned to this week's thrilling adventure!

Spoiler: Kind of

OK once you remove the lump of solder that was bridging a couple of rows of copper trace (whoops) and you discover that your amazing soldering skills had caused part of another row of coppper to detach from the vero (ooops) and you re attach that cable elsewhere, and you re wire the boost pot the right way round, well we have some success. The normal tremolo works, although it seems less choppy now (not that that is a bad thing, I quite like it). The depth is also not there as much as it was - I don't think it fully cuts the signal out, but I might wait until my son is around tomorrow to ask him to use his fully functioning ears to see what he hears. I've also appeared to have soldered the depth pot the wrong way around...d'oh... maybe changing that would fix the depth amount?

Onto the tone switch fun. The middle (off) selection works fine - standard tremolo as mentioned above. Switch down (yellow and blue cables) gives either a very interesting choppy / glitchy / ticking tremolo (if the rate switch is set to slow and the boost is on maximum) or if the rate switch is set to normal (taking the extra 10uF cap out of the circuit), no audio will go through the pedal at all. How's that for weird? Hmmm re testing this I find constant ticking is present, but if the rate switch is set to normal and the boost is turned down I do get glitchy trem, but one where the amount of guitar signal in the audio gets less and less as the boost is turned up (unfortunately it is replaced with loud ticking). When the boost hits maximum all audio (and ticking) is removed and the circuit does nothing except make loud static hiss (great white noise generator!)

Tone switch up - (purple and blue cables active) yes definitely works, sounds great, lovely pulsing soft sound - works when the speed switch is at either setting.

The speed switch. The extra 10uF cap halves the speed of the tremolo at the slow end, but seems to be able to still reach near ring mod territory at the fast end of the rate pot. Would increasing the 10uF to something bigger (47uF?) make the tremolo slower? I've got some 22uF and 33uF if those are more appropriate?

Oh yes the boost is very fuzzy; but in a good way - I like the pedal with it turned up to the maximum although the fuzz is strongest on the lowest strings - the high E string comes through as louder but not fuzzy. With the boost set to minimum the effect lacks much character and the tremolo seems weaker. I don't recall it being as fuzzy as this before! But I like it so let's not panic about it!

At the moment I am tempted to say I'll keep it. If the speed switch could go slower that would be good. If the depth was stronger that might be useful (a larger pot value maybe?) but it's no major issue. If the ticking on that one mode of hte tone switch could be fixed that would be coool - I like the odd stutter it has!

[duck_arse]

this evening's cliff hangar

where do you park the planes, then?

circuit diagram first, more of your fooling and fixing, then we worry about what is right and what is working and how to mod faster or slower. and photos, as per the rules. please.

[moid]

where do you park the planes, then?

In a vertically orientated stack of hangars, going up the cliff of course - they are only for helicopters and Harrier jump jets (what other planes are suitable for such an exciting post?)

Anyway luckily I managed to bump into my wife's brother's cousin's girlfriend's dog (you wouldn't know her; she goes to another school) and ask for the schematic file from their laptop and so here it is! Good thing I kept that fully up to date

I got my son to play through the circuit today and we discovered the fuzz sound from the boost is not fuzz, but me not realising the high volume I had the pre amp on my DI box set to... whoops! Turning that down to something sensible makes the boost clean. However fuzz fans, all is not lost, because while playing with the circuit (contemplating adding a larger capacitor to the speed switch to slow the LFO down more) I accidentally touched a 10uF cap from ground (actually to where the 10uF stripe side leg - marked cap2 on the schematic) to pin 3 of the boost and the circuit turned into a super loud fuzz! My son immediately said keep that! So he wants that added as a switch (SPST should do). It did sound pretty good, I have to say - it keeps the tremolo, just adds a massive fuzz on top. We also tried a 1uF instead of the 10uF but that just made things slightly louder but clean. Adding a 47uF seemed to cut the entire signal, and a 22uF removed all the high frequencies and added very distorted bass only and sounded awful, so 10uF seems the magical one to keep. Turning the boost pot down does tame the fuzz if required.

Anyways you wanted some pictures:

Schematic


Photos (please don't scream when you see the soldering - this was quite neat until I had to start desoldering things and putting them back together - that's why there are some unused sockets on one side - and there are other components floating about a bit...

whole circuit


Close up of top of board


Close up of underside of board


Thanks again!

[duck_arse]

a few prelim q's from your circuit diagram before I off to scrute the whole - that 1k between the speed pot and the 10uF cap - what's that for and where did it come from? it will really limit the slow speeds for sure. your added 10uF big boost switch cap - it is bypassing the 10k R in the inverting in leg of the opamp, so it is kind of legit. would probably be as easy, and better, to just switch a low value resistor in parallel with the 10k, tho, I think and get shot of that extra cap. the moid-reutz gain-leg mod.

[moid]

Well we are really into Alice in Wonderland territory! Curiouser and curiouser...

I was adjusting things today and swapped the 10uF capacitor on the rate switch for a 22uF and that worked - I got a much slower tremolo which is also slower at the fast end of the rate pot so that was good (I did also try a 47uF but that was too slow; the notes decayed before the LFO completed a cycle - probably OK on synths pads with reverb, but no good for guitar). So that was the good part. While testing the fuzz switch I noticed the massive volume boost when using it (not an issue, it sounds great, but wow is it loud - although tameable by reducing the Boost pot). So I switched off the fuzz, and started testing the normal boost part of the circuit and it seems that the circuit only gets to unity when Boost is on maximum - anything else is quieter... I don't think I ever switched between bypass and the circuit up to this point (d'oh) so didn't realise that the Boost isn't working as I thought... have I wired the pot backwards? Or done something else stupid?

I also noticed I wired the depth pot backwards, so go me!

[moid]

a few prelim q's from your circuit diagram before I off to scrute the whole - that 1k between the speed pot and the 10uF cap - what's that for and where did it come from? it will really limit the slow speeds for sure.

Hi Duck, you must've posted just before I did! The 1K was a suggestion of someone in the thread... oh it looks like I suggested it, how did I come up with that? You then advised on some different values to try in post45 https://www.diystompboxes.com/smfforum/index.php?topic=129499.msg1253431#msg1253431

I'm not sure why I settled on 1K though - should I try 10K (one of your suggestions?) Oh in post 48 I think you said to try removing it? Maybe I should do that?

your added 10uF big boost switch cap - it is bypassing the 10k R in the inverting in leg of the opamp, so it is kind of legit. would probably be as easy, and better, to just switch a low value resistor in parallel with the 10k, tho, I think and get shot of that extra cap. the moid-reutz gain-leg mod.

Wouldn't using a resistor change the sound compared to using the capacitor? Or is the capacitor merely acting as a jumper in this case and so as little resistance as possible is required? I could take a cable out from C9 on the board to an SPST, to a resistor and then back to C17 on the board - is that what you mean?

[moid]

The second harmonic tremolo now seems to do nothing but add ticking... urghhh I think feature creep may be killing this circuit. Maybe I should just swap that switch for an SPST and have normal tremolo and the one harmonic that does work (I think that's the 100nF). It's got hot today here and I think the sun nuked my brain this morning (was out all morning looking for a colony of rare wildflowers for a conservation group, sadly it looks like climate change has nuked them all).

[moid]

Today's update: In the interests of science, I tried removing the 1K stop resistor - and if I do that, the circuit stops all tremolo (guitar still passes through, but not tremolo). So I put that back! The ticking horribleness seems to be coming from the 100nF capacitor, which goes into a socket that I made from bits of a broken socket from another circuit (I like to recycle!) but when I tried to put a new capacitor in place on the 100nF (just hoping it was a dud capacitor), one of the legs would not fit into the socket so I will try removing my recycled socket and place a new on in the same spot and see if that helps. Also the boost seems to work today! Although I'm now getting a high pitched oscillation when the fuzz is on and also the switch that selcts the 100nF now cuts all audio when that option is one... I wonder if this circuit needs to be in a box so it is shielded? It is certainly tempermental! At least I'm in a better mood today, I managed to build an modified Autowah last night and it worked first time (that's pretty rare for me!)... now I might need to add just one more wafer thin mod to it to make perfect... hope you're all having a good Friday!

[duck_arse]

good friday was at easter.

now see, the thing I did rong last night was to delete my local of your layout, so I had no guide while lookink at yore bilt. scuse my typing. and I looked at the underside of your board .................



that 1k stop resistor - you have misplaced it on your circuit diagram, so we point and say - what's that? it should be drawn in series with the speed pot, whereas you have it parallel. so it was boarded right, and should be left well alone.

about your bonus 10uF boostering cap. the gaining is set by the 10k in series with the 10uF, from (-)input to ground. and the formula tells you at what low frequency the boost will start from, and how much gain is determined by the 10k and the feedback pot setting [and, obvs, its series stop resistor]. when you add that 10uF, it is parallel to both the 10k and the 10uF, so you are basically saying FULL BOOST at all freqs, negating the effect of the resistor. changing the resistor value will have the same/similar/not much difference to the sound, and will behave in a much nicer fashion - no whumps or chargings.

so just switch-add in parallel a resistor, ?220R? 100R? 330R? I dunno R? but across the 10k only, and be done. or complain, we take both types.

don't be boxing a non-working build, you are asking for trouble when you do. and that cap tone switching business - we need to see the toggle switches wiring a little clearer before we can say. I say we. oui.

[moid]

good friday was at easter.

How time flies when you're having fun!

now see, the thing I did rong last night was to delete my local of your layout, so I had no guide while lookink at yore bilt. scuse my typing. and I looked at the underside of your board .................



that 1k stop resistor - you have misplaced it on your circuit diagram, so we point and say - what's that? it should be drawn in series with the speed pot, whereas you have it parallel. so it was boarded right, and should be left well alone.

This one is confusing to me - the 1K is in exactly the same place on the vero as it is on the layout? Maybe what looks odd is that DIYLC has this annoying habit of drawing an extra row of holes at the bottom of the vero board. I've done a new layout (showing other changes) - hopefully this looks okay now?



So other changes - the switch on the left of the layout has had its cables untangled, and now I get normal tremolo in the middle setting and harmonic tremolo when the 82nF is engaged, but now just silence when I switch to the 100nF (better than the awful shrieking noise that used to be present I guess). I could try removing the socket that holds the 100nF and soldering a new one in and trying that if you think that's a good idea?

The fuzz switch has been added as you described. 100R turned out to be the best value - lower than 100R and the tremolo vanished and I just got fuzz; higher than 100R and there was terrible pounding thumping noise that never went away (the pulse of the tremolo)... actually I still have that with the 100R, but at a lower volume; it's a bit annoying. Neither is quite as chaotically strong as the original 10uF cap trick, although I tried socketing that cap in to the sockets that hold the switch cable and 100R (instead of the 100R) just to see if that would do anything and it worked, but with a high pitched pulse noise that was timed to the tremolo speed... yikes. So 100R and heartbeat it is I guess... I can lower the volume of the heartbeat by reducing the boost level and also the depth level on the pots (but the tremolo is reduced as well). I'm tempted to leave that where it is at the moment! It's only really noticeable when the fuzz is on, the rest of the time it is very quiet. I'm not sure if that thumping heartbeat was present when I ran the 10uF cap straight from Lug 3 of the boost to ground... I don't remember it being there. Also when I used the cap, the fuzz 'filled in' the tremolo sound, so that the tremolo only appeared as the note decayed which was pretty awesome, and that has vanished by using the resistor... how bad an idea would it be for to go back to that plan? - I know you mentioned there might be whumping noises, but I think I've got those now anyway!

And the boost is also back to not being a boost anymore (if it ever was). If the Fuzz is off, the boost needs to be on maximum to keep the signal at unity (maybe slightly higher than unity?). I started AB ing the bypass and tremolo, and the bypass sound is louder, so the Boost pot starts by removing all volume and slowly adds the volume as you turn it. Quite what I've done to this circuit is anyone's guess. Feel free to say "Enough! Let's drop this damn thing"; it's driving me nuts as well, and I hate passing on my misery to those who don't deserve it. Thank you for your time and sanity!

[moid]

Some more fiddling today, and some embarrasing mistakes  . I started changing the fuzz part of the circuit to run a 10uF from the boost pot lug 1 to ground (not lug 3 as i said before, I can't count!) because it gives better tone to the fuzz (kind of like a %^&*ed wah) and I realised a couple of issues. The fuzz tone is actually mostly just the boost absolutely hammering the pre amp of my DI box... I wasn't paying attention to how loud I must've had the input volume on the DI box set to!! If I turn it down so that the incoming volume is not clipping then the boost is just loud and clear until I get near the maximum end of the pot sweep at which point it is clipping nicely (with tonal modification courtesy of the 10uF cap). So the fuzz is kind of a lie The boost pot is making things louder, but in a clean(ish) way! If I switch between bypass and boost pot turned down to nothing the volume is almost the same (bypass is slightly quieter). Things get considerably louder when the 10uF cap is switched in, with additional tonal shaping. Ho hum... I guess I will just have to push this into a fuzz pedal in future (or just overload my DI box!)

The 1K resistor does not sound as good. No idea why, but it sounds loud and distorted but without the tonal shape of the 10uF, and with more thumping heartbeat noises... So I think I will move the switch back to my original design. Sorry I'm going back against your good advice Duck but it honestly sounds better.

If anyone has any idea why one of the harmonic tremolo switch settings kills all audio then that would be cool! With that solved I could start boxing this mass of wires!

[duck_arse]

ohhh, I love embarrasing mistakes .....

which 1k resistor doesn't sound as good?

the stop resistor I confused you with was drawn wrong on your last posted circuit diagram/schematic. it was correctly placed on the board, build and layout. the tone switch, well, if it works in two positions, I can't see a reason for it not to work in the other, except build error.

I was thinking to switch the gain-leg resistor instead of the cap as the cap would almost certainly whump each time you switched it in. the osc whump is a bonus? I suppose the 10uF across the full leg is still valid, if it does what you want. but further fiddle has muddied your results - which bits still work and which don't?

[Eb7+9]

I think the loading on the Cv side is too low in the OP schematic ...

case in point, notice the op-amp isn't driving that side-chain node directly - but rather thru the SPEED control resistance

for one, an overly low output loading produces a squarish Cv voltage to the base of the bipolar transistor
it also prevents sufficient signal swing from forming there as well

... at least according to TINA, which i don't think is wrong here

notice also, as Rob pointed out, my inclusion of an input 10k resistor to form a voltage divider,
similar to how the Arbiter Trem-Face does it ...

https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/

this change allows for the potential of a more rounded TREM response
as opposed to that of a hard clamp ...

---

now, if instead we reduced this loading by increasing the side-chain resistance to around 50k (versus 5k or so as posted) two things happen:

the Cv swing increases to the point where we get (full trem) "choppy" action,
and the Cv waveform is now more triangular, what we would expect it to be in an a passive square-to-RC-expo-triangle conversion

http://www.lynx.net/~jc/LAYLAND-TREM-50k-MOD-linear-range.png

---

the question, can this passive bipolar-clamper do a little better ?!

the above simulation shows that the TREM action is pseudo linear in a very narroaw range of Cv voltages
which is just around where the bipolar transistor turn-on voltage (just below 600mV dc)

as is, I don't see the circuit doing more than a bumpy chop ...

if we could "stick" the BASE inside that range and modulate it, we might be able to get a two-sided TREM response
and this is indeed what I'm seeing if we introduce a back-bias on the 50k DEPTH pot

a simple way to do this is by biasing a grounded bipolar diode thru a (variable) resistor,
and maybe adding a fat cap to help improve AC grounding

http://www.lynx.net/~jc/LAYLAND-TREM-MODS-JCM2023.jpg

of course, the main drawback here is that when the DEPTH control is lowered so will the AC gain of the straight signal
since the back-bias provides an attenuating effect when Cv has zero AC component ...

therefore, this is not meant as a completely flexible improvement ... but rather a partial one
(ie., better shaped trem at strong settings)

btw, the back-bias can be made variable (with a rough range of 520mV to 670mV DC)
and thus playing with the resultant offset derived SHAPE becomes somewhat of a possibility as well

just some ideas to play with ...
(*!*)

[moid]

Thanks chaps! Sorry about the slow reply, have had to do some repairs to my house (a local cat decided to jump off our extension roof and land on the plastic lean-to roof, at which point the plastic decided to shatter and I had to repair it - and also the gutter at the front of our house decided it was time to crack and leak water onto a bay window which makes a hell of a sound when it rains... yay, ain't DIY fun?). Anyway I made some progress, and also encountered new failures! As Dylan says, there's no success like failure!

ohhh, I love embarrasing mistakes .....

Well have I got a super example for you! This afternoon I finally got round to picking up the circuit again, looked at the socket that holds the 100nF capacitor (C4-D4 on the vero layout) and decided to remove it (it was a recycled one) and replace it with a new one. After doing that I also switched the cables on the on OFF On SPDT switch to the original layout of them and noticed I had forgotten to put a cut on the vero at C5!!!! So I did that, added a capacitor back, turned on the circuit and guess what, I get tremolo on all three positions of the on OFF on switch! 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. My only thought here is that perhaps I should swap the cables attaching to the SPDT back so that they are in the order in this image? Would that enable the 100nF capacitor?


Now not to outdone by this news, I then decided to switch on the loud extra boost circuit (oh the normal boost is working fine), this is the extra switch you suggested to add a 100R resistor, or my mod to switch in a 10uF - that's added with crocodile clips at the moment; your 100R suggestion is on an SPST as can be seen above. Whenever I either add my 10uF mod to the circuit and turn off your 100R switch, or just add the 100R and detach the 10uF I get awesome fuzz - even when its coming into the DI box at a non clipping volume, it sounds great except... it now has a high frequency PEEEP noise that osciallates in time with the tremolo... oh and did I say that PEEEEP was loud? My wife thought our smoke alarm was going nuts - it's about the same frequency... so ermmm help? My son says the fuzz is great, how do we get rid of the PEEEEP sound?

which 1k resistor doesn't sound as good?

I turned it into a 100R (attached to the SPST) and that gave me the fuzz sound back. The 1K was too polite and genteel

I was thinking to switch the gain-leg resistor instead of the cap as the cap would almost certainly whump each time you switched it in. the osc whump is a bonus? I suppose the 10uF across the full leg is still valid, if it does what you want. but further fiddle has muddied your results - which bits still work and which don't?

I think I've mentioned those above duck - yell if you want me to try something. I'd love the fuzz to work without the high pitch noise please! And if you have any ideas about getting the capacitors that affect the low pass filter to work that would be cool. I'm in two minds about whether I've wired that switch wrong...

Eb7+9 I will reply to you in another post soon, still trying to understand what I need to ask you - thanks for the suggestions!

[moid]

I think the loading on the Cv side is too low in the OP schematic ...

case in point, notice the op-amp isn't driving that side-chain node directly - but rather thru the SPEED control resistance

for one, an overly low output loading produces a squarish Cv voltage to the base of the bipolar transistor
it also prevents sufficient signal swing from forming there as well

... at least according to TINA, which i don't think is wrong here

notice also, as Rob pointed out, my inclusion of an input 10k resistor to form a voltage divider,
similar to how the Arbiter Trem-Face does it ...

https://viva-analog.com/dallas-arbiter-trem-face-rare-re-build/

this change allows for the potential of a more rounded TREM response
as opposed to that of a hard clamp ...

---

now, if instead we reduced this loading by increasing the side-chain resistance to around 50k (versus 5k or so as posted) two things happen:

the Cv swing increases to the point where we get (full trem) "choppy" action,
and the Cv waveform is now more triangular, what we would expect it to be in an a passive square-to-RC-expo-triangle conversion

http://www.lynx.net/~jc/LAYLAND-TREM-50k-MOD-linear-range.png

---

the question, can this passive bipolar-clamper do a little better ?!

the above simulation shows that the TREM action is pseudo linear in a very narroaw range of Cv voltages
which is just around where the bipolar transistor turn-on voltage (just below 600mV dc)

as is, I don't see the circuit doing more than a bumpy chop ...

if we could "stick" the BASE inside that range and modulate it, we might be able to get a two-sided TREM response
and this is indeed what I'm seeing if we introduce a back-bias on the 50k DEPTH pot

a simple way to do this is by biasing a grounded bipolar diode thru a (variable) resistor,
and maybe adding a fat cap to help improve AC grounding

http://www.lynx.net/~jc/LAYLAND-TREM-MODS-JCM2023.jpg

of course, the main drawback here is that when the DEPTH control is lowered so will the AC gain of the straight signal
since the back-bias provides an attenuating effect when Cv has zero AC component ...

therefore, this is not meant as a completely flexible improvement ... but rather a partial one
(ie., better shaped trem at strong settings)

btw, the back-bias can be made variable (with a rough range of 520mV to 670mV DC)
and thus playing with the resultant offset derived SHAPE becomes somewhat of a possibility as well

just some ideas to play with ...
(*!*)

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:) 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.

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

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.

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

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?

Thanks very much