panaman Posted October 26, 2014 Share Posted October 26, 2014 secret modulation input revealedopen up the pod to a whole new world of modulation!(without necessarily having to open the pod)first, the obvious:i`m happy with the pod as is. the pod has plenty modulation built in already:- almost all effects have their independent modulator/LFO with speed and depth settings.- mic input can modulate the vocoder- internal and external pedal can be assigned to almost everything.these are all fine and can go a long way. however, there is mostly no LFO waveformsetting, and they cannot be linked or synchronized.far as i know, midi is poorly implemented in the pod hd series and basically hasswitching functionality only.if you are like me and like to get a little more experimental (and have some experiencewith soldering), read on: i will be taking it in small steps starting from non-invasiveand going on to daring/hazardous. its not too hard, really. cost is marginal, compared tothe reward: a few $ or € will have you connecting extra modulation with very little effort. .possible modulation source:- modulation output from anything providing a CV (control voltage) or pwm like synths,sequencers etc.- midi to cv interface (lets you freely draw the modulation curve in your daw, how coolwould that be? just imagine!), over midi or usb. wish the edit program could be automatedby a vst host, changing modulation target.- dedicated modulation source, like Lfo section of older modular analog synths, e.g.formant system (which is what i am using, extended version with 4 lfo, some 20 dipswitches and mixing stage, 16 outputs), circuitry is not all that complicated. 1 quadopamp per lfo does it, can easily be expanded/modified. documentation is available.sections are independent.link: http://www.sequencer.de/forumsynth/forumsynth.html#formantany other lfo will do, results may vary.________________________________________________________________________________________now, the disclaimer: please excuse my english, not my 1st language.always pull the plug when messing with electrical appliances.anything you do to or with your pod is at your own risk, please dont blame me.things can go wrong. you have been warned.if in doubt, dont get started. get a savvy friend to help you or a second opinion.for all of the below, i have tried to make sure things are failsafe: even in a worst casescenario, they may not work but should not do any damage or adversely affect the podpermanently either. (if applied properly. only you can do the damage. people in Fukushimamay have a different attitude towards failsafe, but were not dealing with rocket sciencehere).where there is a risk i will warn.one real danger is probably from statics at the pod input and semiconductors in general,so always keep everything on the same outlet, which will also help reduce general noiseissues.plug away before switching on (just a recommendation. i know noone really does it). incase of EXP2, you do need to plug in before powering up, else it wont be recognized. ifthe modulators cannot be disabled it may help to bring the pedal to heel position whichwill short any parallel input.try to stay grounded, especially when opening the pod. same goes for your solderingequipment.the exp in a/d does not detect the pedal`s ohm value directly. instead, a current is fedinto the pot resulting in a voltage which can easily be converted.the pedal 2 input expects voltages from roughly 1.75V toe to 0.0V heel position.see if your modulation source sends output of > 5V, or negative output.resistor and pot values may need to be adjusted, or some op amps and/or diodes may needto be added to make up or level output range. these will follow in the more advancedparts of this article.always use strong diodes like 1n4007, they will be able to handle any malfunction oroverload.i will be using 1 diode in reverse which will direct any voltage below -0.7V to ground,and 2 or 3 diodes forward in series to cut any voltage above 1.x to 2.1V.alternatively, a single 1.5 - 2.x V zener diode could do both, but isnt as sturdy.the diodes in turn are being protected by resistor(s) where needed.if your modulation source is not adjustable, it may hit the ceiling and floor given bythese diodes, making changes to resistors necessary so the mod signal stays withinbounds.all below non-invasive steps (without removing the pull up resistor inside the pod) are acompromise due to the low ohm pedal pot.they can either be plugged into the pod hd pedal 2 input as standalone or with the pedal2 attached in parallel or series.a simple y-adapter will let you use modulation and pedal in parallel, else the modulationinput and circuitry could be fitted inside the pedal 2.The EXPx a/d has its limitations. LFO frequencies > 10Hz will not work and may giveunexpected results (artefacts) due to the low sample rate of the conversion, 500x usersmight get better results due to dsp headroomplease note: pedal calibration of the internal pedal may require to temporarily removebelow options except where explicitly stated) if the modulation source cannot be muted.there is no pedal calibration for EXP2.removal is easy for all non-invasive options please note the difference between pod and pot: where pod is the pod hd, pot is apotentiometer.there are 2 kinds of pot mentioned here: the actual pedal pot and a pot to limit/set themodulation voltage or set the current for a led, op-amp or fet.since i dont have access to a pod hd X model, i can only assume the pedal input circuitryhasnt been changed much. not sure if it has a EXP2 input at allin general, any device and brand with a pedal or other mod input can be used with thesecircuits, with some changes to resistor values.__________________________________________________________________________roadmap:non-invasive, input modulation via EXP2, using:LDRresistor/capacitorop-ampinvasive:double your new modulation input capabilities:all above measures can be translated to apply for internal pedal 1 just the same. useEXP1 simultaneously and independently by giving it an extra input jack (or rewire oneexisting jack you wont use otherwise)remove pull-up from EXP1 and EXP2, making it easier to level your modulation source tothe pod EXPx a/d range.to do:diagrams and schematics______________________________________________________________________________________________________________1) non-invasive options:for starters, the external pedal 2 input EXP2 is well suited, except for its low ohmvalue. the pod feeds a current into the pedal`s 10k pot resistor. the resulting voltageis a/d`d and that value applied to any assigned effect (max. +1.75V).setting the pedal to heel position is more or less shorting the input which is worstcase, so this is an expected and legit state, no danger here. none of the procedures willactually physically short the input ever, other than the pedal in heel position.the following can be used standalone even if you dont own the external pedal, or inparallel with an existing pedal, allowing for even better control.- y-adapter: one 1.4" plug, 2 sockets can take the pedal in parallel, easily removable.- or use a cable from inside the pedal/pot with extra plug/socket as modulation input. adummy plug/socket can be used to protect it when not in use.in this case the pot in the pedal could be used in parallel or in series.______________________________________________________________________________________________1: using an LDR (light dependent resistor) without modulation input:really passive, for the faint of heart, no danger whatsoever.a real starter`s project with nothing required except some wire or cable with a 1/4"plug, and 1 (or more) LDR, and the soldering.optionally your 1/4" y-adapter if using the exp2 pedal in parallel, or a 10k resistor totrick the pod into thinking there`s a pedal there (in virtual toe position, if/while theldrs are kept in the dark).LDRs are not polarized. it doesnt matter which end goes to ground, nothing to consider.in real life, ldrs need a protective resistor. i use the pull-up resistor inside the podwhich feeds the exp.2 pot.LDRs are in the M-ohm range when in the dark, and can get as low as k-ohms or even lesswhen exposed to light. the amount of light in your shady shag will not cut it though.if you have a lighting crew youre in luck, else get it in front of a strong light sourceand move your hand over it for shade. could be mounted on your guitar for easy reach, themechanics are off my topic though. then the resistance can be changed by moving it in andout of the light, by moving the axe, or by dancing in front of it.since infrared is similar to light, only @ a different wavelength, the ldr will alsorespond to temperature changes from outside, as well as to those from the current runningthrough it.there are some pretty good looking ldrs out there, more like gems than electronicsdevices.if you want more info on ldrs, there are plenty good articles on the web, with diagramsfor different types. you want as lo-ohm as possible, and probably many. one thing i did a while back is use the reflector of a flashlight to collect light, mountthe ldr in the position of the bulb, and stick it all to a headband. nod away while yourenoodeling...advantages:absolutely foolproof,no modulation source required. no external voltage involved.1 LDR, one wire from pedal to LDR (if it can be grounded on the other end, like theguitar, else: 2 wire), 1 10k resistor if used without the pedal in parallel. worst case: the current from the pod avalanches the ldr in which case it may be beyondrecovery, shorting the exp2 input. unplug, no damage done.of course we dont expect the current to be strong enough to blow the ldr, we are on thesafe side and well below the danger zone by a factor of at least >20.at low voltages, the ldr can take up to 20-30mA.in theory, ldrs will produce a voltage when exposed to light. this effect can bedisregarded in this application.disadvantages:ldrs are generally hi-ohm and need a lot of light to produce like 10k or less.you may need several (or more) in parallel to get good results, below 1k ohm.results will vary and may be hard to reproduce, depending on the ambient light intensity.a lens could help to collect and focus light on it.if used standalone, you need to put a 10 k resistor in parallel to the ldr or the EXP2input may not get recognized and switched off.you will not get full heel position zero ohms with this simple circuitry.not for the purists (the whole project isnt for you, i guess):if you are willing to add 2 capacitors, one to your guitar out and one to the other endof the guitar out, or an extra cable, the ldr could be mounted on the guitar and fedthrough just 1 mono or stereo cable while also taking the audio from the same cable. __________________________________________________________2: using an LDR with external modulation input: (the real thing)if manually modulating is not for you, while youre busy playing, here`s an equally safeway to start.using an LDR (light dependent resistor) with LED as optical interface:ldrs have been used in effects early on and still are, e.g. opto compressors, optotremolo.they are inexpensive and reasonably reliable and come in all shapes and sizes.anything analogue could be controlled or replaced by ldr. advantages:- there is no electrical connection between the pod and the modulation source at all,only light, which cannot do any damage. very safe, as long as the separation ofmodulation/led input and ldr output is not compromized. even if it were, there are nodangerous voltages involved. both signal and ground are kept separate.- only few parts required: ldr, led, a couple resistors, pot, diodes, wire, jack/plug,box, optional activity led. could be built in less than an hour.box being a matchbox type housing which keeps surrounding lightsources from influencingthe ldr unless intended.disadvantages:- needs a battery or other psu unless the source (the lfo, interface) is able to drive aled (20mA @ 5V`= 250 ohms.the formant lfo can.if using a usb midi cv interface, supply voltage could be taken from there for a leddriver (just a little invasive, but not at the pod end.)- ldr curve is not linear- ldrs tend to be high-resistance. zero values are impossible to reach (without damagingthe component: if it has zero resistance, it needs replacement). you could use 2, adozen, or more in parallel to improve response and range. use mirrors inside the box to save leds- ldrs are temperature sensitive, a bridge type cirquit may be required for compensation,- results may vary depending on the environment and may only be poorly reproduceablecircuitry is pretty much straightforward and basic:input jack from modulation source with in ground --- pot (to set operating min/maxvalues and operating current for the led) --- resistor --- led --- source groundoutput jack/plug from LDR --- pod pedal 2 in pod ground to other end of ldr (polarity doesnt matter to the ldr)values of resistors and pots will depend on the source`s output resistance and voltage,and the type of ldr, since the pedal 2 cannot be calibrated in the pod.except for what is described in the following paragraph "not for the purist", the led/ldrcombination has to be encapsulated to avoid any ambient light other than that from theled to affect the ldr, unless intended.you need a 10k resistor in parallel with the ldr, or the EXP2 pedal in parallel so thepod can recognize it. r4 r5 -- --opt. 5V in )---l__l--l__l---- pot l LDR pedal r1 __ -- l r2 r3ext. mod in )---l__l--l__l---- ---------------------------( to pod pedal 2 in I I r6 l l l l l l_ l _ _ / V ---> l l l l/ led ___ ---> l_l l_l l l l ---( to EXP2 gnd l l l l )- l l l l l l === === === ext. gnd -=- -=- pod gndr3 is the pot in the pedal, or a 10k resistor if used without a pedalr2 is the LDRr1: a value of 200-250 ohms for each led is good for 2V to 5V input range, depending onthe led type, output resistance of the mod source.pot r6 is around 100 ohmsthe type of led needs to be taken into consideration: leds differ in voltage (1,4 to 5V),current (10-40mA) and light intensity where green and white are probably brightestif input voltage goes below its working voltage, the led needs to be supplied (additional5V input and resistor/pot r4, r5 required in parallel to r1). needs to be adjusted so theled will just barely be off when the input is zero or @ it`s lowest. negative input ispossible/allowed. the led current needs to be in middle then, allowing to go from maximumbright to completely dark.if many ldrs are required, a light bulb may be better suited, it radiates in alldirections while a led emits ln 1 direction only. bulbs tend to afterglow, furtherlimiting max. modulation speed. diodes on the pod pedal2 input are not really necessary here, since there is noelectrical connection from input to output, neither signal nor ground connection.only light passes from led to ldr as symbolized by the 2 arrows --->the input could even be driven by an audio signal. ldrs have a typical reaction time inthe milli second range. audio would be rectified by the led, the upper half of the signalends up as an envelope at the ldr. could use a capacitor across the ldr to buffer, 100nFwill do. _________________________________________________more to come soon... if any of you are interested Quote Link to comment Share on other sites More sharing options...
panaman Posted October 26, 2014 Author Share Posted October 26, 2014 thats right: its as invasive as plugging in the external pedal. that plug could hurt that pod. you can trust me though: im not going to mess with your inputs. ever. or you could ask someone whoreallyknowsathingor2 if they think there is any risk involved as far as it went today, you could have it deleted by an op Quote Link to comment Share on other sites More sharing options...
BlueViolince Posted October 26, 2014 Share Posted October 26, 2014 I did something similar, but non-invasive a while ago. I hooked up an ldr in a hammond box with a 1/4" jack. Used an led lamp as my light source that I could block with my foot, and hooked up the jack to exp-2. Simple. If you can drill, solder, and use basic tools, it's as simple as positioning an external strobe light properly. Of course, do you want a strobe light flashing at your feet while you play? Might be a non-issue for some people. Quote Link to comment Share on other sites More sharing options...
Rewolf48 Posted October 27, 2014 Share Posted October 27, 2014 I can understand what the OP is going on about - producing a device that looks to the HD as if it is an Expression Pedal and which plugs into the Exp 2 socket, but is actually controlled by an external modulation source. The thing that I find to be a problem is the early presumption for the whole post: "far as i know, midi is poorly implemented in the pod hd series and basically has switching functionality only". As is clearly stated in the Advanced guide (second page of Appendix B) [edit -> B... stupid emoticons] Exp1 and Exp2 can be controlled via MIDI Continuous Controller messages: MIDI CC # Value Function 001 0 - 127 EXP-1 Pedal Assignment 002 0 - 127 EXP-2 Pedal Assignment How would the rack HD Pro manage if all of the Pedal functions on the HD 500 couldn't be controlled over MIDI as it is basically the same device? So at least for the use-cases where the LFO source is via MIDI the HD500/Pro(&X) already have this covered Quote Link to comment Share on other sites More sharing options...
panaman Posted October 27, 2014 Author Share Posted October 27, 2014 i read up on the midi functionality, the manual clearly states for midi in: midi control message 1 and 2 can change the assignment of the pedals, not it`s values. you can also not set any values of effects or amp controls. all there is is looper control and footswitch assignment and toggling. that i call switching capability only. for midi out: The EXP1 and EXP2 pedal controls can be assigned to each send one MIDI CC with a definable Value Range, which allows you to sweep a variable parameter on your target device. that is used to control other devices that do have full midi implementation. its poor compared to a full midi implementation, but better than nothing. could be handy in combination with my project though. i`ll have to check how many times per second the pedal assignment can be changed over midi, if its fast enough this could be really useful like a multiplexed modulation input. thanks for pointing that out. Quote Link to comment Share on other sites More sharing options...
Rewolf48 Posted October 28, 2014 Share Posted October 28, 2014 I think you have misunderstood it a little bit - the expression controller "position" is varied using cc1/cc2. The same is true for all of the CC messages - the switch ones change the position of the switch - as the CC increases past 64 the switch is treated as down and as it comes down below the switch is treated as up. You can control all of the main foot controls via MIDI as well as Program Change. This is confirmed by uber guru phil_m here http://line6.com/support/topic/187-has-the-fix-been-done-to-allow-volume-control-of-the-hd-500-using-midi-cc-7/ and zubala here http://line6.com/support/topic/2677-pod-hd-pro-fcb1010-midi-foot-controller/ (HD Pro which is identical MIDI implementation) and numerous other discussions across the web. You are quite correct that you cannot set Amp or Effect control settings directly via MIDI.. that is because you control them indirectly through Exp 1 and 2. External MIDI Source -> CC1 -> Exp 1 position -> Effect control position (50+ all changed at the same time) You might not know that if you attach a JTV via VDI that Exp 3 and 4 appear to give two additional Expression Controls - the positions of these can only be varied by the Volume and Tone knobs on the JTV. Quote Link to comment Share on other sites More sharing options...
panaman Posted October 28, 2014 Author Share Posted October 28, 2014 i have to take it from the pros. i like it already. glad you brought this up. too bad the manual couldnt be more specific or even helpful. still, for any analog mod sources, the analog expx in is easy enough to handle and inexpensive to hook up. my uneducated guess; wouldnt it take less dsp to midi-control a parameter directly rather than controlling it with the exp and assigning that to the parameter i checked, the exp2 shows on the assign page even if none connected. testing the midi i`ll have to wait til the weekend. Quote Link to comment Share on other sites More sharing options...
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