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Posts posted by doughadfield

  1. Hi, This is becoming a major issue for me. whilst I appreciate and am grateful for regular firmware updates, it's a REAL PAIN having to reset everything to factory on every firmware update, then try to remember all the global setting changes I've made when tweaking my helix over time for live performance. It can be very damaging to a performance to suddenly find a setting not set, when it should have been. Therefore I need a way to save and restore global settings in the same way that setlists are saved and restored, so I can be sure the helix is back to where I left it, after the upgrade.


    Line6, if you're working on a fix for this, please let us know so we can stop fretting and simply hold our breath for the update!


  2. Hi, I'm flattered at the kind words on this thread - thanks all. The diagram that a2dconverterguy posted is truly impressive, and illustrates the solution beautifully. As for the issue of ground loops, as you suspect, the CV/FET solution is unlikely to make any difference, as the ground loop issue is due to the common ground between the Helix and your amp, which is still present with the FET solution. However, it may be possible to think of a creative solution to your problem. If a resistor is inserted in the common ground, the ground loop current is reduced and your problem may go away. The beauty of the FET is that it's a voltage-controlled device - it requires almost no current at all at the gate. So, we could put a large resistance in the ground circuit and still generate the gate voltage necessary to turn on the FET. Try that - in the excellent diagram above, put a 10K resistor in the ground line between the Source of the FET and the Jack connected to the Helix. Give it a go and let us know how you get on :-)



    • Upvote 2
  3. Minor correction  - the FET I used was a "2N7000" not "SN7000" (typo in my previous post). Also yes, it's only a single channel solution. I did toy with the idea of switching multiple channels when particular CV voltages were set, but abandoned the idea as it would be fairly complex (involving an analog comparator and stable power supply regulator). I only needed the one additional channel, and I liked the simplicity of just modding the cable - no other alterations necessary :-).

  4. ANSWERED!!: I'm currently using the CV output of My Helix to drive a relay input on my AMP. I measured the properties of the CV output and it delivers 0-5V at an output impedance of approx 660ohms. This is far too weak to drive a relay coil directly (which my AMP uses) so I've embedded a Field Effect Transistor (FET) into the body of the Jack plug inserted into the CV output socket of the Helix (I used a 2N7000 FET - cheap and easily obtainable).


    The Gate of the FET connects to the CV output, the Drain connects to the AMP switching line, and the Source connects to ground.


    I then set up a Helix footswitch (from the control centre on the Helix) to toggle the CV between 0 and 100. This drives the Gate of the FET and turns it ON and OFF (the Gate saturation voltage of the 2N7000 is around 2.1V). When on, the FET effectively shorts Drain to Source, so acts like a mechanical footswitch or relay contact, shorting the AMP switching line to ground.


    Simples ;-)



    • Upvote 3
  5. Helix CV Output Impedence Measured!! - My Helix arrived at the weekend and I've just got around to measuring the output impedence of the CV output..... and the answer is..... 695ohms (allowing for inaccuracies in the measurement process, assume between 600 and 700ohms). This is nowhere near enough to drive an external relay directly (it will source around 7mA into a short circuit - far too little for relay coils). I'm guessing the output circuit of the CV is an op-amp (output impedence around 100ohms) in series with a 560ohm resistor (nearest standard value to 600ohms) making around 660ohms.


    Also, the CV output is 0-5V, not 0-10V, as I'd assumed!! (I was thinking of old lighting controllers, with their 0-10V signals).


    So, now we know ;-)




    PS - this output can still be used to drive the relay input of an external amplifier, simply by putting a FET into the jack plug body, as I mentioned above (I'm doing this now, with my own amp).

    • Upvote 1
  6. Unfortunately, the solution suggested by fukuri won't fix your problem, as you've found one of the significant shortcomings (IMHO) with the Helix as "system controller" - with present firmware. This should be very easy to fix with a firmware update, but we need to persuade Line 6 of the importance of this. Just about every other controller board or module I've used, which has relay outputs for controlling amps, has the ability to reverse the polarity of the relay outputs. This is because many (most) "vintage" amps drove their footswitch units this way:

    The relay coil was connected internally with one end to relay supply (+9-12v typically) and the other end of the relay coil to the footswitch connector. Therefore, when the relay was "out" (coil not energised) the supply voltage appeared in the footswitch line and could drive an LED in the footswitch unit. Therefore, the function would be ON when the coil was un-energised, so the LED would be ON in the footswitch unit. When the footswitch was pressed, it shorted the relay terminal to 0v, thus energising the relay and switching the funciton OFF as well as shorting the LED and turning it off.

    So, Line6 needs to realise this and add a "relay polarity invert" function, probably to the global settings in the Helix. Until then, we'll be confused by the switch light being ON when the amp function is OFF (not exactly the "world class system controller" yet.... but hopefully will be fixed soon... (please!!)

  7. Just wanted to say how helpful I found this post. I too have a beautiful hand-wired vintage valve amp that makes all my guitars sound amazing, so I'm very skeptical about  modelling (having tried HD500X among others) - but I have a helix rack on order (since August last year - should arrive next week!!!) and now I can't wait, after reading this very balanced and relevant post. 

    I particularly appreciated the "preamble" establishing the author's credentials as a "tone snob" so as to understand how the helix was being evaluated and what it was being compared to - very helpful indeed.


    • Upvote 1
  8. Hi again, to answer the reply from HonestOpinion, you can't change the electrical characteristics of the CV output simply by changing firmware, as it's a hard-wired variable voltage output and not a relay contact. However, you can *easily* use it as an additional amp switching output simply by setting the CV value to switch between 0v and 10v in the "Command Centre" section of helix (using a switch or "instant location" setting; not an expression pedal!). The CV output voltage will then "switch" between 0 and +10v as you enter the patch or hit the stomp mode foot-switch. The issue is then how to drive your particular amp. It may be that the CV output can source (or actually, sink) enough current to engage the relay in the amp (typically around 20-30mA). If so, then happy days. If not, you'll need to add a transistor to act as an amplifier - the simplest would be simply to embed a single FET (2N7000 would be ideal - at around 8p each!) into the jack plug at the helix end - Gate to CV output, Source to ground and Drain to Amp relay input. The FET will then switch on when the CV voltage is above about 2v (10V will do it!) and pull the relay line to ground, switching on the relay in the same way that a foot-switch would.


    So, back to my original question - Line6 guys, what's the output impedance (sink current capability) of the CV/Expression output?






    EDIT!! - the CV voltage output of the Helix is actually 0-5V, NOT 0-10v, as I'd incorrectly assumed above!

    • Upvote 1
  9. Hi Dave,

    thanks for replying. I'm an old electronics engineer too ;-). I was planning to use the CV output like a switched output, by using simply 0v and "Max"v values - clearly you don't want to continuously vary the CV if you're trying to switch something on or off. As you rightly say, loading the CV output with a low impedance load such as a relay coil will change the voltage (depending of course on the output impedance of the CV) but the relay coil won't care what the precise output voltage is, as long as it's high enough to reliably switch the relay. This is what I'm trying to ascertain.


    I can, of course, build an external buffer amp using a transistor to drive the relay coil, but I want to avoid that complexity if possible.




  10. Hi, I can't find anywhere the specification of the CV control voltage output on the Helix - specifically what's the output impedance - in other words, how much current can it drive?


    I'm intending to use the CV output as another amp switching output (my amp has three remotely switchable functions that I want to automate with Helix) so I'm keen to know whether I can drive a relay coil directly from the CV output, or whether I need to buffer it with a custom-built transistor stage.


    Any indication would be nice (in fact, a "specifications" section at the back of the manual would be even nicer!! :-))


  11. According to the manual, the AUX input has a 10Mohm input impedence. Frankly I think this is a typo, as this would be insanely high (great for unbufferred piezo pickups from acoustics, but very noisy!!). However, if, like me, you're using the Line 6 wireless (I have a Relay G50) the output impedance of the receiver unit will be quite low - like an active pickup output. So connecting the wireless receiver output to the aux input should be ideal. This is exactly what I intend to do - I have a helix rack unit on pre-order and I plan to mount my G50 receiver in the same (4U, portable) rack, connected to the Aux input in the back, so no messy cables visible at the front.



  12. Hi, it is getting increasingly difficult to source 2GB SD cards, as they are technically obsolete, having been replaced by SDHC cards of higher (much higher!) capacities. As the JM4 is still a current product from Line6 (and rightly so, as it's one of the best loopers out there - particularly for the price and meets a strong market need) will line6 update the JM4 with support for larger SDHC cards in a future (near future!) software update?


    thanks for a great product! 




  13. Thanks a lot, guys, for your prompt and authoritative replies. I've got my pre-order in for a rack unit and controller. Now I've just got to keep a lid on my excitement while I sell everything in my music room that's not bolted down, to save up!! ;-)


    ....while polling the line6 website every four hours... ;-)


    Musicians can be a very obsessive lot!

  14. Hi, Please can you confirm for me the relative screen size (dimensions and resolution) of the main colour screen between the rack and floor models - in other words, are they identical? I'm looking at getting the rack version, but want to make sure the screen resolution isn't compromised with respect to the floor version.


    Also, are the scribble strips the same size between the floor Helix and the controller for the rack unit?


    One more question - when the manual is (finally) published on-line, will you put it in the current "tech support->manuals" section of your website, or somewhere else? (I need to know where to look obsessively twice a day, like I'm doing right now... ;-)



    thanks a lot


    ...I'm holding my breath!


  15. Hi, I've just put my pre-order in for a rack with control board, and am now frantically selling any piece of kit not biologically attached to my body!! I have one HUGE request though, please - PLEASE PLEASE PLEASE make the looper sync to tempo - it's utterly useless for live use without being able to sync to the drum machine or other tempo source! I had an HD500X for a time, and the looper was simply a home practice tool - useless for live use as it had no sync capability. With the Helix aimed firmly at the more professional market, synchronising the looper is, in my view ESSENTIAL. 


    What's the chance?


    Thanks again for producing such an awesome product!



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