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Guitar In-Z Full Clarification?


supertonic_jack
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The Guitar In-Z is the simulation of the impedance, right? I had most of my presets on 1M Ohm. Most of them were to bright on most of my guitars. But I turned down the tone knob on my guitars to around 50%, then it was fine. An electric engineering friend of mine just told me that 1M Ohm is not a realistic value in the real world. The amp inputs of real amps are not that high. He said they are up to 100k Ohm. 

I just googled and this article says something different:
 

Impedance Considerations With Electric Guitars

The pickups generally used in electric guitars and basses are primarily inductive rather than capacitive (because of the coils used under the strings), and are also highly resistive simply because of the sheer amount of wire involved (typically up to 10kΩ), although different styles and makes of pickup can vary enormously. Since the pick-up presents a relatively high output impedance, it is normal to provide guitar preamp and DI inputs with a hugely high input impedance. A minimum value is typically 470kΩ, but many are over 1MΩ and a few, designed for accepting feeds from magnetic pickups in some acoustic guitars, are rated even higher than this.

 

source: https://www.soundonsound.com/techniques/understanding-impedance

 

 

So know I am really confused. Who is right? What is right?

The question to you out there:
What impedance do you use at your Helix input? 70k Ohm? 1M Ohm? Auto? And why?

Why not use Auto all the time? Or why should I use Auto all the time? What does Auto really do? Is it reliable with all guitars?

Thanks and Kind regards ;)

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Fwiw, I'm using a fixed impedance (usually 1mOhm) for pretty much all my patches, the reason being "reliability". That way, I just know how things react, especially as the Helix keeps the impedance of the first hit block in "auto" mode, which sometimes (see the link qwerty42 posted) yields less than desirable results. In addition, I sometimes use other buffering devices in front of the Helix, which usually render any internal setting useless (or at least very different). With a fixed impedance of 1 mOhm this is way less likely to happen. I'm also used to that because my previous live rigs always had a buffered input stage, likely introducing something around 1 mOhm.

I do fool around with the settings for recording and on some selected patches, though - but my main ones are all fixed.

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Thanks guys! I already read the linked posts and had a look at the spreadsheet. I will stick to 1M Ohm input like I did before ,yeah. I will adjust everything else so that it sounds good after that. I will keep in mind what effects could sound terrible due to the mismatched input of 1M (mostly fuzzes and delays anyway. ok the screamer is important for me but I sounds good anyway). 

Do you guys also have the feeling that via most PAs and Monitors the Amps (in a full chain with effects and cabs) in the Helix sound a bit too bright sometimes? Well I have the tone knob I use quite a lot on my guitars, depending on the system I play the Helix over. 

Of course I adjust the Amp (Treble e.g.) and the effects and EQing so that it sounds good at home. But live sometimes it can be a bit harsh. 
I know this all sounds wishywashy (since every speaker has a own frequency response, and the room and treatments have huge impact on the overall perception of my presets) but It is just some rough feeling I got about the helix stuff. You share the same view?

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Your friend is wrong... 1MOhm is a typical input impedance for guitar pedals and even amps nowadays. Perhaps in vintage amps, it was more variable, but it’s certainly not unusual today. But use whatever sounds best to you. One clarification, though, the variable input impedance isn’t a simulated or modeled thing - changing the setting actually changes the input impedance of the Guitar In. If you hooked up a meter to it, you’d see it change.

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12 hours ago, supertonic_jack said:

Of course I adjust the Amp (Treble e.g.) and the effects and EQing so that it sounds good at home. But live sometimes it can be a bit harsh. 
I know this all sounds wishywashy (since every speaker has a own frequency response, and the room and treatments have huge impact on the overall perception of my presets) but It is just some rough feeling I got about the helix stuff. You share the same view?

Are your adjustments at home done at the same volume as your live setup? If not, could just be the well-known Fletcher-Munson curve

As volume goes up, our perception of what we hear as high treble frequencies goes up at a greater rate. It's a very real effect that has to be compensated for.

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9 hours ago, qwerty42 said:

Are your adjustments at home done at the same volume as your live setup? If not, could just be the well-known Fletcher-Munson curve

As volume goes up, our perception of what we hear as high treble frequencies goes up at a greater rate. It's a very real effect that has to be compensated for.


damn I know this curve, but I didn't think of it! pretty clever to suggest that ;)
I mostly play/played smaller venues and quieter rehearsals, but yeah some of the difference could be due to the increase of trebles (and bass) during the increase of volume. 

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This is one of the things that the Global EQ is great for. Since it’s global, it applies to all of your presets, and you can dial it in at the venue at performance volume to compensate for the room and loudness differences. When you’re back home, just turn it back off.

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4 hours ago, qwerty42 said:

This is one of the things that the Global EQ is great for. Since it’s global, it applies to all of your presets, and you can dial it in at the venue at performance volume to compensate for the room and loudness differences. When you’re back home, just turn it back off.

yep like that thing too.
wish there were more bands and more eq settings possible though. Then it would be a piece of cake to recreate something like the inverted fletcher munson curve for the trebles and so on...
still great though yep

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This debate regarding how the auto setting for impedance should work leaves me with a couple of core questions.  We start with the premise that for many pedals and amps 1M ohm is a good default per their design although certain pedals e.g. fuzz, function better at a lower input impedance. In practice for pedals designed with a lower than typical impedance, this effectively filters out some of the high range of the input from the guitar that might result in an undesirable tone when passed through the effect. The Helix when set to 'Auto' sets the impedance to the "ideal" impedance as determined by Line6 for the first pedal in the chain, regardless of whether it is bypassed or not.  That means that when set to auto-z, if the first pedal is bypassed the next pedal very likely is not receiving an output signal that is optimized for its specific impedance requirements. Sorry to repeat all this for the majority of users here who are already aware of how the auto-z setting works but it leads to my next questions.

 

Let's say you place for example a fuzz pedal in the first position and set the impedance to 70k, the recommended impedance for that particular pedal.  It seems that to optimize the sound when it is bypassed, the Helix would have to adjust the impedance automatically so that the next non-bypassed pedal in the signal chain receives signal at the optimal impedance level. As auto-z does not work this way I set up my impedance level to switch according to whether or not the snapshot I'm using has, for example the fuzz pedal in first position engaged or not;  a method that was proposed by others on the forum years ago and seems like the best current option.

 

In the most general of terms whether in the digital or analog world, it seems like the goal should generally be for any pedal, located anywhere in the signal chain, to receive input signals that allow it to sound its best and to provide an output signal that yields the best results when processed at the impedance setting of the next block/pedal in the chain. In practice this is almost impossible to consistently pull off in the analog world but certainly much easier in the digital realm where you have greater uniformity and control over a given block's input and output requirements and the ability to instantly shuffle settings virtually. In many ways impedance is a blunt instrument to use to make a pedal sound better, specific filters, buffering, and processing might often be a better alternative. Altering impedance can have such a detrimental impact downstream when a pedal is bypassed.

 

To summarize, I am not sure why there is a debate over how the auto-z should work. What possible advantage is there to the auto-z being only able to set itself to the first pedal in the signal chain? IMHO the only way for the sound to remain "optimal" as the signal is passed from pedal to pedal is if the impedance automatically adjusted the signal being delivered to the first active pedal in the chain. In lieu of that the best alternative I can see is that all the blocks be designed to work at the same impedance. Any necessary adjustments to tone as required to faithfully emulate a pedal that achieved its tone via an impedance change in the analog world would have to be rendered by digital means though methods like pre-EQ within the block. That would leave the impedance setting strictly for those who use it to modify their overall sound or accommodate different guitars/pickups.  It seems however that just modifying the operation of the auto-z setting such that it adapted to the first active pedal would be easier and more faithful to the original pedals

 

 

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1 hour ago, HonestOpinion said:

This debate regarding how the auto setting for impedance should work leaves me with a couple of core questions.  We start with the premise that for many pedals and amps 1M ohm is a good default per their design although certain pedals e.g. fuzz, function better at a lower input impedance. In practice for pedals designed with a lower than typical impedance, this effectively filters out some of the high range of the input from the guitar that might result in an undesirable tone when passed through the effect. The Helix when set to 'Auto' sets the impedance to the "ideal" impedance as determined by Line6 for the first pedal in the chain, regardless of whether it is bypassed or not.  That means that when set to auto-z, if the first pedal is bypassed the next pedal very likely is not receiving an output signal that is optimized for its specific impedance. Sorry to repeat all this for the majority of users here who are already aware of how the auto-z setting works but it leads to my next questions.

 

Let's say you place for example a fuzz pedal in the first position and set the impedance to 70k, the recommended impedance for that particular pedal.  It seems that to optimize the sound when it is bypassed, the Helix would have to adjust the impedance automatically so that the next non-bypassed pedal in the signal chain receives signal at the optimal impedance level. As auto-z does not work this way I set up my impedance level to switch according to whether or not the snapshot I'm using has, for example the fuzz pedal in first position engaged or not;  a method that was proposed by others on the forum years ago and seems like the best current option.

 

In the most general of terms whether in the digital or analog world, it seems like the goal should generally be for any pedal, located anywhere in the signal chain, to receive input signals that allow it to sound its best and to provide an output signal that yields the best results when processed at the impedance setting of the next block/pedal in the chain. In practice this is almost impossible to consistently pull off in the analog world but certainly much easier in the digital realm where you have greater uniformity and control over a given block's input and output requirements and the ability to instantly shuffle settings virtually. In many ways impedance is a blunt instrument to use to make a pedal sound better, specific filters, buffering, and processing might often be a better alternative. Altering impedance can have such a detrimental impact downstream when a pedal is bypassed.

 

To summarize, I am not sure why there is a debate over how the auto-z should work. What possible advantage is there to the auto-z being only able to set itself to only the first pedal in the signal chain? IMHO the only way for the sound to remain "optimal" as the signal is passed from pedal to pedal is if the impedance automatically adjusted the signal being delivered to the first active pedal in the chain. In lieu of that the best alternative I can see is that all the blocks be designed to work at the same impedance. Any necessary adjustments to tone as required to faithfully emulate a pedal that achieved its tone via an impedance change in the analog world would have to be rendered by digital means though methods like pre-EQ within the block. That would leave the impedance setting strictly for those who use it to modify their sound or accommodate different guitars/pickups.  It seems however that just modifying the operation of the auto-z setting such that it adapted to the first active pedal would be easier and more faithful to the original pedals

 

 

 

I generally agree with the above, but just want to highlight a couple things:

 

- The reason the input impedance circuit exists in Helix is to re-create the characteristics of the pedals they've modeled. It's not an 'optimum value' for each pedal's sound, but rather, it's the real-life value (or darn close to it) of the real pedals.

 

- I think that simulating this via only an EQ or filter of some type on the start of each pedal is not going to be as accurate. They way pickups respond to impedance varies according to the specific pickup (humbuckers/single coils; whether you them switched in a way that has multiple pickups active, etc.) To match this correctly, you need the analog reality of the circuit. You could get in the ballpark somewhat if you had an EQ with options for different pickup types and configurations, but the input impedance changes the response/sensitivity of the pickups somewhat too. Line 6 was going for accuracy; that's why they did it this way. Fractal Audio does the same thing in AxeFX.

 

- My own opinion, for whatever it's worth, is this could be 'fixed' for everyone if every pedal just had a switch for 'true bypass' as an option. If set to 'yes', then when bypassed the next pedal downstream sets the Auto value of Z. If the next pedal downstream is also true bypass, it goes to the next, and so on, all the way up to the amp which of course won't be true bypass. If people are trying to re-create a real-life rig in Helix and make it sound/feel the same, there are some cases where you probably don't want the pedals to be true bypass, although I agree that would be rarer than wanting them to just stop coloring the signal when bypassed. However, we've already seen how much confusion the existing way of dealing with impedance causes, which is pretty simple -- so adding this would probably be another nightmare can of worms.

@Digital_Igloo  Maybe a great compromise is to add one more option to the Guitar In-Z settings, which is  "Auto - True Bypass", which would make every pedal behave as true bypass (so the first active one sets the impedance), and still keep the existing Auto option without changes. This would be backwards-compatible with old presets, so nothing would break there, but it would be a very simple edit per-preset to change the behavior too. If that option was added and then made the default setting for new presets, we probably wouldn't have to see another one of these Input Impedance threads again :) Whatcha think?

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5 hours ago, qwerty42 said:

 

I generally agree with the above, but just want to highlight a couple things:

 

- The reason the input impedance circuit exists in Helix is to re-create the characteristics of the pedals they've modeled. It's not an 'optimum value' for each pedal's sound, but rather, it's the real-life value (or darn close to it) of the real pedals.

 

- I think that simulating this via only an EQ or filter of some type on the start of each pedal is not going to be as accurate. They way pickups respond to impedance varies according to the specific pickup (humbuckers/single coils; whether you them switched in a way that has multiple pickups active, etc.) To match this correctly, you need the analog reality of the circuit. You could get in the ballpark somewhat if you had an EQ with options for different pickup types and configurations, but the input impedance changes the response/sensitivity of the pickups somewhat too. Line 6 was going for accuracy; that's why they did it this way. Fractal Audio does the same thing in AxeFX.

 

- My own opinion, for whatever it's worth, is this could be 'fixed' for everyone if every pedal just had a switch for 'true bypass' as an option. If set to 'yes', then when bypassed the next pedal downstream sets the Auto value of Z. If the next pedal downstream is also true bypass, it goes to the next, and so on, all the way up to the amp which of course won't be true bypass. If people are trying to re-create a real-life rig in Helix and make it sound/feel the same, there are some cases where you probably don't want the pedals to be true bypass, although I agree that would be rarer than wanting them to just stop coloring the signal when bypassed. However, we've already seen how much confusion the existing way of dealing with impedance causes, which is pretty simple -- so adding this would probably be another nightmare can of worms.

@Digital_Igloo  Maybe a great compromise is to add one more option to the Guitar In-Z settings, which is  "Auto - True Bypass", which would make every pedal behave as true bypass (so the first active one sets the impedance), and still keep the existing Auto option without changes. This would be backwards-compatible with old presets, so nothing would break there, but it would be a very simple edit per-preset to change the behavior too. If that option was added and then made the default setting for new presets, we probably wouldn't have to see another one of these Input Impedance threads again :) Whatcha think?

 

Appreciate the highlights. Good point about pickup behavior being modified in addition to how the pedal responds when the impedance is changed. You're right. It would be very difficult to capture that interaction between the pickups and the pedal by replacing an analog impedance change with digital processing. I also agree that for example emulating the impedance change in the block's processing via EQ and other means would be a less preferable solution as well as having alluded to the impact changing the impedance can have on different guitars/pickups (my comment above  -  "In lieu of that the best alternative I can see is that all the blocks be designed to work at the same impedance. Any necessary adjustments to tone as required to faithfully emulate a pedal that achieved its tone via an impedance change in the analog world would have to be rendered by digital means though methods like pre-EQ within the block. That would leave the impedance setting strictly for those who use it to modify their overall sound or accommodate different guitars/pickups.")

 

I also agree that retaining the impedance change is likely to be the most accurate way to maintain the closest emulation of the original pedal. (My comment above - "It seems however that just modifying the operation of the auto-z setting such that it adapted to the first active pedal would be easier and more faithful to the original pedals.")

 

I like your suggestion above for true bypass of each pedal but it has its pros and cons. The pros including as you mentioned that people's existing presets could be left unaffected by a change to the auto-z operation. Another pro might be the provision of yet another option to change the sound of a block. The cons would be having to add a new per block option and using an extra parameter knob to set it. I suppose an alternative to that would be to have a global true-bypass setting.

 

There can be more than one block in a signal chain that requires a modified impedance setting. If we were to go all the way down the rabbit hole I think you might have to consider the potential in the digital world for every block to modify its input and output for optimal impedance matching to the block before and after it. When I say optimal I mean the best sound or the one truest to the original pedal, subjective to some extent I know. I have no idea how much DSP an approach like that would consume and if the changes could be made quickly enough on the fly not to introduce some switching lag. That approach would also require that the impedance changes between blocks be made digitally, not with an analog circuit as it is currently done in the Helix. I suppose you could develop a hybrid approach where the initial impedance setting for the first active block was done using an analog circuit to stay truer to the interaction of a guitar pickup going into a specific impedance on a pedal.  The impedance settings for subsequent blocks would be managed digitally. In the end run though I'm not even sure that the benefits to the sound would be substantial enough to warrant the level of effort required. 

 

I suspect having a per block true-bypass option would still leave new users perpetually asking on the forum why their fuzz pedal sounded like crap and requiring someone to inform them regarding the true bypass and impedance operation on the Helix. Maybe I am overlooking some other potential benefits for that setting though. Might it not be easier, and require less user intercession just to modify the behavior of the current auto-z behavior to work transparently by adjusting to the first active block and bite the one-time bullet to adjust any presets that required it?  Most presets probably would not require modification.

 

 

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35 minutes ago, HonestOpinion said:

I suspect having a per block true-bypass option would still leave new users perpetually asking on the forum why their fuzz pedal sounded like crap and requiring someone to inform them regarding the true bypass and impedance operation on the Helix. Maybe I am overlooking some other potential benefits for that setting though. Might it not be easier, and require less user intercession just to modify the behavior of the current auto-z behavior to work transparently by adjusting to the first active block and bite the one-time bullet to adjust any presets that required it?  Most presets probably would not require modification.

 

This is why I suggested adding one new setting under the Guitar In-Z options, called "Auto w/ True Bypass". This retains the old Auto setting, so existing presets don't get changed unexpectedly, but would make it trivially easy to set any old or new presets to use 'first active block' auto-impedance. Everyone wins, ba-da-bing, ba-da-boom.

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Fwiw, I wholeheartedly support the notion that auto-impedance should offer an (alternative, as described by qwerty42) option to act exactly as things would in an analog chain of true bypass pedals.
This should actually be doable quite easily, because, as we all know, you can already do it yourself manually, using snapshots or switches.
Fwiw, I considered doing one of the latter two but ultimately gave up on it, simply because I'm usually using a healthy mixture of snapshots and (usually multiple-assign) switches - getting impedances right in this scenario is barely possible (as I may add a drive withing snapshot set to another impendance than what the pedal may like to deal with, whereas on other snapshots it'd be doing fine).

Whatever, for the time being I'm usually getting along fine with a fixed impedance of 1mOhm or 230kOhm for my live patches. Fortunately, I discovered the Top Secret OD, which does a nice job for all my fuzzy needs, even at 1mOhm

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  • 1 year later...

Things have changed since the earlier impedance discussions in this topic. As many are aware of, later firmware versions added a global setting to allow the player to set the 'Auto Impedance' parameter to either 'First Enabled' or 'First Block' ('Global Settings' --> Preferences --> 'Auto Impedance').  

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12 minutes ago, HonestOpinion said:

Things have changed since the earlier impedance discussions in this topic. As many are aware of, later firmware versions added a global setting to allow the player to set the 'Auto Impedance' parameter to either 'First Enabled' or 'First Block' ('Global Settings' --> Preferences --> 'Auto Impedance').  

omg.... I just set my presets with whatever setting there was.  And don't intend on messing with anything at this point.  It's done and done for me.  I think that this auto impedance is kind-of going overboard... could always tweak the EQ to get the same result IMO. 

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1 hour ago, theElevators said:

omg.... I just set my presets with whatever setting there was.  And don't intend on messing with anything at this point.  It's done and done for me.  I think that this auto impedance is kind-of going overboard... could always tweak the EQ to get the same result IMO. 

 

I actually think this setting was a welcome and extremely useful addition.  I used to assign my impedance('Guitar In-Z) value to snapshots and switch it according to which block was the first active in the snapshot, so for me the 'First Enabled' option gave me an automated and more elegant solution, active in every preset/snapshot, that does not require additional snapshot editing.

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On 7/19/2021 at 2:42 PM, theElevators said:

impedance is kind-of going overboard... could always tweak the EQ to get the same result IMO. 

 

 

Not really.... physically loading down a guitar will be more reactive than simply setting an EQ. I think it's great that this "purist" option is available in the Helix. 

 

There were generally two ways people ran their traditional pedal boards... whether they new it or not. 

  • if you always had a buffered pedal at the front of your chain then your guitar ALWAYS see's that impendence regardless of whether or not it was on/off. This was the way the Helix was setup for AUTO by default. 
  • If you have True Bypass pedals at the front of the chain... then the impedance is changing all the time, depending on the first pedal that is turned on. This is the new "option" available on the Helix and will make the purist crowd much happier.... 

FWIW... I run wireless so none of this effects me in any way. I just set my input Impedance to 1M to avoid any surprises along the way. 

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On 7/19/2021 at 9:42 PM, theElevators said:

could always tweak the EQ to get the same result IMO. 

 

Nah, that's an entirely different thing, really. Especially once you're using the volume and tone pots of your guitar, different input impedances can make a difference almost like night and day.
And the new global "impedance follows first active block" option (fwiw, I wish it wasn't global...) to allow the Helix to impersonate an analog pedalboard, is highly useful.

Fwiw, in many patches I chose 230k, even when just running a single amp block. That setting just seems to work better than 1M with some of my most used guitars (almost all of them feature a 500k volume pot and a treble bleed cap). Hence I can't use "auto", because that'd automatically set the impedance to 1M in most situations (and I couldn't be bothered assigning the impedance to snapshots or switches). That's why I wish things weren't global - or, alternatively, I'd like to select 230k as the default for all things by now defaulting to 1M.

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  • 2 years later...

From what I've learned, the ideal impedance setting can vary depending on your guitar, pickups, and personal taste. Some guitars and pickups work better with higher impedance settings, while others prefer lower ones. It's all about finding that sweet spot.
In practice, it's often about experimentation and trusting your ears. So, try different settings and see what works best for your setup. And hey, that guide I want to mention (https://guitarsrepublic.com/) might have more insights to help you navigate this impedance maze!

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