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POD HD500 volume pedal response curve
by jimi00 on 2012-02-26 01:25:50
Hello,

Long time user of a Pod XT Live and now happy owner of a pod 500 HD, let me ask you a question.

I noticed that the behavior of the volume pedal has changed on the HD500 compared to the XT Live.

The response curve of the volume pedal is not at all linear, which is really annoying.

At the end of pedal travel, a few millimeters greatly increase the sound level when at the beginning the sound increases slowly.

The response curve seems to be like that :

<a target=new href=http://t0.gstatic.com/images?q=tbn:ANd9GcQuKVbpVARfV3iYPfcLjhV9LFgzl5V7psTlxpeSyxfPn8qJjnQS"class="jive-image" src="http://t0.gstatic.com/images?q=tbn:ANd9GcQuKVbpVARfV3iYPfcLjhV9LFgzl5V7psTlxpeSyxfPn8qJjnQS"/>


Does the response curve can be changed? If not, would it be possible in a future update?

Thank you for your answers



Re: POD HD500 volume pedal response curve
by jimsreynolds on 2012-02-26 03:14:48

I don't think there is any way to set a curve for the Volume Pedal FX Block but I don't recall anyone mention non-linearity as a problem either.

Only things I can suggest ...

  • Calibrate the pedal using the procedure here just in case it is out --> http://line6.com/support/docs/DOC-2223
  • Try">http://line6.com/support/docs/DOC-2223">http://line6.com/support/docs/DOC-2223
  • Trychanging the location of the volume pedal in the chain.  Typically, it might go after the amp and before the reverb/delay effects but experiment.
  • If you use amp models:  try assigning the expression pedal to the Volume parameter for the amp in the 'Contollers' screen of HD Edit instead of using a Volume Pedal FX Block.  This may have a different curve.


Re: POD HD500 volume pedal response curve
by jimi00 on 2012-02-26 03:27:17

I have already done the calibration. This is also on this occasion that I could verify that thiscurve is not linear.

At the end of pedal travel, we realize very well that the value increases from 220 to 255 for just 1 mm of the pedal travel, while in the beginning, I have to move the pedale on more than 1 cm to get the same variation of the parameter value ...

(you can easily try and you'll see...)

I played live yesterday, and i found that fact very boring as very fine variations on the volume pedal lead to volume getting the sound to be very loud and it's very hard to use while playing...




Re: POD HD500 volume pedal response curve
by addytsoi on 2012-02-26 05:40:29

Yes!

It is a real annoying problem!

That's less response at low level and too sensitive at high level.

I have performance frequently and it is very hard to control the Volumn balance.

Please line6 can you assist to fix this.



Re: POD HD500 volume pedal response curve
by jimi00 on 2012-02-26 09:48:48

I'm very surprised that this problem hasn't already be mentionned as when you play live, the volume pedal is really necessary...

And as i said, I didn't had this problem with my POD XT Live....



Re: POD HD500 volume pedal response curve
by phil_m on 2012-02-26 10:09:07

Most volume pedals aren't linear in their response. I think the tap onboard expression pedal is modeled to match an audio taper, which pretty much matches what you have drawn there. I think the idea is that more people use the volume pedal effect to do volume swells rather than set the volume at a certain level. If you're doing a volume swell, linear tapers don't work very well. Also, wah pedals usually have an audio taper as well.

If you use an external expression pedal like the EX-1 or the Mission Engineering EP1-L6, they would have a linear taper and would respond in more of way in which you're wanting. Other than that, Line 6 would have to do something like offer selectable response curves for the onboard pedal, and I don't know if they will ever do that or not.



Re: POD HD500 volume pedal response curve
by jimsreynolds on 2012-02-26 10:39:31

A feature request may be in order.  This is a "pretty please with sugar on top" message to the Line 6 Developers that requests that a new feature be implemented within the software.  There are no guarantees but you don't ask .... you don't get right?

Link is here.  http://line6.com/company/contact/productfeedback/

">http://line6.com/company/contact/productfeedback/">http://line6.com/company/contact/productfeedback/



Re: POD HD500 volume pedal response curve
by meambobbo on 2012-02-26 17:16:18

actually I believe this has been addressed in another thread but I can't find the thread.  I think the problem isn't that the volume pedal is non-linear, but that it actually IS linear, where traditional volume pedals follow a logarithmic curve, which is basically the opposite of what you posted.  It has something to do with how as volume in db increases linearly, it sounds more like an exponential increase.  So with the logarithmic curve, the volume change sounds linear.

There is no fix as of yet.  It would be really nice if you could set the expression pedal to follow a linear path or logarithmic path when you set it to any effect's parameter.  The next best solution would be to change the volume pedal effect to follow such a curve.



Re: POD HD500 volume pedal response curve
by meambobbo on 2012-02-26 17:23:06

the only other solution is to get an actual volume pedal.



Re: POD HD500 volume pedal response curve
by phil_m on 2012-02-26 19:55:51

I actually double-checked it tonight. The onboard pedal has a logarithmic or audio style taper. It's much like what the first post here describes. There's a lot more travel at the top of the sweep than at the bottom. When the pedal is at the halfway spot, the actual value is about 30%. Then in the last 10% of travel or so, there's about 25% or more change in value. For me, it actually works like I'd expect a volume pedal to work. If you attach an external pedal with a regular linear pot, than the volume effect would be linear. That would work for having the percentages correspond with the physical position of the pedal, but it wouldn't work too well for volume swells.



Re: POD HD500 volume pedal response curve
by meambobbo on 2012-02-27 09:02:56

i really think you have it backwards:

http://en.wikipedia.org/wiki/Potentiometer#Logarithmic_potentiometer

"Logarithmic">http://en.wikipedia.org/wiki/Potentiometer#Logarithmic_potentiometer">http://en.wikipedia.org/wiki/Potentiometer#Logarithmic_potentiometer

"Logarithmictaper potentiometers are often used in connection with audio amplifiers as human perception of audio volume is logarithmic."

http://en.wikipedia.org/wiki/Logarithm

">http://en.wikipedia.org/wiki/Logarithm">http://en.wikipedia.org/wiki/Logarithm



Re: POD HD500 volume pedal response curve
by phil_m on 2012-02-27 09:40:46

No, I think you do...   And actually, the links you put up just confirm what I'm saying. Most volume controls (and volume pedals) are designed to mimic the human hearing response, hence they're logarithmic taper.

Seriously, though, it's been discussed here a number of times, and you can try it out for yourself. The onboard pedal behaves more like a traditional volume or wah pedal.

I also know for a fact that the that the pots the EX-1 pedal are linear taper. That's why some people don't like the way they respond when used as a wah or volume pedal.

Try it out for yourself by setting up the onboard pedal to control a parameter on an effect. You can see where the values are during the sweep of the pedal. If it were linear, the values would pretty well coordinate with where you were in the sweep. But they don't. There's a lot more movement in the top part of the sweep than at the bottom.

EDIT: I should add, I'm really not trying to be adamant about the actual response curve of the onboard pedal. It may be off from an audio taper by a bit. But it isn't linear. It would be nice to have selectable curves for it, though, because the type of taper you want changes based on what you want to do with the pedal. I think this is definitely something worth putting feature requests in for.



Re: POD HD500 volume pedal response curve
by Pezza on 2012-02-28 06:09:46

The Vetta had a choice of 3 expression pedal curves. As I remember they were linear, log and double log. The extra choices were added in one of the later updates. I would have thought it could be done on the Pod HD if it could be done on the Vetta. It was a very useful feature which I have missed on the HD500.



Re: POD HD500 volume pedal response curve
by meambobbo on 2012-02-28 07:45:17

yeah, i need to check it out when playing with it like you did.  i'm not saying i don't believe you - i do.  i'm just saying that I thought volume pedals use a log curve to match human hearing, meaning it is adding more signal from 0-50% than from 51-100%.  I think you're saying that they normally do the opposite.

A logarithmic curve I would believe behaves as I describe.  as X moves from 1 to 20, there is a greater difference in Y than from when X moves from 20-40.  That's why I posted the wikipedia link to a logarithm.  IE - a logarithmic curve is the inverse of an exponential curve.

Making things more complicated is that a decibel is a logarithmic unit of measure http://en.wikipedia.org/wiki/Decibel

IMO,">http://en.wikipedia.org/wiki/Decibel">http://en.wikipedia.org/wiki/Decibel

IMO,it doesn't match up linearly to how I'd quantify volume: http://www.gcaudio.com/resources/howtos/loudness.html

But">http://www.gcaudio.com/resources/howtos/loudness.html">http://www.gcaudio.com/resources/howtos/loudness.html

Butit works better than the input data used to calculate db's, which would get exponentially larger in relation to perception of volume.  So our perception is logarithmic but likely not using the same base as how db's are measured.

There's a huge aspect of this we're not talking about. What are the % values of the expression pedal actually being fed into?  how is volume actually being calculated on the Pod?  For instance, how does the Volume knob on the amp relate to output db?  To me, it sounds like the volume is exponentially getting louder as you turn up the knob.  It seems like a linear db movement - if 1% = 1 db and 100% = 100 db then 50% = 50 db.

So if the pedal's movement is exponential to produce a linear db value, which actually relates to an exponential increase in volume, that's a double whammy - you are multiplying exponents.  If it was simply linear, the result would still be exponential, only less so.  If the pedal used a logarithmic curve, then you'd have a more linear increase in volume IMO.

That's why I think audio tapers are logarithmic - they feed into amplifiers that are exponentially increasing the signal.  So a logarithm into an exponent gets you a linear increase, more-or-less.

And FWIW, I thought the expression pedal was controlled by an optical sensor, not an audio taper/potentiometer.



Re: POD HD500 volume pedal response curve
by phil_m on 2012-02-28 08:11:49

You are correct - audio tapers are roughly logarithmic. The two terms are used interchangeably a lot of the time. To me, the way the volume pedal effect reacts on the HD500 doesn't really seem to be that out of whack. It actually seems to be a pretty nice sweep that is similar to my Ernie Ball Jr. volume pedal. So I guess what I'm affirming here is that the curve the original poster drew seems right. The thing is that to get a perceived doubling of volume, the signal needs to be 10 ten times greater. So whatever the actual value of the signal is at the 50% sweep of the pedal, it should be 10X that amount the top of the sweep. The whole idea is that the position of the pedal roughly corresponds with what we think we're hearing. At 25% of travel, the sound should be perceived as 1/4 as loud. Now how close to being linear the HD500 pedal sounds - I don't know to be honest. I've honestly never paid that much attention. I don't typically use the volume pedal to do fine tuning type of adjustments. I use it to do swells, and other than that it's either full up or full down. It's a log taper of some sort. There are people who spend a lot of time analyzing the response curves of different volume pedals on the internet. It's not something I care about that much.

I took a few classes in college in acoustics - one even a 400-level, and this stuff still confuses me. I always have to double-check the equations. This page does a good job in summarizing things: http://www.sengpielaudio.com/calculator-levelchange.htm

Oh,">http://www.sengpielaudio.com/calculator-levelchange.htm">http://www.sengpielaudio.com/calculator-levelchange.htm

Oh,and you're also correct in saying the HD500's pedal is optical. So the curve is just something that's in the software anywhere. It seems like adding user-selecatable response curves could be something that could be done in a firmwware update pretty easily.



Re: POD HD500 volume pedal response curve
by phil_m on 2012-02-28 08:22:07

By the way, if the curve of the onboard pedal were truly linear, you'd actually be seeing kind of the opposite problem the original poster is talking about. You'd have a lot of perceived increase at the bottom of the sweep and relatively little as you moved toward the top. It's what happen with some amps' master volume knobs. Between the 0 and 3 ticks on the knob, there's a huge amount of play. Nudging the knob a millimeter or two either way makes a big difference in the volume coming out the amp. But as you turn it higher, like past 5 or 6, the amp won't get all that much louder. The signal is increasing in linear way, but the perceived loudness is only increasing slightly.



Re: POD HD500 volume pedal response curve
by pb00067 on 2012-03-03 00:06:36

I agree with phil.

If the curve is just something that's in the software anywhere, then adding user-selecatable response curves should be something that could be done in a firmwware update pretty easily.

Please Line6, provide such user-selecatable response curves in one of the next firmware updates.



Re: POD HD500 volume pedal response curve
by jimi00 on 2012-03-24 05:50:32

Yes please Line6... give the users the ability to choose the response curve.

Once again, the difference is very noticeable between my old POD XT and the HD500.

I use the volume pedal a lot during my live sessions, and on the HD500, it's really really hard to use the volume pedal to switch between Solo and rythm performances.

I've never felt that with the XT...



Re: POD HD500 volume pedal response curve
by pb00067 on 2012-04-11 02:26:53

I'm begging you Line6... please give us the ability to choose the response curve!

I play in a Rock-Band and had 2 Gigs so far with the PodHD500: the volume pedal was a really catastrophe to me:

have put it around 75% of max volume before I had to start with my accompaniment riff while the rest of my band was already straight playing (drums,bass + keyb).

The result was, that I heard almost nothing coming out of my guitar, I had to put the volume pedal to something between 70% and 80% have an adequate volume for

accompaniment. While putting the volume pedal to 100% for soloing is no problem, it is really hard to guess the right accompaniment-volume with your foot.

Especially doing some dynamic crescendo or decrescendo over the volume pedal becomes very difficult, when all has to happen within 70% and 100% of volume.

When I use my old Amp with my analoge volume pedal in the effect-loop, I have no problems like this.



Re: POD HD500 volume pedal response curve
by jimsreynolds on 2012-04-11 02:32:51

You should be able to fix that by setting a minimum setting for the volume pedal.  Normally, the minimum volume is set to 0 but if you changed it to around 70 then heel-down would be rhythm level and toe-down would be lead level.  The only thing you would lose is the ability to turn off your signal with the volume pedal.

I take your point on the curve being subobtimal though.



Re: POD HD500 volume pedal response curve
by meambobbo on 2012-04-11 08:30:31

If you wanted to kill the signal you could assign a footswitch to the amp and set bypass volume to 0.  Or I think you could assign 0-100 for EXP-1 and 75-100 for EXP-2, but maybe that's wrong...



Re: POD HD500 volume pedal response curve
by att0m on 2012-04-11 08:50:52

I think Line 6 intended the pedal to be used for wah effects in which case a linear pot (or its digital equivalent) is great. However when the pedal is assigned volume, it should obviously be the digital equivalent of a logarithmic pot. Guitar volume knobs (and amp volume knobs) use log pots and this is why the "perceived" volume is relatively uniform across the dial. I'm not sure what Line 6 was thinking by not changing the default behaviour of the pedal when it is set to volume mode...!



Re: POD HD500 volume pedal response curve
by meambobbo on 2012-04-11 14:12:55

esp since the feature was already implemented in the vetta 2



Re: POD HD500 volume pedal response curve
by pb00067 on 2012-06-11 05:10:05

Thank you very much for the hint jimsreynolds.

Although it is rather a workaround than a final solution, it solves my biggest problem with HD500, thanks again.




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