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Topic: sweet spot on a passive pot volume pedal |
Quentin Hickey
From:
Nova Scotia, Canada
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Posted 16 Aug 2015 5:10 pm |
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| I have a bit of a theory about my observations with using a passive pot pedal and I was wondering if any of you have found the same. I was measuring the impedance of my pickups tonight on my multi meter. My MSA single coils read 18.2 k ohms on both necks comjng out of the guitar. I decided to measure it out of the volume pedal just to see what happens as I open and close the volume pedal. Something very interesting happenes that raised my eyebrows. At closed the meter read 0. At wide open it read 128 k ohms. I than backed off the pedal to the position I find give me the tone that satisfies my ears and the meter read around 18 to 20 k ohms. So I figured that this postion is where the impedance are matched up and the pups are not loaded so they are resinating at there designed properties. Thats actually pretty neat how the electrics work between these devices. |
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Larry Dering
From:
Missouri, USA
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Posted 16 Aug 2015 6:17 pm
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| Quenton, that's good information. I will have to test the theory and see what I get. It makes good logical sense. |
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Quentin Hickey
From:
Nova Scotia, Canada
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Posted 16 Aug 2015 6:25 pm
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Larry.
With my particular setup, my honey money spot on the volume pedal is a little bit past one third open. Of course everyones rig will vary due to your pot taper and pickup impedance etc. I think it is impotant for the passive volume pedal users to be aware of. |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 17 Aug 2015 5:52 am
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Quentin,
Please know that I write this with all due respect, but your "theory" would be like saying: "Cottage cheese on a bed of lettuce is fattening. It must be fattening because the only people I see eating it are fat people."
If you were to place a .1 mfd coupling capacitor in series between your guitar and your volume pedal pot, you would hear the same sound that you're hearing now, but your multi meter would present a very different set of numbers; if you have a 500K pot, you would read zero at closed and 500K at full on. The sweet sound you enjoy is a product of impedance, inductance and capacitance, but your meter is only reading dc resistance. A couple points come to mind.
Impedance is probably the least understood term in a musicians vocabulary.
With a guitar pickup, you're dealing with very small ac voltage and no power is being developed, therefore, there is no need to match impedance. The only caution is to make sure you don't present too much load on the pickup. A 500K pot is fine, while a 10K pot would drag your signal down. (consider a pickup truck trying to pull railroad cars.)
The inductive pickup's impedance varies with frequency so it is not only unnecessary, but impossible to "match" its impedance. Even if you wanted to, you would have to pick just one frequency to match.
There is probably a scientist somewhere who understands all of this and has all of the answers. I certainly don't. I say set amp's volume and tone controls where you like them. . . and enjoy the music.
Play well,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 17 Aug 2015 10:23 am
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| Craig Baker wrote: |
| Impedance is probably the least understood term in a musicians vocabulary. |
You got that right. Good thing I'm not a musician, but only an engineer that like to play 
| Craig Baker wrote: |
| With a guitar pickup, you're dealing with very small ac voltage and no power is being developed, therefore, there is no need to match impedance. The only caution is to make sure you don't present too much load on the pickup. A 500K pot is fine, while a 10K pot would drag your signal down. (consider a pickup truck trying to pull railroad cars.) |
The entire "match" term seems to be seriously misunderstood. Although the "match" term in itself is fine when understood correctly, it may be better to say that we can "optimize the load" for the PU at hand, to get the sound(s) we want.
When it comes to the "load" in a passive set-up, the entire passive load "seen" by the PU has to be taken into account: cable-from-PU-to-VP capacitance ... VP resistance-division ... cable-to-amp capacitance ... amp input's resistive and capacitive load.
What Quentin seems to have proved is that a load of about 500 Kohm is about ideal for the sound he wants ... when measuring 20 Kohm out over a 500 Kohm put, the in resistive load is close to 500 Kohm - where only the capacitance of the cable from PU to VP add extra load that affects the higher frequencies.
That in itself is as expected - about the same as the PU-load we get with the VP fully off, but has nothing to do with "impedance matching" as such. The result is good, but the "logic" behind it is flawed.
When opening up the VP more towards fully open, the PU will see more of the cable-from-VP-to-amp capacitance and the amp-input load, with increasing effect on the higher frequencies as result. The effect is changes in the PU's internal R-C-L resonances, that mainly are heard as reduced high frequency range or "tone loss".
Unless one calculates in all passive series and parallel resistances and capacitances for the entire PU-to-amp-in chain, it is impossible to pre-calculate effects and resulting sound for various VP positions with any degree of accuracy.
Now, one can "reverse engineer" the entire passive sound chain based on what one can hear. I do it all the time, as it helps me eliminate unnecessary components in my own sound chains.
For most musicians that's simply a waste of time though, and it is much easier to just find the sweet spots for ones own sound chains, and just play on them. |
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chris ivey
From:
california (deceased)
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Posted 17 Aug 2015 11:10 am
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| Georg Sørtun wrote: |
For most musicians that's simply a waste of time though, and it is much easier to just find the sweet spots for ones own sound chains, and just play on them. |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 17 Aug 2015 12:30 pm
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Georg,
It never occurred to me before, but after reading your post I'm convinced that everyone needs at least two buffers and it wouldn't hurt to have a third one for a spare.
Why didn't I think of that before now?
Craig
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 17 Aug 2015 12:56 pm
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| Craig Baker wrote: |
Georg,
It never occurred to me before, but after reading your post I'm convinced that everyone needs at least two buffers and it wouldn't hurt to have a third one for a spare.
Why didn't I think of that before now?
Craig |
Well, since you know that all "PU matching" calculations stop at/past the first active stage, maybe you are overthinking that one 
All that is needed after that first active buffer stage, is low resistance outputs going into high resistance inputs, which is why I use active buffers, followed by <50Kohm>=1Mohm main amp inputs.
As I sometimes also want the "passive VP" effects, an active buffer with switchable input components, that has resistive load controlled by the post-buffer VP, is on my list |
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john widgren
From:
Wilton CT
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Posted 17 Aug 2015 1:40 pm sweet spot
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One of the most wonderful things about the Telonics FP100 volume pedal is this:
-Use the impedance setting to get the "sweet-spot" tone you like, or are used to. Now the volume pedal will have that sound throughout the entire taper. No tone change from minimum on to full on.
We are now able to use the volume pedal as a TRUE volume pedal... without the inherent volume/tone changes that happen with pots. It also helps for those who play too deep into the VP to get thicker tone. It means less noise floor and more reasonable playing volumes, resulting in better dynamics and improved VP sustain technique.
_________________
Steel Guitar Services:
Live performance and recording. Instruments, repairs and lessons. Fresh bait/discount sushi.
(203) 858-8498
widcj@hotmail.com |
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b0b
From:
Cloverdale, CA, USA
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Posted 17 Aug 2015 1:45 pm
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I don't use any buffer, and I like my tone. Just sayin'.
It seems to me that the fullest tone is when the volume pedal is all the way on. As you back it off, you hear less high end and it it cuts through the mix less. I like that that effect. Between that and various right hand techniques, a player can get the full range of tones out of any guitar.
_________________
-𝕓𝕆𝕓- (admin) - Robert P. Lee - Recordings - Breathe - D6th - Video |
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Tommy Mc
From:
Middlesex VT
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 18 Aug 2015 12:49 pm
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Tommy,
The circuit you describe is similar to the bright switch on a Fender Twin. The real problem goes well beyond the volume pedal. A large part of the problem is within the human ear. It's complicated, but well documented. Here's a link to an interesting article:
http://www.extron.com/company/article.aspx?id=loudnesscontrol_ts&version=print
I agree with the author; things sound better with the loudness button pushed in. Perhaps some day guitar amp manufacturers will catch up.
Please don't hold your breath.
Best regards,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 18 Aug 2015 3:18 pm
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| Craig Baker wrote: |
| The real problem goes well beyond the volume pedal. A large part of the problem is within the human ear. |
Allow me to comment that I do not see the way our ears work with respect to perceived audio-level relative to frequency and volume, as a "problem" that needs to be compensated for. To me "equal loudness" sounds unnatural.
On the other hand, if one wants actual "equal loudness" control for the steel and sound chain, it has to be split on all volume controls - not just the VP, to achieve "perceived equal loudness" in all settings. Otherwise it will be too easy to get too little compensation in typical "practice at home" settings, and over-compensation in "live on stage" settings.
It is of course quite possible to add "a degree of automatic equal loudness" circuits to steel guitar sound chains, but I am under the impression that steel players don't like those - probably because they haven't tried them. |
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Tommy Mc
From:
Middlesex VT
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Posted 21 Aug 2015 8:00 am
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The article talks about perceived volume, but isn't the treble roll-off on a pot something different?
Two scenarios:
1. Volume pedal full open
2. Volume pedal at half, but amp turned up to same perceived level as #1.
In both cases, the perceived volume would be the same, but in scenario #2, wouldn't there be a decrease in the highs? |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 21 Aug 2015 10:00 am
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Tommy,
You are correct. They are two entirely different issues. Aside from the human ear topic, Considering a 500,000 pot, when it is full on, your pickup's impedance is in parallel with a 500,000 resistor. A 20,000 ohm pickup would present a little over 19,000 ohms at full on. The same pickup across the 500,000 ohm pot set at half resistance would now present close to 130,000 ohms. Now we're back at a much higher impedance than just the pickup by itself and because of the capacity of the longer cord going from the pedal to the amp, we can not avoid high frequency loss.
It easy to understand why today's active pedals are so popular. They offer a low impedance output and eliminate one source of high frequency loss. Since the birth of buffers, I have always recommended one right at the steel, to protect your signal before any cords can kill the instrument's overtones, and a second buffer at the output of a volume pedal. (or an active pedal). With a totally low impedance system, it would be interesting to see just how much difference a loudness circuit would offer.
Thanks for making an interesting point Tommy.
Best regards,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Matthew Dawson
From:
Portland Oregon, USA
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Posted 22 Aug 2015 12:52 am
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Does anyone else like the fact that the high frequency content becomes more pronounced as you raise the volume with a passive pedal?
I set the pot pedal halfway open and adjust the eq on the amp to where I like it. Then as I use the pedal to sustain the notes the highs come up to compensate for what I presume to be the more transient parts of the note fading out. Do I have that right?
I still have a long way to go with volume pedal technique but I find myself preferring a pot pedal over an active one. |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 22 Aug 2015 6:21 am
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That is correct, Mathew. You are very observant. I prefer pot pedals over the newer electronic ones for that very reason. If I raise the volume for solos I get a little more bite. But when I'm just comping, I like a little less high end so as to not interfere with other lead instruments.
I've never understood why a player would want an absolutely constant tonality throughout the pedals entire travel. To me, a pot pedal's slight tone change is useful, and musical.
YMMV 
_________________
Best regards,
Mike |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 22 Aug 2015 7:42 am
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Matthew - you asked,
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| Does anyone else like the fact that the high frequency content becomes more pronounced as you raise the volume with a passive pedal? |
Note what b0b said, above,
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| It seems to me that the fullest tone is when the volume pedal is all the way on. As you back it off, you hear less high end and it it cuts through the mix less. I like that that effect. |
_________________
Lee, from South Texas - Down On The Rio Grande
There are only two options as I see it.
Either I'm right, or there is a sinister conspiracy to conceal the fact that I'm right.
Williams Keyless S-10, BMI S-10, Evans FET-500LV, Fender Steel King, 2 Roland Cube 80XL's,
Sarno FreeLoader, Goodrich Passive Volume Pedals, Vintage ACE Pack-A-Seat |
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b0b
From:
Cloverdale, CA, USA
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Posted 22 Aug 2015 8:30 am
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You can play softer or louder with your right hand. You can control the presence or absence of harmonics with your right hand. But you can't roll off the high end with your right hand. That's why I prefer a pot pedal without a buffer. It gives me more control of the tonal spectrum.
_________________
-𝕓𝕆𝕓- (admin) - Robert P. Lee - Recordings - Breathe - D6th - Video |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 22 Aug 2015 4:15 pm
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| I have always recommended one right at the steel, to protect your signal before any cords can kill the instrument's overtones... |
It may be a small point, but I contend that cords don't really "kill" the overtones. They may reduce them, but there are usually enough overtones left to bring them back up to near normal, provided the amp has a capable EQ circuit, and sufficient power. (And providing you're not using long, or crappy cords.)
Obviously a ton of good-sounding music was recorded before there were buffers, George-L cords, or powered volume pedals. Therefore, the one thing to keep in mind is that there is no right-or-wrong in the sound department, there are just different personal opinions. In truth, there is no such thing as "bad tone" or "good tone", there is only what you (personally) like, or don't like. And once you accept that, the reasons for arguing about tone go out the window. |
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Lane Gray
From:
Topeka, KS
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Posted 22 Aug 2015 8:42 pm
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While I totally agree with you that the crucial thing isn't fidelity of reproduction, but pleasantness of tone, I gotta say that once a cable bleeds highs to ground, the stuff that was in the signal is gone, and upper overtones brought up by EQ may or may not be the same as what got bled off.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 22 Aug 2015 11:43 pm
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| Donny Hinson wrote: |
| [...] the one thing to keep in mind is that there is no right-or-wrong in the sound department, there are just different personal opinions. In truth, there is no such thing as "bad tone" or "good tone", there is only what you (personally) like, or don't like. And once you accept that, the reasons for arguing about tone go out the window. |
Agree ... "tone" in itself is all about personal preferences. "How it works" OTOH ... is not.
I'm not gonna argue about "tone preferences" for this or that set-up - what works for the individual player is of course fine with me. I don't like or dislike other players' "tone" as such, and I am not for or against passive or active set-ups. I just find something missing in the reasoning behind arguments for or against this or that solution.
Remember that there is no "one way" for the signal to travel from the PU to the first active amp-stage in the sound-chain. The entire passive chain becomes a bandpass filter, and what happens in this bandpass filter can not be "corrected" well by introducing variables via (eq) filters after the first active amp-stage.
The PU and all passive components following it, all the way to the first active (amp) stage, makes up an "RCL bandpass filter". Changing the value of one component in this "bandpass filter" - which is what we do when using a passive VP - does more than change the degree of "high frequency dampening". It also modifies the resonance frequencies in the PU-coil as more or less of the capacitance in the cable after the VP gets loaded back onto the PU-coil. And, the input impedance (mainly resistive load) of the amplifier following that VP and cable, is also fed back to the PU-coil at varying degree as the VP's purely resistive division-factor is altered.
Typical Hi-Z input impedance for instance in an NV-112, is 220Kohm (mainly resistive load). Other amps (or inputs) introduce different loads, but most Hi-Z inputs are in that "around 250Kohm" range. Depending on the VP's position, more or less of this load is applied to the "PU/cable/VP/cable" chain in passive set-ups.
Now, change PU...
Conclusion (to avoid having to write the book on audio filters): there's no problem to set up a passive sound chain that sounds good - regardless of individual "tone" preferences. Transferring one player's ideas of how to achieve "good tone" onto another player's set-up, is near impossible though - unless the entire passive sound chains are identical. Not even two pot-VPs of the same type/brand may "bottom out" at both ends at exactly the same resistive values.
With a good buffer-amp before VP and all (or most of) those cables and amp-input components and their loads, transfer of ideas from one player to another becomes much easier because a whole bunch of variables are eliminated, but a buffer may of course not result in better "tone" as the individual player sees it. There's (luckily) no way to bypass "personal preferences".
Oh, and although I'm OK with playing through passive set-ups, I prefer to have a dynamic active buffer before the VP. There's no (need for) actual EQ'ing anywhere in my sound-chains, and I prefer to modify the amount of overtones by modifying my picking style. On the steel next to me now I can even move the PU to find the "sweet spot" for the day and taste. Works for me... |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 24 Aug 2015 6:42 am
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| Lane Gray wrote: |
| While I totally agree with you that the crucial thing isn't fidelity of reproduction, but pleasantness of tone, I gotta say that once a cable bleeds highs to ground, the stuff that was in the signal is gone, and upper overtones brought up by EQ may or may not be the same as what got bled off. |
It's not "gone", it's just reduced, and that's an important point. Also, everyone seems to be disregarding the capacitance in the pickup itself. Since everything starts there, at the pickup, attention should also be given to the amount of windings on the pickup! I think this has significant effect on the better amount of "clarity" (high overtones) we hear when we're dealing with lightly-wound, single-coil pickups. |
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b0b
From:
Cloverdale, CA, USA
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Posted 24 Aug 2015 8:00 am
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A passive low-pass filter removes frequencies above a certain threshold. They are indeed "gone", Donny. The threshold frequency changes constantly with the movement of the volume pedal. I like that!
_________________
-𝕓𝕆𝕓- (admin) - Robert P. Lee - Recordings - Breathe - D6th - Video |
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Quentin Hickey
From:
Nova Scotia, Canada
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Posted 24 Aug 2015 4:12 pm
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| Matthew Dawson wrote: |
Does anyone else like the fact that the high frequency content becomes more pronounced as you raise the volume with a passive pedal?
I set the pot pedal halfway open and adjust the eq on the amp to where I like it. Then as I use the pedal to sustain the notes the highs come up to compensate for what I presume to be the more transient parts of the note fading out. Do I have that right?
I still have a long way to go with volume pedal technique but I find myself preferring a pot pedal over an active one. |
Great idea Mathew. |
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