Touch responsive circuits...

[koulis]

Hi all , what is the secret behind touch responsive circuits ???What is the most responsive od pedal in your opinion?


Koulis

[John Lyons]

Touch responsive in that every nuance is clear and articulate, or in the way that if you play soft there is mainly clean sound and if played hard the sound breaks up and distorts (in a nice way)?

John

[koulis]

I was thinking about the soft/clean  hard/distort kind of thing...Like a zendrive!!!

Cheers

[Steben]

I would argue that, although the definition may be very much the "soft to hard" progression, there are many ways to achieve this and even the definition itself eve is somewhat vague.

when playing soft to hard...

an overdrive pedal can be called touch sensitive if it goes from clean to distorted with some volume added, but also:
-the famous power sag magic of tube amps, where the distortion rises quicker, yet still in function of the input signal, achieving with the same signal change a very broad clean-to distortion range.
-an already well-overdriven pedal can be called touch sensitive if the distortion itself becomes harsher, without changing volume
-a fuzz (face) can be called touch sensitive when it distorts assymetric first before symmetric, achieving a somewhat dynamic distortion
etc...

[John Lyons]

Yes, It's all very subjective. There are many ways to get to many sounds called touch sensitive. Vauge enough?
I guess you really need to be specific.. you did say zendrive though... I don't know about that one... Just heard of it...

John

[koulis]

There is a sound clip at   http://www.hermidaaudio.com/ .
At products page look for the Test Drive clip...

Koulis

[JimRayden]

Yes, It's all very subjective. There are many ways to get to many sounds called touch sensitive. Vauge enough?
I guess you really need to be specific.. you did say zendrive though... I don't know about that one... Just heard of it...

I agree. "Touch responsiveness" is in about the same category of debates as "transparency". It's ought to get ugly. In a good way.

---------
Jimbo

[george]

just more boutique pedal marketing BS ....

Touch sensitive to me is, just touch the string and the note sustains for days or morphs into screaming feedback .... mmmm nice.

[Steben]

just more boutique pedal marketing BS ....

Touch sensitive to me is, just touch the string and the note sustains for days or morphs into screaming feedback .... mmmm nice.

Well, there you go, I disagree.
As I see it, it's called way out distortion and compression, not much sensitivity there. Compressors tend to break the sensitivity down, resulting in small changes of volume and harmonics.

[MartyMart]

I dont see why folks have such a hard time with these terms, it's black and white, `i'm repeating myself
but I just dont see that they are up for interpretation, when the OP say's "touch sensitive OD" !
It isn't like saying "my lollipop tastes better than yours" but these threads seem to always turn into that
for some totally unknown reason !!
Touch sensitive OD/distortion  = CLEAN sound at gentle pick of strings DIRTIER sound as we pick harder

.... see , it's not so wierd at all  !

Transparent = does not change or mask  the sound/tone of your particular guitar EG: Transparent Boost
just "turns up" what you plug into it and does NOT alter the sound at all

MM 

[Paul Perry (Frostwave)]

Touch sensitive OD/distortion  = CLEAN sound at gentle pick of strings DIRTIER sound as we pick harder

Indeed..... but, (depending on design) there are quite a few different ways in which the 'dirt' increases.

[blustrat]

IMHO circuits with jfets are better touch responding than IC based projects.
Greetings from Italy  .

[Paul Perry (Frostwave)]

IMHO circuits with jfets are better touch responding than IC based projects.

Well, yes, in the sense that a simple jfet amp circuit usually distorts gracefully as you overdrive it. But it is entirely a matter of what the circuit is; an op amp configured correctly with non-linear feedback elements will get you where you want to be.

And greetings from Melbourne Australia, blustrat - I'm a few hundred yards from Lygon Street, the "Little Italy" of Australia

[blustrat]

Op amp with non linear feedbak? Can you tell me more about this kind of circuit?
Yes.. i know Melbourne is full of Italian people!
Thank you Paul 

[WGTP]

Can you have touch sensitivity and dynamics at the same time?  For a given amount of sustain, how much distoriton/harmonics are present?  Do the notes of running chords all run together into mush, or can you hear each string?  Can you hear the difference between old strings and new?  Does a PAF type pickup sound different than a Distortion?  A Les Paul vs. a Strat?  Can you hear the difference between a thin nylon pick and a Peso?  Does tuning down to D give it a different sounding set of harmonics?  We want it all.   

[StephenGiles]

How long is a piece of string?

[Mark Hammer]

"Touch sensitivity" implies that variations in picking strength will yield different amounts of both clipping (harmonic content) as well as noticeable volume differences.

A great many distortion circuits employ diodes to accomplish the clipping.  Diodes have fixed absolute thresholds for accomplishing clipping.  If the voltage drop is 523mv then relatively little is going to happen to the signal when it is below 523mv, and it is going to be "clamped" and clipped whenever it reaches or exceeds that voltage. 

Though it may seem sometimes like clipping occurs in gradations, in reality it is essentially all-or none in many many contexts.  What creates the appearance of graded degrees of clipping is how much of the signal falls above that critical threshold.  If only the initial pick attack falls above the threshold, and the instant the pick has left contact with the string the signal level falls rapidly, then you can expect clipping to only be present at the outset and not likely thereafter.  If the string maintains an output level above the threshold for a while, then it will sound like "more" distortion because a larger percentage of the entire signal is a high enough amplitude to get clipped.  If you listen to a lot of old "psychedelic-era" soul and funk records, the fuzz sounds will always be really hard to peg down, and hard to replicate.  Why?  I suspect it is because a lot of those players are using big body jazz guitars in the studio.  Guitars with floating wooden bridges that have a fat tone but a very pronounced quick decay from the initial peak.  Because the amplitude envelope of those guitars is so different from a solid body, the fuzz behaves differently.

So, how do you produce what feels like greater touch sensitivity?  One way is to use diodes with a higher clipping threshold.  That could be simply 1N914 silicon diodes instead of germanium ones (bumping the threshold up from around 230-250mv up 500-630mv), or multiple silicon diodes in series, or LEDs.  The more headroom there is between the lowest possible signal level and the clipping threshold, the more possible it is to achieve slight differences in picking strength that result in small but perceptible differences in how much of the signal is clipped.

Another approach that can be fruitfully adopted is double and triple-clipping.  Here, a signal is clipped by one stage, and that signal output is then clipped again by a subsequent stage, and maybe even again by another stage.  This approach sounds suspiciously like what happens in a tube amp, doesn't it?  You're right.  But it won't always do so unless several rules of thumb are observed.  The Big Muff is a double clipper but there is relatively little about it that could be described as touch sensitive.  Indeed, part of its great reputation comes from how consistent the distorted tone is across 95% of the lifespan of any picked note.  So how come I'm touting multiple clipping stages when we have a clear example that seems to contradict that?  Because the touch sensitivity comes from having the thresholds of each cascaded stage just right, and their bandwidth and gains set just right as well.  The general principle is that when you have several cascaded gain stages, there should be a bit more headroom added in each stage, but the gain of each should be just enough that a little more than the clipped part of the signal from the previous stage will get clipped.  Additionally, I find it useful to have just a bit more bandwidth at the top end on each successive stage; to essentially "open up" the treble in later stages.  This way, if the most clipping occurs in the earliest stage, it will sound a little restrained due to the filtering/treble-limiting.  At greater and grerater picking strengths, more clipping will be added in later stages and that extra treble content will be permitted to be more audible.  So, the touch sensitivity comes from not only producing more harmonic content but from allowing it to be heard more clearly.  Again, that's why so many of the gest distorted tones come from multi-stage tube amps.  It is the quality of distortion generated by the last stage that we like, and the quality of that distortion depends on the harmonic shaping occurring in earlier stages.

Again, please note that I am talking primarily about diode-based clipping, not gain adjusting designs like the Fuzz Face.

Make sense?

[John Lyons]

Every circuit will have a different sound and different attributes.
Just like food or art, you try to decribe what it tastes like, what the color is, what it "feels" like.
Marketing BS? Well sure, why not and at the same time NO.
Were trying to desctribe something that makes a sound and we all hear differently and process the sound and feel differently.
It can get a little out of control trying to decribe something but all we have to go on is words unless you can actually hear it.

What these mean to me:

Trasparent = something that does not change the sound but only amplifies it. (marty said this above...)
Other similar descriptions: Clean, Clear

Touch sensitive = a sound that is dynamic and follows how hard you pick and goes with the sensitivity of the player.
Other descriptions: Dynamic, uncompressed, articulate,

The zendrive clip sounds like a combonation of the terms above. Keep in mind that the amp by itself sounds killer so adding just a touch of overdrive with a "transparent" circuit stills sounds much the same but adds a bit of drive.

Nice guitar, nice amp nice pedal, nice player.

John

[WGTP]

To me, a part of the issue is that compression allow the nice sustain and feedback and even picking and string volume and you can hear the subtle nuiases, but it also works against dynamics when to much compression is used, because everthing is at the same volume.

Going from nice vintagey clean to moster crunch harmonic feedback etc. with the turn of the volume know on the guitar... could be a function of... not sure.

One thing I think I hear, is reducing the bass thru the clipping stages (dual thanks to Mark Hammer) and boosting it afterwords - producing a nice combination of "smush" or compression, at the same time, chunck or lower frequency dynamics.  Since the lows aren't as distorted and compressed, you maintain some dynamics, at the same time the highs have more compression/sustain, distortion, and fatness.  Mosfets seem to help this with there softer clipping.

Most of the dynamics are going to happen with the higher order harmonics from the pick attach.  These normally don't last that long, as discussed above.

I seem to have issues with the optimum tone balance at low gain being different than at high gain.   

[Steben]

Which brings us to the tube power sag, which I try to emulate in a SS project.

It's simple.
In a sagged amp, two things happen. The origin is the following: In function of the signal, more current is drawn from the power supply, which has a resistance and gives a bigger voltage drop, lowering the supply. because the power supply has large capacitors, that voltage drop stays a little (like in compressor rectifiers).

- the first thing is a small drop in gain. This is becasue the tube's internal gain drops a (very) little with the voltage; This the most complex feature, but it is however, in contradiction to some statements, a marginal effect.

- the main thing is the drop of headroom when the voltage drops. this is rather obvious and is independent of the power tubes used, or even whether it are tubes. It's in the power supply.

The result is very complex in it's interaction with the guitar player. power sag is in fact a sort of clipping "expander", not a compression. With rising signal, the headroom drops, achieving clipping sooner than in a normal circuit. As soon as you play soft, the headroom rises again and cleans the harmonic contents. This all in a very small loudness range. This mean you have sustain, without too long too much distortion!
In fact, the FUZZ face has a similar response. No wonder the combination of a fuzz face and a vintage tube amp respond so well, especially when you bring the individual gain DOWN! and you have a clean sound when playing soft.