I do not use output resistors for losses and dissipation of heat and it is more complex, although it can, but if it seems to me positive the hybrid mix if you adjust it properly, it is a good idea if you put the resistance with adequate dissipation, And adequate impedance.
If the subject of tones is very interesting, my experience in guitar is that many amplifiers even simple with trafo is that they sound very dark or opaque, without brightness, without grace, and ask for an equalization.
This with the OTL does not happen,
And this also lowers the total cost
* It seems as if the tone control was there to compensate for the losses of the output transformer, in addition to the hysteresis losses.
If this small OTL amplifier of only 12 v without infraalimentar the valve is curious,
I wanted to put the minimum components in the signal step, the purest possible sound so only 1/2 triode, and my surprise was that it did not require control of tones, with the guitar not being made lacking lacking and treble, But if you want to add you can always reinforce the clear real pure signal.
In the 12v /0,6w OTL it move the speaker for hifi or line signal or small salon, but for guitar in higth impedance it need impulse whit 0,6 w, i impulse this whit one pedal of guitar, whit " bsiab Ii" and of this at the OTL only in this small power amp.
Whit more states on preamp valve or two valves in power not is netcesary the guitar boster pedal.
The funtion of the impedance an volumen whit 600 or more ohms is inverse at the normal standar speaker, if this less value, less volume or reducing work.
Whit more states on preamp valve or two valves in power not is netcesary the guitar boster pedal.
The funtion of the impedance an volumen whit 600 or more ohms is inverse at the normal standar speaker, if this less value, less volume or reducing work.
The funtion of the impedance an volumen whit 600 or more ohms is inverse at the normal standar speaker, if this less value, less volume or reducing work. And if his value is more hight of recomendated impedance, identical reducer work in this speakers of 600,800, etc ohms. I probe speakers whit 3 impedances in one one cone, of philips, and see this very well how this work and response whit 700, 1300 and 1500 ohms
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The breakup of the speaker cone is a vital part of any guitar amplifier's overall sound! Certain paper cones are valued for this very reason.
I have experienced that myself, at least in some cases. In particular, one dirt-cheap speaker intended for ceiling-mounted PA use in warehouses gave my guitars a very "vocal" quality, almost like a good hollow-body archtop jazz guitar. Sadly, that particular speaker also produces very little bass.
But preferring a specific speaker doesn't exclude having a solid-state power amp driving it. You can always connect your favorite guitar speaker to a solid-state power amp, if speaker breakup is a big part of your preferred sound.
I know this thread is about OTL valve amps for guitar - but, for me, valve OTL is a very narrow evolutionary niche with no long-term future, given that nobody makes those special valves any more, nobody makes 800 ohm speakers any more, and the power requirements of OTL-capable power valves are insanely high. You guys have all done heroic work, in the face of heavy technological challenges, but ultimately, the history of valve OTL designs speaks for itself.
On the other hand, you and SemperFi and efeemeka have all shown that you can get great guitar sounds without an output transformer. That means you should be able to get great guitar sounds straight from a (valve) preamp, using small signal pentodes where necessary. I think this is very interesting.
We all know that most transistor guitar amps don't sound great. A lot of them sound awful, in fact. But one thing that transistors are very good at is driving lots of current into low impedances. OTL with transistors has been routine for decades now. And another thing transistor amps are good at is perfectly transparent amplification, adding no sound of their own.
Which is why it seems to me worth experimenting with the hybrid concept. Not the way manufacturers have done it in the past, with a token 12AX7 in the preamp. But with a properly designed valve preamp that uses the techniques you guys developed for OTL, to generate really good valve guitar amp sound.
I myself have been tinkering with small-signal pentodes in a guitar preamp for a while now. I have a design using a 6JW8 (triode-pentode valve) that I think sounds pretty good. I guess one could look at it as a tiny OTL Fender Champ, except mine operates at milliwatt power levels, and then drives a (valve) power amp. I can get decent overdrive sounds from the preamp, even without overdriving the power amp.
Along similar lines, if you Google, you can find a home-brewed design called the Tweed Overdrive Special that was published on a guitar forum some years ago. It uses four gain stages in the preamp - three triodes, followed by a small-signal pentode. The pentode then feeds a normal valve power amp. Once again, most of the "tone" of this amp actually comes from the preamp, which you could view as a very low-power, OTL, single-ended guitar amp.
Decades ago, commercial valve guitar amps threw a "master volume" into the box, after a couple of 12AX7 triode stages, and considered the job done. That didn't work very well, and nowadays it often read that "preamp distortion isn't as good as power amp distortion".
The people who say that don't have enough technical knowledge to realize they are comparing apples to oranges, and the right preamp design should, in fact, be able to sound just as good as overdriven power valves. I think efeemeka's and SemperFi's work might just produce that "right preamp design".
-Gnobuddy
Gnobuddy there is so much to do that I am very focused on only a small part, that is everything otl, as simple and pure as possible, and it is not enough, I do not have much time for more things, my budget is modest, , I only dedicate time of my free time, so I have to stay focused on this part that I consider little explored and very exciting and almost unknown ... for the sake of plurality on the guitar ... (smiles).
But it is very well that you can find your own motivation in what you are passionate about ... and we may be surprised with results in the field of hybrid amplifiers, it is good to know that there are several lines of good work parallel and interlaced, that is good too.
And that the people of hifi and guitar try very real solutions or more daring with possibility of success ... now that it is already known that works and that the transformer output is not everything, but rather the opposite.
On the other hand the OTL world has just peeked into the world of amplification, making loudspeakers High impedance is very easy nowadays, it has no mystery, I use high impedance speakers because it is still easier and cheaper than Manufacture them ... when they finish the NOS speakers are manufactured, no problem, that is ensured.
But it is very well that you can find your own motivation in what you are passionate about ... and we may be surprised with results in the field of hybrid amplifiers, it is good to know that there are several lines of good work parallel and interlaced, that is good too.
And that the people of hifi and guitar try very real solutions or more daring with possibility of success ... now that it is already known that works and that the transformer output is not everything, but rather the opposite
.On the other hand the OTL world has just peeked into the world of amplification, making loudspeakers High impedance is very easy nowadays, it has no mystery, I use high impedance speakers because it is still easier and cheaper than Manufacture them ... when they finish the NOS speakers are manufactured, no problem, that is ensured.
Actually, I've been building OTLs for about 40 years. Most of them are entirely practical on 8 ohm speakers.
The tubes to do so are readily available. Some are even still in production (6N13, PL519). We are working on getting a third and much higher powered tube in production at this very moment.
The power requirements are not all that crazy either. The guitar amps I've made all use the 6N13 (6AS7G) which has a 2.5 amp filament and otherwise is good for about 10 watts if properly loaded. My amps have used 4 power tubes and make a bit more than that... I run them on a 32 ohm load by putting either four 8 ohm speakers in series or two 16 ohms speakers in series.
The fact that several manufacturers have jumped into the market with knock offs of our design suggests that the OTL is still viable. I've yet to see a solid state amp keep up with one, given the right speaker (right now I'm talking about hi-fi, not guitar).
Its true that for guitar, OTLs are a bit of a novelty. But they can make acceptable overdrive distortion and power; the thing that they bring to the table is less weight for the power made (no output transformer) and the cleanest clean sound out there. They can do electric violin with ease in the way that no guitar amp can. So they have application in the folk scene.
Whether they do any serious numbers is more about marketing than the technology!
On another note, if you will pardon the expression, solid state amps are by no means free of any 'sound of their own'! They don't make the lower ordered harmonics normally associated with tubes but they are well-known for having higher ordered harmonics that tubes don't normally have.
The thing is, although these higher harmonics are in trace amounts as far as bench testing is concerned, the human ear is tuned to use those harmonics to gauge sound pressure (rather than the fundamental tones). Because of this we are extremely sensitive to the presence of these harmonics, and this is why transistors are known to be harsh and bright the ear converts all forms of distortion into tonality). This is a 'sound of their own' and is why transistors are usually shunned by guitar players! Its also why tubes are still made.
If you are willing to state that you are ignoring how the human ear/brain system perceives sound, then you have a deal.
Humans don't have robot hearing; its the result of millions of years. We can't change it to our whims, usually the best we can do is damage it. If you look into how the ear perceives volume in particular, its hard to imagine that any solid state amp is uncolored!
But you don't have to know anything technical about the ear at all to know that solid state isn't quite right. If it was, it would have supplanted tubes long ago and no looking back, no mistake. But in audio, it didn't do that. The market keeps tubes around for a reason. And that reason isn't that we want them because they color the sound.
Tubes are quite linear- so why would they have more distortion? That has entirely to do with topology (how they are used) rather than their inherent characteristics. I figured out long ago that if you want a tube amp to be low distortion and really neutral, you have to eliminate the traditional distortion sources that are in most circuits.
That is why I have made OTLs for so long. If you want to hear what neutral is about, they are far closer than solid state! For example, they don't make that ever-loveing tube sound because they are fully differential and balanced, so no 2nd harmonic.... and that's the tip of the iceberg!
Humans don't have robot hearing; its the result of millions of years. We can't change it to our whims, usually the best we can do is damage it. If you look into how the ear perceives volume in particular, its hard to imagine that any solid state amp is uncolored!
But you don't have to know anything technical about the ear at all to know that solid state isn't quite right. If it was, it would have supplanted tubes long ago and no looking back, no mistake. But in audio, it didn't do that. The market keeps tubes around for a reason. And that reason isn't that we want them because they color the sound.
Tubes are quite linear- so why would they have more distortion? That has entirely to do with topology (how they are used) rather than their inherent characteristics. I figured out long ago that if you want a tube amp to be low distortion and really neutral, you have to eliminate the traditional distortion sources that are in most circuits.
That is why I have made OTLs for so long. If you want to hear what neutral is about, they are far closer than solid state! For example, they don't make that ever-loveing tube sound because they are fully differential and balanced, so no 2nd harmonic.... and that's the tip of the iceberg!
Your reasoning does not convice me at all. What you do is repeating well known audio myths.
This entirely depends on what kind of distortion you wish them to make. It was shown already in early 1970's that characteristics of distortion dominantly depend on circuit architecture, not what devices the circuit uses.
Pardon? Since dawn of transistors they have quickly obsoleted tubes in almost every application imaginable, yes, very prominently in audio applications too. For obvious reasons.
True. Tubes have retained -some- popularity but it's mostly due to very different reasons than why they were favoured in the old days. Today folks identify "tube sound" as something that means plenty of coloration and distortion. Heck, today it would be ridiculous idea to choose to use tubes for their "transparency" and lack of distortion.
Go ahead. I challenge you to add a "transparent" tube stage to a solid-state guitar preamp. People will regard it as a gimmick and even wonder if the tube is connected because they can't hear any obvious "tubeness". Sorry, but that's what will happen. No one will chime in to defend how highly linear devices triodes are. It's not the 1950's anymore.
Because they really aren't THAT linear. Look at characteristic curves. Let's pause there and think for a second.... Curved lines? Straight lines? Linearity?
I'm pretty sure my ears aren't overly sensitive to high order harmonics at 0.1% THD. I'm quite sure I can hear the lower order harmonics at 10% THD.
Exactly. You need external linearisation to achieve lower distortion. Guess what? Pentode, for example, has higher distortion than a triode tube, but with external negative feedback one can turn pentode characteristics close to triode characteristics. Then you can go on and add things like higher open loop gains and increase magnitude of feedback, you can add more linear loads like current sources, you can do this and that trick in order to linearize operation of some circuit. Guess what? In the end you have an architecture and performance similar to generic solid-state amps, realized with devices that are not as fit for the job as transistors.
I see very little point in OTL and cathode follower outputs driving low impedance loads. Terribly inefficient architecture that's still lightyears behind follower circuit architectures of the solid-state type. While folks have spent years and years to figure out how to make an inexpensive, efficient and high power OTL power amp they haven't. During that time some other people have, however, perfectly figured out how to make solid-state power amps that have characteristics of generic class-AB push-pull tube power amps.
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yup!
This is an eye-opener for everyone who is really interested in technical background of guitar-amps
http://www.jeanpierrepoulin.com/PDF/transistor.pdf
This is an eye-opener for everyone who is really interested in technical background of guitar-amps
http://www.jeanpierrepoulin.com/PDF/transistor.pdf
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What audio myth? I bet you can't name them, I suspect you are engaging in some yourself!
So- I'll agree to disagree if you agree to admission that you are ignoring human hearing perceptual rules.
This is false. My amps have measured THD of 0.5% at full power with zero feedback. Think about that for a moment.
So- I'll agree to disagree if you agree to admission that you are ignoring human hearing perceptual rules.
This is false. My amps have measured THD of 0.5% at full power with zero feedback. Think about that for a moment.
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This is exactly what I was hoping to avoid, an argument that ultimately doesn't change anyone's mind, but kills the friendly atmosphere of the thread.
I am here because, by pure accident, very simple valve circuits are prone to generate large amounts of low-order harmonic distortion, which helps to compensate for the lack of natural rich harmonics in the output of electric guitars. And a guitar happens to be the only instrument I can play reasonably well.
-Gnobuddy
I am here because, by pure accident, very simple valve circuits are prone to generate large amounts of low-order harmonic distortion, which helps to compensate for the lack of natural rich harmonics in the output of electric guitars. And a guitar happens to be the only instrument I can play reasonably well.
-Gnobuddy
For me it is not so important if theme is transistors or valves, nor is it better or worse.
For electric guitar I, or my ear prefers valves, I can not see just a schematic, I also have to hear it.
With the guitar, if the final result does not pass the auditory test, the intermediate steps or the topology will not make sense.
I am sure Atmasphere amplifiers are exceptionally good on hi-fi even with low-impedance loudspeakers, I have also proven that hybrid solutions are attractive, but once inside the unexplored and under-documented field of guitar OTLs, To walk forward, and without losing sight of the current standard implanted that is the valve amplifier type Fender, Marshall or Vox, to name some of the best known by all.
Hmmm from the experience I draw that I will not use output transformers because partly I feel cheated by the standards and industry as they are not absolutely necessary for the same or better end, saving some unnecessary costs again.
So does the tone controls.
But what is more transcendent and we must know is that, again there is another and very attractive posibility for our guitars (harmonicas, keyboards, pianos, violins, Spanish guitars and acoustic ... etc) that is simple and effective and at the same time Or higher. ) Than what we already know.
Is another tone with its own personality within the color palette in solutions for guitar, which does not detract from what exists, and extends a plot that is necessary to bring the amplification of guitar (and hifi) a step higher if it is possible.
The data and experiences always necessary:
I have compared these OTL amplifiers with high impedance loudspeakers, compared to very high-end, classic amplifiers, and my contribution is that the OTL in general plays at a very high level and these in particular have been compared hand in hand with:
- "Fender deluxe blackface original of the year 1965." & OTL's
These Otl, in particular my OTL model Nefertiti,
Competes at his side and in clean sound perfectly without blushing.
- "champtone = reproduction of a 5w boutique blackface fender from a champ with tones, presence, media, and voice control.
Same OTL results as with the original blackface, since it is the same as the original blackface but in 5w version.
- "Marshall JCM800 or plexi":
OTL nefertiti
Is an amplifier with an excellent clean sound but I have obtained an excellent saturated sound with the saturation pedal
"BSIAB II" (Brown Sound In A Box), which is a pedal similar to "MXR Edie Van Hallen" and similar ones.
-Vox:
These OTL also play hard against vox and previous equipment with valves type ef86, and with pedals with much saturation they have a touch of stability and aviolinado very desirable.
- Other amplifiers with which they have been compared have been:
The "Faustone Thirtyteen" model from Faustone.com, an excellent Spanish manufacturer that wears this very exclusive amplifier with a Marshall 5150 channel with el84 and another Vox channel.
Was compared to other hybrid amplifiers, transistors and other vintage as
"Sinmarc" or "Krundall" with el34 both.
In summary of all these good classic amps that I have always at home, the ones I finish using are the two OTL, the 0.6 watts and the 5 watts.
I am now mounting a new member of the OTL family with 2 EL34 at 800/1000 ohms approx. I will put the valve on the metal base of 1955.
I have some work ahead of me.
Great talk and a success, you need more debates and meeting areas as specialized as this.
Best regards.
For electric guitar I, or my ear prefers valves, I can not see just a schematic, I also have to hear it.
With the guitar, if the final result does not pass the auditory test, the intermediate steps or the topology will not make sense.
I am sure Atmasphere amplifiers are exceptionally good on hi-fi even with low-impedance loudspeakers, I have also proven that hybrid solutions are attractive, but once inside the unexplored and under-documented field of guitar OTLs, To walk forward, and without losing sight of the current standard implanted that is the valve amplifier type Fender, Marshall or Vox, to name some of the best known by all.
Hmmm from the experience I draw that I will not use output transformers because partly I feel cheated by the standards and industry as they are not absolutely necessary for the same or better end, saving some unnecessary costs again.
So does the tone controls.
But what is more transcendent and we must know is that, again there is another and very attractive posibility for our guitars (harmonicas, keyboards, pianos, violins, Spanish guitars and acoustic ... etc) that is simple and effective and at the same time Or higher
. ) Than what we already know.Is another tone with its own personality within the color palette in solutions for guitar, which does not detract from what exists, and extends a plot that is necessary to bring the amplification of guitar (and hifi) a step higher if it is possible.
The data and experiences always necessary:
I have compared these OTL amplifiers with high impedance loudspeakers, compared to very high-end, classic amplifiers, and my contribution is that the OTL in general plays at a very high level and these in particular have been compared hand in hand with:
- "Fender deluxe blackface original of the year 1965." & OTL's
These Otl, in particular my OTL model Nefertiti,
Competes at his side and in clean sound perfectly without blushing.
- "champtone = reproduction of a 5w boutique blackface fender from a champ with tones, presence, media, and voice control.
Same OTL results as with the original blackface, since it is the same as the original blackface but in 5w version.
- "Marshall JCM800 or plexi":
OTL nefertiti
Is an amplifier with an excellent clean sound but I have obtained an excellent saturated sound with the saturation pedal
"BSIAB II" (Brown Sound In A Box), which is a pedal similar to "MXR Edie Van Hallen" and similar ones.
-Vox:
These OTL also play hard against vox and previous equipment with valves type ef86, and with pedals with much saturation they have a touch of stability and aviolinado very desirable.
- Other amplifiers with which they have been compared have been:
The "Faustone Thirtyteen" model from Faustone.com, an excellent Spanish manufacturer that wears this very exclusive amplifier with a Marshall 5150 channel with el84 and another Vox channel.
Was compared to other hybrid amplifiers, transistors and other vintage as
"Sinmarc" or "Krundall" with el34 both.
In summary of all these good classic amps that I have always at home, the ones I finish using are the two OTL, the 0.6 watts and the 5 watts.
I am now mounting a new member of the OTL family with 2 EL34 at 800/1000 ohms approx. I will put the valve on the metal base of 1955.
I have some work ahead of me.
Great talk and a success, you need more debates and meeting areas as specialized as this.
Best regards.
This is exactly what I was hoping to avoid, an argument that ultimately doesn't change anyone's mind, but kills the friendly atmosphere of the thread.
I am here because, by pure accident, very simple valve circuits are prone to generate large amounts of low-order harmonic distortion, which helps to compensate for the lack of natural rich harmonics in the output of electric guitars. And a guitar happens to be the only instrument I can play reasonably well.
-Gnobuddy
I prefer to keep things civil as well.
But your initial post that elicited my response contained a number of falsehoods! What is a person to do- let them pass as truth when they were off by a country mile? I think the one that really got me was the idea that OTLs can only drive speakers of hundreds of ohms!
I've listened to OTLs with only two 6AS7Gs per channel playing my speakers at home which are 16 ohms. They played fine. When faced with such obvious issues and particularly on a thread that is engaging the topic of OTLs it was obvious some truth needed to be injected. Was it possible that Gnobuddy had never heard of any of the OTL manufacturers- Futterman, Atma-Sphere, Joule Electra, Graff and so on?
I'm a big fan of Norman Crowhurst! When people post stuff that flies in the face of his writings, again I feel like I have to say something rather than allow that to pass as truth.
I don't mind being corrected but this is the internet and I have found that others often do.
The important thing here is don't take it personally! I don't know anyone here and don't feel a need to attack them; as a moderator on another site I know full well to attack the argument and not the poster!
I agree with you totally on this.
There are good logical reasons for this too. For example, the DC operating point of a valve invariably shifts when you overdrive it, and these bias shifts change the sound. I can't look at a schematic and predict how that bias shift will sound - I have to build it and listen to it.
But, to get really good electric guitar sound, I am also curious if it is absolutely necessary to have an all-valve signal path or not. The traditional answer is always "Yes!", of course.
But the fact is that all the best guitar sounds I have ever heard, have already passed through dozens of solid-state devices before they reached my ears: I have never heard David Gilmour or Eric Johnson or Mark Knopfler live! I have only heard their guitar sounds after they have gone through a long chain of solid-stage devices, from mic preamp all the way to the power amp in my living room. So I'm really listening to a very long and complicated hybrid amp, in a way.
For me, the next question is, can we make that guitar amp at the front of the chain smaller, lighter, simpler? And here is where you and Semper Fi come in, because, to my ears, you both have shown very clearly that an output transformer is not necessary. That's one component gone. You also removed the tone controls - another major building-block gone.
Can we remove anything else without compromising the guitar sound? Right now, I have a little guitar amp design that has a high-voltage, small-signal MOSFET in it, acting as a phase-splitter, a "sourceodyne" instead of a cathodyne. As far as I can hear, there is no difference in sound, and a number of benefits - less cost, size, weight, heat, much lower saturation voltage and so more drive voltage for the output valves, et cetera. This makes sense, because, with 100% local feedback, cathodynes have such low distortion that they have no "sound" of their own. Same thing with the "sourceodyne".
For what it's worth, I really like the sounds in the two guitar clips you posted - they are certainly among the best-sounding guitar amp clips I've ever heard. Congratulations!
-Gnobuddy
That really isn't coming through in your last few posts.
And yet, this supposed "falsehood" never actually existed. I never wrote "OTLs can only drive speakers with hundreds of ohms". Re-read my post and see for yourself!
Also, please don't forget the context: efeemeka has been discussing amps that use 600 and 800 ohm speakers, and the original Phillips OTL designs also used high impedance speakers. It is efeemeka's OTL guitar amp designs that have piqued my interest, because my only interest in valves is for use with electric guitars, to create large amounts of intentional distortion.
As far as using lower impedance speakers goes, we both know that you can certainly connect a 16 ohm speaker instead of an 800 ohm speaker. But because these valve OTL circuits are current-limited, your power output immediately falls by a factor of 50, to 2% of it's former value.
Then you have to either modify the amp to generate much more output current (at the expense of cost, weight, size, heat generation, and wasted power), try to find speakers with much higher efficiency, or learn to live with much lower SPL levels. Any way you look at it, you have to deal with heavy compromises.
250 mA max cathode current per 6AS7G, according to the data sheet. If you could deliver all of that to the speaker, you'd still only have 2 watts RMS, at maximum output.
I believe you when you say that they "played fine" for you. But that would not be true for most people. For Hi-Fi, full-bandwidth, audio reproduction, we both know there are unavoidable severe compromises when you have so little audio power available to drive speakers.
2 watts can certainly make a lot of noise when fed to a guitar speaker with a 100 dB SPL @ 1W @1m sensitivity. But that sort of speaker is anything but Hi-Fi.
Then why make blanket negative statements about all solid-state amps, statements that are entirely subjective, extremely implausible, and have no objective data to support them? That's not truth, by a long shot.
Is it possible? Certainly. Is it true? Nope. And you left out Phillips.
In any case, I'm really not sure what the relevance of historical OTL brands is. Do we need a deep knowledge of the 1912 Stutz Bearcat (arguably the worlds first sports car) in order to discuss a 2017 Mazda Miata? Or do we simply need to understand how internal combustion engines and other major automotive sub-systems work?
By the way, I'm quite sure that you know a lot more about the fine details of valve OTL amps than I do. That's not in question at all.
But I understand the fundamental engineering factors quite well. Compared to contemporary solid-state output transistors, output valves (of practical size for home use) suffer from limited peak current capability; from large saturation voltages; and from the requirement for large amounts of heater power.
That doesn't sound much like scientific objectivity to me.
Agreed! Right or wrong, your beliefs about the relevance of OTL and/or the flaws of solid-state amplification are your own business, as far as I'm concerned. That doesn't mean they're correct in some objective sense, only that you certainly have the right to hold your own opinions.
Which is why I said "Lets agree to disagree". To which you, essentially, said "I'll agree with you when you stop disagreeing with me." Not quite the same thing!
-Gnobuddy
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