# Tube swapping: rewarded or regretted?



## elliottmoose (Aug 20, 2012)

I'm just wondering if many of the congregation have tried swapping tubes and what the outcome was. I know that I've tried it on a couple different amps and gotten mixed results. For instance, swapping the 6L6s in a Traynor YCV40 for a pair of old KT-66's sounded pretty good: felt punchier with more bottom end and more highs coming through. In the same amp, I tried swapping the preamp tubes (12ax7's) one at a time, and all I was rewarded with was nasty microphonics and a really glassy reverb. 

Also, I've been eyeing a ing a couple low watt amps that advertise seemingly endless plug'n'play tube compatability: everything from the industry standard 'guitar' tubes to the more obscure and intriguing types. Any success or failures I should keep my eyes peeled for? A couple of examples for this type: THD Univalve, Emery Superbaby, any others you guys have experience with?


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## dtsaudio (Apr 15, 2009)

I hope Wild Bill doesn't see this. LOL


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## keto (May 23, 2006)

I haven't done much power tube swapping, but have done lots of preamp tube swapping. There is a clear audible difference between different types. I went from Shuguang Chinese in my JCA22, to old Mullards in V1,2,3 and a Sovtek in the PI. Wayyy smoother, less hissy, less bright and bitey. Yesterday, I swapped out a current Tung Sol 12AX7 for a current Mullard 12AX7 in my Triwatt. Again, clearly audible difference immediately noticeable.


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## Wild Bill (May 3, 2006)

Before we get too deep into each subject I think it important that everyone who claims to hear differences first state their birth sign. I'm a Libra, myself!

That being said, has ANYONE actually done a blind, scientific test? 

I am getting very, very tired of this.

Maybe people should record the month they buy the tubes to establish the birth sign of the tube, as to any possible differences in sound. Or maybe it would be better to follow the date codes.

Would a Scorpio tube tend to sound more shrill?

I can hear the difference between a Leo tube and a Sagittarius. Honest! 

However, if you want me to participate in a true scientific test I'm afraid I'll be rather busy for a while but I'll get back to you someday to set up a time, honest I will!

Meanwhile, since I am a self-proclaimed expert on the astrological differences in sound between brands of vacuum tubes, I will expect everyone to believe everything I say, no matter how much it conflicts with basic physics and electrical theory. After all, I was the first man to discover that some tubes have maple elements inside and some have rosewood, which clearly would lead to a different sound!

Oh, and of course, buy anything I am selling, at whatever price I ask! It has to have good sound if I charge more, doesn't it?

Wild Bill/Busen Amps


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## sulphur (Jun 2, 2011)

I personally prefer maple Libra tubes.


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## bluzfish (Mar 12, 2011)

sulphur said:


> I personally prefer maple Libra tubes.


Yeah, for a nice woody sound, maple IS the best. But for metal, nothing beats a good rosewood/kevlar/Aquarius plate. To each his own, I guess...


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## sambonee (Dec 20, 2007)

I'll prep a blind test. I have an amp that takes loads of different tubes (Carr hammerhead II) for the power amp swaps and the Bernie for the 12ax7 test. 

We could make it all scientific. Same amp guitar, settings volume. Even channel settings. Post the mp3s and do the Coke /Pepsi thing. 

What ya think? 





Wild Bill said:


> Before we get too deep into each subject I think it important that everyone who claims to hear differences first state their birth sign. I'm a Libra, myself!
> 
> That being said, has ANYONE actually done a blind, scientific test?
> 
> ...


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## elliottmoose (Aug 20, 2012)

sulphur said:


> I personally prefer maple Libra tubes.


Haha, nice! I'm personally fond of anything with 'Leo' on the label -- fender or lion.

Maybe I need a private lesson on the reason different tubes sound the same?


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## WCGill (Mar 27, 2009)

Libra here also and yes, there is a difference. Randall Aiken, another Libra I'm told, says so, but enough said.


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## Wild Bill (May 3, 2006)

sambonee said:


> I'll prep a blind test. I have an amp that takes loads of different tubes (Carr hammerhead II) for the power amp swaps and the Bernie for the 12ax7 test.
> 
> We could make it all scientific. Same amp guitar, settings volume. Even channel settings. Post the mp3s and do the Coke /Pepsi thing.
> 
> What ya think?


It would be fun! We would need to add extra people, of course. The "listener" cannot be the person changing the tubes. Ideally, the listener would be in a different room, unable to see what tube has been changed or even IF a tube has been changed! He must be kept "in the dark"! He would be brought into the room with the amp and allowed to plug in his guitar and wail.

All he would know is the test number. He would then fill out a report on each test. He would spell out the differences he heard for each test.

To my knowledge, there is no record of someone actually passing such a test that we can google. There IS a report of a test using some audiophile "gurus" with different kinds of speaker wire.

Apparently, the winner was a couple of pieces of rusty old coat hangar wire! :sSig_busted:

http://www.roger-russell.com/wire/wire.htm#house

"When confronted with the truth, believers do not want to hear about it. They want to remain in the magical world of fantasy where they think they can hear improvements in their wire, often arrived at by making listening tests without adequate controls or understanding of the problems involved including speaker impedance and amplifier stability. One of the prime tools in creating such a faith for the average consumer is by capitalizing on fear and ignorance as in many other things that aren’t readily apparent. There is fear that the wire currently in use is not good enough. There is ignorance because most people do not have scientific knowledge in this area and lack adequate measuring equipment to prove otherwise."

http://consumerist.com/2008/03/03/do-coat-hangers-sound-as-good-monster-cables/

"_After 5 tests, none could determine which was the Monster 1000 cable or the coat hanger wire. Further, when music was played through the coat hanger wire, we were asked if what we heard sounded good to us. All agreed that what was heard sounded excellent, however, when A-B tests occurred, it was impossible to determine which sounded best the majority of the time and which wire was in use. Needless to say, after the blind folds came off and we saw what my brother did, we learned he was right…most of what manufactures have to say about their products is pure hype. It seems the more they charge, the more hyped it is."
_
Google around and you will find LOTS more! You will see at first zillions of sites claiming this wire or that wire is better but when you look close they are all either selling something or not making claims based on any sort of technical testing at all. There are very few sites relating actual REAL testing!

This of course is just human nature. Everyone reads the "Inquirer" type supermarket rags at New Years, to see what the latest Hollywood "Asrologer To the Stars" is predicting to happen over the coming year.

Have you ever heard of someone checking out the LAST year's predictions, to see how right they were?

Regardless, even if you hit some people over the head with irrefutable evidence, they will still believe what they want to believe. As a species, human beings are not born with their brains wired to think in a logical and scientific fashion. It must be taught and learned and at an early age or it just won't "take". Schools are not as good with this as they used to be.

Perhaps I shouldn't expect more. It IS the Age of Aquarius, after all.

Wild Bill


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## bzrkrage (Mar 20, 2011)

I was listening to the "Home Recording Show" archives, I think episode 31-33.
There is a great pre amp 12A_7 swap comparison with different amps there. Worth a listen if you want to hear but not do the tube swap.


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## Wild Bill (May 3, 2006)

bzrkrage said:


> I was listening to the "Home Recording Show" archives, I think episode 31-33.
> There is a great pre amp 12A_7 swap comparison with different amps there. Worth a listen if you want to hear but not do the tube swap.


Was it a true test? Did the listeners know a tube had been swapped and/or what brand it was?

If it was testing different tubes of the 12A*7 family I agree there are sonic differences. A 12AY7 will dramatically change the tone of a guitar preamp that was using a traditional 12AX7, since among other things the 12AZ7 has a MUCH lower voltage gain!

The same cannot be said for comparing two tubes of the same type made by different manufacturers. A Mullard 12AX7 MUST sound the same as one made by ElectroHarmonix! It's just physics!

Last year we had a long thread about this topic. I offered to post a bottle of scotch against anyone claiming they could hear differences in a true scientific test. I suggested we all meet at a local bar and make a night of it. It would be a lot of fun and a great social event for guitarscanada.com

A lot of folks were enthusiastic until I made it clear that I was not DONATING a bottle but rather BETTING a bottle! Someone who disagreed with me and who thought they COULD hear differences was expected to pony up a bottle themselves before they could participate in the test!

The thread died faster than an Ontario Liberal promise to be careful with our tax money. I did not get even ONE taker!

'Nuff said!:acigar:

Wild Bill


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## mrmatt1972 (Apr 3, 2008)

My opinion, as far as preamp tubes goes, is that you pay more for longevity and low noise (hiss and mechanical). Preamp tubes make more of a difference in simple circuits than they do in high gain, multi stage monsters. I can easily hear a (small but tasty) difference in EQ and gain when I use vintage Mullards vs stock tubes in my Class A Handsome Devil, but none in my Laney GH100TI. YMMV.

Power tubes are a whole different ball of wax. HUGE differences can be heard from manufacturer to manufacturer.


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## elliottmoose (Aug 20, 2012)

Ah, looking back, my original post may not have been as clear as it should've been. Points of clarification:
1. When swapping preamp tubes, I went from stock 12ax7 to 12at7 or 5751 (and one more type I think)
2. I was less concerned about brand of the same tube type and rather the use of different types of tubes: KT-66, 6L6, EL34, EL84, THD YellowJackets, that kind of thing. Same goes for preamp tubes.

This is whole idea got started in my head when reading about the Emery Sound 'Mad Professor' tube kit that supplies a bunch of different types of tubes for experimentation. I don't really want to get into the whole NOS thing again, but does swapping a 6Y6 in place of a 6G6, or 12AU7 in place of a 12ax7 change the sound. I've got half of my answer already, but I'm also curious about swapping power and rectifier tube TYPES, not necessarily if NOS Mullards have 'moar gooier tonez' or if Brand 'A' beats Brand 'B'. 

Post-clarification: Better? Worse?


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## gtone (Nov 1, 2009)

Wild Bill said:


> Was it a true test? Did the listeners know a tube had been swapped and/or what brand it was?
> 
> If it was testing different tubes of the 12A*7 family I agree there are sonic differences. A 12AY7 will dramatically change the tone of a guitar preamp that was using a traditional 12AX7, since among other things the 12AZ7 has a MUCH lower voltage gain!
> 
> ...



Beg to differ Bill, but IIRC, I accepted the challenge on my terms (I pick/play the amp, the guitar, the tubes and the settings). Problem is, I don't make it your way, so we have a bit of a logistical challenge ahead of us to make this happen. 

IME, you will notice the difference in tubes in a simple circuit, but you would be hard pressed to notice little, if any difference in a more complicated circuit.


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## keto (May 23, 2006)

Yeah, I'd be happy to drink your scotch too if you come out west


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## blam (Feb 18, 2011)

not this again....

I recently swapped the tubes in my phaez. i was pleasantly surprised. however, what I swapped was a 12ax7 for a 12at7. gave me a little more headroom, much more pedal friendly (due to lower gain) 

also tossed whatever russian? tubes it shipped with for some JJs. because I swapped the 12ax7, I cant say if that made a difference.

when I had my egnater tweaker I tried swapping the 6V6s for EL34s. I much preferred the EL34s


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## Wild Bill (May 3, 2006)

Sometimes I wish I could move out west but I'm too old now for that kind of change. Too poor, too!

Yet my heart would likely be more comfortable out west. I was perhaps the first in Ontario to take out a Reform membership. Still proudly carry the card in my wallet.

Randy and his mentor Lenny are two of my favourite guitarists!

Still, who knows? I'm not dead yet!

Wild Bill


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## keto (May 23, 2006)

So, Bill, are you saying that, despite obvious internal construction differences between different brands of tubes - let's say 12AX7 for example - that their gains are all identical and their sonic properties as they pass electrons through the circuit are identical? There's no way they're introducing any resistance or capacitance? Even just signal noise from a noisy tube, be it less well constructed or just plain worn out, can make a difference, no? So, if a worn out tube (how do they wear? I don't know the physical characteristics of a worn tube) sounds different than a fresh one, what is the difference and why wouldn't that difference be something that could be native to different manufacturers' tubes? Not that they are trying to replicate worn out tubes, I hope you get what I am trying to say.

I mean, to me it's clear as day....if I put a current Shuguang 12AX7 in my little Jet City, the amp is hissier, gainier, and sharper in the high frequencies than if I put in a current Tung Sol, which is quieter, less gainy, and rounder in the high frequencies. A Sovtek is close to the Shuguang but a little quieter and a little tighter when I palm mute. And so on, and so forth. Blindfolded, I may or may not be able to tell you which is which but I could certainly tell you all day long that, assuming the same guitar and settings on the amp, and that you only changed V1 or V2, that a tube had been changed. And which I liked best.


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## gtone (Nov 1, 2009)

Ya ever work on a BF Bassman or a Tweed Champ, Wild Bill? If so, I find it incredibly difficult to believe that you cannot feel/hear a difference between a modern Sovtek 6V6 or 6L6 and an RCA blackplate version of those tubes in those amps. The fullness of the RCA's, especially in the lower end, is definitely noticeable. In fact, I'd make sure to bring my '66 Bassman head to the challenge as well as my Blackplate 6L6's coz' there has to be something in the order of 20% more gut-pounding, percussive bass that you can feel via those tubes.

I'm no scientist or engineer, but I've heard it explained that different plate materials used over the years and the physical size of the plates, getters, etc can make a difference.


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## GuitarsCanada (Dec 30, 2005)

I recommend an amp fest and challenge


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## elliottmoose (Aug 20, 2012)

GuitarsCanada said:


> I recommend an amp fest and challenge


A dual!

or full out civil war (we are Canadians, after all)


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## vadsy (Dec 2, 2010)

http://www.guitarscanada.com/showthread.php?55841-5E3-Power-Tubes

This was Bill's last go at it. 
I think it immediately came out that he didn't believe in tube differences unless he was making a few bucks on the side, after that we just did the same old internet back and forth that had been done a million times without results. I predict this will end the same way and after this thread gets abandoned another will take its place in 4 months with similar results.


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## zdogma (Mar 21, 2006)

I must say i've done a ton of tube swapping over the years, and to be honest I don't really notice much difference in sound. A few exceptions: EL 84-For me the "rugged" 6P14P EV tube is worth it cause it lasts and doesn't rattle like other EL84's. I also find the the russian 12AX7a/b have a lot of hum.


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## cheezyridr (Jun 8, 2009)

ok, so, this thread is kinda timely for me. i just bought that lil nite train. i like it alot but i think the distortion is a little on the fizzy side when using the bright channel. the thick channel sounds pretty sweet to me, it bypasses the tone controls. so if not tubes, what might i do to tame some of the brittleness of the bright channel? i otherwise really like this amp and the way it behaves.


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## Wild Bill (May 3, 2006)

vadsy said:


> http://www.guitarscanada.com/showthread.php?55841-5E3-Power-Tubes
> 
> This was Bill's last go at it.
> I think it immediately came out that he didn't believe in tube differences unless he was making a few bucks on the side, after that we just did the same old internet back and forth that had been done a million times without results. I predict this will end the same way and after this thread gets abandoned another will take its place in 4 months with similar results.


You believe WRONG! Go back and look at what I had written! I have always accused those who DO claim differences in tone to be either trying to feather their own ego and/or sell you something. I admit that initially when asked to review tubes for ANOTHER BUSINESS I used the observations of OTHER MUSICIANS for the review. That was just marketing. Since then when writing or speaking for myself I have never agreed with the premise.

What is your goal? Do you think that even if you prove me a crook you will change physics and you yourself be right? Grow up, Vadsy. Mother Nature doesn't care if you understand how her Universe works or doesn't work. Go open an electronics book and READ it!

For the record, I have never disagreed with modern tube brands differing a bit with gain and certainly with noise, microphonics and such factors. So what? Those have nothing to do with TONE!

Gain is something flat across ALL frequencies! Also, with a few tubes in cascade in the typical amp the total amplification factor is so high that differences are swamped out anyway. They become mice nuts to the total. Just look up any voltage amplification chart and do the simple math.

Tone is UNEQUAL gain across a spectrum of audio frequencies! To change the tone you must perhaps boost the bass or cut the mids, changing the gain differently for different frequencies involved in the entire signal.

Tubes operate by electron flow. Vibration of the grids and other elements can cause unwanted modulation of that flow, resulting in noise. Yet there is no difference to the amplification gain of any different audio frequency. In fact, the entire audio spectrum is moth nuts for a 12AX7. We can hear at best from perhaps 20 cycles per second to 20,000 cycles per second. A 12AX7 tube has a flat amplification factor to tens of MILLIONS of cycles per second!

Tubes are not and were not used just for audio, you know! They work for DC control signals, video signals and ultra high radio and television signals. To expect a tube to have different gains within that mice nuts sliver of frequencies we hear as audio is like the old joke about measuring with a micrometer and cutting with an axe.

What I find most amusing about this sort of discussion is that those of you championing the idea of different tone from different brands of the same tube are virtually never those educated in electronics. What's more, tubes were king for around half a century of use in electronic circuits. I have never heard of a single engineer from those days, or even from today, who would agree with such an idea! More likely, he would laugh his ass off!

Guess all those engineers for all those years were just both deaf and stupid!

I'll still post a bottle of the Glenlivet if someone will also put their money where their mouth is. I forgive someone who lives far away from me for refraining to participate but there are a LOT of musicians within practical range of the Hammer who both believe tubes make such a difference and could attend a test night.

Just don't expect me to do all the work setting it up for you! I'm too old, fat and poor to do it. Besides, I really don't expect to change many people's minds. I firmly believe that no one will pass the test yet they will still go home thinking they are right! Whereas, in the unlikely event the test shows someone CAN hear TONAL differences I will admit that not only am I wrong but that every audio engineer who ever lived and worked with tubes was also wrong!

How easy is it to change someone's religion? Faith amongst faith people is not bothered by facts. Me, as a "techie", I have never had much to do with faith. I have confidence in something that makes sense and has a lot of evidence but that is not the same thing at all.

Perhaps a local band might take up the challenge while holding an open jam night? With a sheet or two to screen someone while he changes tubes and some proctors to keep applicants either outside or in the can while changes are made it shouldn't be hard to have a REAL test!

If we have the time, maybe someone could bring along some coat hangars and we will do some speaker wire tests as well!

Wild Bill


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## gtrguy (Jul 6, 2006)

I try to stay out of these types of discussions (cap types, tubes, etc.) but here is what I can tell you. I have a bunch of different brands of 12AX7 from different eras and modern production. I've spent an afternoon swapping out tubes (V2 in a Fender Deluxe Reverb and playing through the Vibrato channel) and comparing to see if I could hear any differences. Most of the tubes sounded the same... no appreciable difference in sound though some seemed noisier. However, there were a small number (2 or 3) that did sound different. Maybe they were defective or worn out, or maybe I'm crazy (likely), but I can only state that I heard a difference with a couple of the tubes that I didn't hear with the majority.

If the premise is that a 12AX7 either works or it doesn't, does that mean a tube will sound and function the same for the entire life until it simply ceases to function? Do tubes lose brightness or bass with age? I don't know.

I'll also state that I have heard a difference between two different pairs of 6V6 in the same amp (current EH versus current JJ). Biased to the same static dissipation using the cathode resistor method. Again, maybe this means one of the tubes or one of the pairs was defective or was manufactured to different specs. All I know is that there was a clear difference.

For the record, I have no horse in this race- I don't sell tubes or amps. Just my 2 cents.


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## Wild Bill (May 3, 2006)

gtrguy said:


> If the premise is that a 12AX7 either works or it doesn't, does that mean a tube will sound and function the same for the entire life until it simply ceases to function? Do tubes lose brightness or bass with age? I don't know.
> 
> I'll also state that I have heard a difference between two different pairs of 6V6 in the same amp (current EH versus current JJ). Biased to the same static dissipation using the cathode resistor method. Again, maybe this means one of the tubes or one of the pairs was defective or was manufactured to different specs. All I know is that there was a clear difference.


The problem is, YOU were changing the tubes! That totally invalidated the test!

We are human beings and it is just the way we are wired that we attempt to see patterns, even when they are not there! There is a term for it - "psychoacoustics".

Only a truly blind test, one that is repeatable by anybody who does it the same way is useful. Anything else is just voodoo.

Try it again with a friend. Leave the room, close the door and let him change a tube. Or even NOT change a tube but let you try to tell for yourself!

A good test means the subject has no way of knowing what tube is in use or even if a tube was changed at all.

See if you get consistent results. 

If so, you will be the first.

I totally fail to see any reason why anyone who believes that different brands have different tone would have any problem with a truly scientific test. After all, if the idea is indeed true then the test would show it, wouldn't it?

Wild Bill


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## elliottmoose (Aug 20, 2012)

WildBill: I'm a little confused about the volume/gain vs tone argument you're making. I have always been under the impression that volume is interactive with tone (ie adding a clean boost in front of an amp). Does this also apply with tubes, like the GrooveTubes number system, or is that hokum as well?

Also I will match your bottle of Glenlivet IF it's a blind test to the terms of my intended question of this discussion: different types of tubes swapped in the same circuit. 

It it was never my intent to flame an old tire fire back into existence but rather to understand if and how various tube types affect the same circuit (ie, 6L6 to KT77 to EL84 to EL34 in the same amp, etc). Make sense?


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## bzrkrage (Mar 20, 2011)

Wild Bill said:


> Was it a true test? Did the listeners know a tube had been swapped and/or what brand it was?
> 
> If it was testing different tubes of the 12A*7 family I agree there are sonic differences. A 12AY7 will dramatically change the tone of a guitar preamp that was using a traditional 12AX7, since among other things the 12AZ7 has a MUCH lower voltage gain!
> 
> ...


Bill, have a listen to the show. I'm not saying that there is a right or wrong, but they use 3 different amps, 3 different tubes , up to you to decide.

http://www.homerecordingshow.com/20...ping-tubes-in-amps-and-simplifying-a-session/


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## Wild Bill (May 3, 2006)

elliottmoose said:


> WildBill: I'm a little confused about the volume/gain vs tone argument you're making. I have always been under the impression that volume is interactive with tone (ie adding a clean boost in front of an amp). Does this also apply with tubes, like the GrooveTubes number system, or is that hokum as well?
> 
> Also I will match your bottle of Glenlivet IF it's a blind test to the terms of my intended question of this discussion: different types of tubes swapped in the same circuit.
> 
> It it was never my intent to flame an old tire fire back into existence but rather to understand if and how various tube types affect the same circuit (ie, 6L6 to KT77 to EL84 to EL34 in the same amp, etc). Make sense?


Nope! Gain is gain and tone is tone. Sometimes circuits are built where there is some interaction between the controls, which might make things a bit more confusing. Still, they are different terms and if you don't use dictionary definitions for words then no one can discuss anything to any useful result.

Adding a clean boost WILL affect tone when the boost is sufficient to overdrive a tube stage into distortion. Distortion can and does occur at levels below what the human ear can easily distinguish. Normally our ears can't hear anything less than 5% distortion, which makes some of those audiophile power amplifier specs seem silly, when they sneer at one amp that has .15% THD compared to one that boasts .12 % THD.

So with what we CALL a clean boost between a guitar and the input of an amplifier we can have distortion at volumes below what sounds obvious. Especially when in most amps including the King of Clean, the BlackFace Fender we have a stage of tube amplification between the input jack and before the first volume control. So we can have distortion without the amp being overly loud, as if there was a master volume involved.

When you drive an amplifying stage into distortion you get distortion products that DO change tone, because unlike pure gain they do not affect all frequencies equally. Some of that distortion may be heard mostly in the mids and highs, without seeming to affect the bottom end.

The Groove Tubes number system is just a reference to match tubes to the same idle current for the same bias voltage. It has nothing to do with gain or tone. Since guitar amps typically use only one common adjustment for the bias voltage to ALL output tubes, it can be important to have them reasonably well matched, so that all tubes share the load equally. In extreme cases if one tube "loafs" and another does all the work the working tube will be exceeding its ratings and can burn out.

Different types of tubes if being used in a hifi, audiophile situation, will all sound exactly the same. That's the idea of high fidelity amps, after all! The sound was generated by the recording, be it vinyl, a CD, FM radio or whatever. The reproduction system is not supposed to change that. So all the circuits are designed to have the least possible distortion. You have an overall gain (volume) control and maybe a bit of tone shaping controls to compensate for the acoustics of your speakers or your listening room. Or maybe your personal taste!

Guitar amps are different. Usually we WANT the amp to have distortion available! However, some forms of distortion are pleasing and some are not. Personal taste is also a factor, but a MUCH bigger one!

Different tubes have different sensitivities. An EL34 needs less than 2/3 as strong a driving signal as a 6L6 to reach full output. After that you are overdriving the tube into distortion. This is why the different tube types can sound very different. Nobody compares them when they are used in a hifi amp! They compare them when rocking the amps out at high volume!

This factor was responsible for the creation of the Marshall sound! Back in the mid 60's, Marshall made their first amp, the BluesBreaker. It was a knockoff of one of Fenders BassMan circuits, using 5881s, which is an industrial number for a tube of the 6L6 family. As you would expect, the amp sounded like the Fender, except for using a British speaker which was probably a Rollo Celestion.

They made a reasonable number of amps because being produced at home in Britain they escaped the punishing customs duties and tariffs Brit players had to pay to buy a Fender amp. Then after a few short years there was a delivery panic in the industry. There was a world wide shortage of 6L6 tubes!

Deliveries became so long as to be silly and prices went through the roof. Marshall needed an alternative. The EL34 looked like a good fit. The pinout was pretty well the same. The bias voltage needed was different but hey! That's why we had bias adjustment controls anyway! The re-working needed was trivial and Marshall began to put EL34s into their amps.

Immediately players noticed a BIG difference! Since the amp circuit had sufficient gain for 6L6 type tubes they now had lots of EXTRA drive for EL34s! When you cranked up the amp you got that Marshall "snarl", epecially with pickups like humbuckers or better yet, P90s.

Marshall then had its distinctive sound and has never looked back.

No Elliot, I have always understood the difference in tone between a Fender and a Marshall, or with other amps using different tubes. As a general rule, EL84s sound like Marshalls with a lower wattage, since they have similar drive level needs. It's all about being definite in your terms and paying attention to what your circuit is actually doing.

So no point in matching my bottle. We actually agree!

My beef is with those guys who claim that they can hear a difference in tone between perhaps a Mullard 12AX7, one made by RCA and perhaps one made by JJ. I just don't buy it. My ears don't hear it. I have never heard of a scientific test that proves it.

What's more, no one should waste their time trying to convince me. They must try to convince every engineer that ever lived or is living today.

I worked for the Canadian Westinghouse Tube Division at the end of the 80's. It was a shadow of its former self. The factory had been closed for years and there was only a handful of people left. They bought tubes from the surplus open market and re-branded them as Westinghouse. I was privileged to work with those old-timers and am forever grateful for what they taught me.

One day an audiophile phoned wanting to buy some 12AX7s. He didn't mind that we were re-branding but he insisted we use Mullard tubes. I asked him why it mattered and he told me it was because "Everyone knows Mullards sound better!". So I put him on hold and went back to talk to Ed, one of the engineers still with us. 

When Ed heard my story he stared at me like I had grown a second head! Then he started to laugh so hard he fell over backward on his chair! His only comment as he got up was to say "The crap some people believe these days. Doesn't anybody actually READ an electronics book any more?"

So I went back to the phone and gently explained that our engineers did not subscribe to that idea and he should find another source. Of course, he easily did! There are lots of people who will say anything to get you to give them money!

I respect my friends at thetubestore.com. They do not take a stand on this issue one way or the other. They simply try to please the customer and if pressed will only say "many customers believe...".

Mind you, they must have some great stories they tell privately amongst themselves! 

Wild Bill


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## gtrguy (Jul 6, 2006)

Wild Bill said:


> The problem is, YOU were changing the tubes! That totally invalidated the test!
> 
> We are human beings and it is just the way we are wired that we attempt to see patterns, even when they are not there! There is a term for it - "psychoacoustics".
> 
> ...


So a defective tube isn't a possibility? There aren't differences in internal construction that result in different internal resistance, inductance or capacitance from one tube to the next? Every 12AX7 is identical in performance in every way?


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## nonreverb (Sep 19, 2006)

I think you partly answered your question in your first post although I'm not going to get into the debate regarding the differences between tubes of the same number.

There is a difference when tubes are old and tired. You can definitely hear really low emission tubes as their dynamic range begins to suffer which results in a dull farty sound. This is especially true where power tubes are concerned. In the preamp, you really notice the change in the phase inverter and reverb drive as these tubes operate in an entirely different way from the signal preamp tubes. You can see a really tired PI on the scope with a signal generator when comparing it to a new one.

The reverb drive tube in a Fender amp for example, is being used as an output tube driving an output transformer! You can actually hook up a speaker to the secondary of the reverb tranny and it will work like a mini amp. Therefore you can see how this tube can eventually go as it's delivering more current compared to the other tubes.



gtrguy said:


> So a defective tube isn't a possibility? There aren't differences in internal construction that result in different internal resistance, inductance or capacitance from one tube to the next? Every 12AX7 is identical in performance in every way?


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## gtrguy (Jul 6, 2006)

nonreverb said:


> I think you partly answered your question in your first post although I'm not going to get into the debate regarding the differences between tubes of the same number.
> 
> There is a difference when tubes are old and tired. You can definitely hear really low emission tubes as their dynamic range begins to suffer which results in a dull farty sound. This is especially true where power tubes are concerned. In the preamp, you really notice the change in the phase inverter and reverb drive as these tubes operate in an entirely different way from the signal preamp tubes. You can see a really tired PI on the scope with a signal generator when comparing it to a new one.
> 
> The reverb drive tube in a Fender amp for example, is being used as an output tube driving an output transformer! You can actually hook up a speaker to the secondary of the reverb tranny and it will work like a mini amp. Therefore you can see how this tube can eventually go as it's delivering more current compared to the other tubes.


So different tubes of the same type can or can't sound different? Sounds like you're saying they can...


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## nonreverb (Sep 19, 2006)

I think some truly believe the idea that different brands of 12AX7's, 12AT7's etc can sound different. When you really think about it though, back in the day when these tubes were made, nobody questioned it because nobody cared therefore everyone using them considered them the same without question. It's only in the last 15 or so years that it's become some kind of issue. Why? Because you can sell old tubes for lots more money now that they're out of production. I own a vast supply of tubes and really, I usually install new preamp tubes in the amps I service. Old Mullards, Amperex and Telefunkens are good tubes but suffer the same problems as new tubes such as microphonics. I wouldn't say they're necessarily better as they all are designed to do a specific job with specific charateristics. 

There are exceptions however. Some companies in the past had a penchant for rebranding a certain tube types as something else. A reckless business practice IMO.


gtrguy said:


> So different tubes of the same type can or can't sound different? Sounds like you're saying they can...


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## keto (May 23, 2006)

nonreverb said:


> There are exceptions however. Some companies in the past had a penchant for rebranding a certain tube types as something else. A reckless business practice IMO.


If they're all the same, why would it matter?

(That isn't a *real* question, by the way.  )


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## gtrguy (Jul 6, 2006)

Tube manufacturing expertise, material quality and likely manufacturing tolerances were probably much better back then also... but I'm sure that a modern tube made in a chinese sweat shop is going to perform exactly like a tube made in the heyday of production in a US factory. Or not...


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## Wild Bill (May 3, 2006)

gtrguy said:


> So a defective tube isn't a possibility? There aren't differences in internal construction that result in different internal resistance, inductance or capacitance from one tube to the next? Every 12AX7 is identical in performance in every way?


A defective tube is always a possibility! However, differences in performance are quite a different matter.

First, forget about resistance. It's not a tone thing! A resistance is an opposition to current flow. It doesn't care about the frequency. So it will not affect one band of frequencies differently than another, which once again is the very definition of tone.

Inductance and capacitance in a tube is too trivial to matter at audio frequencies. They DO matter at much higher radio frequencies! This property is called REACTANCE and is not really a factor for this discussion.

The type of differences in construction that would make more than a trivial difference in performance would have to be so large that the tube could not be called a 12AX7 anymore. It would be something completely different.

In electronics manufacturing, devices with universal part numbers MUST have virtually identical specs for a very simple reason - no manufacturer will buy them! A design engineer has to be able to expect any device he uses in his circuit to perform the way the data sheets say it will perform. Otherwise, when his units come off the assembly line they will likely not work properly!

I used to sell HUGE quantities of electronic parts to manufacturers. Do you know what would have happened if I supplied parts that didn't meet specs? I would have had my ass sued off!

At that point, the offending supplier is stricken from the buyers' list and likely goes out of business. You can't make electronic parts onesy-twosy. You depend on volume sales and if you don't keep up the quality you are out of the game.

I too have heard "gurus" talk about "differences in internal construction". Like most myths, there is a grain of truth that has been stretched all out of proportion. Yes, there are differences but you can't say they matter without specifying in what application! Just because they affect UHF television frequencies doesn't mean diddley-squat at audio ranges.

This sort of thing is called "technobabble". It is a marketing tool used to rip off the ignorant.

It's always the details. Electronic theory is complicated enough that without actually opening a textbook and studying the basics you can't get by just by quoting buzzwords and terms borrowed from other folks who don't really know anything. 

It's like thinking you can give a speech in French 'cuz you picked up a few words from a cereal box!

Or thinking you can play a guitar because you read a book, without actually having picked one up and fingered it!

Wild Bill


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## GTmaker (Apr 24, 2006)

Wild Bill said:


> In electronics manufacturing, devices with universal part numbers MUST have virtually identical specs for a very simple reason - no manufacturer will buy them! A design engineer has to be able to expect any device he uses in his circuit to perform the way the data sheets say it will perform. Otherwise, when his units come off the assembly line they will likely not work properly!
> 
> Wild Bill


Once again Wild BIll explains what is important and what is not.
Thanks Bill for adding to my information base. Much appreciated.

G.


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## elliottmoose (Aug 20, 2012)

I too have learned a great deal about tubes from this, and I'm glad I'm not in opposition of science (for once!). Generally I'm arguing with my engineering brother about fluid flow dynamics and getting my *backside* handed to me. 

He believes ERTW and that he wears the Iron Ring of Truth -- who needs accuracy and computer simulations for safe drinking water? Just pour A into B and stir. Right?


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## Budda (May 29, 2007)

I feel like the original question was not answered, unless i am missing something. Not comparing two tubes of manufacturer but rather of model. I *think* Bill said that the different types affect
tone (marshall going from 6l6 to el34) and that was my understanding of the original question; who has swapped tube types and to what end. 

I'm not worried either way; i have done it twice and heard a difference. I will agree there is a lot of myth surrounding tubes and tube amps. I will also agree that they can change (warming up after a cold drive for example).


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