A TUBE PRIMER FOR GUITAR AND BASS PLAYERS WHAT TUBES SHOULD I USE IN MY GUITAR OR BASS AMPLIFIER? Part 1 of 2

Guitar Amplifier Blueprinting Myles S. Rose www.guitaramplifierblueprinting.com THIS DOCUMENT WAS FORMATTED FOR “LANDSCAPE” RATHER THAN “PORTRAIT” AS IT WAS INTENDED TO BE ABLE TO BE VIEWED ON A COMPUTER. ON COMPUTERS, MOST SCREENS ARE WIDER THAN HIGHER. THERE ARE ALSO NUMEROUS LINKS WITH ADDITIONAL INFORMATION PROVIDED. THIS WILL PRINT OUT NICELY USING ACROBAT.

What are the differences between tubes? What is a phase inverter? What about a matched phase inverter? What is matching? Static versus dynamic matching? Aren’t all tubes really the same? Is 100 watts twice as loud as 50 watts? How much power do I need? These questions and more are covered in this document 1

Version 3.30 9/23/04 part 1 of 2 BEFORE WE EVEN GET STARTED … IF YOU JUST WANT A FEW BASICS AND HATE TO READ ....................................................... 4 BRIEF TUBE AND SOLID STATE DIFFERENCES ........................................................................................................................................ 4 DITTO – THE SWISS ARMY KNIFE OF THE RECORDING STUDIO AND FOR LIVE PERFORMANCE TO THE HOUSE SYSTEM......... 5 MY PERSONAL FAVORITE OR MOST IMPRESSIVE AMPLIFIERS............................................................................................................. 5 MATCHING IN BRIEF .................................................................................................................................................................................... 12 BIASING IN BRIEF ........................................................................................................................................................................................ 13 WHAT TUBES SHOULD I USE IN MY AMPLIFIER? - A MODERN DAY TUBE SELECTION PRIMER .................................................... 13 PREAMP TUBES ........................................................................................................................................................................................... 17 SAG – SPECIAL APPLICATIONS GROUP (SPECIFICALLY SELECTED TUBES FOR SPECIFIC NEEDS) ............................................ 17 THE BASICS OF PREAMP TUBE DIFFERENCES ...................................................................................................................................... 19 12AX7 (ECC83, 7025, 12AT7, 12AY7, 12AU7, AND MANY OTHERS) PIN CONNECTIONS..................................................................... 21 12AX7 RATINGS............................................................................................................................................................................................ 21 12AX7 SHORT DATA .................................................................................................................................................................................... 21 CHARACTERISTIC NOMENCLATURE USED BY TUBE ENGINEERS ...................................................................................................... 22 PREAMP TUBE OVERALL CHART OF SOME NOS AND MANY CURRENT TUBES ............................................................................... 32 ADDITIONAL SMALL SIGNAL TUBE TESTS AND REFERENCE .............................................................................................................. 35 RECENT TUBE TEST RESULTS .................................................................................................................................................................. 37 THE OUTPUT TUBES – THE PENTODES AND BEAM PENTODES .......................................................................................................... 46 BIASING – A NEEDED CONSIDERATION WHEN REPLACING OR CHANGING POWER TUBES .......................................................... 47 2

6V6 OUTPUT TUBES .................................................................................................................................................................................... 49 6L6 / 5881 / KT-66 TYPES............................................................................................................................................................................. 52 EL34 – E34LS – AND 6CA7 TYPES ............................................................................................................................................................. 59 MISCELLANEOUS AND OTHER OUTPUT TUBE TYPES........................................................................................................................... 64 6L6 / KT66 / 5881 / EL-34 TUBE OUTPUT CURRENT OUTPUT COMPARISONS..................................................................................... 66 POWER OUTPUT COMPARISON TEST RESULTS OF VARIOUS OUTPUT TUBES ................................................................................ 67 6550 / KT-88 TUBES...................................................................................................................................................................................... 70 POWER COMPARISON CHART OF CURRENT OUTPUT FOR THE KT-88 / 6550 FAMILIES .................................................................. 77 THE EL-84 TUBES......................................................................................................................................................................................... 78 TECHTIP ON EL-84 AMPS............................................................................................................................................................................ 78 OUTPUT POWER CHART FOR EL-84 FAMILY ........................................................................................................................................... 82 7027 AND 7591 TUBES................................................................................................................................................................................. 85 RECTIFIERS – VACUUM TUBE AND SOLID STATE .................................................................................................................................. 85 THE GT RATING SYSTEM – AN EXPLANATION OF “DISTORTION RATING” ALSO KNOWN AT TIMES AS “HARDNESS RATING” 92 CONVERSION INFORMATION – GT NUMBERING, FENDER COLOR CODES AND MESA COLOR CODES......................................... 92

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Before we even get started … if you just want a few basics and hate to read There are three items that are the foundation of most of what is in this document. Tube and solid state differences, matching, and bias. I will cover these briefly.

Brief Tube and solid state differences Much is available on this subject, but from a very high level there are a few points worth mentioning. Some folks feel that solid state and digital components have greater frequency response than tube devices. I suppose this may be true in some area out in areas that are so far out in the frequency spectrum that it’s crazy, but for our purposes, this is not the case. Remember, there are tube devices operating in the gigahertz range, way beyond what we need in the world of audio. There are devices such as the DITTO, which have a bandwidth of 6 Hz – 200 kHz which are tube units, as an example, in the audio business. Solid state devices have sort of an “on or off” aspect to their operation. This is something akin to one being in a dark room, with their eyes closed, while another in the room flips the light switch on and off. You cannot see the light, but know that something is going on, as you hear the switch being flipped. This is true in the digital realm, and is sometimes called “hash” or has other terms, for this by-product if digital products. You think this is no big deal or does not matter? Thankfully today, there are very powerful tools available to mere mortal men, only available in the past to folks that worked at places like Bell Labs. Pro Tools, a popular recording suite, can illustrate this pretty easily. Look at any digitally recorded aspect of one of your recordings. Drum tracks are great for this. Zoom in on one short area of a sample of the sound. You will see a lot of information there. Now, borrow something like a DITTO box or Brick. “THE BRICK” is something of a DITTO but has onboard phantom power so you may use it for microphones also. THE BRICK shares some of the ViPRE technology. More can be found on THE BRICK at http://www.groovetubes.com/product.cfm?Product_ID=2084

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DITTO – The Swiss Army Knife of the recording studio and for live performance to the house system Take the original track, reroute it through the DITTO, and reproduce it to another unused track area. Now listen to the difference. Look at the difference. You will notice that the DITTO rerecorded track lost NONE of the original material, has more dynamic range, sounds much more open and alive, and yet has less on the display. Why is there less on the display? Zoom in on the “missing” part of the waveform. LISTEN to only that aspect of the sound. I think you found it was clicks or noise, or whatever you want to call it … but in any case, stuff you did not want and stuff that did not help your sound. Try plugging a POD XT into one of these before you go to the board or the amp. You may be surprised Tubes do not have the “on-off” aspect. They are always conducting and flowing the electron flow. This is one of their differences. This is not better or worse, it is different. Before you think or buy the fact that sticking a tube in the front end of a digital or solid state amp is going to turn it into a tube amp, think again. It may give you everything you are looking for, and that may be just what you wanted, tube or no tube.

My Personal Favorite or Most Impressive Amplifiers Being a big fan of Aspen Pittman’s “The Tube Amp Book” for almost two decades, one of the first sections of the book that caught my interest was Aspen’s Top Ten amps of all time section. Today, there is a wider selection of amps than ever before, and although many of the original amps are still considered the classics, some of todays amps are what I consider to be the classics of today, and probably tomorrow. I picked these amps for various reasons, but some of the aspects are unique features, design, and superior build quality. I will explain some of my thinking as I go along. I do not own all of these amps by the way, but have had access to them and they impressed me enough to stick in my mind. I know many will complain as there are not amps such as the Matchless DC30 and many other great amps here that they feel should be here. These are amps that a higher number of folks out there can afford, and amp that in their price range give up nothing in the way of tone and build quality compared in cases to amps with two or three times their retail cost. This book is primarily a tube document, but I could not keep myself from saying a little more about the amplifiers themselves.

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HIGH POWER MODERN PCB CHANNEL SWITCHER AT A STEAL $$$$$ – THE RIVERA KNUCKLEHEAD REVERB 55 AND 100 WATT AMPS This amp is one of the few, if not the only, that has two differently voiced channels, one British and one American. Most other amps just alter the gain on the channels. The amps are built using aspects such as threaded inserts in the cabinets, and machine bolts, rather than just self tapping wood screws. I have NEVER had any client Rivera amp fail due to design or workmanship. VERY flexible front end with great EQ and tone controls. Sub level control if you use a sub system. With the Rivera Head Master controller, total control of the amp is just a tap away. The amps are really nicely priced compared to a lot of things out there that might do as much and are not built as well. To my way of thinking, Rivera amps are the best made production channel switching amplifiers today; heads or combos using PCB construction. For more info: http://www.rivera.com/prod_khseries.htm

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THE ‘MARSHALL” STYLE AMPS in the non-master volume style Dr Z Delta 88 There are a number of great “non-master” volume “Marshall” type amps out there. This is one I have found that gives the tone and feel of the EL34 and 6550 Marshall amps but is not just a copy or modification of the original design. Much more pedal friendly than the originals and with a very simple front end and over 100 watts on tap via a duet of KT88 output tubes these amps are worth a test drive. More things than I can really say here. http://www.guitaramplifierblueprinting.com/doctorz88.html

“VOX AC-30” AMP - THE VOX THING AND MORE WITH SIMPLICTY AND EVEN MORE VERSITILITY Dr. Z Mazerati and new Prescription Extra Strength Lots of clean headroom if you need it, lots of AC-30 tones it you need that, only one tone and one volume, and trust me, that is more than enough. It also seems to be enough for Brad Paisley who chose this amp to replace his own vintage AC-30. If you want more controls and a more “conventional amp”, then look at the Dr. Z Maz 38 which is voiced more like a Fender Tweed Bassman / Marshall Plexi, but can do the Vox AC 30 stuff as well. Dr. Z can even optimize the Maz 38 in more or less of either direction. Read the Guitar Player Magazine March 2004 review at: http://www.guitaramplifierblueprinting.com/gp032004.pdf http://www.drzamps.com/mazerati.html http://www.drzamps.com/maz38.html http://www.guitaramplifierblueprinting.com/zpaisley-rx.html

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BLUES / SMALL CLUB AMPS – TWO STANDARDS OVER DECADES The Victoria 20112T (tweed deluxe) and Fender Deluxe Reverb The Fender Tweed Deluxe (on the right in the photo). There is little to be said about these Deluxes, and this Victoria is one of the very best. The phase inverter on the tweed amp is only one half of a 12AX7, and the tone control works directly on that triode. This lets one balance the ratio of preamp to output distortion just so, a feature that I miss on the Black Face Deluxe Reverb that came in later years. Then again, pick either of these amps, depending on taste! For a lot more info on this amp head to http://www.guitaramplifierblueprinting.com/Victoria1.html MY FAVORITE CLEAN AMP – FOR COUNTRY PICKERS, RHYTHM PLAYERS, BUT ALSO HUGE LEAD CRUNCH FOLKS ALA JOE WALSH / TED NUGENT The Dr. Z KT-45 for Fender Twin Reverb or Super Reverb fans This amp puts out close to 70 watts or more. Again, simple controls, but not limited tones. The EF86 in the front end has huge gain and is driven by the tone stack, so a very huge sound with massive sound stage image is possible with this amp, more so then with the old classic, the Fender Twin Reverb. These amp are currently with Brooks and Dunn, and many others. This is the amp Joe Walsh used on the Eagles “Hell freezes over tour”. http://www.guitaramplifierblueprinting.com/doctorzamps2a.html

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HUGE ROCK AMP COMBO FOR THE CLASSIC 1950S AND EARLY 1960S TONES Victoria 80212T and 50212T Massive clean tones, more headroom and larger transformers than a 100 watt Hiwatt. The Tweed Twin is what you see being used by folks from Clapton to The Stones these days. This is one huge sounding amp, the sound of Rock and Roll. If this amp is too much for you, there is also a 50 watt version which frankly, is more than enough for most stages and outdoor venues. I know some folks are going to say, “what about the Victoria Bassman”? I don’t think there is any reason to list that amp in here, doesn’t everybody already have a tweed Bassman? http://www.guitaramplifierblueprinting.com/Victoria2.html

MONSTER GAIN IN A SMALL PACKAGE – STUDIO MASTERPIECE – SMALL CLUB MASTERPIECE Dr. Z Carmen Ghia – “if I could have only one amp for the rest of my playing days, it would be a Ghia” … msr

One tone, one volume, and can be pretty clean at less than 10 o’clock on the volume with a decent amount of clean headroom, a bit louder than my Deluxe Reverb. The amp is rated at 18 watts … don’t let that fool you, look at the power transformer! Hand wired turret board, the best parts, and turning the volume past 10 o’clock the fun starts and the surprised looks never stop. A necessity in any studio. Conjunctive tone filter and fixed bias phase inverter … you won’t see these in other amps http://www.guitaramplifierblueprinting.com/doctorzamps3.html 9

JUST GREAT ALL AROUND, SUPER AMP(S) IF YOU CAN ONLY HAVE ONE AMP Okay, I cannot pick one, as this is for the great all around amp. The Rivera Quiana is a departure from Paul Rivera, as it uses 6L6 output tubes rather than EL-34 tubes. This amp does Fender on channel 2 and high gain Brit (sort of the Bluesbreaker thing on Channel 1. A lot of versatility and features and the 2x12 configuration will fill any venue. http://www.rivera.com/prod_latest.htm The Dr. Z Maz 18 (MAZ Jr.) Hand built, PTP, best parts and construction, ultra versatile, compact, light, loud, reliable in the worst situations, and at a price that is generally less than ½ of what many amps hand built amps of this class sell for. A lot of output and great reverb too, in an easy to move package. This amp has a different sort of flair than the Rivera, quicker to distort as it is based on a duet of EL84 tubes. These amps are very loud, much louder than their power rating suggests. These are also one of the few EL-84 based amps that can do the Vox sound AND the Fender sounds. This amp should also be in one of the other sections above, as one of the best club and blues amps. This is perhaps one of the most versatile amps anywhere …. Rock, jazz, blues … and pedal friendly to boot. This amp is also very portable. 1x12, 2x10, and head. http://www.drzamps.com/maz18.html The Dr. Z Z-28 (not shown here but can be seen from the below link) All the great Fender tones and more. This amp has replaced many of my Fender amps for those applications. The Z-28 puts out more level than one would expect though. Think of the amp as bigger than a Black Face Deluxe. It easily keeps up with a BF Super Reverb. http://www.guitaramplifierblueprinting.com/doctorzamps2a.html

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Great designs with something worth considering – MASTER BUILT, PTP TURRET BOARD, ATTENTION TO DETAIL AND GREAT TONES AND FEEL. The Mako amps Hand wired, PTP, turret board, channel switchers. Hand built PTP channel switching amps. An amp where there is no room for improvement. Even the transformers are done in house. There are not a lot of PTP wired channel switching amps out there, only one other crosses my mind. These have a waiting list, and are generally only sold direct unless things have changed, but they are worth the wait. The wood cabinet in the photo I stole here from the Mako Website was a custom cabinet. These folks also have some of the best speaker cabinets in the world, from my point of view. http://www.makoamplification.com A BRITISH FLAVOR / USA HAND BUILT AMERICAN STANDOUT – 60 WATT MASTERPIECE – A GREAT ROCK OR CLEAN AMP The Victoria Sovereign is not really a master volume amp. With an EF86 in V1 (huge clean headroom or gain) an amazing reverb driven by a 6BM8 Pentode/Triode and 60 watts easily out of a set of even 25 watt EL-34 tubes such as Svetlanas, this is an amp that is a real masterpiece. There is too much to say here, but you can read a detailed PDF format review at http://www.guitaramplifierblueprinting.com/Sovereign.pdf There is also more at: http://www.guitaramplifierblueprinting.com/Victoria1.html

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Matching in brief There is a lot more on matching deeper in this document. Let me just briefly say here, that folks need matched output tubes and at times, matched triodes. If you have what is termed a Class A amp, such as a Vox AC-30, Matchless, Fender Blues Jr., and think you got lucky as there is no bias adjustment, you are wrong. These amps are what is termed cathode biased, but are not what are called single ended. They have two or four output tubes, and operate in push-pull, just as the class AB brothers. What gave the Vox AC-30 the reputation for being unreliable, was the heat that was generated, the lack of ventilation, and a few other aspects. Balanced output tubes are critical in these amps. They are idling at close to 100% idle dissipation, much higher than their AB counterparts. An unbalance in the output set is akin to two riders on a tandem bike. If one is tired or slow and does not contribute 50% to the effort … no more, no less, the other rider will tire more quickly due to additional work effort required. This is the same with tubes, one tube or duet is working harder than the other, and this causes a few problems. The first aspect is the sound most would surmise. Yes, this is true, a lack of sustain, less power, less clarity. There is another important side effect. Heat. Lots of heat that is not nearly as high as when balanced tubes are used. The tubes of the past were not matched at times. Vox AC-30 amps were known at times to also catch on fire and have reliability issues. It was common for groups using these amps to have more than one, and “matter of factly” just wheel one in to replace the one that failed on stage. Don’t believe it? Read a bit or ask around some of the folks from the sixties. Look in the Vox Book where this is mentioned in passing. Lower chassis temperatures also give longer life to the resistors and capacitors that also reside in the amp’s chassis, extending their life. There are big differences in the ways tubes are matched, and this is covered later in this document. From an Internet post I answered in regard to “matching” preamp tubes, specifically the phase inverter:: quote:

Originally posted by proudmore Hey Myles, for a PI, what brand of tube would be the best? What should I look for, other than matched triodes? Should be a high gain tube, high output..? Does it matter? The brand of the tube or tube type is not really critical. Some runs have more balanced tubes than others. The PI is not part of the tone generation stage, so it is picked for specs and performance, tone is not an issue. You want proper gain, but proper output current is MUCH more important. This is why simple gain matching or transconductance matching is pretty good, but will not yield the same results as a tube that has proper current drive (most are about 1/2 of what is spec) for today's tubes on average, or at least 3% down for the most part. Even more important is the tubes curves and rise time. In some amp designs that balance (actually they average) the output or gain of the two sides ... they cannot average rise time. Sort of think of it in a way, that is you have a rise time of 20 "counts" on one side and 40 on the other, now you have a wobbly window of 20-40 counts overall, or a 20 count spread. This is a lot less articulate and defined than a count of 0-2 or so. This is where pretty sophisticated test rigs come into play, and cannot be done with conventional tube "matching" equipment. 12

Biasing in brief Bias your amp properly every time output tubes are replaced, if not of the same distortion rating, type, and maker. The bias is something like the idle of your car in a simple way. Setting your bias so the amp runs really hot is something like using this faulty logic to set the idle on your car to 5000 rpm. You want your bias set for great tone at low, mid, and high levels … not just at high levels. Bias effects tube life, tone, playability, dynamics, and other areas. You also need to bias the amp properly. This does NOT mean pulling the old tubes out, slapping in the new ones, and THEN trying to bias. This will only lead to problems, or at best, take a big chunk out of the life of your new tube set. A proper bias method is described later in this document.

What Tubes Should I Use In My Amplifier? - A Modern Day Tube Selection Primer Today in 2003, there is a lot of misconception on where tubes come from, how they actually perform, and what their characteristics are. Information that was valid only a year or two ago, is not always valid today. “Chinese tubes are less powerful than the Russian tubes”. “Chinese tubes do not hold up to high voltages”. “Matching is matching”, or “there is no need to match tubes”. This information gets passed along, and becomes something of gospel, when most of it is just plain rubbish. In the case of the Chinese tube issue, a few years back, this generally was the case. Today, the typical Chinese power tube is 15% stronger in many cases than its Russian counterpart. The Chinese have great tooling, and money. They are putting a lot of resources into tube manufacture. The Chinese 12AX7 as one example, is the most consistent tube in quality and specifications when compared to a lab spec 12AX7. As you proceed with this paper, examples and characteristics of many tubes will be given. These are not bits of data collected from magazine clippings, Internet spatter, or hear say. This data comes from my personal time sitting with thousands of tubes, one at a time, with very high end test equipment – not simple tube testers. Amps come in all types, sizes, styles, etc. You cannot turn a Marshall into a Fender, or visa versa, no matter how hard you try. If you “need “ both of these sounds, the bottom line is, you need one of each of these amps. Some folks like Paul Rivera, have two different voicings in the same amp. This is pretty unique, as most folks just change the gain structure on the various channels, with the same voicing.

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A 60 watt Sovereign amp from Victoria Amplifier – very versatile with it’s variable front end which uses an EF86 in the front end, a 6BM8 in the reverb circuit, a cross between a Plexi era Marshall and Tweed Bassman. This is not a master volume amp. You can turn the gain all the way down and it’s pure Plexi era. Turn the gain up, and it moves through JCM 800, 900, 2000, and beyond Mesa Rectifier territory. This is one example of an amp that is very unique, and built, and very unique. I have a full write-up on this amp someplace on my personal website. If you would like a copy of the review sent to you via email, just drop me a note. You can also learn more at http://www.guitaramplifierblueprinting.com/Victoria1.html for Victoria in general. A review of the Sovereign is at http://www.guitaramplifierblueprinting.com/Sovereign.pdf

Some of the proven classic amps ……… Fender Black Face Deluxe Reverb and the Tweed Deluxe (in this case a Victoria 20112T) Perhaps to some folks thinking, the best small club and blues amps around. This Victoria Deluxe is simply, one of the most amazing and touch sensitive amps one will ever play. This is just one of Victoria’s amps in an extensive lineup. To see more, head to www.victoriaamp.com

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The Dr. Z Carmen Ghia. Sure, the good Doctor makes lots of amps, but this is one of the most amazing pieces of gear around. This is a studio amp masterpiece and also a super club amp, Dr. Z is one of the folks out there that copies nobody. His amps are all very unique and built to the very highest standards of construction. His Route 66 has won awards that were not political, they were from real players. The Z-28, MAZ 18 and 38, and other models each do their target aspects VERY WELL. For much more on Dr. Z amps, internal photos, comments, pricing and more, head to http://www.guitaramplifierblueprinting.com/doctorzamps.html

If you are one of those folks that thinks that wattage = manhood … this older amp may be your cup of tea. The top section is two 60 watt EL34 based amp sections, and the bottom slave is 8 GE 6550 tubes, for a total of about a ½ a kilowatt of tube power. This amps runs with four 2x12 cabs and four 4x12 cabs. For more on Rivera, and their amps (which are a lot more current that this particular example, head to http://www.guitaramplifierblueprinting.com/rivera.html There are amps for every taste and need out there! This is a very old Rivera model, no longer produced. For their new and great amps see www.rivera.com Some of my other personal favorite folks out there can be seen in the amps / guitars area of my website at http://www.guitaramplifierblueprinting.com/ampvendor.html

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This is a THD Univalve. This is a single ended class A amplifier that one can change the tubes in with no adjustment necessary. There are a lot of other features on this amp. This amp is a great tool in the studio or for smaller club live work. Some folks think of amps such as Vox AX-30 amps as class A amps. Although this is somewhat accurate, they are really cathode biased push-pull amps. The Univalve is a true class A amp with no feedback loop. The THD UV is a MUST for any studio. For more information go to www.thdelectronics.com

Two Doctor Z amps, perhaps on each end of his product line. The red one is a Carmen Ghia, one of the coolest amps around and a great studio and recording amp. The tan amp is a KT-45 with loads of clean headroom, but with it’s tone controls pushing a pentode front end (an EF-86, this amp is capable of a lot of gain too. The pair of these amps will cover just about any music base. Dr. Z has a LOT more amps, all of original design, and all built hand wired to extremely high standards. For more see www.drzamps.com

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Preamp Tubes Please note that the tests on tubes were done on raw factory samples. Some tube vendors test and/or select or grade, and some do not. Many rely on the end user’s reluctance to return a single tube such as a preamp tube for problems, so just send their tubes out with no testing or minimal testing. A preamp tube that is not microphonic when first installed, can become microphonic in short order after a few heat up and cool down cycles with expansion and contraction. This is one reason to know and trust your vendor. Some companies such as Groove Tubes have a very long warranty on tubes, in the case of preamp tubes, six months. Some reasons for the cost of GT premium tubes are due to the labor intensive testing process (each tube, one at a time, in place in high gain amps and tested for various attributes), and their cost for the tubes initially when buying from the major tube factories. In many cases, the GT reject rate is in excess of 60%. The data below, are for the raw factory samples, not GT tested examples. This is the way they come from the factory, and the sort of performance you can expect if your vendor does not test for gain, output, noise and microphonics. In the case of power tubes, gas leakage, grid leakage, and low vacuum are also test parameters that require expensive and complex test equipment which very few vendors have in house. The complete list of Groove Tubes preamp tubes can be seen at: http://www.groovetubes.com/tubes_list.cfm?ObjectGroup_ID=107

SAG – Special Applications Group (specifically selected tubes for specific needs) As you will learn throughout this document, all tubes, new or NOS are subject to very wide variations in characteristics. As an example, a 12AX7 is supposed to have as spec, a gain of 100, a transconductance of 1600 and a current output of 1.2 milliamps at a reference test voltage and bias. Tubes will typically vary +/- 50% or more, even ones tested from most vendors. For GT preamp tubes, this spread is much narrower, as the testing acceptance margins are tighter. Still, you do not know what you are actually getting in any case. One problem that kept coming into play, was a player would decide to retube the preamp section of his or her amp. The amp sounded worse in some cases with the new tubes. It was noted that perhaps the old tube had a current output of 1.0 milliamps, while the new tube only had a current output of 0.7 milliamps. This was a 30% drop in actual power off the first gain stage. Searching through tubes until one was found that met or exceeded the specs of the original tube would solve the problem and bring the amp back to life. It was found that things could be made even better, actually moving up or down in various tube characteristic parameters, to dial in to a particular player’s taste of needs. Tubes with more or less gain, more or less current, faster or slower rise time (more or less compression), and other factors were “tweeked” as the player went from one tube to another. This is one of the cornerstones of amplifier blueprinting. Matched phase inverters also came to pass in this process, there is more on this later.

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One of the biggest benefits of SAG tubes, is that the end user KNOWS what is in the amp. They can replicate this later, or go “up or down” in various parameters. For very critical requirements, the rise time of the matched phase inverter is also optimized to the characteristics of the output tube set. Most GT offered tubes can be processed through the SAG (Special Applications Group). It costs about $10.00 per tube to have one found, and in some cases, some tubes may not be able to be accommodated in short order. Some tubes from some vendors, have such a high reject rate, or extremely bad characteristics, that one would need to go through over 100 of them to find one example. You may contact Myles Rose for specific requirements. Some of the more common SAG tubes are available off the GT website or may be special ordered through any Groove Tubes dealer. There is more on the SAG on the Groove Tubes website at http://www.groovetubes.com/product.cfm?Product_ID=1773 where one can also add the SAG labor cost to any of the tubes in the GT product line. Some of the more common SAG tubes generally in stock are: SAG-AT7-MPI - matched phase inverter (on a tracer, not just statically matched) generally used in Fender Black Face, Silver Face, and early Tolex era amps. http://www.groovetubes.com/product.cfm?Product_ID=1722 SAG-AX7-MPI - matched phase inverter (on a tracer, not just statically matched). Used on most amplifiers http://www.groovetubes.com/product.cfm?Product_ID=1723 SAG-FHG – Fender High Gain Kit for Black Face and Silver Face era amps, many of the newer amps also. http://www.groovetubes.com/product.cfm?Product_ID=1766 SAG-FST – Fender Soft Touch Kit – same as above, also used for any 12AX7 front end based amp where a slower rise time is desired, a quieter tube, more clean headroom, and a higher ratio of output tube distortion compared to stock V1 and V2 tubes in these amps. This was the old “SRV” trick, where he would use 5751 tubes in the first gain stage. Unfortunately, there are not a lot of great new 5751 tubes around today, so finding tubes with the same sort of characteristics was the goal here. http://www.groovetubes.com/product.cfm?Product_ID=1767 SAG-MHG – Known as the “Marshall High Gain Kit”, this should really be called the high output kit. This kit is very popular in not only Marshall amps, but in Mesa, Bogner, Fender amps that need a more aggressive nature, Diezel, Rivera, and many other high gain amps. Most of these amps have very complex front end design. Having a tube that is down 30% or more on current drive ability will zap the life out of the best of any of them. Many folks love these with the included AX7 phase inverter in Fender Blackface and Silverface amps for an aggressive update on these amps. http://www.groovetubes.com/product.cfm?Product_ID=1737 18

The basics of preamp tube differences The primary and most common family of preamp tubes is the 12AX7 / 7025 / ECC83 family. These are directly interchangeable in most guitar or bass amplifiers. Contrary to popular opinion, these are not the same sounding tubes in many ways. They each have their own sonic signature and sound characteristics. Below one can see the difference between a commonly used Sovtek 12AX7WA (the green line) and a long smooth plate 7025 (the blue line). The 7025 is a brighter tube, with more treble and high mid response. The 7025 was used in the Black Face Fender era, and was one aspect of the bright clear sound of these amps. There are many factors in a tubes character. In the case of preamp tubes, aspects such as gain (Mu), output, transconductance, and other factors, are all part of a bigger picture. Many people use the terms gain and output interchangeably. This is NOT correct. A tube can have high gain, but be very low in output current capability. This is a very common mistake today. In a clean front end preamp circuit, such as a tweed or blackface era amplifier, low output is less of a factor than in a modern channel switching amp with a complex circuit topology design. These newer amps perform their best if a high current drive tube is utilized. Today’s most common factory tube, the Sovtek 12AX7WA, is picked for many reasons. It is not expensive, it is sturdy (so the amp makers have less warranty return), and it is generally low on gain and output. The latter characteristic makes the amps more quiet with less background noise, and this helps cover up other manufacturing or design shortcuts.

Today’s tubes are VERY inconsistent. You may re-tube your amp, just to find that is sounds worse than before the replacement. Why? As one example, a “spec” 12AX7 should have a gain of 100 for a “typical” tube based on specs set many decades ago. It should have a transconductance of 1600, and an output of 1.2 milliamps. If your V1 (first gain stage tube) had an output of say 1.0 milliamps before it was replaced, and the new tube had an output of 0.8 milliamps, right there you just lost 20% in your front end. Remember, this signal gets amplified now down the rest of the amplifier chain. 1.2 milliamps is the “spec” number we look for in a 12AX7 / ECC83 / 7025. Unfortunately today, the vast majority of the tubes we see made newly are on average, much less, and at times 0.7 milliamps on average. This is almost a loss of 50% of our expected output. Poor plate materials that are inconsistent, fast work, incomplete vacuum pump down procedures, cathode coatings with high percentages of impurities, and more. These all contribute to today’s inconsistency. These are some of the areas where the Chinese are improving faster than in other geographic areas. 19

The most important tube(s) in the preamp section are in the first stages, the tone and gain stages. Changing V1 in many amps will yield the most results. Tubes used for current drivers as their primary function, such as reverb drivers or effects loop drivers, do little in most amps to change the tone. This is generally not part of the tone or gain stage. The exception to this is the phase inverter or driver, of the power tubes. There will be more on this subject later in this paper.

Moving on to the tubes What we are looking for are specific factors in testing, and other factors in sonic aspects. Rather than list all the technical data for each tube, where I have this data, I will provide additional information for gain, output, and consistency. The consistency factor I will call QA for quality. For this “spec”, the lower number, the better. A perfect tube factory run would have 0% inconsistency. A factory run where the tubes were +/- 20% off target factory expected specifications, would have a number of “20”. The standard specs that are the target numbers for gain is 100, and output is 1.2 milliamps, in the case of the 12AX7/ECC83/7025 family. Output will be shown as a percentage of factory expected target. If a tube has 1.2 milliamps of output, it’s Output would be 100%. The most important factor in all of the above, is know and trust your tube vendor. Tubes need to be tested for microphonics, low output, and noise. With today’s material inconsistency, a tube that is quiet today may become microphonic after a few hours of use, so a vendor with a good warranty is one that one may wish to have in your corner. NOTE: This test data is from bulk factory batches of large quantities of tubes, at times 1000 tubes of each type from each factory run. This illustrates how random these tubes are, and shows what a chance you may be taking with untested tubes in general. These tubes, after testing using good methods, will narrow this inconsistency considerably. In one Tube Company’s case, Groove Tubes, their reject rate on factory tubes can exceed 50%. You can sometimes easily tell how well a tube has been tested easily … price. When there is a lot of test time and labor, and half of your stock hits the trash bin, the end retail cost has to be higher. The data below was collected at one part of late 2002 and early 2003. For the most current data, see the updated information elsewhere in this document.

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12AX7 (ECC83, 7025, 12AT7, 12AY7, 12AU7, and many others) pin connections 12AX7 (ECC83, 7025, 12AT7, 12AY7, 12AU7, and many others) pin connections.

12AX7 Ratings 12AX7 ratings

12AX7 Short Data 12AX7 short data Note the Mu, or sometimes called gain, in a “spec” tube has a target of 100. Few tubes made today will reach this, most falling below 90. 21

NOTE: THESE TYPES OF CHARTS WILL BE USED THROUGHOUT THIS DOCUMENT. HERE IS A LEGEND SO ONE MAY KNOW WHAT THE COLUMN HEADINGS MEAN. SEE BELOW

Characteristic nomenclature used by tube engineers

22

Keep in mind, the specs on the tubes below was, at the time of testing. This is an average of many factory runs. These numbers are always changing from factory run to factory run. The most current data which is more detailed, can be found elsewhere in this document.

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12AX7-C – Chinese 9th generation tooling Gain: 93 Output: 92% QA: 17% This is possibly the best of the current 12AX7 family. This is a warm and linear tube. It is suited to rock, blues, and jazz. It is perhaps the most versatile of the 12AX7/ ECC83/7025 family. There are many Chinese variants, and many tube vendors sell older tooling versions. http://www.groovetubes.com/product.cfm?Product_ID=1158 This is perhaps the most linear and most warm of new 12AX7 / ECC83 / 7025 tube production. It is also the most close in specs and the QA from the Shuguang (not to be confused with Sino), is higher than any current production tube in this family. The Chinese are pouring money into new tooling that is of very close tolerances, and has the money to do so. This is not true in the case of other companies generally. This is a great all around tube for 60s rock, blues, and is a favorite of jazz players or players that wish to tone down a harsh amp.

12AX7-R – Sovtek 12AX7WA and Sovtek 12AX7WC Gain: 86 Output: 77% QA: 42% This tube comes from the Reflektor factory in Russia. It is perhaps the most commonly used tube by many amp makers. It is reliable, and quiet. The main reason it is quiet, is it’s generally lower gain and output. http://www.groovetubes.com/product.cfm?Product_ID=1166 This tube is the “old standby”. It is the most commonly used preamp tube. It is lower in gain and current output than most of the others in this family. This is a long lasting tube, and amp makers like it (and have influenced it’s production specs) to have lower gain and output, so their amps will pass their own QA easier, and the amps will be quiet. It is a good all around tube, but there are others that are sonic improvements with more detail and harmonic content. The newest (2004) Sovtek 12AX7WC looks the same to the eye but is a VERY different tube than the WA. The WC has all the “proper numbers”. It’s gain, current, and transconductance are right on original NOS 12AX7 spec. A job well done by Sovtek on this tube.

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12AX7-R2 – Sovtek 12AX7LPS Gain: 83 Output: 83% QA: 42% This tube is made in the Reflektor factory and sold under the Sovtek name. It is also known as the Groove Tubes 12AX7R2. It is a long plate structure, that is brighter than a 12AX7WA, 12AX7R3 (EH), or ECC83. It is not as bright as a 7025. It’s long plate structure can be more prone to microphonics is some combo amplifiers. http://www.groovetubes.com/product.cfm?Product_ID=1167 A newer tube with a long plate structure, these can tend to be microphonic in combo amps more often than the shorter plate tubes. These are brighter in most amps than the 12AX7WA or 12AX7C. These need to be selected by a good vendor that really tests these tubes, as the factory out of spec range is very high in my own testing, they are somewhat more inconsistent than many other tubes, and can become microphonic in short order. Their curves are not as smooth or linear than the 12AX7C.

12AX7-R3 – Electro Harmonix 12AX7EH Gain: 87 Output: 83% QA: 17% This tube is made in the Reflektor factory on newer tooling and also sold as the Electro Harmonix 12AX7EH. It is a shorter plate structure, a linear tube. It is not quite as warm or linear as the 12AX7C, but is just about as versatile. It is a quiet tube, and works nicely in many amplifiers. It is a touch brighter than the 12AX7C, but not as bright as a 12AX7R2 (LPS) or 7025. One of the photos shows a factory tube on a Kaye Audio Labs tester, before it goes through any GT processing. This is one aspect of the factory testing I perform at Guitar Amplifier Blueprinting. From noise data here, these tubes move on to other test equipment such as curve tracers. I go though thousands of samples each month from all the tube factories collecting the raw data to see how close or consistent to specs they come. http://www.groovetubes.com/product.cfm?Product_ID=1586

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The 12AX7R3 is the second most consistent tube made today in this family, just about a tie with the 12AX7C (9th generation). This tube is great in Rivera, Bogner, and Diezel amps of my clients.

This is typically how factory bulk tubes come to the tube vendors from the factory. This happens to be 200 Sovtek 12AX7LPS tubes (2 layers of 100 each). On average, the reject rate on most new tubes can run 50% and higher if the tube seller has tight specs. Many vendors just ship whatever they buy, and hope for the best from the end user as far as them not complaining. After looking at a LOT of tubes, my advice is; trust your vendor.

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ECC83-S - from the JJ factory Gain: 85 Output: 112% QA: 58% This is the sound of Marshall and the British era amps. A stronger mid range response, with a bit of roll off on the high end compared to many other tubes (but not the 12AX7WA). The BLUE line shows the typical response curve of the ECC83 in an average tested sample compared to the reference 12AX7WA (as the WA is a common tube in so many amps today). This tube may be brighter or darker depending on amplifier. This is due to the higher output of this tube and it’s ability to “push” signal with it’s high current through complex front end circuits where other tubes show their limitations. ECC83’s need to be purchased from a trusted tube vendor that tests tubes pretty extensively, as they can be very inconsistent. A good one is a find for sure. These are the masters of current drive in MOST, but not all factory batches. In modern amps such as a Bogner, Diezel, Rivera, or Mesa Recto series, these are the tubes that will push signal through those complex front ends. http://www.groovetubes.com/product.cfm?Product_ID=1587 Also limited SAG in High Gain Kits: http://www.groovetubes.com/product.cfm?Product_ID=1737

The curves of an ECC83 in blue, compared to a Sovtek 12AX7WA in green. Notice the increased response across the range, with an even stronger mid range response.

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7025-Y from the Ei factory Gain: 90 Output: 46% QA: 25% - 60% Long smooth plates, the most bright of the current tubes. The graph on this tube is at the start of this paper. These are the characteristic sound of the Fender Tolex years. These are very articulate. In V1 and V2 of a Fender Tolex era amp, these give the original sound signature. These tend to be too bright in Marshall Plexi era amps for some tastes when used with a Strat or Tele, but if you tend to load these amps down with pedals in the front end, they can help resolve the loss of treble from the pedals. Long plates can tend to be microphonic in combo amps. The Ei factory was the OEM for many “premium” tubes folks in the past, such as Siemens and Telefunken at times, so if the plate structure looks familiar, this may be a clue. http://www.groovetubes.com/product.cfm?Product_ID=1588 These are VERY inconsistent from the Ei factory. Over at GT, their reject rate can exceed 60% and I saw one batch go through test where Groove Tubes tossed 90% of them. These are the tubes that many other vendors just pass on along that do not test, so beware. When you find a great one of these though, they are magic. They are very close to the original long smooth plate Telefunkens, so close in fact, that some folks screen these with Telefunken logos and counterfeit them. Look for a diamond molded into the base of real Telefunkens to be sure when buying NOS.

These are some NOS 5751 tubes. The famed GE 5 star is on the left, another NOS in the middle, and the RCA Command Series black box plate is on the right.

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5751 New Manufacture Expected Gain 70 Expected Output 1.2 milliamps Used in V1 by some folks like SRV to change the ratio of preamp distortion to power tube distortion. Current manufacture from Russia is so far outside of NOS sample specs on curve traces that this tube is not at all like NOS 5751 versions. Perhaps down the road things will change, but in 2002-2003 this is the case. If you use these new 5751’s and like them, that is great, but they are not a vintage 5751. When there is a good new 5751 available, it will be noted here in an update. 12AT7-Y Ei / 12AT7-C / 12AT7-A USA NOS JAN spec Expected gain 60-70 Expected Output 10.0 milliamps These are commonly used as phase inverters and reverb drivers. In the first gain stage of an amplifier, they will drop the gain a bit, make some amps a bit quieter in background noise, and yield more clean headroom. This is also one way to change the percentage of output distortion to preamp distortion in non master volume amps when used in the first gain stage. One of the differences between the later Fender amps and the Marshall JTM-45 / Fender tweed era amps, was the use of the 12AT7 in the Fender tolex era amps in the phase inverter position, rather than the original 12AX7. The 6201M is a selected low noise tube for use in some microphones. It is an NOS JAN selected tube. As of May 2003, GT will generally be offering the 12AT7A NOS as it’s 12AT7 if marked as 12AT7 without the Y or C designator. 12AT7-A http://www.groovetubes.com/product.cfm?Product_ID=1589 12AT7-Y http://www.groovetubes.com/product.cfm?Product_ID=1590 (currently not in stock – replaced by 12AT7A) 12AT7-C http://www.groovetubes.com/product.cfm?Product_ID=1591 (currently not in stock – replaced by 12AT7A) 6201M – This is a low noise selected tube generally used in studio gear or microphones. http://www.groovetubes.com/product.cfm?Product_ID=1212 12AY7 – various makers / 6072M NOS JAN Spec selected low noise Expected Gain 44 Expected Output 3.0 milliamps This tube was the first gain stage of many Fender tweed era amps for many years. It has about ½ the gain of a 12AX7, but much greater current output. In modern Marshall type amps such as a DSL or TSL series, this tube in V2 will bring the touch, feel, and sonic qualities, closer to Plexi era Marshall amps if this is an objective. This tube is also known as a 6072 or 6072M, a selected low noise version used in studio equipment and some microphones. These are the common V1 in Fender Tweed era amps in many models. 12AY7 http://www.groovetubes.com/product.cfm?Product_ID=1779 6072M http://www.groovetubes.com/product.cfm?Product_ID=1215

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12AU7-Y – Ei Expected Gain 16-18 Expected Output 10-11 milliamps These are commonly used as phase inverters in McIntosh Hi-Fi amps, some Ampeg amps, and will yield the most clean headroom in many amps. In the latest Fender Pro Series amps such as the Pro Reverb, Concert, and Twin, this tube in V2 (or a 12AY7), will drop the gain of the gain channel where some feel the tone is of a less intense or “buzzy” character. This will then allow a much wider range in the sweep of the volume and gain controls of this channel. http://www.groovetubes.com/product.cfm?Product_ID=1592

To the left is a GT EF86 adapter. This was developed as new production EF86 tubes are very inconsistent, and can be noisy, or hard to find at times. For a group on tour using an older Vox amp, a Matchless, Victoria Sovereign, Bad Cat, or Dr. Z amp, these can be a life saver. These allow a 12AX7 to be used in the place of the EF86 / 6267 pentode tube. This adapter can be seen at http://www.groovetubes.com/product.cfm?Product_ID=2044

EF86 – 6267 Expected Gain 400-2000 and higher Expected Output 3.0 milliamps QA: 50% + A 9 pin pentode, used in the first gain stage of some newer amps such as the Matchless, Bad Cat, Dr. Z, and others. The current versions of this tube from the Russian factory, are very inconsistent. Their output is way above spec, sometimes as high as 50% over what is to be expected. They have transconductance that is not close to the original tubes 80% of the time in factory sample tests. These factors make finding a low noise version of this tube very difficult. These need to be closely screened and tested by a tube supplier that has very sophisticated test gear that is generally out of reach for most Internet tube vendors or smaller vendors. http://www.groovetubes.com/product.cfm?Product_ID=1593

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The famed 7199 gold pin of the past.

The GT 12AX7M “Mullard” reissue was shown at the NAMM 2004 show and has been hard to keep in stock since. The M is not as bright as the ECC83S and many folks have chosen this tube as a replacement in Fender Blackface/Silverface amps in V1 and V2 and in Marshall amps. Dr. Z is using some of these as phase inverters for their strong current drive. More info at http://www.groovetubes.com/product.cfm?Product_ID=2100

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Preamp Tube overall chart of some NOS and many current tubes Tube

Tolerance

Ave output % of mA expected

Ave TC (gm)

TC %

Average gp

Average Gain

Guitar Amplifier Blueprinting

1600 Reference small signal tubes - in some cases, single tube tests. Items marked * were three to five tube test averages

GE 6072A 1970s Date Code * GE 6072A Black Plate 1963 * GE 12AX7WA (1980s) * GE 5751 (1950s) JAN/Philips 12AT7WC 1980s * RCA 12AX7 NOS 1950s-60s RCA 5751 Black Plate (1950s) * RCA 7025/12AX7 NOS 1960s * Telefunken ECC83/12AX7 - diamond base * RCA 12AU7 NOS Cleartop * 12AX7 Telefunken smooth plate new Dynaco 12AX7/ECC83 Telefunken Diamond Bottom Ribbed Plates * 12AX7 MINIWATT / SUPER RADIOTRON AUSTRALIA 1960s 12AX7 Amperex Bugle Boy Holland LONG PLATE 1950s * (10) 12AX7 AMPEREX BUGLE BOY HOLLAND 1967 * 7025 Amperex Holland orange Globe Logo 1971 CV4004 Brimar 1961 CV4035 / 12AX7 Brimar NOS flying leads 7025 GE ribbed plates 1950s * 7025 GE ribbed plates 1960s M8137/CV4004/12AX7 Mullard Box Plates * 12AX7 Raytheon black ribbed plates square getter halo 1950s * JRC-12AX7 RCA Black Plates 1954 * 12AX7A RCA gray ribbed plates 1960's-1970's * ECC83/12AX7 Siemens long plates early 1960s * 12AX7 Sylvania Gray Plate square getter halo 1958, 1959 *

2.6% 1.9% 8.7% 2.5% 11.6% 8.8% 3.7% 6.6% 11.6% 2.1% 12.6% 2.7% 0.8% 4.4% 6.1% 7.7% 4.5% 9.8% 2.2% 3.7% 11.2% 5.4% 4.9% 12.6% 9.9% 8.2%

96% 100% 92% 98% 105% 99% 96% 97% 102% 96% 102% 94% 100% 112% 109% 94% 92% 108% 100% 100% 92% 94% 101% 93% 95% 102%

1710 1750 1520 1190 5780 1620 1251 1580 1680 2180 1610 1680 1606 1640 1580 1690 1570 1740 1610 1590 1640 1520 1590 1660 1620 1710

1750 1750 1600 1200 5500 1600 1200 1600 1600 2200 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600

42/44 44/44 98/100 69/70 72/70 100/100 69/70 97/100 102/100 18/18 98/100 105/100 100/100 105/100 101/100 92/100 91/100 112/100 99/100 102/100 92/100 100/100 100/100 96/100 104/100 101/100

12AX7R3 Electro Harmonix (10/7/02)

25.0%

95%

1507

94.19%

#DIV/0! 32

12AX7R3 Electro Harmonix (10/29/02) 12AX7R3 Electro Harmonix (12/12/02)

16.7% 16.7%

85% 83%

1382 1403

86.38% 87.69%

0.0162 0.0161

85.31 87.14

12AX7C - Chinese (10/28/02) 12AX7C - Chinese (12/13/02)

25.0% 16.7%

83% 92%

1461 1588

91.31% 99.25%

0.0160 0.0170

91.31 93.41

ECC83 JJ (10/07/02) ECC83 JJ (11/07/02) ECC83 JJ (12/13/02)

33.0% 66.7% 58.3%

93% 113% 112%

1467 1664 1604

91.69% 104.00% 100.25%

0.0195 0.0189

#DIV/0! 85.33 84.87

12AX7R - Sovtek 12AX7WA 10/7/02 12AX7R - Sovtek 12AX7WA - (10/28/02 batch) (note a) 12AX7R - Sovtek 12AX7WA - (12/13/02 batch) 12AX7R – Sovtek 12AX7WA (5/16/03) - This batch was stronger than the prior groups, but was more inconsistent. There was generally a very large spread between the A and B sides of most of these dual triodes so these are NOT recommended for phase inverter use.

41.7% 41.7% 41.7%

78% 88% 78%

1190 1293 1180

74.38% 80.81% 73.75%

0.0147 0.0137

#DIV/0! 87.96 86.13

Average output – 1.1 mA (closer to spec of 1.2 and better than the past) 91% of expected output. Good by today’s new tube production from all vendors, and better than their past production of this tube. Output ranged from 67% of what was expected as spec to 125% of what is expected. Very inconsistent current output. Average gain – 82.99 (spec 100) Good by today’s production standards in new made tubes. Average TC – 1278 (1600 spec) – slow rise times, not all that great for high articulation players such as metal folks or folks that play harmonics. Lack of harmonic content and detail. Tolerance range – 58% Still not good at all. There is a lack of consistency from one tube to the next, near the bottom of the batch of vendors for the most part. More noisy than past production – due to more proper output and gain.

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50.0%

83%

1469

91.81%

67.0% 75.0% 42.0%

70% 83% 97%

1418 1505 1557

88.63% 94.06% 97.31%

0.0182 0.0186

#DIV/0! 82.69 83.71

7025 – Ei (10/31 batch) 7025 – Ei (12/12 batch) 7025 – Ei (4/03 batch) Output = 1.1 / TC = 1490 / Gain = 93.1 / QV = 33% - Nice gain this run, current way up too, great batch.

33.3% 25.0%

87.50% 46.67%

1419 1064

88.69% 66.50%

0.0155 0.0118

91.55 90.17

Svetlana 12AX7 4/8/03

42.0%

72.50%

1369

85.56%

12AX7R2 Sovtek LPS (10/7 batch) 12AX7R2 Sovtek LPS (10/23 batch) 12AX7R2 Sovtek LPS (10/31 batch) 12AX7R2 Sovtek LPS (12/12 batch)

JJ 12AT7 / ECC81 4/7/03 - output = 8.9/ 10.0

gain = 58.8 / 60.5

#DIV/0!

90.66

TC = 4711 / 5500

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Additional Small Signal Tube Tests and Reference Tube

Tolerance

Ave output % of mA expected

Ave TC (gm)

TC %

Average gp

Average Gain

Guitar Amplifier Blueprinting

1600 Reference small signal tubes - in some cases, single tube tests. Items marked * were three to five tube test averages

GE 6072A 1970s Date Code * GE 6072A Black Plate 1963 * GE 12AX7WA (1980s) * GE 5751 (1950s) JAN/Philips 12AT7WC 1980s * RCA 12AX7 NOS 1950s-60s RCA 5751 Black Plate (1950s) * RCA 7025/12AX7 NOS 1960s * Telefunken ECC83/12AX7 - diamond base * RCA 12AU7 NOS Cleartop * 12AX7 Telefunken smooth plate new Dynaco 12AX7/ECC83 Telefunken Diamond Bottom Ribbed Plates * 12AX7 MINIWATT / SUPER RADIOTRON AUSTRALIA 1960s 12AX7 Amperex Bugle Boy Holland LONG PLATE 1950s * (10) 12AX7 AMPEREX BUGLE BOY HOLLAND 1967 * 7025 Amperex Holland orange Globe Logo 1971 CV4004 Brimar 1961 CV4035 / 12AX7 Brimar NOS flying leads 7025 GE ribbed plates 1950s * 7025 GE ribbed plates 1960s M8137/CV4004/12AX7 Mullard Box Plates * 12AX7 Raytheon black ribbed plates square getter halo 1950s * JRC-12AX7 RCA Black Plates 1954 * 12AX7A RCA gray ribbed plates 1960's-1970's * ECC83/12AX7 Siemens long plates early 1960s * 12AX7 Sylvania Gray Plate square getter halo 1958, 1959 * Tesla ECC802S Tesla ECC82

2.6% 1.9% 8.7% 2.5% 11.6% 8.8% 3.7% 6.6% 11.6% 2.1% 12.6% 2.7% 0.8% 4.4% 6.1% 7.7% 4.5% 9.8% 2.2% 3.7% 11.2% 5.4% 4.9% 12.6% 9.9% 8.2%

96% 100% 92% 98% 105% 99% 96% 97% 102% 96% 102% 94% 100% 112% 109% 94% 92% 108% 100% 100% 92% 94% 101% 93% 95% 102% 10.9 of 10.6 11.1 of 10.6

1710 1750 1520 1190 5780 1620 1251 1580 1680 2180 1610 1680 1606 1640 1580 1690 1570 1740 1610 1590 1640 1520 1590 1660 1620 1710 2153 2601

1750 1750 1600 1200 5500 1600 1200 1600 1600 2200 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 2200 2200

42/44 44/44 98/100 69/70 72/70 100/100 69/70 97/100 102/100 18/18 98/100 105/100 100/100 105/100 101/100 92/100 91/100 112/100 99/100 102/100 92/100 100/100 100/100 96/100 104/100 101/100 16 / 17 18.8 / 17

35

12AX7WA General Electric JAN NOS Green Printing 12/85 batch. 50 samples tested 5/21/03: All very quiet. Some popping on turn on, but after the tube warms up this stops. More gain than current production 12AX7 tubes. A touch more output than industry spec, far above current production 12AX7s from any current factory. A very nice tube, in a high percentage of samples, very close matches on two sides. Test Specs: Average Output/TC High mA % Low mA % Average gp Average gain Tolerance Range

1.2 1.4 1.1 0.0154 93.12 25.0%

1434

102.50% 116.67% 91.67%