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This page is informational.  It's got a lot of "stuff".  If you know what you want you probably don't need this page.  Then again, you may just think you know what you want.  If you don't know this will give you food for thought and perhaps load you with questions as you check out the more commercial amps on the market.


With a Club Amplifier you have 4 basic power options.  These options are based on the power and output transformers used, but influenced by the choice of bias and output tubes.  The basic options are:

  • 20W-Great for the studio or small-to-medium clubs the 20W series can be run at full volume for great tone without destroying the ears.  But, keep in mind that 20W driving a 15 inch, 2 x 10  or 2 x 12 speaker(s) optimized for use with a 20W amp can be really loud! 

    The output power from a 20W chassis will be about 20W.  With fixed bias and a tube rectifier the output is at 18-20W as compression begins (actual power depends on the tube choice).  With a solid state rectifier the power is a little over 22W.  With cathode bias (not our standard, but an option) the output of the 20W series may be as low as 15W.  Check the bias section for explanation.  The 20W series can use either EL84 or 6V6 output tubes.  Both provide classic sounds.  Each is different.  Very different.  Unfortunately, they use different sockets.  You can't have both in one amp.  You have to choose one or the other.
  • 30W-This is the strength of the Club Amplifier line; really great for working the club scene or the studio.  It's also the most complicated when it comes to a decision.  The 30W series can be built with 4 x EL84 output tubes, 2 x 6L6 or 2 x 5881 output tubes (interchangeable with a bias adjustment), or 2 x EL34 tubes.   Each of these tube options "sounds" different.  More on that in the section on tubes.  And, each is available with fixed or cathode bias and tube or solid state rectification.  Each of these variables effects the sound of your amp.  They will be explained in their respective sections.  The final comment for this section is that the 30W series will have power output from 30W to 35W depending on the choice of tube, rectifier, and bias.  The 30W designation reflects on the output/power transformers used to build the amp.
  • 50W-Again the 50W series reflects on the output and power transformers used.  The actual power output varies from 50W at compression (6L6 with tube rectifier) to 60W at compression (EL34 with solid state rectifier).  The 50W series is only offered with fixed bias, but tube or solid state rectifier options are available.  We stock the standard and blues transformers.  "Precision" is by special order.  Tubes can be 2 x 6L6, 2x5881 or 2 x EL34.  We will build with KT-66 output tubes by special request.  It's been suggested that we check out the Tung Sol 7581 (which is very similar to a 6L6GC), but we don't have any first-hand experience yet.


We believe the transformers, in combination with the choice of output tubes, (and of course speakers) are key to the sonic signature of your Club Amplifier.  We spent years selecting our transformer supplier, a true magnetics master.  Our power and output transformers are made in the USA.  We must give credit where due.  The sonic options reflect on his skill as a magnetics "artist".  You benefit from a truly artful product built with pride to very conservative standards.

  • Standard-The best choice for most musicians the standard series output transformers offer truly great sonic performance that rivals the best of the best that has ever been built; strong tight bass, breathing mids and sparkling (but smooth) highs.  We call it our "standard" but there is nothing standard about it.  It sets THE STANDARD for great guitar sonics.
  • Blues-You know the sound.  The blues is a special sound.  Our transformer manufacturer has a way of gently shifting the sonic signature of our blues series from the center ground of the standard transformer to that earthy, smokey, bluesy spot that you are looking for.  This is a great jazz and classic rock sound, as well. 
  • Precision-Hard to describe, but simply "precise".  This transformer is very muscular yet articulate.  It's detailed with very little coloration; clear and revealing.  It excels at capturing dynamic riffs.  When we bring up a next generation website we'll try to include some sound bytes that help you understand, but the differences are very subtle.  The detail lends itself to acoustic amplification.
  • Fender or Marshall-We can supply a hand-wired amp that sounds much like (we think better than) the best Fender or Marshall you've ever heard.  We find that most who want to sound like a Marshall buy a Marshall.  But, we aim to please.  If you want custom craftsmanship we will be happy to build for you.  You'll have to give us time, though.  We don't stock the transformers.

A final comment on output transformers, our transformers are very conservative and what I would call high-end.  They are muscular and articulate; no flabby, tinny or mushy sounds.  I talk about "retro" sounds in many sections of this site.  Many of the classic amps of the 40s and 50s (pre-'59 Bassman) were layer wound on light cores and, well, were anything but high-end.  We can offer a broad range of sounds with our product, but our output transformers will not sound like these "stretched to the limit" 40s or 50s style transformers.  Just so you know. 


A bit of Don's trivia before I talk about output tubes.  Every wonder why almost all contemporary tubes come from Eastern Europe or China?  It's partly because semiconductors (transistors) started replacing tubes in the 60s and 70s.  All of the US and Western European tube makers closed up shop as the demand for tubes went away.  Do you know why the Soviets and Chinese kept making tubes?  It's because normal semiconductors will fail if exposed to high levels of radiation such as a nuclear bomb or the radiation experienced in space.  Things like communications systems and missile or aircraft guidance systems and satellites with normal semiconductors fail very quickly when exposed to radiation.  The US and Western European semiconductor manufacturers had to develop very special semiconductors and systems to tolerate radiation.  Tubes, on the other hand, are not significantly effected by radiation.  Even though the equivalent tube circuits are much larger and heavier than their semiconductor equivalents, the Soviets and Chinese chose to stick with tubes for their critical military communications circuits.  That's why you find the tubes still being manufactured in Russia, Czechoslovakia, Yugoslavia and China.  Many of the current tubes are built with tooling or designs from the classic manufacturers of the US and Western Europe.  Are they the same as the Western classics?  No!  But, they are manufactured by companies who know what they are doing.  I think there are some very good current production tubes.

The choice of output tubes has impact in two ways.  The way we "bias" the amp has to be right for the type of output tube chosen.  We'll talk more about that in the next section.  The type of output tube chosen can have a big impact on the sonic signature of the amp.  An amp built with 6L6s will sound different than an amp built with EL34s, though they both support virtually identical circuits and substantially similar output power.  A similar comment can be made about EL84s vs 6V6s.  Having chosen one tube type or the other, then the choice of tube manufacturer and bias starts to become a key part of the fine tuning of your sound.  Each tube manufacturer makes tubes of an industry type, but each sounds a little (or sometimes a lot) different.  This gives the user, working with a qualified amp technician, the ability to field tune the amp over time within the limitations of the choices made when the amp is purchased.  On the "Why a Club?" page we said that the amp's sonic signature was one of the five fundamental influences in what your audience hears.  The amp's sonic signature is a marriage of transformers, tubes, bias, gain distribution and the tone control settings you choose.  You have some influence or options over time to make subtle sonic signature changes to the tubes specifically used, but you have to make a choice about what type of output tubes can be used.

  • EL84-This tube has been a workhorse of both the guitar amp and hifi industry worldwide (called an EL84 in Europe and a 6BQ5 in the US).  It is an option for the 20W (2 x EL84) or 30W (4x EL84) Club products.  Of all of the tube options it is the most versatile, but also the most confusing.  It was used by Gibson in some of their classic amplifiers (you've heard them in many early classic rock and roll recordings).  It was the sound of the early Beatles and other "British Invasion" groups having been used in the Vox AC15 and AC30.  The Marshall model 1958 uses the EL84 as do contemporary Fender and Peavey amps.  One of my personal favorites (albeit a little bright for some music), the Traynor Studio Mate (with 4 x 8 inch speakers) used EL84s.  Sometimes EL84s are biased with fixed bias.  Historically, I'd say more often they are biased with cathode bias.  The legendary Vox AC30 uses 4 x EL84 with a low supply voltage and very hot cathode bias (often claimed to be class A) and no feedback to create a really "lively" and harmonically rich 30W product.  Fender, Crate, Peavey all use EL84s for classic rock and blues products (usually fixed biased these days).  Depending on the tubes chosen you can get quite a wide range of sonic signatures that varies from manufacturer-to-manufacturer and even within a given manufacturers product line.  Many suppliers or sellers of EL84s offer them graded for "clean", "standard", and "early distortion" properties.  This is a function of the transconductance (amount of amplification) and bias properties of the tube.  Many of the EL84s in the contemporary marketplace, but not all, come from the Reflektor manufacturing plant in Russia.  The EL84 was the mainstay audio power tube of the Soviet military (as a 6P14 and derivatives).  The Reflektor plant makes EL84s under contract to, and "branded for" many tube companies.  They are not all made with the same tooling.  They are different, just made in the same factory.  By the way, this practice of "branding" was common to many Western tube companies in the 50s, 60s and 70s.  There are also EL84s made in Czechoslovakia and Yugoslavia.  (I'm not certain, but I believe I've seen some Chinese EL84s recently, as well).  Each is designed to emulate American 6BQ5s or 7189s, Western European EL84s and/or Soviet 6P14s, all of which now fit under the general heading of "EL84".  Each has it's own sonic signature.  And, there are still NOS (new old stock) tubes from the 60s, 70s and 80s available (at very high prices).  So, if you choose an amp with EL84s you and your amp tech have many options to work with when it comes to "your sound".

    We stock Sovtek, JJ, Groove Tubes and Soviet NOS 6P14 tubes at the moment.  I'd say the JJs are my favorite for clean and crunch and the NOS 6P14s my favorite for hard drive. 
  • 6V6-The 6V6 was to America what the EL84 was to Europe; the workhorse tube of the military circuits and a "standard" in many classic amps.  And, they were common to many car radios.  The smaller Fender's like the Champ, Princeton and Deluxe all used 6V6s.  So did many of the Gibsons, Supros, Silvertones and others.  It has a "biting" sort of sound similar to the larger 6L6 and 5881 (all beam power tubes).  By the 70s the US military was making a transition to solid state audio.  The hifi industry was way ahead of the military.  Vacuum tube production in the US dried up and the 6V6 became hard to find.  Because the EL84 or 6P14 was the "standard" of low power audio output in Europe, and widely used in the US as well, there was little incentive for the European and Soviet tube makers to tool for the 6V6.  That is, until recently.  Because of the demand for 6V6 for guitar amps the Eastern Europeans and Chinese are now making a tube which is form, fit and functionally a 6V6.  Some argue that the new 6V6s aren't as good as the US made 6V6s, but those same folks often say any new tube is not as good as the old tubes.  Until recently we used only EL84s for our 20W amps, but I am pleased we can work with you if you want the beam power tube sound of a 6V6.  It's really great with our blues transformer for blues, rock and jazz.

    Our stock tubes are JJs.  To me they sound as good or better than many of the 6V6s of times past.
  • 6L6-The 6L6 is the classic American rock-and-roll tube.  If the 6L6 wasn't used then a 5881 was.  For the most part they are interchangeable.  There are some subtle issues here as the 6L6 has been around for a long time and some members of the family cannot handle higher supply voltages (there are 25W and 30W versions of 6L6).  The 5881 is a 25W tube.  All contemporary 6L6 and 5881 tubes can be used in your Club 30W or 50W amp.  The bias is different for a 25W vs 30W tube.  Like all tubes the choice of manufacturer and the bias will have an impact on the detail of the sonic signature.  If you choose the 6L6/5881 option then you will be using the classic American rock choice and the contemporary choice of Fender, Peavey, Crate, Soldano, Mesa, and a long, long list of others.

    We stock JJ, Sovtek, Winged C, Ruby.  The Winged C and Ruby would probably be called our "standard" for the 50W amps, but we've used the Sovteks with great results.  For a jazz amp we might use JJs.
  • 5881-Most all of the comments that apply to the 6L6GC apply to the 5881, though it is a 25W tube.  This is a great choice if you play American rock, blues, jazz, country or anything in serious overdrive mode.

    At the moment we are only stocking Tung-Sol 5881 which we use in our 30W amps.  They sound great in the 50W amps as well, but we normally use 6L6GC for 50W.
  • EL34-The sound of European rock.  During the rise of Vox, Marshall and HiWatt to the rock forefront it was hard to get 6L6/5881s in Europe.  The EL34 (6CA7 in the US) was much more readily available and became the standard for medium and high powered amps in Europe.  Vox, Marshall, Orange, HiWatt and a host of others have used the EL34 to make legendary rock music for decades.  Not quite as "biting" as the American beam power tubes, the EL34 pentode has a more glassy, clear and spaceous sonic signature, with the bass response very different from supplier to supplier.  It's a great tube for overdrive applications, with an overdrive often described as "creamy".  The EL34 is suitable for Club 30W or 50W products.

    Our "stock" tubes are Electro-Harmonix, Winged C and Ruby.  We are evaluating Mullard re-issues.


If you are not technical this can be a tough decision; fixed bias or cathode bias?  If you want something close to the sound of a Vox AC30 the answer is simple; hot cathode bias.  For most of you fixed bias will be the best, most flexible choice.  For a select few who play retro jazz, retro rock or the blues you may find that to really hit your sweet spot you need classic cathode bias (or even grid leak which is not at all common these days, but does have a definite place...we can do it).  90% or more of what we build is fixed bias, but let's talk before you decide if you have any doubts.

  • Fixed bias-Fixed bias is actually adjustable (though some amps don't provide a way to adjust).  Confusing?  Sorry about that.  The "bias" determines how much current is flowing in the output tubes when no signal is present.  Since not all output tubes of the same type have the same bias characteristics fixed bias allows your amp tech to optimize the bias when output tubes are changed.  The amount of current has an effect on the sonic signature.  Too little current and the crossover distortion (a bad kind) is high.  The sound is often described as "thin" when the bias current is not too low, but not high either.  Too much bias current and your output tubes will have a short (perhaps very short) life.  And, if you burn out the output tubes you may cause some very expensive damage to your amp's output transformer. 

    If your Club Amp has fixed bias it will have an adjustment potentiometer and test terminals to measure the cathode current.  It's actually the plate current that your amp tech would like to know.  The cathode current is the sum of the plate and screen currents.  But, measuring the plate current is very, very dangerous.  If you make a mistake it can kill you.  Measuring the cathode current is safe and easy and if your amp is a Club Amp it can be done from the outside of the chassis.  It gives your amp tech a very good indication of the plate current and allows for confirmation that both (all) output tubes are biased with nearly the same current.  This may be more than you wanted or needed to know.  Hopefully you will leave any adjustments to a well qualified technician.
  • Cathode bias-This historic form of bias gives up some power.  It is not adjustable to accommodate differences in output tubes.  Some think it provides a better sonic signature for retro and blues playing styles.  If you want the type of sound of the classic Vox AC30 or early 1950s vintage amplifiers we'll use cathode bias.  We offer a "standard" 4xEL84 amplifier with some similarity to, and yet some difference from the AC30.  This 4xEL84 amp uses a hot cathode bias.  Cathode bias is an option that's available for the 20W and 30W chassis.


Most electronic circuits require DC voltage to operate.  That's a constant voltage like a battery.  Most modern circuits like computers or stereos use a pretty low DC voltage.  But most vacuum tubes, like the picture tube in a conventional TV or the vacuum tubes in your guitar amp, need a high voltage to operate.  Your power company has to distribute power over wires to your home or business.  They can't distribute DC voltages.  They have to use alternating voltages/currents referred to as "AC".  Some electric motors can use AC directly.  Electronics almost always need DC.  In the case of your guitar amp the AC from the wall has to be converted to DC for the circuit to work.  The tubes in your Club Amp need high voltage (300-500V) and they need DC.  In the US the AC is usually about 120V.  In Europe it's usually about 240V.  Both fall short of the 300-500V needed by the tubes.  So, your amplifier has a power transformer that converts the AC from your power company to a higher voltage.  The current gets smaller, but the voltage gets larger as the AC is processed by the power transformer.  But, it's still AC.  The circuit needs DC.  A circuit called a rectifier only lets current flow through in one direction.  As the AC goes from small to large the rectifier let's current go through, but as the AC reaches it's peak then gets small again the rectifier won't let the current go back.  It holds the current on the output (cathode) side of the rectifier and stores it as a peak voltage on a "filter capacitor".  The capacitor acts like a short term battery.  As your amplifier circuit uses current it pulls it from the capacitor "draining the battery".  But, the AC is recharging the battery 50 or 60 times every second.  If designed right the "power supply" will keep up with the demands of your amp for current and voltage.  Each amp design is different and the rectifier plays a role in how the power supply effects the overall sonic signature of the amplifier.   Confusing?  Sorry!  If this helps you understand then, good.

  • Tube rectifier-This historic method of rectification uses a specially designed vacuum tube which functions as a rectifier.  The rectifier tube used in your Club Amp will have two elements (diodes) creating what is called a "full wave rectifier" that allows current to pass only in one direction and to be stored on the filter capacitor as the AC signal from the power company gets converted to high voltage by the power transformer.  While the process is "effective", it's not totally efficient.  Part of the up-converted voltage is lost as it passes through the tube rectifier "diodes".  The larger the amount of current being used by the amplifier circuit the more voltage gets lost in the rectifier.  The "voltage drop" across the rectifier can be 15-40V depending on the current and the type of rectifier tube.  So, when you play with more power output the supply current increases (power is the product of voltage and current) causing the power supply voltage to drop.  This is referred to as "sag".  It actually influences what you hear.  Is it good or bad?  That's a matter of musical taste. 
  • Solid state rectifier-While a tube rectifier may "drop" 15-40V a solid state rectifier typically has a voltage drop of 0.7V-3.0V across each "diode" used, no matter how much current is flowing through it.  They don't sag.  Because the solid state diode rectifier doesn't contribute to "sag" the sonic signature is different than with a tube rectifier.  It's not better or worse, just different.  You will get more power from an amp with a solid state rectifier than with a tube rectifier for the same no-signal supply voltage. 


There are a number of influences in the design of a vacuum tube guitar amplifier.  Most suppliers make decisions for you about how the amp will sound.  At Club Amps you have a choice of power, transformer properties, tubes, bias and power supply.  If you don't want to make decisions we offer models that reflect on what has been most popular over time.

 
   
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