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Amplifier Myths, Fantasies, and Facts.

The guitarist cannot begin to make intelligent gear decisions without a basic understanding of tone, power, and volume. Many experienced guitarists still nurse and cherish “facts” that are incorrect and border on pure fantasy. Some of these guitarists have achieved great tone – but only after years of very expensive trial and error and without ever really understanding what they did to finally get the killer tone they were looking for. Knowing some facts about amplification can help guitarists take the fast track to their ideal rig and save thousands of dollars along the way. Each of the following paragraphs debunks a popular myth and tells the real story. Since most readers are probably more interested in playing than becoming technicians and engineers, I’ve intentionally simplified some of these subjects somewhat. You’ll find a lot less bias against solid-state amps here than in most articles. So much so that you might think I’m a fan of solid-state amps. That is not the case at all – I strongly prefer tube amps and suspect I always will (I just love glowing lights and shiny things). However, this article is about facts and it is a fact that solid-state amps have come a long way, especially in recent years and are an appropriate choice for some players and some situations.

White jmp head

Power Myths.

Several common myths about amplifier power are debunked below. The bottom line is that you should select an amplifier for its features and tone, and consider power level as the least important criteria in your selection.

1) My 100 watt amp is twice as loud as your 50 watt amp. This is a myth that just won’t go away in spite of volumes of empirically and mathematically proven, unambiguous, clear, undisputed, scientific knowledge to the contrary – knowledge that every tech worthy of a soldering iron learned very early in their training.

Here are the facts:

•  All other things being equal, a 100 watt amp will only be just perceptibly louder than a 50 watt amp. It takes about a ten-fold increase in power to double perceived volume. That’s right, you’d need a 500 watt amp to be “twice as loud” as your friends 50 watt amp. Even more thought-provoking is the fact that a 50 watt amp will only be perceived as a little bit louder than a 15 watt amp driving the same cabinet! There is more detailed information regarding this on the GM Arts page.

•  All other things are almost never equal. There are so many variables controlling sound pressure level (SPL) and perceived volume that it is quite common for a small amp to sound louder than a much more powerful amp.

•  Cab design, speaker size and efficiency, signal compression, and several other factors have far greater impact on perceived volume than does power level.

•  The initial purchase price of a 100 watt amp will be significantly higher than a 30 watt amp with similar features.

•  It will cost you significantly more to re-tube a 100 watt amp.

•  If you are driving a 30 or 50 watt amp hard enough to require frequent re-tubing, chances are very good that you will also drive the 100 watt amp hard enough to require frequent re-tubing (at significantly higher cost). Am I saying 100 watt stacks are evil? No. No one really needs one (see below) but if you want one, be my guest. All I’m saying is that you should be aware that you are spending a lot of money to purchase a minuscule increase in volume.

2) ‘I need a 100 watt amp ’cause my band has started gigging in clubs’. This is a myth that I believe originates with hormonally imbalanced teens (like me, back in the day) who have more experience watching movies about teen bands than they have playing real gigs. Unfortunately, it’s a self-perpetuating myth because the rhythm player is going to get a big amp ’cause he’s being drowned out by the lead player, then the bass has to get a 400 watt amp to be heard at all, then they need a 1200 watt PA system so that the vocals have some chance of being heard over the cacophony from the guitars and bass, and finally they end up having to mic the drummer even in a small club because the drummer is breaking sticks and skins and still can’t be heard over the racket. Within a few years their hearing has been permanently damaged and they all decide that they need bigger amps! Three-quarters deaf, they finally make the big time and the guitar magazines write about the three 100 watt stacks that the guitar hero uses on stage and all the wannabees have just gotta have the same rig.

Well, here are the facts.

•  There is absolutely no venue that requires a larger amp and cabinet than one suitable for use as a stage monitor – provided that the members of the band don’t get into a competition to outdo each other. Need more feedback? Fine, move closer to the amp. Typically, a really good 30 watt rig with a suitable cab is ample! Depending on the composition of your band and the variety of venues you play, an even smaller rig miked to the PA and then pumped to stage monitors may be even better. Note that while a good 30 watt rig has ample volume you may end up having to buy a more powerful rig to get other desired features. At a small venue, a 15 to 30 watt amp can be placed behind the band in a traditional position and used without a mic.  In this position the rig serves as a monitor for the guitarist and as the primary amplification for the guitar. At a medium venue, the small rig can be placed in front of and facing the guitarist as a monitor, and be miked and run through the band’s PA. The band’s PA speakers are placed along the front of the stage and facing out. This arrangement allows the sound to be balanced at the mixer and allows the band to flood a medium to large venue without damaging their hearing. At a large to giant venue, that same small rig can be arranged much as described above but now the band’s mixer feeds the house PA. This is the only way to reach the back of the room without dangerous SPLs near the stage at a large venue and would be required no matter how powerful a rig the guitarist has. •  Smaller equipment takes up less space on cramped stages.

•  The money you save by purchasing a smaller amp can fund a nice power conditioner to protect your equipment and clean up power line noise – the conditioner will cost less too since now you don’t need one that will handle a billion watts.

•  If the band members will agree not to compete, all of them can recognize significant savings by not having to purchase unnecessary equipment.

•  Your band is far more likely to be called back for a repeat engagement if you provide a well-balanced, easily managed performance than if you are just obnoxiously and uncontrollably loud. •  Many guitarists already have the monster amp – it isn’t necessary to get rid of it. You can use an attenuator (see the attenuator myth) and perhaps a smaller cab.

3) I need a small combo because I live in an apartment. This is sort of the opposite of myth two, above, and is closely related to myth one, above. While a small combo will certainly take up less room, it may or may not be easier to get good cranked tone out of it at apartment levels. First, read myth one again. If it’s true that we have to increase power ten times to double perceived volume, then it is also true that we have to reduce power ten times to cut the perceived volume in half. Thus, even a tiny 5-watt single ended tube amp is going to sound about half as loud as a fifty-watt stack (actually, it will be a bit quieter than that because it is probably driving an eight or ten inch speaker instead of a 4 x 12 cab). Even that five-watt amp will be way to loud to run cranked in an apartment unless your neighbours are very tolerant. Here are some facts you should consider:

•  Even a 5 watt tube amp with an eight inch speaker is very loud by the time you crank it into distortion.

• You can use an attenuator with either a large amp or a small combo. Keep in mind, however, that attenuating below about 1 watt per speaker starts to adversely affect tone – it seems that a certain amount of speaker drive is required to round out distortion (see recent articles on 3-stage amplification architecture tests at amptone.com). Even one watt into an 8″ or 10″ guitar speaker is likely to get you evicted.

• Many small combos do not offer a master volume, thus making it impossible to even get preamp saturation at acceptable volume levels.

• To get true “cranked tube tone” in an apartment at lease-safe levels you are almost certainly going to have to use a combination of attenuation and a sound-proof speaker isolation box with a microphone running to a mixer or stereo. This is true whether you are running a 5-watt, single-ended, class A combo with an eight-inch speaker or a 100 watt stack with a 4 x 12 cab.

• It’s not a good idea to run an amp inside of a sound-proof box, so even with a small combo you will need an extension speaker.

• It’s not much fun to try to enclose a 4 x 12 cab, so you’ll also need an extension speaker with that kind of rig. The lesson here, once again, is to select amplifiers based on features, not on power level. A tiny five watt class-A amp with an eight-inch speaker and no features may not be very satisfying after a while, and will be wholly inadequate for gigging, and still isn’t quiet enough to run cranked in your apartment! Add a few features such as footswitchable channels, master volume, and an effects loop and that 5-watt amp starts to become pretty attractive! 4) My tube amp has a master volume control that lets me get power-amp distortion at low volume levels.

The facts are:

• With the possible exception of some very rare and expensive “boutique” amps, a so-called master volume does not reduce power output after the power-amplification stage as the name would seem to imply.

• The master volume controls found on popular amps cut the power between the final preamp stage and the power amp.

• In all popular tube amps, when you turn down the master volume, then turn up the gain controls to achieve overdrive, you are over-driving the preamp stages, not the power stage. It’s possible manufacturers deliberately misnamed the “master volume” control to deceive consumers – but that does not mean that the control is useless. Quite the contrary, I regard a “master volume” control as an essential part of a good amplifier. The “master volume” control permits running the preamp at full saturation or beyond at reasonable volume levels and allows one to balance preamp and power amp saturation for a wide variety of sounds. I love “master volume” controls and it plays an extremely important role in getting the sound I like out of an amp. 5) Power attenuators damage amplifiers. There is some truth in this and I have had to replace the output transformers in a couple of Marshalls that have been burnt out using attenuators. But attenuators can be safely and successfully used – and every guitarist should know how and when they can be safely used. Here are the facts:

• A properly designed power attenuator does not apply any more stress to the amplifier than does a speaker cab – in fact a good attenuator will usually apply slightly less stress than a cab alone. However, when using an attenuator, guitarists typically drive their amplifier much harder than they ever would when driving a cabinet directly. Driving the amp this hard will significantly reduce tube life regardless of whether the amp is driving an attenuator or a cab. As a consequence, it seems like the “attenuator wore out the tubes.” In reality, the guitarist was just enjoying much more overdrive than he/she ever would have without the attenuator and is paying the piper.

• Some amplifiers are simply not built to be driven hard. When the guitarist uses an attenuator and then runs the amp harder than he would have into a cabinet, very bad things happen and then the guitarist says, “that attenuator ruined my amp.” No, driving the amp at “10” ruined it – the attenuator is only incidental in that you never cranked the amp to 10 because it was just way too loud! This problem is particularly common with low-power combos. I had a little 15 watt class A Ampeg Jet J-12T. It’s a great sounding little amp that I never cranked higher than about “4.” One day I decided to see if it would do “metal.” Using a guitar with hot humbuckers I cranked the little Ampeg to “10” and played for about 2 minutes before the volume just became too painful (I was not using an attenuator, this was directly into the built-in 12″ speaker). When I turned the amp back down to reasonable levels I could hear a crackling sound. In two minutes or so I’d blown both of the screen resistors and ruined the tubes. I fixed the amp but never turned it up to 10 again! This amp was just not designed to be driven at these levels.

• Attenuators can be used safely if you follow these rules: Make sure that the attenuator contains some inductance. This will help maintain natural tone and causes the impedance to increase with frequency. The attenuator should either have approximately the same inductance as a speaker or should be of slightly higher resistance than a speaker. It is better to reflect a slightly higher than normal impedance through the output transformer than too low of an impedance.

Have a reputable tech “cool off” your amp. Explain to the tech that you are going to be driving the amp very hard into an attenuator and you want it biased a bit cold to save the tubes. This will cost a bit in tone (chances are you won’t notice this because you probably never drove the amp so hard anyway) but will make the tubes last a lot longer and reduce the chances of damage to other components such as the expensive output transformer. A knowledgeable tech can also tell you if the model of amp you are using is known for blowing transformers and what have you (many guitar amps have output transformers that are not rated anywhere near the amp’s max output).

6) Power attenuators kill tone. Actually, it seems that well-designed power attenuators with inductive elements have little effect on tone until you attenuate to below about one watt per speaker. I suspect that the real issue is not so much the power level as the excursion of the speaker coil. At very low power levels the coil has very slow linear movement for a given frequency and thus has very little momentum accumulated when it reverses direction. At higher power levels the linear movement rate is much higher and the speaker tends to overshoot much more, rounding out sharp corners in the input signal. That’s just a hypothesis on my part but, whatever the cause, the effect has been tested and measured by cybermonk at amptone.com.

Distortion Myths and Solid-State vs. Tube.

There are so many myths, many of them conflicting, that it is hard to know where to begin. Probably the most important thing to realize is that distortion can be broadly characterized as “hard” and “soft.” “Soft” distortion is the Holy Grail for most but it’s important to realize that both types of distortion are useful.

1) Preamp distortion is bad. Preamp (even tube preamp) distortion is much harder than tube power-amp distortion but the fact is that most rock-distortion uses both preamp and power amp distortion.

2) You can get great tube tone using tubes only in the preamp. The fact is that the “creamy” soft distortion most of us desire occurs only in a saturated power tube section. Tubes in the preamp do warm up the signal by introducing small impurities not typically present in a solid-state circuit, however.

3) Tube and solid-state preamps sound the same.

The facts are:

•  Tubes “warm up” the signal by introducing impurities not present in most solid-state circuits.

• Tubes, even preamp tubes, go into clipping more gently than most solid-state circuits resulting in a slightly smoother transition to distortion. Running preamp tubes just at full saturation gives a very full tone that simply isn’t found in solid-state preamp circuits.

• Amp and effects manufacturers have been fairly successful in modelling tube preamp sounds using digital (DSP) and analogue solid-state techniques.

4) Solid state amps suck. This is only half true.

The facts are:

• Many solid-state amps do suck, especially older models and entry-level models.

• Some newer solid state amps actually sound really good, especially for clean tones. None have truly “nailed” power tube distortion but modelling amps are getting very close.

• Many guitarists and most non-musicians can’t tell the difference between the best of the solid-state amps and a tube amp except in a side-by-side A/B test – and some can’t tell even then.

• A good tube circuit anywhere in the amplification chain can “warm up” a sterile clean signal.

• Solid-state amps are much lighter, more rugged, and generally more reliable than tube amps.

• Solid-state amps typically deliver a much more consistent sound over a wider range of output volumes.

• Many, many, guitarists who absolutely swear by tube amps and won’t even test drive a solid-state amp, never push their tube amps into power-stage distortion – and power stage distortion is about the only thing that a good solid-state amp can’t do well! Solid-state amps have come a long way but are still not quite “there,” in my opinion. Some of them do a pretty good job of modelling preamp distortion but they aren’t quite over the top modelling the power amp with its complex interaction between power tube, output transformer, and speaker. Even so, nine out of ten people in the audience at a typical live gig aren’t going to know or care whether you are using a good solid-state amp or a tube amp. If you do the weekend warrior thing and either play mostly clean or mostly with very heavy “metal” distortion then your best choice of gear might well be a multi-effects unit with a tube preamp driving a good solid-state amp!

 

5) The entire signal path must be tube: There mustn’t be any solid state circuitry in the signal path. A lot of players make inappropriate and expensive gear choices based solely on the presence or absence of an “all tube” decal on the front panel.

The facts are:

• We like what tubes do to tone because of colouring they add to the tone. This is true both of clean and overdriven signals.

• Clean (non-overdriven) solid-state circuitry of even mediocre quality reproduces a signal extremely faithfully. It will not “sterilize” a signal that has been “warmed up” in a tube stage.

• At least one tube stage should be present in the preamp chain to warm up clean tones. This can be a tube preamp in a tube or hybrid amp or it can be a tube pedal or tube preamp in a multi-effects unit such as the GSP-2101 or RP20.

• Until modelling is perfected, tube power amp sections provide the most “liquid” distortion. But remember, this is only important if you are looking for liquid distortion! If you’re playing mostly traditional country then you want an almost painfully clean signal anyway. Similarly, if you are playing in a hard-core or heavy metal band you probably want mostly “hard” distortion anyway.

• For clean tones there is little practical difference between a solid-state power amp and a tube power amp provided that the signal has been suitably “warmed up” in a tube preamp. I’ve seen people pass up a good deal on a great-sounding tube amp because it had a solid-state reverb driver or tremolo circuit and then stick a half-dozen cheap solid-state pedals in the effects loop of the less-capable amp that they purchased because it was “all tube.”

For more audio myths that cover things like cables, loudspeakers and ‘magic components’ please check out Rod Elliott’s very informative pages here. Also an interesting take on the mythology surrounding vintage amps, here.

 

Warming Your Tubes Up is a Bad Idea!

Do you believe that your standby switch on your tube amp is necessary?

Do you think that you need to warm your tubes up before playing?

Well, I have some bad news; it looks like you’ve been living a lie.  Don’t worry, up until fairly recently, I too was living this lie, but now I’m about to set you free.

Using the standby switch on your tube amp is more likely to damage tubes inside (especially rectifier tubes) than it is to extend their life!

There’s no real reason for having one on guitar tube amps, and the standby switch is there like a lot of things in the guitar world.  People would be upset if it vanished and aren’t very receptive to change.  The only reason that the very first guitar tube amps featured a standby switch is because they didn’t really know what they were doing, and nobody since has really bothered to remedy this.

A lot of guitarists falsely believe that warming your tube amps up with the standby switch is necessary to avoid putting wear and tear on your tubes.  This supposed wear and tear is cause by cathode stripping, which is when particles of the oxide coating are ripped from the cathode when the cathode is exposed to the extremely powerful electrostatic field from the anode.  There’s also the threat of cathode sputtering but…

You don’t actually need to worry about either of these when it comes to guitar amps because the only time it becomes an issue is when you are using extremely high power tubes (and I don’t mean KT88s!) that don’t really find themselves inside of amps.  According to London Power, guitar amps usually run at less than 500V – which is far below the threshold for tubes requiring anything resembling a warm up.

Warming up guitar tubes might even be bad for them because of something known as cathode poisoning.  Cathode poisoning is primarily caused by a fully heated valve without any anode current running to it.  Over time, a permanent undesirable layer is created between the oxide coating and cathode tube.  Valve Wizard claims that amps with tube rectifiers should not be used in conjunction with a standby switch because switching from standby into your amp’s operating position causes current to surge into your tube which eats tubes up very quickly.  This most notorious example of this are some Vox models.  Many familiar with tubes know this as hot switching…which is a practice most companies that manufacture tubes say is very bad for the longevity of a tube’s life.

If your amp does have a standby switch, fear not.  Simply stop using it and enjoy longer tube life!  Now spread the word by sharing this article on Facebook and enlightening your uncivilized friends that are chewing through tubes because of their standby switch.

It would appear that the standby switch is put in place mainly due to customer expectation than anything else!

A number of pro amp techs were asked about their views on the use of the standby switch. Here are some of the choice comments from some of the guys.

First to respond was Roland Lumby from The Amp Clinic in North West England, Roland is the go to man in the area for the maintaining and upkeep of your vintage and modern amps… He said “You put it in standby to stop it making a noise while the band takes a comfort break. There’s no technical requirement! Using standby means you don’t have to wait for the valves to warm up.” I must admit, this threw me a little as I was not expecting such a dismissive answer basically stating that the standby switch is just not ever needed. 

Next up to offer something was James Hamstead of Hamstead Ampworks. “Better to turn the master down or unplug the guitar. Standby doesn’t do the valves any good. The cathode emits electrons, but they have nowhere to go, so they go back down to the cathode. It’s called cathode poisoning, and it will change the characteristic of the valves for the worse – noisier, reduce gain etc.” – The theory of cathode poisoning was bought up a couple of times. I must admit, this kind of made sense to me in a “sounds logical but I have zero scientific logic or reasoning to support my thought process” type of way. So, after this I started to think that maybe the standby switch would start to harm my amp rather than protect it?

Then in swoops Mike Fortin. Designer of signature amps for Ola EnglundScott Ian and Kirk Hammett. So you know, he understands gain structures and valve amps! He just posted the following line: “Fender essentially misinterpreted the requirements, and everyone else copied Fender. Leo tended not to put anything into the circuit that he felt was unnecessary – but he came from a repair background where a standby switch is a service convenience.” This was supported by Jamie Simpson of Booya Amplifiers. So, obviously – the valves carry a lot of juice when they are in full flow so you’ll want to restrict the flow to a safe level when servicing them, so the standby switch appears to have been put in to protect the health and safety of the people working on the amps rather than any need in normal operation. The article even goes as far as stating that the best way to deal with your standby switch is “Bypass the standby switch internally so that it does nothing.”

The standby switch is “Unnecessary if your output tubes see 500 volts or less. If they see 800 volts like in a Musicman (on not half) it might prolong their non microphonic life” (Harald Nowark). “When you turn the first switch on you send 6.3 volts to the heaters… This warms the cathode which is treated or coated with material that promotes the expelling of electrons. By warming up the cathode before hitting the tube with high voltage it protects the coating on the cathode. When you take the amp off standby the big voltage hits the tube. Also, I think you should turn the entire amp off if you take more than a 10 minute break… No use baking your components for no reason when it only takes a minute to warm it back up….” (Phil Bradbury – Little Walter Tube Amps).
Questions were asked about unplugging speakers in standby mode “Still wouldn’t do it” (James Hamstead) and so on and so forth. This really jumped out at me “You see all those amps warming up before a concert? They’re not on standby… your amp won’t start to cook (class A amps excepted) without the HV on, the amp barely gets warm with just the filaments (when biased right, I must add). And… it’s not the tubes warming up that does the most for your tone… it’s the electrolytic caps… the ESR goes way down as the temperature goes up… so warm your big tube amp up good before you play. Standby is good for soft-start… cathode stripping is not really a problem with indirectly-heated cathodes (like all tubes we use now), so using standby and separating the HV from the filaments just lowers the inrush current, doesn’t really prolong cathode life. There have been wars fought over this, google cathode stripping for more. Cathode stripping happens to thoriated (directly heated filament) cathodes, found on large transmitting tubes.” (Stephen Cowell). “The standby switch is for convenience as a way of keeping your amp ready to go between sets or a quick way to mute when making changes to your rig. There have been millions of pieces of tube gear made (tv’s, radios, hifi, etc) that never had standby switches and worked just fine. If there is any validity to the “cathode stripping” theory, let me just say I have seen more tubes blown from the instant surge coming off standby than from improper warm up. And yes, an amp does sound better after it is fully warmed, but you don’t have to have a standby switch in order to warm it up. All this being said, most Shaw Amps will continue to be produced with standby switches for your convenience.” (Kevin Shaw – Shaw Audio)

In regard to Cathode Stripping, Roland made this excellent point: “During the 40s,50s and 60s, the best sound we heard was from a Juke Box. This machine stood all day, all week, for many years in the corner of the Cafe, waiting for the coin. How did it play right away? That’s right, it was in standby. The valves were heated by the main jukebox transformer .. The amp had a mains transformer which was switched off, it fed the rectifier valve which was directly-heated (usually a 5U4) When you put a coin in, the amp transformer was powered up, and HT would appear after 5 seconds or so, quick enough to beat the record onto the player. This meant that the valves were running the heaters continuously. Cathode poisoning was such a problem that they would have to put a new set of valves in the Juke Box every thirty-forty years!”

Trace Davis, head of Voodoo Amplification came in with this marvellous insight, not only into the industry but to tone. “When it comes to manufacturing amps, it’s a great deal easier & faster to include a Standby Switch than to deal with daily emails & phone calls from those asking ‘Why is there no Standby Switch? My local tech said that’s bad for the tubes?’ As one can imagine daily emails & phone calls like this consumes a great deal of time so consequently most companies continue to implement Standby Switches as it’s more cost effective” and “To varying degrees this also enters into the topic of tone. Does an amp sound & feel better once the tubes have come up to temperature & the bias has settled in? In my very humble opinion, yes, so once you do engage the Standby Switch into the ready-to-be-played mode it takes a minute or so (depending on the design, how long the power switch has been on, etc) for everything to settle in to where the tone is consistent.”

To support this, Roland came in with “Trace is right about the amp sounding better when hot, particularly when the output valves get older, they don’t achieve full emission until the cathode has been heated for around 2 to 5 minutes. This is actually testable, and is not speculation”.

So, you know, I could rip apart all the comments by all the fantastic amp builders and repairers who contributed but instead I will summarise with the following, written in language that we can all understand.

Your standby switch is a hangover from Fender being more interested in the early days of repair and servicing. In terms of normal playing, in a normal amp, your standby switch is pretty useless. It’s just there as we guitarists expect it. Your amp will probably sound better after a few minutes once everything has warmed up and settled down. Cathode Stripping, do you want to risk it? I don’t, so I won’t be leaving my amp on standby when I’m not playing it. I’ll just turn it off (as like most people, my amps sits in that fraction of a millimetre between “Can’t hear it?” and “Ermhagerd!” so turning the volume down isn’t really an option. I use me Boss tuner to mute everything between sets). Please do not turn your amp on at all without the speaker plugged in and please – if you love your amp – give your valves a few minutes (minimum) to cool down before moving your amp after use. And, of course, there are no user serviceable parts inside – leave it to the professionals!

And who said social media is full of cats, politics, beard combs and pictures of people’s lunch?