Gain, Distortion, and Other Mysteries!

I decided to devote a full page to this subject rather than include it in the FAQ page. We get emails and phone calls every day asking for power tubes that will get more gain in both single channel amps and multiple channel amps. So let's open this can "O" worms! I thought it best to quote some of the questions we get here everyday and give simple answers. So here are a few of the most common questions and their answers. #1. "I just have to have a lot more power tube distortion from my amp at much lower volume levels! What tubes do I need?"    Answer: In 99.9% of all guitar amps power tubes will not get you more distortion at lower volume levels. An amp designed to make 100 watts using a quad of 6L6's will make right at 100 watts with just about any 6L6. Even if you use some of the lower power 6L6's like the GT GE's and you drop the power down to about 90 watts you will not lower the decibel level by any more than a fraction of one decibel which is barely perceivable.  In most 100 watts amps you can pull either the inside two tubes or the outside two tubes to run in half power. #2. "Will running my 100 watt amp with two power tubes make it half as loud?"    Answer: No. It will only drop the sound pressure level by three decibels. If you have ever plugged into a 50 watt half stack and then compared it to a 100 watt half stack then you know what I mean. The 100 watter has a little more grunt but the 50 watter is not far behind. In turn, players running 50 watters and looking for more power are often disappointed that a 100 watter is not twice as loud. This is simply because every time you double your power you only get three decibels louder. So you players looking for a bedroom amp need to look for amps that are between one to five watts. #3. "Which power tubes in my amp are for the lead channel?"    Answer: All of them! This is one of the most misunderstood things about multiple channel amps. I can't tell you how many players ask this question and believe that their power tubes or some of them are used specifically for the lead, gain or drive channels in their amp. In 99.9% of all guitar amps the distortion and gain comes from the front end of the amp by over driving the preamp tubes. So in amps like Marshall's, Peavey's, Mesa's, Laney's, Engl's, Bogner's, Traynor's and Fender's when the amp is in the drive channel and you are playing at anything but very high volumes you are getting no power tube distortion what so ever. If you want to experience power tube distortion then turn the master volume up all the way, switch to the clean channel and then start cranking the channel volume up. On most amps when you get to about 5 or 6 you will be getting a little power tube, preamp tube and speaker distortion. This is commonly known as "the sweet spot" and in 50 to 100 watt amps this will be quite loud. So if your pant legs are not blowin in the wind, your not there yet! #4. "What is gain?"    Answer: Gain equates to, and is volume. In older amps there was volume or gain meaning exactly the same thing. When master volume amps entered the scene in the early 70's then the word "gain" gathered a new definition meaning distortion. In modern amps distortion is referred to as gain which is a product of over driving and / or cascading the signal from your guitar thru several preamp tubes to compound the gain. #5. "Can I get high gain power tubes?"    Answer: The short answer is no. This is a tough one to explain so I'll start from the beginning. When tubes are born (it's a beautiful thing!) they all draw different amounts of natural plate current which is why they need to be matched for amps using multiple power tubes. Cold tubes are paired up with cold tubes just as hot tubes are paired with hot tubes. Some tube resellers grade tubes very loosely into three color grades. This is VERY inaccurate to say the least. Other resellers offer up to 10 grades which is more accurate. At Eurotubes we have between 25 to 30 different grades of all types of power tubes. If your amp is a fixed non-adjustable bias amp like all Mesa's, some Peavey's, the new Traynor's and some Fender's then choosing the proper grade for the power tubes is VERY important because depending on where the bias is fixed, colder tubes will lower the bias where hotter tubes will raise the bias. This is why we spend a LOT of time here at Eurotubes testing and documenting what grades will get the bias in fixed bias amps as close as possible to where it should be to accommodate different playing styles. Now back to that "Can I get high gain power tubes?" question. (Told you this was a tough one) There is an acceptable window of bias in any amp and keeping the bias cooler at between 60% to 70% of max dissipation will get a good warm tone and your power tubes will breakup or distort a little later. Leaning on them harder and getting the bias up to 80% to 90% dissipation will cause you power tubes to brown out slightly and breakup or distort a little earlier. The difference between 70% and 90% is very noticeable but the difference in where you will get power tube distortion is not a night and day difference. If your amp will breakup at 6 on the clean channel with the tubes biased at 70% then on average it will start to breakup at about 5 with the tubes biased at 90% and tube life will decrease by about 20% to 25% (Ah, the cost of tone!). So in a fixed bias amp the grade of the tube is very important to get the desired results. In an adjustable bias amp the grade is MUCH less important because it's where you set the bias that counts. #6. "How can I get power tube distortion at low volumes?"    Answer: There are two answers to this one. #1 would be to use a much smaller amp that can be turned up all the way. #2 would be to use an attenuator. These are referred to as Hot Plates and Power Brakes and are available from lots of different manufacturers including THD, Marshall, Alessandro, Dr Z and of course Weber. The Weber attenuators are unique because they actually use a speaker motor and these are also one of the most economical. #7. "I bought an attenuator and now I don't have a clean channel, what happened to it?"    Answer: Believe it or not, this is a VERY common question. A player will buy an attenuator, wire it up to his multi channel amp, switch to his drive channel, dime out the amp, attenuate down to a very low volume level and experience massive power tube and preamp tube distortion. In most cases a big smile will ensue and all is well! (Picture Snoopy dancing in the fields) At some point the player decides to switch to the clean channel and quickly finds that it's gone?!?! Well of course it's gone! The amp is playing at full volume so you will get power tube distortion no matter what channel you are in. Attenuators were originally designed help players get to that "sweet spot" where you were just getting into preamp and power tube distortion which most of the time is too loud. You simply crank the amp up to where you like it and then attenuate down 2, 4 or 8db until you blended into the stage mix. #8. "I like my attenuator but it just doesn't sound the same as when the amp is cranked up by it's self, why is this?"    Answer: Correct! An attenuator can only simulate two out of the four components that are involved when you crank up an amp. The four components are #1 preamp tube distortion, #2 power tube distortion, #3 speaker distortion and #4 the physical movement of air that your speakers produce at high volumes. So the two components missing are speaker distortion and the physical movement of air and these are VERY BIG components! Some attenuators have built in EQ to help modify the tone but if you are looking to get the exact tone and feel of your amp at higher volumes, you can't get all the way there from here... Think about your car stereo and how the loudness button works, when you turn down the volume you loose that full sound and there is no punch to the music, the manufacturers know this so for lower volumes they give you the "loudness" button which miraculously brings back the fullness of the music by boosting the low frequencies. An attenuator drops your volume but does not discriminate when it comes to frequencies and has no loudness button. Ted Weber took his Mass Lite units a step further incorporating dual controls for Low/Mid and Mid/High. This helps quite a bit but if you want to get more of a full sound at lower volumes you will need to run parametric or at least a ten band EQ to get anywhere close and you will find a lot missing in the 60 to 140 cycle range. The harder you work a speaker the better it sounds until you reach the point where the voice coil is out of travel so players using a 4/12 cab will find that when attenuated down to a low volume their sound will be particularly thin. If you want a better sound at lower volumes try running a single 12 where you can work the speaker a little, this will make a lot of difference over using four speakers that are barely working. #9. "I like my attenuator but when I dig in the amp just doesn't respond like it does without the attenuator, why is this?"    Answer: Correct again! This is because an amp that is dimed out is out of headroom. Headroom refers to how much power the amp has left to hit peaks. If you turn the amp up to say half way and play with a moderate attack and then really dig into a note or slam a chord you will hear a volume difference because your amp has the reserve power or headroom to respond to your increased dynamic. When you're playing thru an attenuator and the amps is dimed out then there is no reserve power or headroom to respond when you dig into a note. The amp is compressed and flattened out. #10. "My wife says my amp is still too loud, what do I do?"    Answer:   #11. "Why do I lose definition at higher gain settings?"    Answer: Ah yes, definition versus distortion. Most of the time I get this question from good players who have practiced and developed good playing technique. This is NOT to say that players who have not been at it for long can't hear this and I'm sure my answer will stir controversy but here goes! There are two basic camps here, #1 players who have a good precise technique who want to hear every little string nuance and want to play with lots of gain, ala early Eddie VH or Petrucci or Satch. #2 players who like a lack of definition simply because its easier to sound like a shred master even if the technique is sloppy. Now here comes the controversial opinion part of this answer. I like to hear definition and love to hear a good player shred away and this is one of the main reasons I always liked the older European tubes and was drawn to the JJ Electronic tubes when I played and heard them. In my opinion the russian and chinese tubes lack definition and "fuzz up" when saturated. This "fuzz" is what a lot of players refer to as distortion. We hand pick a lot of high gain preamp tubes for our customers who want and need lots of gain but also want the definition and the JJ ECC83S preamp tubes deliver with the hottest gain of any brand. If you want or like the "fuzz" then seek out the russian and chinese tubes.  #12. "I saw this thing on ebay called the "Suck Knob" does it work?"    Answer: Yes, it works but in general, it sucks... It does not do what an attenuator does, and if you have read the rest of this page then you know what limitations attenuators have, if you have not read it I recommend it. The suck knob simply allows you to lower the signal from the front end, or preamp section of your amp that feeds the back end, or power section of your amp. It does NOT let you get power tube distortion at lower volumes, so the sound you get is all front end distortion and no power tube distortion, I repeat NO power tube distortion! So if you want power tube distortion at lower volumes, then only an attenuator will do this. However, if you simply want more preamp tube distortion at lower volumes then by all means, go for the "suck Knob", then you too can suck!

By Bob Pletka