The One Place Where Bias is Good
Hey loyal Solo-ites…welcome to February. Seems; just like last year, this year is bound to race past us at the speed of ….um sound? Lol NAMM is done, the boys in the front are home with great stories, great meetings and hopefully some great new products to show us very soon! From all accounts, a great time was had by all and the show was well attended…. pretty much, great.
Ok so February blog…. New product time! If you have checked out the New Arrival section on the website, you will notice that on top of amp parts and cabinet accessories, we have increased our selection of vacuum tubes!!! If you are an amp person…you will have either owned or used a tube amp, or you hope to…. despite the world turning digital, this is one area where most guitarists still stick to the past. There is nothing like a tube amp, and tube tone. Now, whether you agree with that or not, tube amps are not going anywhere soon. I personally have owned probably 50 plus amps over the years…you know looking for the holy grail like everyone. Whether I found it is a different story…
There are three types of tubes available on our site, rectifier tubes, pre-amp tubes and power tubes and in case we aren’t up on our tech-talk, let’s see what they do in the amp…more or less in order. Rectifier tubes have a very specific purpose in an amp. Rectifiers convert the positive and negative lines of AC (Alternating Current) from the amp’s power transformer, into a single line of DC (Direct Current) which enables the other signal amplifying tubes to do what they need to do. Rectifiers come in both tube circuits and Solid State circuits…so clearly, the rectifier tubes we carry are to replace the obvious. As long as the style and value of the tube matches your amp, they can be a simple change over…take the old one out, put the new one in.
Pre-amp tubes power the Pre-amp…imagine…. Pre-amps basically amplify the weak signal that comes from your guitar pickup(s) to a Line Level signal, which can be shaped and modified by things like the EQ, Tremelo or Reverb circuits. Pre-amp tubes are typically shorter and smaller with pin bases and can affect the tone and quality of sound your amp produces, but they are also a direct change as long as you have the correct value.
Finally the Power Tube….so much has been said, argued and written about power tubes. Basically, Power Tubes are the engine of your amp…they take the line level signal from the pre-amp and amplify that signal as efficiently as possible. Different styles provide different power and headroom (the amount of clean sound before the amp begins to distort) This brings us back to the title of this blog….bias. Depending on the output of your amp, and what kind it is, it is possible to simply replace the power tubes and get sound. However, for the amplifier to function properly and efficiently, the tubes should be ‘biased’ within the circuit so they run at the correct temperature and with the correct amount of voltage.
First let’s get something out of the way. Amp service is no place for first time DIY’ers to start playing around. There is enough voltage in an amplifier to kill you, even if it’s turned off and not plugged in. Capacitors can store voltage for a long time, and touching the wrong thing to the wrong thing can lead to serious injury, fire and or death…no joke…DEATH. It’s always best to go to a qualified technician who is trained in electronics and let them deal with whatever the issues are. Plain and simple…you have been warned! We do not promote the service or adjustment of electronics by anyone who is not qualified.
Tubes are an electrical device made up of 4 active components inside a glass tube that is void of gases (hence vacuum). The 4 components are the Heater, the Cathode, the Grid and the Plate. In simple terms, the heater (that’s the glowing filament) warms up the cathode which is negatively charged and therefore emits electrons. The ever-growing cloud of electrons flows through the vacuum and attaches itself to the positively charged plate (remember, opposites attract). The flow of electrons to the Plate is controlled by the Grid (also called the Control Grid), so that flow does not get out of hand.
Biasing controls the amount of DC voltage that gets delivered to the tube which will control the flow of electrons inside the tube. If the Grid inside the tube is too negative, it will slow or stop the flow of electrons. This is also called cold bias or cutoff. Your amp will sound dull and lifeless and could possibly distort earlier in a way you don’t want it to. If the Grid isn’t negative enough, the flow of electrons increases, could become out of control and will exceed the rating of the output tube being used. This is called red-plating and will not only shorten the life of your tubes but will reduce output power and punch of your amp. Hence, biasing is extremely important to the output, life and sound of the amp.
This is the shortest explanation of tubes and bias I think you will find…. Aspen Pittman (The Tube Amp) always used the analogy of an idle-tuned car to compare to biasing. If the car is tuned at idle, it will sit there and run all day, just waiting to be called on. When it is, it will accelerate smoothly and efficiently. If it’s not, it may be coughing, sputtering and stalling. So obviously, when your amp is properly biased, it will sit there idling along until you hit that first big chord or note and take you to rock and roll quickly and efficiently!
So remember to check our stock of tubes when you need to replace yours…and always remember that a qualifies tech is a safer and better way to go! Despite vacuum tubes having become really expensive this past couple years, our prices are very competitive.
