The typical tube amp is a fixed bias amplifier. Self-Biasing Amplifiers: Yes they do exist Think of it as a rough adjustment before you do the fine bias adjustment. These two (or three- 6L tube are basically the same tube) tube types can be designed to work in the same amp, but the bias range is very different, so the switch places the bias adjustment control range for the tube type selected. This is where the bias voltage range for the different tube type is adjusted. Why does the amp have those little switches on the back that are supposed to ‘bias’ the amp for one tube type or another, if you have to adjust the bias every time anyway? For example, the Tremoverb amplifier mentioned in the comment, the Carvin V3 and Legacy amps all have a selection switch on the back to adapt the general output circuit for E元4 or 6L6/5881s. This may be a hassle, but getting it done properly is the only way you will know your tubes are dialed-in correctly. Otherwise every new set of tubes will need to be biased. Then if you keep using tubes from the same supplier with the same current-rating, you can just put them in without re-biasing, although it is still good to have it rechecked at some point to make sure it is still at right setting. If you buy premium tubes that are matched by current-rating (or ‘hardness’) then you can have your amp adjusted professionally for the first set. As mentioned in the previous article most amps have one bias adjustment for all of the tubes, so you can’t adjust for each tube. And this is why tube amps like matched tubes. Out of 100 tubes 10 may have similar current output for the same input bias voltage. It must be fine-tuned for each tube, because the voltage input controlling the resulting current flow varies greatly in tubes. This is a negative voltage which sets the flow of electrons or current through the tube. The bias voltage on your amp energizes the input control grid inside the tube.
![cathode bias guitar amp cathode bias guitar amp](https://i0.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/5E3_ProductsPage_MarsAmps.jpg)
There may be a start spot that puts you in the range, but it must be fine tuned for the right performance.
![cathode bias guitar amp cathode bias guitar amp](https://i.pinimg.com/originals/b3/fa/72/b3fa72fb767f6e4779e8891387f2e2a6.jpg)
If you went to your mechanic friend and asked, “What is the correct idle setting for this model?” Chances are they will say, “When it’s right.” Every motor runs a little differently, so you can’t set it to the same spot on every car. The bias voltage is like the idle adjustment on a classic car. Let’s look at what’s happening inside your amp’s power tube. When it comes to your output stage, you want lots of power, but you don’t want unflatteringly crossover distortion or to fry a tube! Simply being in the middle of the adjustment range doesn’t mean your amp will sound and perform properly. But it is equally unlikely that your new tubes will just happen to draw the same current as your old tubes. In most cases, it is safe to say that if your bias voltage is adjusted to the factory setting for the same type of tube, you probably won’t have catastrophic failure and the amp will function. But there is not a specific single bias voltage for a particular tube type that magically biases your new power tubes. There are rule of thumb formulas using the tube’s wattage, the voltage of the particular amp and a percentage of operation that help a technician know the bias voltage starting point. There are bias voltage ranges for the different types of output tubes like 6L6, E元4 or EL84, but inside of that range you need to set the actual bias voltage for the particular amp and for the new tubes being installed. To answer the question, “What is the correct bias voltage?” We need to look at what is being set with the bias voltage. You will not see a switch on an amp for tube brands. The first thing is Electro-Harmonix and Sovtek are brands of tubes and in fact some Electro-Harmonix tubes may be Sovtek tubes.
![cathode bias guitar amp cathode bias guitar amp](https://i.ebayimg.com/images/g/qdIAAOSwC11Z0VZw/s-l640.jpg)
Is there a specific bias voltage? The short answer is no. All I had to do was select EL-34, 5881, or 6L6…It self adjusted to whatever power tubes I decided to use.” If I want to use Sovtek EL-84s what must the voltage for the output tubes be set at? Lastly, I hope Carvin Audio can develop a power amp with a self biasing output section like my Mesa Tremoverb had. Ex: I own a Carvin Audio V3M head, but it uses Electro-Harmonix power tubes. I would like to see an article that describes how the power tubes are correctly biased. In response to our recent article about replacing tubes in your amplifier, we received the following question from a Carvin Audio enthusiast.