Comparable Properties of Tubes When Making a Selection
Assuming you already own a tube amp and it's time for you to replace the tubes because of age or degradation of tone or dissatisfaction with the tubes you presently have on board, you now have to make a choice between the numerous tubes available from different brands. Some brands offer three or four versions of a particular tube type so there are quite a few to choose from. How do you make your selection?
First off it's important to understand that while a specific type of tube, 6L6GC, EL34, EL84, 12AX7, 12AT7, etc., is required for your application there are numerous variances in tube construction that can make one brand / model of EL34 or 6L6GC sound quite a bit different from another brand / model of EL34 or 6L6GC or whatever tube type your looking for. For eggheads that want to investigate vacuum tube construction there are multiple sites dedicated to this very subject. The average Dino has little desire to wade through all the what's and why's and theory involved. They just need a method to gauge one tube against another.
There are many tube dealers on the web and quite often they offer comparisons between the tubes they offer. Below is a brief description of comparable factors they might offer to help you make your selection.
1). Microphonics. Generally noted by a player as a ringing sound in the backround. The less microphonics produced the better the tube in this catagory.
2). Harmonics. Think of this as the richness in the voice produced. The amount of backing or layered harmonics to the picked note. In this case more is better.
3). Detail. The crispness and accuracy of picked note production. Again.....a higher rating is better.
4). Frequency Productivity. Flat? Favoring the lower mids? Excellent in the highs and lows? Rich in mids? You get the idea.
5). Mechanical Noise. Vibrational. Popping. Hissing. etc. Pretty easy to identify.
Vacuum tubes are old technology. They have faults a player has to take into consideration. Tonally, when well made and meeting the desired voicing of a player, they are still the best thing going. While many advances in solidstate and modeling technology have advanced these newer formats into the lower range of acceptability almost all Dinos still show a strong preference for tube tone.
When it's time to replace your amplifiers tubes seek the advice of other Dinos. If possible try to actually hear different tube brands / models used in an amp similar to your own. Don't assume that the original tubes chosen by the manufacturer are necessarily the best. In production amps the cost of a tube plays as big a role in a manufacturers selection as the quality and tonal properties, (See notes below). Use the comparison tables offered by tube sellers. Just like pickups, speakers, etc. a tube, whether in the preamp or power / output stage of an amp, plays a very important role in the quality of sound your rig will be able to deliver.
Note #1. High Quality Boutique builders do not worry about the cost of a tube and often times build their amp to sound it's very best around the use of a specific brand and model of tube. If your using an amp built by Bogner or Cornford or Badcat or a brand / model of similar quality it's usually best to go with the tube recommendations of the builder. For this kind of money you should assume the builder has selected the best of the best.
Note #2. Certain brands, Mesa for example, will void your warranty if your amp experiences a failure and you admit to using other than the tube brand and model in the power / output stage that the amp originally came with. While this might be a moral issue for some, and I consider myself to be a very honest person, save the tubes the amp came with and if the amp fails while using other than the original tubes on board take the replacement tubes out and place the original tubes in the sockets before sending the amp in or taking it to an authorized dealer for repair. My personal opinion is that if your power amp tubes have the correct bias and are rated to handle the power supplied to them the brand and model shouldn't matter.