Tubescreamers were first developed during the late 1970s and early 80s. Ibanez was one of the first companies which pioneered the technology with their TS808 and TS9 model. Both pedals function as an overdrive pedal to give your amp a boost to create a natural, overdriven sound from your amp. There are countless other models of other brands on the market which function in a similar fashion as the TS9. For sake of simplicity I will mainly concentrate in this article on the Ibanez TS9 Tubescreamer.

                —Why were Tubescreamers Developed?–

Common guitaramplifiers of today do come with a lot of bells and whistles. They come often with their own build-in effects such as chorus, flange and delay, they also come often with different kinds of distortion sounds. The typical guitar amplifier of the 1950s, 1960s and 1970s was not like that: They were often capable of only producing one sound. If you liked the sound of raw and loud Rock you went for Marshall, if you wanted a more clean and delicate sound you went for Fender. I know, this is an oversimplification, as there were other brands, but most of these amps were based on the Marshall or Fender design. Ampwise, the situation as described before stayed pretty much the same up and till the early to mid 1980s.
When it comes to guitarsounds most guitar players like distortion, some want a lot of it while others like a slight bit of dirt to their guitarsound. To get distortion from your amp you typically had to turn your amp up in the past, often all the way up to 10, as what is often mentioned in the mytical stories of any Rock ‘n’ Roll band of the past.
Most amps of the past came only with one volume control, to get it loud [and to get some kind of distortion] you had to turn the amp up, there was simply no other way. The downfall with this was that anyone around you had to turn their amps up as well, just to match the volume of the distorted guitar.

               —The Pre-Amp and the Master Volume—

At some stage during the mid 1970s  guitar amp designers started to experiment with adding pre-amps to the signal flow of the amp. A pre-amp meant simply adding another volumestage to the guitar amplifier. This volumestage had its own volumecontrol. The pre-amp could be turned up to create the so much wanted distorted sound. The Mastervolume could be used to keep the overal volume down. The result of this design made it possible to have distortion of good quality at fairly low volume levels.

              —The TS9 as Pre-Amp—

When Ibanez came out with their first type of Tubecreamers they were simply listening to the request of guitar players to get distortion from their amps at low volume levels. The TS9 with its Drive, Tone and Level controls simply acted as another pre-amp stage in front of the guitar amplifier. Turn up the Level, add a bit of Drive and set the Tone to how you like it and you were on your way to create your own type of distortion while you could keep the overal volume level of the amp at listening levels.
The Downside? The TS9 added midrange to the overal guitar sound. For some guitar players this was not a problem. [Listen to the early Punk albums of the early 80s, also some early Chili Peppers, and you will immediately recognize that typical midrange boost in the sound of the guitars] 

             —Why the Name Tubescreamer?—

They were typically designed to break-up the volumelevels of your guitar amp to create a natural overdriven sound. Increasing the Volume, Drive and Tone on the TS9 literally made the tubes of your guitar amp go beserk [read–break-up the sound—] Off course it was also a good marketing name: “If you need distortion [and who does not eh?] you will need a tubescreamer, not any kind of distortionpedal, as only a tubescreamer will be able to give you that natural, overdriven sound”.

             —Only Works with Valve Amps?—

No, while they work very well with valve amps [which were the common amps of the 1970s and early 1980s] they also work well with transistor amps. You can put a Tubecreamer in front of other distortion-and overdrive pedals, and in this manner they will function in a similar way as to how they act when placed in front of a valve amp: They will add boost to your other pedals, they will also add a bit of midrange to your overal sound.

             —Tubesceamers Still Used Today?—

Yes, even though we now have amps which are of a totally different design from the amps of 20, 30 years ago, Tubescreamers are still popular today. You will find their designs popping up among the different distortion/overdrive pedals made today. Some of those pedals are straight copies of the Ibanez design while other may look very different from the typical look [and feel] of a Ibanez TS9. The TS9 can still be bought new today as Ibanez started producing them again since the early 2000s.

              —Super Tubesceamers of Today—

Not happy with the sound of a stock TS9? Too much midrange for your taste? No problem, as you can get your TS9 modified to get rid of that midrange honk. You can get them just to boost the sound of your amp without adding any additional colouring to your sound.
Guitar Players from all around the world find their own unique useage for the TS9. I myself use it typically to boost some of my other distortion/overdrive pedals and my small amps. I use a stock model, unmodified, and yes, I do get that midrange boost but I do not mind as I happen to like that sound: It adds urgency to my solos and riffs.

Start listening to your sound today, what is missing? How could you improve it?
Happy experimenting!
Eddie