Re: el34/6l6/ 6v6
My bad, the kt88 was supposed to be the 6l6 of britain. I dont remember what the 6550 was supposed to be.
The 6v6 is olllllllld though. Its small too. Only puts out like 5 to 10 watts. The el84 is probably britain's version of the small power tube and is about the same output.
Sorry dude but your just flat wrong there... the KT88 is designed as a high power tube a pair should give 100 watts easily in class AB it is not at all just suppose to be Britains 6L6. The KT88 is closest to the 6550 but a 6550 will only take 600v's where a KT88 will take 800v's.
The EL34 is a pentode where the 6L6 is a beam tetrode, so is the 6V6. The 6L6 is actually OLDER than the 6V6 by only 1 year but it is still older. The EL84 is a pentode like the EL34. They werent necessarily desinged to be english equivalents to American designs. Many of those companies had agreements/over seas divisions. Infact the 6L6 was designed by Marconi Osram Valve ( which was owned by GE) but they thought that it would be difficult to mass produce so they licensed it to RCA. The KT66 was designed as their more stable version of the same idea a year or so later. (But RCA proved that they could make the 6L6 stable and had huge success with it) The reason they were doing this was because Phillips held patents on power pentodes in europe. (Thats Phillips as in "Mullard Phillips") Using beam tetrodes allowed them to circumvent this.
Fender didnt choose 6L6's because of their tone but chose them because they were the commonly available valve in America that fit the power requirements. None of these tubes were designed with guitar amps in mind they were designed as signal amplifiers mostly in radios but in other areas too just so happened that guitar amps could use the same technology.
The EL84 was actually designed so that you could eliminate the triode in the preamp of radios. Saving you the socket and space in manufacturing (hence the decisions to use 9 pins instead of the 8 pin configuration like the 6V6) But the EL84 and EL34 are newer designs. They came about in the 50's where the 6L6,6v6,KT66 came about in the 30's In general beam tetrodes produce less THD than pentodes do. But you run into problems with making this a blanket statement.
Over the years many tubes have been sold as EL34 or 6L6 that really arent and dont faithfully follow the original designs. A good case in point was the early 6v6 sold by Sovtek. It was actually a russian tube designed as a 6L6 substitute but slightly smaller it just happened that it would work in a 6v6 application. Many EL34's sold are not actually pentodes but are beam tetrodes they just will work in the EL34's spec.
Another good example are the current KT66's NONE of those sold have the same architecture as the original design infact most are not even the stated KT as in kinkless tetrode. Most are actually heavy duty 6L6 designs in bigger glass.
You can speak of tubes in generalities but not absolutes. Its possible to find big bottom glassy EL34's its possible to find dirty mid heavy 6L6's. These days you almost have to try each brand and version out on their own as 6L6's from Sovtek dont sound like 6L6's from JJ.
Oh and as a very important side note do not forget that discussing tubes without discussing the amplifier design is kinda like talking about engines without talking about the chassis. With the right amount of filtering you can make a 6v6 amp that is uncompressed and clean. Many of the amps that use 6v6's were designed to be small so they dont have adequate rectification and the transformers are too small. So you start pushing them hard and they distort and compress easily. Same goes for any tube type. Then guys want to know well if i take the same design of amp and swap the tubes what will the changes be... it depends... on the amp and the tubes.
