There are a lot of amps that can use different tubes to change or improve their tone for different styles of playing.Until the JJ EL844 came on the scene in 2011 there really were no substitute tubes for EL84 / 6BQ5 tubes. Now if you want a little less power and an earlier breakup you can have it! The JJ EL844 is an entirely new tube that dissipates 9 watts and is a drop in replacement for EL84's in most all amps. It has a very smooth sweet breakup just like the JJ EL84 and it will breakup a couple decibels earlier. These will drop into most cathode and fixed biased amps like the Orange AD amps, VOX AC amps, Laney VC amps, Crate V and VC amps including the Palomino, Budda amps, Fender Blues and Pro junior amps. It is also an option for all the 5 watters like the Valve Junior, Blackheart, Mini Cat and others. Since there are no decent 6V6 tubes being made currently WHAT!! Wait a minute!! Who says?? Thanks to Mark Beach ( a loyal customer of ours who reminded us that we needed to change this page ) there are now two solutions for Fender Deluxe amps. We used to routinely tube all of the old Fender Deluxe’s with the JJ 6L6GC’s but since the JJ 6V6S arrived ( 11/03 ) you can go either way. The JJ 6V6S's are a VERY nice 6V6 and sound stellar in any 6V6 amp or for a little more headroom the JJ 6L6GC's will fit the bill with a simple bias adjustment.The JJ 6V6's are so robust that we have been using them in lots of amps including several of our Blackface Bassman amps and in our Mesa Dual Rec. By choosing the proper grade these can be run in the EL34 mode and have the best clean tone we've ever heard from a Dual Rec. They also have a deeper thump and breakup earlier than 6L6's do. We literally have thousands of customers now using the JJ 6V6's in their Fender Hotrod Deluxe and Deville amps with great success since 2003. The JJ KT77 is a drop in replacement for almost any EL34 type tube amp for a little different flavor. The JJ KT77 is not quite a tight as the E34L but tighter than an EL34. The 77's have even a bit more low end extension than the E34L's and they have a nice sizzle in the top end that is not brittle. The clean tone is very fat and full and the crunch has more of a chunk to it and it's very punchy but not quite as aggressive as the E34L. The JJ Big Bottle 6CA7 is also a drop in replacement for any EL34 type amp. These are real meaty sounding and as close to blending a 6L6GC with an EL34 as you can get. The JJ KT66 can be used in a variety of amps that use 6L6's if there is room! The JJ KT66's and the JJ KT88's are the same diameter as the original GEC KT66's and KT88's which is just under 2 1/8" so you need an absolute bare minimum of 2 1/4" measured from the centerline of one socket to the centerline of the next socket for them to physically fit in an amp. Amps like the Peavey XXX, JSX and 5150's/6505's cannot use them. The only exception to this is if you choose to run one of our Integrated quads using two KT66's or KT88's in the outside two sockets and two 6L6GC's in the inside two sockets and this only works in the 5150 or 6505 heads.Both the KT66's and KT88's use the large diameter bases so if you have an amp that uses the "bear trap" style tube retainers that pinch the base of the tubes then these will either need to be flattened out, removed or replaced with the "spring and cap" style tube retainers.The JJ 6550 can be used in quite a few 6L6 amps that don't have room for KT66's or KT88's but this is a case by case scenario because the heater draw is 1.6 amps and some 6L6 amps can't handle this. In amps that are made to use both 6L6's and EL34's the JJ 6550's are almost universally usable. They are unlike any 6550 ever made and not sterile sounding at all. The breakup is raw, crunchy and gritty, we dubbed them "Angus in a bottle" they are just a lot of fun to play!Another great substitution is replacing the 6550’s in 800 Marshall's with the JJ KT88’s. These are even fatter and make more power than the JJ 6550's. The KT88’s also sound great in the late 70’s Marshall Mark II amps in place of either the EL34’s or 6550’s. You can also use the JJ KT66's to replace the 6550's if you want more of the original Blues Breaker type tone.While we’re talking Marshall, about 90% of the 900’s that we re-tube locally leave with the JJ 6L6GC’s in place of the stock EL34’s. This substitution gives the 900’s some low end punch and smooths out the mids and highs. Watching the look on the owner’s face when they A/B the 6L6’s to their EL34’s is a lot of fun and well worth the effort. Most of them can’t believe how good the 6L6’s sound. The JJ KT88’s also sound excellent in the Hot Rod 50, Soldano amps. We have even run a quad of the KT88’s in a few “Evil Twins” and it is fat! If you want to add some real thunder to your old Ampeg SVT then the JJ KT88’s are the tube. They are big, fat, round and very dynamic. Basically any amp using 6550’s can use the JJ KT88’s. They really sound nice in Leslie’s too. We’ve tubed lots of Bogner amps which usually come with EL34’s and by using 6L6’s they get more of a Fender type tone and with the EL34 they are more British sounding. The Bogner's sound great either way so it’s a matter of choice. A good friend of mine (Brian Hadley) has had two different Bogner amps and I set him up with 6L6’s, EL34’s and KT88’s and the 6L6’s were actually the most versatile. We will occasionally use a 12AT7 or a 12AU7 in an amp that has a gain channel that’s over the top like our 5150 or Prosonic. In the Prosonic gain stage we use an ECC81 (12AT7) to calm it down a little but we stay away from subbing a lower value tube in the clean channel because it usually takes away the sparkle and even adds a little noise. An ECC82 (12AU7) in place of a 12AT7 in the reverb is sometimes nice if you don’t use a lot of verb. If your trying to cut the gain in your amps drive channel you might be interested in a hybrid tube we're using in my Prosonic and 5150 to cut the gain, it's called the JJ ECC832 which is a 12DW7. This tube is half of an ECC83S ( 12AX7 ) and half of an ECC82 ( 12AU7 ). We are using one of them in my Prosonic in V2. This actually sounds VERY nice in amps that cascade the gain through several preamp tubes. It cuts down the gain by about 40% but retains a nice crisp attack and warm tone where just dropping down to a 12AT7 seems to dull the tone a bit. We've got lots of players using the ECC832 in one or two of the gain stages in everything from the Mesa Triaxis to Peavey Triple X amps with great results.