Different Tubes and general purpose?

Tubes though are easy to plug in and out. They can be changed. So audiophools change them. Because they can. Which is exactly as good a reason as it sounds- no reason at all.

The same apply to FUSE?

Thanks millercarbon.  I ask as I’ve read plenty of articles about how there was notable, not step change, improvement in overall sound quality.   I get that that a lot audiophile purchases can either be snake oil or nearly inaudible changes.  
I have spent, at least in my world, a decent amount of $ on my system.  I’m largely pleased but I seam to be chasing the perfect balance and execution of several instruments in certain songs that seem to be not as crisp or prominent as i know they were recorded.  I would like to explore “tweaks” (i guess not upgrades) to my equipment that I’m hope can help me achieve what i want, without wholesale swapping out of equipment.  
My Harbeth HL5 plus sound incredible (coupled with a sub) on several albums (Fleetwood Mac, Tom Petty, New Order - Movement, the smiths - Hatful of Hollow), but on others (Big Country - the Crossing, or Led Zeppelin - 1st album) they seem to fail in the a really crisp and distinct mid range.  I could be the recording, but then again it may just be that these are speakers better suited for classical or jazz.  I was trying to explore other system changes to tease out more. 

The KT 120s are the power tubes. The 6SN7s, 12AU7s and 12AX7s are small signal dual triode preamp tubes, even though the 6SN7s look quite a bit different from the 12XX7 tubes. There are differences between the 12XX7 tubes even though they look the same. Don’t change tube type without checking with the manufacturer first. They’re not interchangeable. Sometimes there are variants (say of a 12AU7) that can be substituted.

Millercarbon likes to make pronouncements from on high rather than relate his experience as just that, his experience. He thinks that what works for him is the only correct thing for anyone else to do. Don’t let him throw you.

I’ve never heard your amp so I can’t really advise you on what to do next, but I can say that changing all the tubes could make a serious difference in the sound you’re getting, if you get the right tubes. You may also get the sound you want from only changing some of the tubes. Listen to your amp for a while to allow it to burn in and for you to decide what changes in the sound you would like to hear, although it sounds like you’ve already done some of that.

The place to start would be the manufacturer or his US distributor. Manufacturers generally use current production preamp tubes because they can’t get enough quality vintage tubes to fill their needs. Vintage tubes usually cost a lot more too. Everyone uses new production power tubes. There are different power tubes to try, though. Most people involved with tube gear try vintage preamp tubes in their amps, though, and are willing to share what they’ve learned with their customers. So if other Line Magnetic owners don’t chime in, give the US distributor a call.


There are a number of tube sellers who may be able to advise you. I’ll list a few, just google the names.  They'll talk to you for free.  Don't buy a bunch of tubes till you've got at least a couple opinions.


Vintage Tube Services
Jim McShane
Brent Jessee
Upscale Audio

Good luck, enjoy!

Great comments and advice from @tomcy6 . I'm a firm believer that each type of tube and each manufacturer has it's own sonic signature. Typically, you don't need to swap all the tubes from stock to vintage, aka NOS tubes (New Old Stock). There are specific tube locations which have greater influence on the amp's sonics. Most of us start with the small signal tubes, but you need to know the function of each tube in its location. Sometimes the user manual will state the function of each tube stage; eg, preamp, amp gain stage, or driver stage. Contacting the manufacturer or dealer is a better way to go. I won't give any advice on tube selection since I don't know your amp and since you're still getting to know it. 
I'll cite one example of a tube which provides an increased emphasis on the midrange and has plenty of "air" in the highs; it's manufactured by Amperex. Some tubes will be more linear, some will add detail to music, some will add warmth, etc.
Here's a primer on tube sonics of different manufacturers and each tube type; You can click on 12AX7, 12AU7, 6SN7. 
http://www.audiotubes.com/12ax7.htm

A member who is familiar with your amp very possibly will chime in.

 I disagree , Differences in tubes can be very noticeable.
A perfect example is a Telefunken 12AX7 vs Mullard 12AX7 is Very noticeable. I have tried many 6SN7 and found very few to have any decent bass. That was verified by Andy of Vintage Tube Services.
The only Vintage 6SN7  with good Bass is the Ken Rads ,but 90 %  are Microphonic, or another with Bass is Tung Sol Black Plates(not sure of the year). The Sylvania 6SN7 has great Mids and highs, but is lacking in Bass. i have not tried New Production 6SN7s
Call Andy  616-454-3467
. tell him your amp . He can help, i promise. Maybe tell him which tubes in  which spots V1.V2, V3 ..etc.
Let us know how it turns out