What genres best suit KT77 vs. KT88 tubes?

I'm planning my next power tube roll for my Elekit TU-8200DX and want to try new production KT77s or KT88s, probably "Genalex" Gold Lions as they seem fairly well-regarded, but having trouble understanding the sonic differences between the two tube types based on the descriptions I've read.

Wondering if there are consensus opinions on which music genres best fit either of these tubes? I listen to mostly acoustic singer-songwriter, 70s soft rolk, folk, alt-country, with some jazz and classical mixed in. The rest of my system is fairly bass-light and slightly over emphasized on top, so would prefer a tube that gets the mids (guitar and solo male vocals) right and anything extra on the bottom is butter.

The preamp tubes will likely be the Brimar CV4003/12AU7s that Upscale Audio currently has back in stock, but it feels wrong to buy those beauties without a new power tube counterpart... so do what you do best and help me spend my money, fellas.

 

I don't know the KT 77s, but, in that family of tubes, I like the KT 66 and 6L6 tubes myself. The KT88 delivers power and punch, but, it can sound a bit brittle or have a hard glare (but not in all designs). If you want to hear the difference between the various pentode/tetrode tube types, go to Deja Vu Audio in Tyson's Corner; this store sells only tube gear (except for used trade-in solid state gear) and they have quite an amazing collection of new, old and their own custom-built stuff. Actually, it is a very dangerous place for those who are bit weak on fiscal restraint.

I have not heard the Elekit TU-8200. The 300b kit they make is terrific sounding for the money, so I you probably made a wise choice.

 

Some people think the KT88s sound a bit bright. The KT77s can give you a warmer sound. These are all just generalities. It’s best to try both and see for yourself. If you are trying to skimp on tubes and tube amps you are in the wrong hobby.

 

If it's midrange you're after, EL 34's are your better bet. KT77's are more about power and the bottom end. likewise with KT88's just more so.

My amp came with EL34's, but I swapped them for KT77 JJ's (good and inexpensive) then eventually Gold Lion Kt77's (great and somewhat more expensive). The 34's were fine, but a bit too polite for what I listen to, but would be perfect for what you are into.

 

Pay a little more then you would and get NOS RFT EL34 tubes. These are real pentode el34 tubes. The Gold Lion KT77s aren’t bad but aren’t especially exciting either, which is par for the course with that brand.

 

Having a quad of GL kt77´s and GL kt88´s myself, I can comment about their differences. I think they cover pretty much the same range of sounds, but the difference I hear in my amp is that the kt77´s sound more relaxed and the kt88´s have more punch. I prefer kt88´s from those, but I prefer EL34´s above those, and I think maybe that´s what you need from your description. I have Winged SED EL34 and I´m very happy with their sound.

 

The Winged SED EL34 have come to a production end. The TubeStore managed to stock up while they could. These tubes have gotten high marks by most tube amp owners who have tried them. This might be another choice.

 

Thanks for the suggestions, all. I actually already have a pair of NOS RFT/Siemens EL34s on the way from that German seller on the 'Bay who has been recommended elsewhere in these threads, so for variety's sake I think I'll complement those with the KT88s since it sounds like they'll be a bit more different in terms of bottom end punch. Appreciate the input!

 

KT77's I think are a bit better sounding than modern day EL34's, which are lacking in the magic midrange that people buy EL34's for.

They appear to have more midrange because they are seriously lacking in bass (IMO).

I agree here also. I like KT77's and had them in a nice Line Magnetic 211iA in place of EL34's and it made for a very sweet amp.

Though, in general, I have a preference for KT88's. I don't find them bright at all and I use Electro Harmonic tubes in modern Rogue M- monoblocks.

Like other's have said, they have more punch, dynamics and deep, strong low end.

Excellent.

Rolltide was the member who made those RFT recommendations to me.

The music you are listening to, will sound excellent with the RFT EL34's. The RFT's do have that magic midrange.

Also, they are some of the only large power tubes that could be classified as affordable in NOS. Try buying NOS KT88's!

KT77's are a modern design, so no NOS tubes here.

Something that I had not expected and really surprised me with the RFT's, is their deep natural sounding bass. I have never heard bass like this from any modern day EL34.

I believe that you will really enjoy your NOS RFT's!

 

I am not following you on this. The original Genalex Gold Lion KT 77 dates back to the 1970s. There are NOS versions but they are rare and very expensive.

The Reissue Genalex KT 77 sounds great to me, much better than its brother KT 88. In my amps (Emotive Vitas) the 77 is more detailed, richer sounding and it has better microdynamics. The 88 has a bit more power but that’s its only advantage in my amps.

 

My apologies, I should have been clearer on this. Most other power tube go way back before the 1950's. When I think of real NOS tubes that is what I think of.

Yes, you can get post 1970 NOS KT77's, but they are very rare and stupid expensive. I actually recently pointed this out to another member.

The RFT's are not real old, probably 1970 or later, but they run about $280 a quad and they do sound like NOS tubes.

There are other NOS EL34's from Mullard and even more expensive tubes from Telefunken, which tend to run in the $1k plus range for a quad.

With tubes, every amp is different. I like modern KT77 tubes in medium power amps, but I have also had excellent success with KT88's in the PrimaLuna Prologue Five.

In more powerful amps like my Rogue's I prefer the KT88's, because I want plenty of slam and dynamics.

I prefer my M-150 monoblocks for their KT88 sound over the Cronus Magnum with the KT-120 power tubes.

But I can run the M-150 in triode mode, where with the CM I, it is only ultralinear.

 

No problem. Age is relative. I have a pair of Cunningham globe 46 tubes in my SE amps right now that date from the 1930s. One of them has a sticker on the glass where someone wrote “Tests ok 11/15/36.” That was over 80 years ago! And it still sounds great.

 

KT-88's are, just right.

 

I am not familiar with the various exotic El34s. When I got my headphone amp, a friend brought over a selection of quads of various EL34s and 6CA7 tubes, including some highly coveted types, like Mullard xf2's. I got to pick any of the quad that I liked. I went with a quad of Telefunkens. It appears that these are somewhat pricey these days.

 

That amp "looks" like it would sound good. Like some cars look fast even when they are sitting still...

 

Here's a colorful description of several tubes from "Humble Texan Fan". In contrast to some above, adjectives include KT88="darker, broader, cleaner";KT77="brighter, mids, hard" although some of this character in a guitar amp is describing the near-break up modes of the tube:

Wow, where to start... For starters the 6550 and the KT88 have the same Gm as the EL34, so they're quite dynamic. The 6550 could be likened to a hard vacuum 6L6 whereas the KT88 is a darker and stronger KT66, which is peakier and more complex sounding.

The EL34 is probably the narrowest of the medium glass octals. The KT88 is broader with less of a mid peak, the 6550 would be perceived as scooped. The EL34 being a true pentode sounds a bit rough and fluffy, even clean. The KT88 and the 6550 are way cleaner.

In an amp designed for EL34s or 6L6GCs you're likely not to achieve the full output of the big bottles or have them perform at negative, due to the fairly high bias feed resistors. Also your OT may not be designed to handle their max output so you're likely to run these on the colder side of things anyway.

So basically: you'd get more headroom, more lows and a broader sound and more detail with the big bottles. They can even sound a bit stiff or dead, particularly if biased cold.


A more direct replacement that's still capable of being biased at 32W is the KT77. It's brighter and middier than the big bottles and has the vacuum closer to the EL34. You could compare it to the love child of a Siemens/ RFT EL34 and a GE 6L6. Can come off as a bit tinny or hard if biased cold.

Then of course you have the fat bottle 6CA7, which is more like a miniaturized, straight sided 6550 w. lower output. EVH and The Who are known for having used these.​

 

I have two deuces with the same signal tubes you use.
SED KT88's in one and SED 6550's in the other.

Just right.

 

I've got a pair myself. Had them strapped for a couple of days but they put out lots of heat and summers approaching. This pic is of the newest unit that has seen a complete mechanical restoration and a light cosmetic touch up. Some say this was a lousy design but those have probably not lived with one very long. This amp tells it like it is and will flush out shortcomings in the rest of your system. My amp hunt is over and I'm stuck with at least 10 amps sitting around. My youngest sons ASL died yesterday so I'll be getting rid of at least one.

 

And I now have one unit running in triode mode. I'm going to bias the tubes a bit hotter.

 

In my single ended pentode I've found the KT77 to be my favorite. It has a mid almost as good as a nice EL34, but the bass and top end are better. Other tubes that are solid uo top and below just don't have the midrange I want.

 

I am also enjoying some KT88s running as triodes this morning.



I don’t actually have a choice though, that’s just how this amp is designed.

 

While my Rogue M-150 monoblocks are designed for either operation, I usually run them in triode mode.

Though they don't have the same sweetness as a true SET, the triode mode does give you both power and the dynamics which come with power but still retaining the qualities of a triode.

While some modestly powered A/B amps can run in either mode, I think that they loose a lot of their inherent character / quality when running in triode mode, where a large amp, like the Rogue's do not.