# kt66 vs EL34 tonal differences?



## cjar66

Hi guys
I have a jtm 45 re issue that currently has EL34 in it. I bought it second hand and figure it wouldnt hurt to update the tubes in the not too distant future. 
I would like to know what tonal differences can be expected between EL34's and KT66's, and are there any other differences IE: power/volume reduction etc.

Thanks
cjar (rob)


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## fdesalvo

The KT66s will give you more bell like cleans with more bottom end, as well. You may not find them to be as bright or barky as the EL34s, either. I would expect a little more clean headroon. These are gorgeous sounding tubes.

Just my .02uf.


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## ECwomantoneman

Well, I'd say the KT66s are a bit "smoother" and cleaner, but EL34s have a bit more classic rock style grit and punch to them. KT66s are probs best demonstrated by the chiming cleans of a JTM45/BB combo, and the EL34s the smooth, dirty sound of Hendrix and Page.


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## cjar66

Hi Guys
"EL34s the smooth, dirty sound of Hendrix and Page" - thats a damn fine sound to me!!
What brand do you recommend? It currently has rubys in the power section and still has the marshalls in the pre amp section
Thanks
Rob cjar


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## stryker59

i put jj's in my jvm and they sound great!!


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## radiomatts

I use the new Groove Tubes Mullard reissues in both my Marshall head and my Laney combo and love them! If you can afford to, buy a few different kinds and see which suits you better.


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## speakerfritz

humm.....I thought el-34's=kt-77's and 6l6/5881=kt66's. Some amps can take all, some are configured for a select....just something to check on....you might have already looked into it.


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## sinrman68

cjar66 said:


> Hi Guys
> "EL34s the smooth, dirty sound of Hendrix and Page" - thats a damn fine sound to me!!
> What brand do you recommend? It currently has rubys in the power section and still has the marshalls in the pre amp section
> Thanks
> Rob cjar



Rob, get ahold of Bob over at Eurotube...he has JJ's and a heckuva selection. Alot of good info to help you make your decision. Funny, I've been thinking about buying a ceriatone clone and I have been bogged down with selection anxiety. I wonder what KT-66's sound like too...I thought about a Bluesbreaker if I could figure out how to disconnect the tremolo tube and use it as an extra preamp stage (evil indeed!). Let me know what you come up with!


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## tdawg0993

ECwomantoneman said:


> Well, I'd say the KT66s are a bit "smoother" and cleaner, but EL34s have a bit more classic rock style grit and punch to them. KT66s are probs best demonstrated by the chiming cleans of a JTM45/BB combo, and the EL34s the smooth, dirty sound of Hendrix and Page.


I'm pretty sure hendrix used kt66 tubes in his marshalls and page later used them in his marshalls when he had them re-wired to 200+ watts. I could be wrong about page but i'm pretty sure hendrix used the kt66's!


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## MartyStrat54

Well, just so you know, the maximum plate dissipation for a KT66 is 25 watts. It is listed as a direct replacement for a 6L6GC. Please note that the GC was the most powerful 6L6 made and can handle super high plate voltages. What has been said about the KT66 is true. It is a clearer sounding tube with more headroom and a little more bottom end response. However, the physical size of the tube limits what it can go into. If you have spring "bear trap" retainers, these will prevent installation. The KT77 is a "direct" replacement for the EL34. These are sweet sounding tubes and like the KT66 offer more headroom. I have a non Marshall amp equipped with these and I really like it for obtaining the 70's rock sound.

There are some amps like my Traynor YCS100 that will take about any power tube that you can throw at it and some power amps will only take a couple. As I said, the KT77 is a direct replacement for an EL34 so it will bias right up in the amp.

Buying tubes is like buying home speakers. It is really up to the end user to decide what they like. Some of the big tube stores will let you try a set and if you don't like them you can return them for a different set. As far as my own experience goes, I put them in this order.

1. Reissue Tung-Sol EL34B
2. Reissue Mullards EL34
3. Winged C EL34
4. JJ's E34L

Please note that all of these tubes sound good and that the difference between number 1 and number 4 is a small value. Again, this is based on my experience.

There is a lot of discussion here on the forum about tubes since they are a critical component of our amps. Please remember that many companies relabel their tubes (just like car batteries). They all buy from the same source and put their label on the tubes and mark them up. New Sensor, an American company owns the Reflektor tube plant in Saratov, Russia. This plant makes many of the tubes you see for sale on the tube stores, even Genalex which is still a very good tube. Winged C has a separate plant in St. Petersburg and makes their own tubes. I won't go into details about the Chinese brands (although there are those who swear by them).

Conclusion: Tubes are a personal choice. It is difficult for someone else to pick them out for you. As with many of the aspects of playing guitar, tubes fall into the category of time and experience. I have over 35 years of tube amp experience and it is easy for me to know "what I like." I've tried amps with just about every power tube made and they all have their own voicings. If you really feel the need to break away from the EL34's, I would strongly suggest the KT77's. Go to the Tube Store or the Tube Depot and you can click on any of their tubes and get a mini review of what the tube sounds like. Good luck.

Marty


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## dook

ECwomantoneman said:


> Well, I'd say the KT66s are a bit "smoother" and cleaner, but EL34s have a bit more classic rock style grit and punch to them. KT66s are probs best demonstrated by the chiming cleans of a JTM45/BB combo, and the EL34s the smooth, dirty sound of Hendrix and Page.



I don't know about back in the day, but the Marshall Hendrix reissue amp has KT66s in it and the Marshall amp Page used at the O2 reunion has KT66s in it.


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## Purgasound

speakerfritz said:


> humm.....I thought el-34's=kt-77's and 6l6/5881=kt66's. Some amps can take all, some are configured for a select....just something to check on....you might have already looked into it.



Those tubes are not the same at all. EL34=6CA7 an a 6L6=5881. The KT66 and the KT77 are in a class of there own and totally different.

For tone, KT66's in a JTM45 is going to be early AC/DC, Bon Scott era. EL34's are going to be more like early British rock, think very VERY early The Who.
If I had a JTM personally I would put KT66's in it. If I had an early plexi or 1959/1987, I would stick with EL34's. Both tubes have their own character, neither one is bad.


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## Bassmec

American Viking said:


> Those tubes are not the same at all. EL34=6CA7 an a 6L6=5881. The KT66 and the KT77 are in a class of there own and totally different.
> 
> For tone, KT66's in a JTM45 is going to be early AC/DC, Bon Scott era. EL34's are going to be more like early British rock, think very VERY early The Who.
> If I had a JTM personally I would put KT66's in it. If I had an early plexi or 1959/1987, I would stick with EL34's. Both tubes have their own character, neither one is bad.


+1 The other thing is that KT Valve types (Kinkless Tetrodes) are better with higher impedance op transformers and should ideally have GEC or Genalex on them or they may be quite unlike any favorite guitar heroes actual sound.

I like the mullard EL 34 reissues.


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## MartyStrat54

Excerpt from www.cathedralstone.net/Pages?GECKT66.htm

The GEC KT66 is one of the best tubes ever made for guitar amps. The GEC KT66 was made by the M-O Valve Company (or the Marconi-Osram Valve Company) which was a part of the General Electric Company Ltd. of England (GEC). GEC also manufactured tubes under the name of Genalex. The "KT" prefix in the KT66 stands for "Kinkless Tetrode" (aka Beamless Tetrode). This refers to the way a valve characteristic curve kinks as it progresses from Class A through Class AB towards Class B. Unfortunately, GEC closed its doors in the early 80's.

The GEC KT66 is basically the British version of the American 6L6. They were used on JTM 45's whenever the 5881 tubes weren't available. They had a 5881 supply problem, so many JTM 45's were sold with the KT66's. They were also used on the very early production Marshall 100w heads (also known as the JTM 45 100 heads). These also had the JTM 45 plexi faceplate, but with a larger head cab. Of course, these tubes were also often used in the original Marshall Bluesbreaker combo's. These tubes can also be seen with the Gold Lion logo on them. 

Good old General Electric in its British version. Currently on Ebay, Genalex Gold Lion KT66, 77 and 88 are some of the most expensive tubes to bid on. I recently saw a pair of NOS 88's (the British version of an American 6550) in their original box go for $322. Wow!


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## dook

dook said:


> I don't know about back in the day, but the Marshall Hendrix reissue amp has KT66s in it and the Marshall amp Page used at the O2 reunion has KT66s in it.



replying to myself, but I wanted to clarify. I only just discovered that the amp Page used at the O2 reunion was in fact a super 100JH (i.e Hendrix reissue).


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## Goshawk

I had NOS Mullard EL34s in my '89 JTM 45 RI
and replaced them with NOS Genelex Gold Monarch KT66s.
I prefer the KT66s by far. The clean sound is fuller and more hollow
or three dimensional than the EL34s. When pushed the EL34s are raunchier and 
more distorted. The KT66s have a clearer more singing sustain and are more touch sensitive 
to pick and fretting attack which is great but you have to play more precise and mute unplayed strings more
or your mistakes will be heard. I would say the EL34s sound more like Billy Gibbon's sound and the KT66s are more like Dickey Betts.


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