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EL34 vs 6550 vs KT88

MarshallLaw

MarshallLaw

Feb 21, 2010
508
578
thieveland ohio
#1
can you guys tell me what the tonal differences between these tubes are?

from what ive been told, EL34s are more mid-rangey and rounded, 6550s are bright and glassy, and KT88s are bassy and boomy.

i dont know if any of that is true.

i know SVTs, and most tube bass amps, come with 6550s.
 
#2
I think that is probably a gross generalization. The biggest difference is the power handling of the tubes. Some amp builders may prefer the response of certain tubes or find that it works better with their respective designs but I wouldn't expect one amp to be more "mid-rangey" just because it uses EL34's in comparison to an amp using 6550s...

6550's are more common in bass I think because of the higher power demands compared to guitar amps which predominantly use EL34's... you need more EL34's to get to 300watts for example which means more tubes to bias/go wrong/replace etc.

KT88's are also quite common in bass and I believe are interchangeable with 6550s in an amp (EL34's use a smaller mounting I think?) and probably give a slight increase in power but I'm not quite sure what other benefits/changes they would make?

some guitar amps are designed with two power tube sections so you can switch between using EL34's or 6550s
 
#3
its hard to make generalizations about the sound of any tube, especially different tube types, since most manufacturer's EL34's (6550's & KT88's) sound different than other's EL34's (6550's & KT88's).

i've been around tube amps along time, and i have always said, believe it or not, from my perpective, a tube kinda sounds like it looks. for example, an EL34 is generally more midrangy (taller and thinner) than a 6550 (rounder and fatter with a brighter, glassier top end). an EL84 sounds thinner and breaks up earlier than a 6V6, and a 6L6 sounds rounder, but a little smaller than an EL34. now this is just a rough guideline and doesn't always hold true, but it does most of the time.

its easy to determine the difference between an EL34 and a 6550, since i've converted alot of people's old US export Marshalls to the british EL34 versions. so with the same exact amp, you could immediately hear the difference in the midrange.

another example is that a NOS 6CA7 is the US equivalent tube to an EL34, however since the 6CA7 is shaped like a large bottle 6L6GC, it sounds more like a strong 6L6 (rounder and fuller) than does the average EL34.

so in summary, i would say that an EL34 is more mid to midbass heavy with earlier breakup than a 6550. and KT88's are very close to a 6550 but sometimes can have a little fuller low end. again, it also depends on the particular brand and design that you're comparing.
 
#5
John, looking at the pics from the links you posted yesteday (the Valve Art KT100 and Winged 6550C), the Valve Art are fatter and stubbier looking - you mentioned that the those two are similar in sound, with a slight preference towards the KT100 - What was in your opinion the characteristic that in your opinion made it better suitited for the SVT (other than the quiet operation of the tube itself)?

I understand it's all subjective, but just a general idea would be great. I'll probably be placing an order today.
 
#6
I have to agree with JohnK assessments on the current tubes being different .... I've just recently retubed a Fender Bassman 300 power section ..... the stock tubes were Fender branded GT/Sovetk 6550's, replaced then with winged C's 6550's ... the tonal difference is very different ... I also have a Peavey VB-2 and that is loaded with JJ's EL-34's and that amp sounds very different from the Fender , In my view, the 6550's have a different crunch than the EL-34's when pushed ... the 6550's are a bit thicker/heavier and the EL-34's have more mid's naturally ...but it can get deep when needed/wanted ... it all boils down to what sounds good to your ears ... both are good tubes for bass amps ... I too have grown up playing tube bass amps and my experience is with the v4-b ( 7027 tubes ) and the Traynor YBA3 ( EL-34 Tubes ) still have the V4 , don't have the YBA3, traded it for a YBA3A, and that sounds completely different .... tubes are very subjective topic and a well designed amp will get good sounds/tones from the tubes that they are designed/set up with ...IMHO
 
#7
The "sound" of tubes is often associated with the amps they are commonly associated with.

An EL34 has just as much low end as a 6L6, 6550, or KT88.

An EL34 has higher gain potential (mu) than a 6L6, 6550, or KT88, so an EL34 can be more harmonically rich than a 6550 or 6L6 at a given drive level. Those extra harmonics fill up the mid range. The human ear hears mids more easily, so you get the illusion of more mids (the lows are still there). But...if you drive the tube less, you don't get as many harmonic overtones that fill up the mids, which makes the low end stand out more. It's all in the amp design.

A 6CA7 is a different type of tube than an EL34. The 6CA7, 6L6, 6550, and KT88 are beam tetrodes, while an EL34 is a pentode. This is probably why the EL34 stands out from the group.

This is the "my opinion part":

I've converted EL34 designs to 6550, and I've converted 6550 designs to EL34. I've gone back and forth from EL34s and 6l6s. I always come back to the EL34. In my opinion they sounds more "tubey". The 6550 and KT88 are certainly cleaner tubes because they add less harmonics. They are certainly more hi-fi. They are "anti-tubes". They bridge the gap between the tube era and the solid state era.
 
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#9
Groover said:
John, looking at the pics from the links you posted yesteday (the Valve Art KT100 and Winged 6550C), the Valve Art are fatter and stubbier looking - you mentioned that the those two are similar in sound, with a slight preference towards the KT100 - What was in your opinion the characteristic that in your opinion made it better suitited for the SVT.
Click to expand...

for me, the KT100's feel like they are a little fuller/richer sounding than the 6550's to me. they don't seem to distort as quickly and have just a bit less mids.
 
#12
that's definitely true, but i'm referring to comparing different tubes in the same amp.

i've rolled EL34's, 6550's and 6CA7's in quite a few Marshall 100 watt JCM's and JMP's, and the results have always been the same.

IMO,
EL34's= fuller midrange, earlier breakup, very smooth.
6CA7's= Rounder low end than an EL34, with more highs
6550's= extended low end frequency response, more ouput, w/glassier highs

as always your taste and mileage may vary.
 
#14
IME they're more like a 6550, with a little less mid bass and a little more low end. they stay cleaner longer too. i just really like the Valve Art's sound, and build quality. i think that they actually sound better than my Gold Lion KT88 Reissues (which are also an excellent tube). the VA's are the closest sounding reissue that i've tried to an original NOS Genalex KT88, which are now ridiculously expensive. their bottle shape is more like the original Genalex than the Gold Lions which are supposed to be a reissue of them.
 

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