EL34 compared to 6550

[steve]

Does anyone know the difference in tone going from el34's to 6550 power amp valves. Cheers.

[indysmith]

can yu even plug them in the same socket? or yu need yellow jackets?

[Bainzy]

You can plug them in the same sockets, and you could probably run them without modding anything. When Marshall switched over to 6550's, they changed the 220k bias splitter resistors in the power amp to 150k's. So you might want to do that too if you're switching Steve.

[Twinfan]

You'll need to re-bias though - you can't just swap them over and play...

[hunter]

You were asking for tonal differences. In my univalve where I can swap tubes like I want, 6550/KT88 have more clarity and punch, pretty similar to 6L6/5881 but a little more body, they can break up in a quite rude way and you need to be easy on treble/presence when cranking the amp, whereas EL34s are smoother in general, but with scratchy/crunchy upper mids that make the tone cut through well.

I would say 6550 are generally better for cleans and Recto / Soldano kinda sound, whereas EL34s are better for 60s to 80s style rock.

In my opinion the ideal is two guitars played with both styles of sounds, that's why I like playing parts twice for recording and swapping tubes to fill a different frequency range with each take.

[steve]

Cheers guys, i have a late 90's trace elliot speed twin and it takes el34,6550 and 6l6. I was considering chucking a set in a seeing what they do.

[TwilightOdyssey]

If your amp can take EL34s, then you should also try KT77s and 6CA7s. These valves are a sonic hybrid between big bottles (like the KT88) and the EL34, while still being beam tetrodes. 6550s have a really big, full sound, not as midrange peaky as an EL34, but less upper frequency detail. (What you would call 'air', or 11kHz or above) EL34s, however, can sound really 'beamy', which is why I love the 6CA7 -- it has the midrange and upper midrange clarity of the EL34, as well as the robust bottom end of a KT88. I have a set of KT77s at home, but haven't had time to try them yet. (Too busy messing with the Holy Diver in my M1)

It's all an organic mix, depending on guitar, playing style, and overall tone. Try them all!!

[Searcher]

I have KT77s in my amp right now (also a Speed Twin).  I changed the EL34s that were in it to 6L6s at the recommendation of Bob at Eurotubes, but I didn't really like the sound.  I found it more balanced, but less full, and I preferred the fatter sound the EL34s gave.

Then I got the KT77s and I'd say that they're right smack in the middle, sonically.  I don't mind them.  They're good for cleans--better than the EL34s--but I think I still like EL34s a little better overall, especially for lead guitar playing and riffing. Of course, that's my subjective opinion.  And the original tubes were nice tubes, but not the same brand as the JJs, so that might interfere with the comparison too.

[HTH AMPS]

6550s require more bias voltage than EL34s so you will need to make sure your bias circuit will cope with that (most can't and require modification).

tonally 6550s will give you more clean headroom, lower/deeper bass & more highs while having more high-mid focus rather than the low-mids of EL34s.

I personally prefer 6550s in high-gain amps & also prefer an ECC81 phase inverter valve.

 :twisted:

[fps_dean]

You'll need to re-bias though - you can't just swap them over and play...

Actually going from a EL34 to a 6550 you wont NEED to rebias, but you will definitely want to so it sounds good!

[fps_dean]

If your amp can take EL34s, then you should also try KT77s and 6CA7s.

There are also KT66s which will be warmer and KT88s which will be cleaner, both of which are acceptable alternatives as well.  KT88s are military versions of the 6550s and tend to take more of a beating and at the same time be warmer.

[Eric]

The 6CA7s are the tubes favored by Eddie Van Halen in his old Marshall, from what I have heard. If that's the case another good reason to try them.

Though I will give this disclaimer. I'm not positive Eddie ever knows what the hell he is using or has used. He looks like a homeless person lately.

Maybe Ben's endorsement of them should be enough now that I think about it.

[HTH AMPS]

Actually going from a EL34 to a 6550 you wont NEED to rebias, but you will definitely want to so it sounds good!

well you don't NEED to rebias but the bias range that EL34s operate within is FAR too hot for 6550s so they will redplate and you'll ruin a new set of 6550s.  if that sounds like fun to you then go ahead.  checkout the datasheets, 6550s require considerably more bias voltage than EL34s

[fps_dean]

Actually going from a EL34 to a 6550 you wont NEED to rebias, but you will definitely want to so it sounds good!

well you don't NEED to rebias but the bias range that EL34s operate within is FAR too hot for 6550s so they will redplate and you'll ruin a new set of 6550s.  if that sounds like fun to you then go ahead.  checkout the datasheets, 6550s require considerably more bias voltage than EL34s

Wait.  You first said that EL34s require more bias voltage than 6550s and then that 6550s require more than EL34s.  Which is it?

It's been my understanding that just like 6L6s, 6550s require more voltage so at the lower EL34 voltages they will just sound too cold but not to any damage.

[HTH AMPS]

Wait. You first said that EL34s require more bias voltage than 6550s and then that 6550s require more than EL34s. Which is it?

no I didn't, read my post again - both times I said that 6550s require more bias voltage than EL34s.

It's been my understanding that just like 6L6s, 6550s require more voltage so at the lower EL34 voltages they will just sound too cold but not to any damage.

If you're very lucky, then maybe.  In most cases I think it's safe to say that putting 6550s in an amp setup for EL34s will result in the 6550s being over-dissipated.

 :twisted: