6550 valves

[jagermike66]

Hi everyone,

I want to try out some new tubes in my amp and was recommended these for the style of music i play (Modern metal....but nothing too extreme, no scooped mids or anything). Anyone had experience with the 6550s? How do they differ from EL34s apart from power handling? I read Zakk wylde uses them in his 800s and im a big fan of his.

Also I was told that i may need to replace some components in my amp in order to run the 6550s....i have never heard of needing to do this before, Iv always just set the bias properly and its always worked fine (a few years ago i tried some 6L6GCs in my old JCM900).

cheers all!

Mike

[Wildone]

My experience is the 6550 tube has more bottom to their sound. For metal you should try KT88 tubes if your am can use them.

[Dave W]

I am not a tech.

Some amp can go from EL34's to 6L6's with just a bias check.

EL34's, KT77, 6L6, KT66 are capable of about 25 watts max each.

6550,KT88 about 35 watts each.

I read about the difference from the Eurotubes website and other tube sites.

I would not go up toi a 6550 or KT88 without asking a tube store like Eurotubes etc. If they have done this. There are factors like watts, inpedence etc. with the tubes. Going up like that may put an improper load on your traansformers etc.

On the Eurotubes site I see KT88's in Mesa Kits and mixes of tubes, but I think that those sets are measured and picked to match. Like a KT88 measured out/graded at a particular level that will work in a regular 6L6 spot.

Real simple, just call Eurotubes or who ever you like and say what amp you have and what you would kike to do and if they have a grade of a particular tube that you want to try that will work in that application and if they ever did that before.

They have schematics on many amps and have measured and tested many amps that have come thru their store to be retubed etc. They have data and will let you know if it theoretically or in real life has worked before.

-- Wed Jan 12, 2011 8:26 pm --

Reread your post....a few more responses.

KT88 compared to EL34.......generally more low end and balls.........can also improve the clean tone from what I heard, but low end thunder when pushed.

Most I have read said if it runs 6550, then replace with KT88 for improvement.

Is it still the JCM 900 you have.......if so then please consider if you must try different tubes trying KT77's......not 66 not 88, but 77's.

I personally do not care for EL34's. Always replaced with KT77's and prefered the difference. No mods, more low end, better cleans when you want them. To each his own though.

[jagermike66]

Thanks very much for the advise. I am waiting to hear back from a couple of tube places at the moment so will wait and see i suppose. I've read that KT88s are in the same family as 6550s but with more power. I want more balls to my tone but i still want to be able to push the tubes a bit, I dont want crystal clean preamp distortion all way up. With that said im leaning towards 6550s.

Not had any experience with KT77s, are they just a straight swap on most marshalls then? (with bias adjustment obviously). Might have to try them out first if thats the case.

Thanks for replies again, very much appreciated.

Mike

[Dave W]

In reference to the KT77's......
I gathered my info mostly from the Eurotubes website and talking with the staff thre. See other tube sites as well. Look under the tube descriptions.

Generally a KT77 is a direct replacement but not exact replacement for EL34's. There are some differences in specifics, but generaly just a rebias for an amp that came stock with EL34's.

Vague description.......the 77 is something in between an EL34 and a 6L6, thats vague, check out the websites, more details there.

What model amp are you using/planning to retube?

[jagermike66]

Yeah i just got a reply of Ed from Eurotubes, funnily enough he suggested KT77s aswell. These will be going in my MA50H (and yes I know a lot of people hate this amp). Its the one I use in my band at the moment because of its brute power to be quite honest. Everyone always says how bad it sounds but it reminds me of a DSL50 but with more useful controls! Anywho before I open up a big can of worms....

The tone im getting is a bit of a mix up of all the JCMs in my opinion. It has a similar cut though and power of an 800, mixed with tonal aspects of both the 900 and 2000 series. Im currently running EL34Ls which im happy with, but if I can get a better tone for the price of 2 power tubes and a bias adjustment then i might as well experiment. Especially as its quite a cheap amp.

Ed said I need to check if there is actually any physical room for the KT88s/6550 due to their bottle neck shape. Also he warned that my bias adjuster pot may not have enough range to satisfy the amps plate voltage (500ish) and the valves current draw.

Also considering a 6l6 swap so been looking at the 5881s u used to find in jcm900s. Im like a kid in a sweet shop! lol