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6550/KT88 valve choice?


danbowskill
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My ampeg cl has a naff power tube so i'm going to pop in a new sextet.

i'm on a budget so it's toss up between these..........

[b] [size=4]Electro Harmonix 6550[/size][/b]


[b] [size=4]JJ 6550[/size][/b]


[b] [size=4]Tung-Sol 6550[/size][/b]


[b] [size=4]Sovtek 6550WE[/size][/b]


[b] [size=4]Sovtek KT88[/size][/b]


[b] [size=4]JJ KT88[/size][/b]

I have read up on the different kind of sounds each produce,but my main focus is reliability above sound.
any input/experience with these would be a great help :-)

(this is my first tube change)

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I use the EH6550, good solid sound to my ear, how you set the bias (HOT OR COLD) will change the sound so worth spending some time with your tech during setup. 6550s are known for big power with little distortion. But remember distortion is what gives your amp caricter so an expensive set of hifi tubes is just a waste of hard earned wonga.

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Reliability (longevity..?) will depend to a great extent on the biasing. If too 'hot', they'll 'bend' a tad easier, but will burn out under hard, frequent, use. Biased 'cold', they'll not bend easily (or, for KT88s, at all...) and will last decades. We use a Hiwatt DR205, 4 x KT88, set up as is a PA, and so 'cold-biased' or 'clean'. The same valves for 30 years, and I'm not looking to change 'em in my lifetime. 6550 will last, too, but you won't get the 'growl' for which they're best known.
Your choice is determined by the 'bend' you want. If you want to hear the valves pushed, I'd say 6550's, and be prepared to change every few years. If you want clean headroom to the sky, a set of KT88's biased 'cold' and forget about them; they'll outlast you.
Just my tuppence-worth.

Edited by Dad3353
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Cheers guys.
I play dropped C with gain in the middle ( not to clean not to dirty). I was kind of leaning towards the tung sol.... £135? there coming up £166 on watfords, £144 hot rox.
Ehx kt88s is what is in at the moment.
So I guess super clean and hi Fi is not what I'm after.

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[quote name='danbowskill' timestamp='1412024779' post='2565058']
Cheers guys.
I play dropped C with gain in the middle ( not to clean not to dirty). I was kind of leaning towards the tung sol.... £135? there coming up £166 on watfords, £144 hot rox.
Ehx kt88s is what is in at the moment.
So I guess super clean and hi Fi is not what I'm after.
[/quote]

I'd say 6550's biased 'warm' to 'hot', and budget for a set every 1-5 years, depending on hours playing hard.

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[quote name='danbowskill' timestamp='1412025185' post='2565066']
Isn't my amp self biasing(ie me).... Then running hot or cold not be an issue?
[/quote]

Here's a link to the manual pdf...

[url="http://www.ampeg.com/pdf/svtcl_om.pdf"]Ampeg CL...[/url]

See Page 9; biasing is nicely explained.

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I have no experience of the SVT however I have used plenty of 6550 / KT88 types in various other amplifiers..

The big Ashton has 6 x KT88s of the EHX flavour. This amp doesn't really distort in that grindy / gritty kind of way but I can best aliken it to a Fender 'clean' on steriods with plenty of soft compression when pushed. Big clean valve in this application. No failures in 3 years service.

I have used the Tung-Sol 6550 (reissue) in both my custom 60 watt and previously in a Trace Elliot V4. This is a great valve -my fave 6550 type- having a pronounced low-mid hump when clean and a smooth transition into really angry territory. Lovely valve. The pair in my 60 watter is two of the original four I bought for my old V4 about ten years ago. No failures. Long Time Fred has a set of these in his V4 currently.

Shuguang KT88 - 98: I used these in the V4 and a Hiwatt 200. A very glassy clean type valve with a big bottom and huge warmth. It's overload characteristics are softer than that of the Tung-Sol but it also offers a little more clean headroom and more of that 'clean compressed' thing going on. I'd happily use these again, usually cheap too. I had one vacuum failure in a Ruby Tubes branded example but I think this is an isolated incident.

The little Trace TwinValve has a pair of PM 6550s which have worked great since I had the amp. I understand these amps were biased quite cool (fixed bias) out of the factory. These valves seem very clean and allow the amp to play far louder (cleanly too) than it's modest 120w rating suggest. Just a touch of compression when pushed although the power-stage finds the limit of the speaker before so it's harder to identify it's character.

These opinions are based on my experiences so be aware your mileage might vary.. Hope that helps. :D

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Top choice..

[URL=http://s778.photobucket.com/user/VTypeV4/media/BeavisChassis.jpg.html][IMG]http://i778.photobucket.com/albums/yy70/VTypeV4/BeavisChassis.jpg[/IMG][/URL]

Mine worked great in the V4 back in '04 and two of the four have worked well in this amp since ~07..

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