Time for a retube...

[Rumblefisher]

...of my Matchless Thunderchief. I don't know a whole lot about this, so a tech will be performing all the work. However, I will buy the tubes before they are installed, so I'd like some TB opinon.

The TC is a 200 watt all tube Class A head, and I believe it originally came with KT100s. When I bought it, it had 4 KT88s, 2 of them blown (By the way, if I've used it with the blown tubes, have I damaged the amp?...haven't used it with any high volume at all).

Should I go with KT88s? Can I use EL34s? 6CA7s? I've done the search and reading so I know the basic differences, but don't know which tube type would be best for this head. I definitely don't want to tax the amp and risk killing it.
Thanks to all for their help, I desperately need it!

 

[Rumblefisher]

Sorry to bump so quickly, I just wanted to add that there's an eBay auction ending soon for some really nice (supposedly) KT88s...if that's the way to go with this head then I'd like to bid for them. Thanks TB, I know some expert(s) will come through!

 

[Jim C]

I would suggest using whatever tube type the manufacturer recommends and then pick a brand that you can afford (that also gets decent reviews).

 

[RoadRanger]

It appears that only the KT88's will power it up to 200 watts - EL34/6CA7's are only good for half that.

 

[Rumblefisher]

It appears that only the KT88's will power it up to 200 watts - EL34/6CA7's are only good for half that.

Sounds good...that's the route to go then. Thanks!

 

[Barkley]

Also thinking of retubing my SVT-CL's 6550s. Any affordable replacements that are warmer while keeping the clarity?

 

[RoadRanger]

Also thinking of retubing my SVT-CL's 6550s. Any affordable replacements that are warmer while keeping the clarity?

That would be the KT88's - but I'm not 100% sure if they require any rebiasing? I think they can just be plugged right in but I'm sure someone will be along shortly to confirm that .

 

[Barkley]

Thank you, Mr Kill! I'll look into it right now. I'll let you know about the biasing if I find out more!

 

[Barkley]

Thank you, Mr Kill! I'll look into it right now. I'll let you know about the biasing if I find out more!

Turns out biasing has to be done.

 

[BassmanPaul]

Turns out biasing has to be done.

Indeed it does. Every time you replace output tubes the bias should be checked and reset as required.

 

[Barkley]

Indeed it does. Every time you replace output tubes the bias should be checked and reset as required.

Would you also say that KT88's would make my SVT-CL sound better vs having 6550's in there?

 

[Rumblefisher]

According to some experts on tb, tubes kind of sound the way they look. The thin, tall 6550s have more top end and can be "harsher" whereas the fatter KT88s have more of a bottom end.

 

[Barkley]

According to some experts on tb, tubes kind of sound the way they look. The thin, tall 6550s have more top end and can be "harsher" whereas the fatter KT88s have more of a bottom end.

Hmmm... That makes things easier. Now to find tubes that are 11 feet tall and 15 feet wide!

 

[RoadRanger]

Hmmm... That makes things easier. Now to find tubes that are 11 feet tall and 15 feet wide!

I actually saw a picture of one like that - it was in a 2 megawatt VLF transmitter used to contact submarines circa 1960 .

 

[ranjam]

What kind of tech doesn't make an extra dollar selling tubes? He would know the amp and measure the B+ in that amplifier. KT88's or 6550's can take more B+, and have the most clean headroom. EL34's have much less headroom, and cannot take as much plate voltage. But the 'tech' should also know which tube he has better luck with in certain situations. And this is also based on what you want the amplifier to sound like.

 

[johnk_10]

i have KT100's (valve arts) in two of my amps (sound city bass 150 and my Sunn 2000S) and they are my current favorite of all of the 6550A/KT88 output tubes by far. and i dare say that i like them as much as my NOS GE 6550A's that i have in my '69 SVT.

here's where i got mine:

Invalid Link Removed

 

[Barkley]

i have KT100's (valve arts) in two of my amps (sound city bass 150 and my Sunn 2000S) and they are my current favorite of all of the 6550A/KT88 output tubes by far. and i dare say that i like them as much as my NOS GE 6550A's that i have in my '69 SVT.

here's where i got mine:

Invalid Link Removed

Thank you so much for the help. I'll check out that link tonight. Where did you get your NOS GE 6550 if you don't mind me asking?

 

[johnk_10]

Thank you so much for the help. I'll check out that link tonight. Where did you get your NOS GE 6550 if you don't mind me asking?

i've been a tech since '73 and owned my own shop from 85-'05 so i stashed 48 of them away back in 1978 knowing that US tube companies (like GE) would soon stop making them. i'm down to my last dozen of them now.

 

[Barkley]

i've been a tech since '73 and owned my own shop from 85-'05 so i stashed 48 of them away back in 1978 knowing that US tube companies (like GE) would soon stop making them. i'm down to my last dozen of them now.

So no chance of getting them from you, huh? Hahaha. I'm gonna keep searching locally for now.