Can KT-88 tubes be used in marshalls

dad99_2000 · Post by **dad99_2000** » Wed Apr 14, 2004 12:07 pm

I am new to the forum I am very happy that I found this place. I came upon looking for ways to improve my 1959 slp marshall RI. I bought a p2p board tubes and a new output transformer should be getting it soon.

Any way my question is can KT-88 be used in the marshall in place of
el-34?

I am trying to get the Jimmy Page song remains the same {aren't we all}

Country Boy Shane · Post by **Country Boy Shane** » Wed Apr 14, 2004 12:56 pm

Hell yes they can. I can't remember whether BlueFuzzGuitar put KT66's in his SuperLead or KT88's. It is possible though. Just set the bias and you'll be set in a jiffy.

bluefuzzguitar · Post by **bluefuzzguitar** » Sun Apr 18, 2004 6:36 pm

Mine has KT66's. Until last Saturday they were Sovteks but they were getting worse as the gig wore on: more shrill highs, flubby bass, loads of compression. My guess is it's the tubes. Damn Sovteks! I should of read what they had to say about these tubes on the Plexi Palace forum. Apparently they're just their 6L6WXT in a bigger bottle. I've had those in my Fender Vibrolux and experienced the same problems after a few months. They sound great for a couple of months but then they become weak and fizzy, plus their 'KT66 tubes' are not real KT66's! My amp tech is checking to see if I didn't fry any resitors or tube sockets (don't think so, tho).

I have a replacement quad of Russian GTKT66HP's but I'm reading bad reports on those at this very forum. The Plexi Palace folks seem to like them a lot better. Oh well, I'll use them for as long as they'll last. I'm thinking of putting 5781a's next or even KT88's. We'll see. I'm not as sure as Shane about putting in KT88's as I don't know your PT and OT would be able to handle those. I think it's best to check with George. Care to chime in, George? I'm kinda curious too as it's possible I might load my Super Bass with 88's too at some point. If you do go for the 88's buy the JJ's. I have them in one of my Super Reverbs and they sound awesome.

Mike

bluefuzzguitar · Post by **bluefuzzguitar** » Mon Apr 19, 2004 7:40 pm

Well, George, CAN KT88's be used as drop-in replacements?

Mike

Post by **VelvetGeorge** » Mon Apr 19, 2004 9:54 pm

"drop in replacements" - no. Installed and biased properly, yes.

The power supply will provide as much current as it able to by design. If the KT88's require more still, the voltage will drop further yet.

There is a dynamic between the power supply and the output tubes. A good design uses a PS that can supply more current than the tubes will require. The tubes themselves limit the amount of current drawn from the PS.

Fortunately, PT in Marshalls are up to the task of supplying current to KT-88's.

Personally, I find the GT KT-66's to be fine tubes. Not exactly GEC KT66's, but robust enough that I offer them in my JTM45 retrograde kit.

George