can you use kt88s in place of 6L6s?

[justinhedrick]

on ebay there is a set of KT88 tubes that are marketed for a peavey VTM 60. those use 6l6s. can you directly interchange those?

[Hemisaurus]

Not without a rebias at least, depending on the range of the controls it may need mod'd more.

It's late, my brains asleep, I don't recall what the plate to plate load recommendations are.

Pasted from eurotubes.com

The JJ KT66 can be used in a variety of amps that uses 6L6's if there is room! The JJ KT66's and the JJ KT88's are the same diameter as the original GEC KT66's and KT88's which is just under 2 1/8" so you need an absolute bare minimum of 2 1/4" measured from the centerline of one socket to the centerline of the next socket for them to physically fit in an amp. Amps like the Peavey XXX, JSX and 5150's/6505's cannot use them. The only exception to this is if you choose to run one of our Integrated quads using two KT66's or KT88's in the outside two sockets and two 6L6GC's in the inside two sockets and this only works in the 5150 or 6505 heads.

Both the KT66's and KT88's use the large diameter bases so if you have an amp that uses the "bear trap" style tube retainers that pinch the base of the tubes then these will either need to be flattened out, removed or replaced with the "spring and cap" style tube retainers.

[justinhedrick]

so . . . someone should tell this guy:

http://cgi.ebay.com/Peavey-VTM-60-Premium-Tube-Set-KT88-/380253322385?pt=LH_DefaultDomain_0&hash=item5888dd3c91

[Hemisaurus]

What's the B+ on a VTM, anyone?

[VOLVO)))]

I thought the vtm60 was fixed bias? No adjustment, just jam new tubes in.

[justinhedrick]

I thought the vtm60 was fixed bias? No adjustment, just jam new tubes in.

yes, but you can fuck them up by thinking that way. you are only supposed to use "5881/6L6wxt (is that the right name)". i don't think you can "jam" in a set of kt88s and go . . . for long!

[Hemisaurus]

Playing the numbers game can be fun. Apropos of nada, you should be able to jam a pair of KT-88's into a Marshall chassis of quad EL-34's and double your load impedance. Haven't tried it, would probably need bias well tweaked.

Look at the datasheets for the 6L6 vs. KT-88, at 450 plate volts, and a 5.6Kohm load, you're pulling 55W out of a 6L6 with a -37V bias

For a KT-88  you pull nearer 70W and need a -59V bias. Or if you look at a different datasheet it says 50W @ 500V ultra-linear and -52V bias

I wouldn't do it on someone elses amp, I might try it if I owned an amp and wanted to experiment, on the theory if I blow my own shit up, I can only blame me.

The KT-88 is designed to start operating at plate voltages above where the 6L6 stops, 6L6-GC tops out at 500V plate, the KT-88 seems to start around 450V from the examples on the datasheet, yes it will work lower, but it's designed to work higher.

Something I'd like to try, for those who look at Dave Chambers amp porn, is his 200W from a quad of EL-34's, he's right, it's there on the Mullard datasheets (and some of the others), 100W from a pair at 800V plate with an 11KOhm plate impedance, so I need to find a 200W transformer with a 5.5KOhm primary impedance or something of the like.