Yes,they can take the KT66s and here is why.

Jim and Walter.
Notice that the Mc240 like other Mac amps and other vintage amps of the day have octal sockets on the front that power the Mac C8 mono preamps in the case of the Mac that each have three 12AX7s,a total six tubes that the amp would have to power along with its existing tube lineup in the amp.The 12AX7s in the preamp are running at 6.3vac where each tube draws 3/10 of an amp filament current,so you at least have 1.8 extra amps of filament current as long as you don't plug the C8 preamps into the amp.

Always remember tho,and it is very easy to test whether or not you have enough juice to drive tubes with higher filament current..Simply plug the prospective tubes in and take a reading between pins 2 and 7 of the octal socket..It if reads between 6.2 and 6.4vac,you are not hurting your power trafo one iota because you are well within tolerance of the ratings.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

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Follow Ups Full Thread

Topic - Mac 240 with GL reissue KT66 . What is your take....... - bouncy ball 13:06:02 04/11/14 (9)

RE: Mac 240 with GL reissue KT66 . What is your take....... - Jim McShane 16:49:37 04/11/14 (8)

Yes,they can take the KT66s and here is why. - Michael Samra 19:07:17 04/11/14 (4)

RE: Yes,they can take the KT66s and here is why. - Jim McShane 09:35:10 04/12/14 (1)

RE: Yes,they can take the KT66s and here is why. - catama 10:48:57 04/17/14 (0)

Mike, what do you bias these new KT-66's to? - FenderLover 02:01:31 04/12/14 (1)

RE: Mike, what do you bias these new KT-66's to? - Michael Samra 03:06:55 04/12/14 (0)

Thanks Jim. That's my concern but I had read some stated no issue by doing so. (nt) - bouncy ball 17:09:06 04/11/14 (2)

yes, they are reissue. thanks Mike, also when you have time - bouncy ball 19:32:38 04/11/14 (0)

Are those reissues something or what? - Michael Samra 19:17:42 04/11/14 (0)

Follow Ups

Yes,they can take the KT66s and here is why. - Michael Samra 19:07:17 04/11/14 (4)

RE: Yes,they can take the KT66s and here is why. - Jim McShane 09:35:10 04/12/14 (1)

RE: Yes,they can take the KT66s and here is why. - catama 10:48:57 04/17/14 (0)

Mike, what do you bias these new KT-66's to? - FenderLover 02:01:31 04/12/14 (1)

RE: Mike, what do you bias these new KT-66's to? - Michael Samra 03:06:55 04/12/14 (0)

Yes,they can take the KT66s and here is why.

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