JTM45/100 Alternate tubes?

[fusionbear]

Hello guys, wondering if anyone has substituted 2-KT88's for the 4-KT66's on a JTM45/100. The reason I ask is that I am concerned that modern tubes can't handle the 560V on the plates for very long. What were the tone results?

I am thinking of building one of these, but with the KT88's. Would like to hear your experiences before I proceed...

[Structo]

Well at first glance the heater current is 330ma greater per tube with the KT88.

The KT66 is a 30w tube and the KT88 tube is 35w but can handle the higher plate and screen voltage.

Somebody else that has actual experience with these tubes will come along but I would just look at the tube data specs and see if it will fly.

[fusionbear]

Well at first glance the heater current is 330ma greater per tube with the KT88.

The KT66 is a 30w tube and the KT88 tube is 35w but can handle the higher plate and screen voltage.

Somebody else that has actual experience with these tubes will come along but I would just look at the tube data specs and see if it will fly.

The specs I saw showed that a KT66 draws 1.3A per tube for a grand total of 5.2A for a quad. KT88's draw 1.6 per tube for a grand total of 3.2A for a pair, so I am pretty sure that is no issue. I am more concerned whether or not the tone and/or feel are the same or close to the same.

[LeftyStrat]

I can't say for sure, but I would guess that KT88's would offer more chime than KT66's. KT66's tend to be a more creamier distortion.

The interesting thing is that you could build the amp to handle both. Some versions of the JTM100 used a 4k output transformer, which would work for a pair of KT88's.

So you could run a quad of KT66, or a pair of KT88, with just a rebias.

[fusionbear]

I'm more interested in clean to "hairy" clean tones. This sounds just up my alley.

[Roe]

a quad of 88s work well in a 45/100 although I prefer the sound of 66s. watch the screen voltage with 66s

[fusionbear]

a quad of 88s work well in a 45/100 although I prefer the sound of 66s. watch the screen voltage with 66s

Holy smokes! A quad of KT88's??? That is way to much power for me. I am gathering parts as we speak. Hopefully in a couple weeks I'll have something to share with you all...

[Roe]

a quad of 88s work well in a 45/100 although I prefer the sound of 66s. watch the screen voltage with 66s

Holy smokes! A quad of KT88's??? That is way to much power for me. I am gathering parts as we speak. Hopefully in a couple weeks I'll have something to share with you all...

it doesn't produce that much power with a quad of 88s really (because of the transformers)

[Reeltarded]

Unless you have them CRANKED and juice from Hell, KT88 isn't just chimey, it's a stiff assed glass billy club.

[renshen1957]

I'm more interested in clean to "hairy" clean tones. This sounds just up my alley.

Hi,

I have had good experience with KT77, JJs. As not everyone likes JJs, there is the RI Gold Lion KT77. I haven't tried these out although I have a pair. The JJs were reverse engineered from an original Genelex tube.

Best REgards,

Steve

[Roe]

remember, a 45/100 has 559v on the screens. not many tubes that handle that

[fusionbear]

A little progress:

[IMG768]http://i169.photobucket.com/albums/u223 ... G_1361.jpg[/img]

[IMG768]http://i169.photobucket.com/albums/u223 ... G_1362.jpg[/img]

[Firestorm]

Nice. Where did you find the mustards?

[fusionbear]

Nice. Where did you find the mustards?

From a friend who got them from someone back East, I think he said Merren, but I am not 100%

[xtian]

Ok, forget I asked you on that other forum. And you already answered the mustard question. So just say which trannies?

Cheers.