KT120 to a vintage MC275? Anyone?

[Brice]

Hi guys,

Has anyone tried the KT120 tube on a vintage MC275 instead of the KT88?

I know the heater current is a bit higher but I believe the PT can take that.
I am more concern at the biasing level.

Any thoughts?

Thanks
Brice.

 

[x3workshop]

Try it. What do you have to lose, Brice.

 

[4-2-7]

Ron always says not to do this at all.

 

[Lesterbest]

It's your amp, your output tubes & your money. Why not roll the dice? The KT120s might not last as long.

 

[Mike Gibson]

For what little you might conceivably gain, I think the potential for less is so much greater. I tried Gold Lion reissue KT-88's in my original and I'm done farting around with output tubes. I have tried Penta Labs, Tung-Sol 6550 reissues, EH, and had original Gold Lions. The Tung-Sol reissues come in second to the GL reissues. The original Gold Lions aren't worth the expense to me for the minimal gain you may receive in SQ.

 

[chuckworkb]

I wouldn't do it. It wasn't built for those tubes. I will also be probably one of the few that vote no for the Gold Lion reissue tubes. I had two go bad and cost me $$$'s to fix the amp, and buy new tubes.

 

[sKiZo]

Can't say about the 250, but they work well in my Latino ST120.

I used to bias them up to 60mV each for a bit more punch, but have dialed that back to 55mV to extend tube life. That really shouldn't be an issue as a KT88 amp won't drive them that hard. Don't expect to get the full rated power on an amp that isn't built specifically for them, but I get a good 10% boost on output over the KT88's.

(I know of folk who've pushed them to 75mV each, but with no appreciable change.)

Excellent sounding tube as well ... real strong bottom, and clear with exceptional detail all the way up as well.

I suppose the acid test would be if the B+ stays within range driving them, so make sure you meter that before committing to the tubes. If that's good, and you're not getting excessive heating on the iron, I'd think you should be fine.

DO keep clearances in mind, and make sure the big uns got room to breathe, eh.

 

[CohibaJoe]

Can't say about the 250, but they work well in my Latino ST120.

I used to bias them up to 60mV each for a bit more punch, but have dialed that back to 55mV to extend tube life. That really shouldn't be an issue as a KT88 amp won't drive them that hard. Don't expect to get the full rated power on an amp that isn't built specifically for them, but I get a good 10% boost on output over the KT88's.

(I know of folk who've pushed them to 75mV each, but with no appreciable change.)

Excellent sounding tube as well ... real strong bottom, and clear with exceptional detail all the way up as well.

I suppose the acid test would be if the B+ stays within range driving them, so make sure you meter that before committing to the tubes. If that's good, and you're not getting excessive heating on the iron, I'd think you should be fine.

DO keep clearances in mind, and make sure the big uns got room to breathe, eh.

Very Nice "sKiZo".....Well KT-150's and 6L6G, 6L6GC, 7581A, EL34, EL37, 6550, KT66, KT77, KT88, KT90, KT120 work in the PrimaLuna....

 

[sKiZo]

Yup ... but a quad of KT150's is a good chunk of change for another 10-12 wpc over what the KT120 can give you. I've got new production KT88's that cost more than the KT120's.

Then again, double the price might actually be worth it if you see increased lifetime for the tubes ... A KT150 should be pretty much idling at those levels ...

 

[Mike Gibson]

How about keep it to what the OP asked please. Those amps are nice.

 

[nj pheonix]

I will say Craig (NOS Valves) was saying a while back that you can safely run KT120s in MC60s. I never tried (it seemed he had some experience). Not sure about a 275. Might be worth a phone call to Mcintosh. Worst that can happen is that they say no.

 

[nj pheonix]

Hey Brice,
Are you looking for more power, tube life, sonics? Why the idea?

 

[Mamrak1]

I wouldn't change to KT120s willy nilly without checking first with McIntosh. I seem to recall reading somewhere that such a change would damage the MC275 amp.

 

[Brice]

Thanks guys for your reply.

Andy, tube longevity and sonic quality is what I was thinking about.

I experienced a big change in sonic quality from a EL34 to a KT88, and even bigger jump with the KT120. All on the same amp.
So I was naturally thinking that if the MC275 could take the KT120, it would be something amazing.

I understand the reasons not to do it from a subjective view, but it would be nice to have facts on why it would not be possible from the experts.

 

[KentTeffeteller]

McIntosh tube amps don't stress the tubes. Stick to what is recommended. It was for a reason!

 

[4-2-7]

I understand the reasons not to do it from a subjective view, but it would be nice to have facts on why it would not be possible from the experts.

Well when @ron-c gets here or call mac, but I distinctly remember Ron saying "Do not use KT150s in the 275 as it will damage it and was not designed for those tubes".

 

[sKiZo]

Thought we wernt talkin bout KT150's anymore? ;-}

 

[4-2-7]

Thought we wernt talkin bout KT150's anymore? ;-}

LOL, I need you to build me a sweet looking amp

 

[SilverTpt999]

I've had anecdotal reports that the MC60s can handle KT90s/KT120s because the power supply was overbuilt to supply the C8 pre as well as the amp. Haven't done this myself, but have been curious.to experiment with my pair of MC60s. They sound far too good to justify it at the moment, and I have enough good KT88s that it isn't an issue.

The 275s were not overbuilt in this way; they are tailored directly to the stated tubes. I wouldn't switch from the KT88/6550 series here, Brice.