KT-120 New Tube on the Block

[Hemisaurus]

So there's actually a new tube been made, I just noticed Ben Verellen saying he's shipping his MeatSmoke's with this KT120 instead of 6550's, looks like it's been made as a drop in for the KT range, but man it's big. Anyone had a chance to use these yet? $30 more than a pair of 6550's (so an extra $90 to retube your SVT) but should last a heck of a lot longer, if they fit in your amp.



http://www.newsensor.com/releases/KT120TungSol.pdf

150W from a pair, so in theory you could do a 300W quad

[justinhedrick]

could an amp that takes 5881/6l6s be modded to accept KTs? or would it even be worth it?

[Hemisaurus]

Yes they can, all the tubes EL-34/6CA7 6L6/5881 and 6550/KT88 are pin compatible, but sometimes changing the tubes will change the required matching impedance on the other side, for example some of the Weber Amps come with EL-34's and you can get them with KT-66's instead, but your 4/8/16 impedance becomes an 8/16/32 instead. Also the heater current requirements of different tubes vary, so it may place too much strain on your power supply.

Marshall's have had EL34's and 6550's in them, you have to change things like bias and screen resistors etc.

If you would be doing it to get more power, don't, you don't get any more power changing your tube type, you may gain more (or less) headroom (aka clean power), and different frequency responses, but to pull more power would require a change in load impedance and/or plate voltages.

[justinhedrick]

Yes they can, all the tubes EL-34/6CA7 6L6/5881 and 6550/KT88 are pin compatible, but sometimes changing the tubes will change the required matching impedance on the other side, for example some of the Weber Amps come with EL-34's and you can get them with KT-66's instead, but your 4/8/16 impedance becomes an 8/16/32 instead. Also the heater current requirements of different tubes vary, so it may place too much strain on your power supply.

Marshall's have had EL34's and 6550's in them, you have to change things like bias and screen resistors etc.

If you would be doing it to get more power, don't, you don't get any more power changing your tube type, you may gain more (or less) headroom (aka clean power), and different frequency responses, but to pull more power would require a change in load impedance and/or plate voltages.

yeah, i would just be doing it to alter the sound of the amp, not the power rating.

[Hemisaurus]

I think a KT-120 might be overkill to replace a 6L6, a 6550, KT-66 or KT-77 would be enough I'd imagine.

[justinhedrick]

I think a KT-120 might be overkill to replace a 6L6, a 6550, KT-66 or KT-77 would be enough I'd imagine.

any idea what kind of sound difference it could make? i seem to remember thinking that kt tubes sounded "harder". if that makes sense?

[inductorguitars]

I'm a big fan of smaller amp. Better tone IMHO. Just listen to ZZ top's first 3 albums - blackface champ ftw.
Tho it's cool that there are new tubes being made.

[blackkrosses]

A 300w quad would be great for bass amps. Considerably less tubes to replace.

[Hemisaurus]

I think a KT-120 might be overkill to replace a 6L6, a 6550, KT-66 or KT-77 would be enough I'd imagine.

any idea what kind of sound difference it could make? i seem to remember thinking that kt tubes sounded "harder". if that makes sense?

If you're putting it in one of your 50W's, I'd say maybe KT-66's or KT-77's might change the tone, whilst still breaking up. 6550's would probably make it cleaner, and you'd never hit the headroom limit of a KT-88/90/120, though maybe a pair of KT-88's instead of a quad of 6L6's is feasible, but not in a 50W obviously.

How about trying EL-34's instead, depending on the head, unless it's got a crazy plate voltage or something (my old HD-130 had a 725V plate, would eat tubes), the guy on http://eurotubes.com/euro-j.htm has a lot of ideas about swapping tubes, have a look.

[Hemisaurus]

A 300w quad would be great for bass amps. Considerably less tubes to replace.

Yeah but the tubes are $30 a pair more expensive $60 is about the cost of a third pair of 6550's. You couldn't just drop a quad into an SVT and expect it to work properly, though it would make a noise.

Haven't had an SVT on the bench for a while, but from memory, it only has the one set of primary windings, no taps, and the secondarys are only 2 & 4 which doesn't leave much wiggle room. I'm too lazy to math it out, but to pull 300W out of a quad you'd need to reset the bias cold and put a lower load on the output, or step up the plate voltage by monkeying with the primary side of the power transformer (do they have 110 or 100 settings on the Ampegs?) and adding in a larger drop resistor for the voltage feed to the preamp.

Please don't do either of these things yourself without having someone with more time and sleep figure out if it's safe to do first 

[Hemisaurus]

I'm a big fan of smaller amp. Better tone IMHO. Just listen to ZZ top's first 3 albums - blackface champ ftw.
Tho it's cool that there are new tubes being made.

Yeah, but I'm playing bass Erik 

Seriously though, most balls from a tube amp was my old HD-130, I should never have sold it, I've tried the Mesa's, Peavey's, Ampeg's and Traynor, and they just didn't have the balls, they'd run out of puff before they got there.

I'd love to make some Class A's with a traditional preamp though, rather than just a tone/vol say a Class A with a single 6550 or KT-88 rather than a pair of EL-84's or something. I think Bumbox do something like that, just for in the house, once I refurbish this Alamo though.

[blackkrosses]

A 300w quad would be great for bass amps. Considerably less tubes to replace.

Yeah but the tubes are $30 a pair more expensive $60 is about the cost of a third pair of 6550's. You couldn't just drop a quad into an SVT and expect it to work properly, though it would make a noise.

Haven't had an SVT on the bench for a while, but from memory, it only has the one set of primary windings, no taps, and the secondarys are only 2 & 4 which doesn't leave much wiggle room. I'm too lazy to math it out, but to pull 300W out of a quad you'd need to reset the bias cold and put a lower load on the output, or step up the plate voltage by monkeying with the primary side of the power transformer (do they have 110 or 100 settings on the Ampegs?) and adding in a larger drop resistor for the voltage feed to the preamp.

Please don't do either of these things yourself without having someone with more time and sleep figure out if it's safe to do first 

Sorry, should have specified; it would be nice to design an amp around these tubes.

[Hemisaurus]

Something like an OR-200, except @ 300W. Assuming New Sensor keep the tube in production. Seems so far it's only use has been to replace 6550's and KT-88's in amps that can cope with the extra draw of heater current, like I said, I noticed it because Ben Verellen is shoving it in the Meat Smoke, instead of the 6550's he was putting in there, so it's still a 300W amp, just nore headroom, and the tube life should be much, much longer. I think that was New Sensor's main idea, make a tube that can be a more reliable 6550/KT-88.

Who knows what their QA is like, or what the tube life is, if you run these things at the edges of their spec.

[inductorguitars]

I'm a big fan of smaller amp. Better tone IMHO. Just listen to ZZ top's first 3 albums - blackface champ ftw.
Tho it's cool that there are new tubes being made.

Yeah, but I'm playing bass Erik 

<snip> Traynor, and they just didn't have the balls, they'd run out of puff before they got there.

I'd love to make some Class A's with a traditional preamp though, rather than just a tone/vol say a Class A with a single 6550 or KT-88 rather than a pair of EL-84's or something. I think Bumbox do something like that, just for in the house, once I refurbish this Alamo though.

Oh yea. I forgot. 
My brother just got a Traynor TS 25 to play with his bass, he loves it. He also has a G&K 800 forgot which cab.

Yeah a nice class A with a KT-88 would sound cool for recording too.

[Hemisaurus]

You know, after having said a full pre and a Class A, backend, every bass/guitar (except mine) has a tone and a volume knob, you could go the other way and have an amp with no controls, just a jack. Everything is controlled from the instrument, that too would be cool. I think a lot of people would dig that.

Man if I only had limitless transformers and turret boards, and someone to build and drill chassis for me.

If I can pull 60W in Class A from a single KT-120, who makes a 60W Class A output transformer? Hammond, Weber?

[inductorguitars]

You'd probably have to get it custom wound.

[Hemisaurus]

No, hopefully not, though i might have to use a centre tapped transformer, and monkey with the output impedances. I think ideally I want a 3K primary, haven't done any math for it yet. There's trannys with a 6K impedance and multitap outs, put 8 on the 16 and you have a 3K primary 

[inductorguitars]

No, hopefully not, though i might have to use a centre tapped transformer, and monkey with the output impedances. I think ideally I want a 3K primary, haven't done any math for it yet. There's trannys with a 6K impedance and multitap outs, put 8 on the 16 and you have a 3K primary 

Oh yea! It's been awhile. 

[dogfood]

you want big tubes?  Check out DAR amplification.  Thems some big tubes.