Tung-sol KT120- new output tube?

[imaradiostar]

Searched the web, found some info but not a ton.

I hate it when there is a potentially interesting tube but little real world data.

Same goes for the KT90EH. You'd think if they really wanted to sell these things they'd give all kinds of data like they did back in the golden age.

Mike Matthews, please build a few output sections with these two tubes and publish data on how they work!! Show me that they're worth building around so that people with money design amps around them!

And by the way, thanks for making lots of great tubes Mike!

jamie

[Wilder Amplification]

Searched the web, found some info but not a ton.

I hate it when there is a potentially interesting tube but little real world data.

Same goes for the KT90EH. You'd think if they really wanted to sell these things they'd give all kinds of data like they did back in the golden age.

Mike Matthews, please build a few output sections with these two tubes and publish data on how they work!! Show me that they're worth building around so that people with money design amps around them!

And by the way, thanks for making lots of great tubes Mike!

jamie

Apparently they exhibit a 60 watt plate dissipation. Ooh...this takes dual rail designing to a whole new level!

170 watts a pair with a 600V B+ on a 3K Zp-p load...or the same wattage with 700V on a 4K Zp-p load...this has got me thinkin'. May have just found a use for a certain Antek torroidal PT Jamie!

[imaradiostar]

I'm debating ordering a pair...not sure though, haven't even tried the KT90 yet.

jamie

[HTH]

bet they'd make a badass bass amp in the SVT vein, but just with the two KT120s.

[Wilder Amplification]

bet they'd make a badass bass amp in the SVT vein, but just with the two KT120s.

Nah you'd need 4 of them to match SVT output power (150 watts a pair roughly).

Of course this assumes that they'll actually live up to their claimed 60 watt plate dissipation rating.

[defaced]

New Sensor now announces the Tung-Sol KT120, which has a plate dissipation of 60 watts, making it the most powerful tube in the 6550/KT88/KT90 family. A pair of these tubes in push-pull configuration can deliver power levels of 150 or more watts.

What am I missing here? How does 60 + 60 = 150?

They definitely sound like an interesting option. I'm a little put off by the price, but big amps aren't cheap and if you figure price per watt, they're on par with most other big bottles.

[Hardtailed]

What am I missing here? How does 60 + 60 = 150?

They definitely sound like an interesting option. I'm a little put off by the price, but big amps aren't cheap and if you figure price per watt, they're on par with most other big bottles.

Plate dissipation does not equal audio power

[imaradiostar]

My (possibly flawed) understanding is that the 60 watt rating is an average over time. If the amp is biased deep into class B operation then each tube can dissipate well over 60 for a half cycle because it's sitting there doing nothing on the opposing half cycle. Is explains how a pair of 25 watt el34's can approach 100 watts a pair with high plate and moderate screen voltages.

JT

[Old Tele man]

...with PP operation you can get close to 3-times a tube's rated dissipation in total output from two tubes in PP operation.

...mathematically, it's actually PI-times (3.14...), but 3X is normal.

[Wilder Amplification]

What am I missing here? How does 60 + 60 = 150?

They definitely sound like an interesting option. I'm a little put off by the price, but big amps aren't cheap and if you figure price per watt, they're on par with most other big bottles.

The tubes don't see the power that the OT and speaker see. They just control the load current that makes that power. Plate voltage and plate current are out of phase (plate voltage drops when plate current rises and vice versa).

In Class AB, the instantaneous dissipation at 1/2 swing can exceed the max up to double the max dissipation because like Jamie said, the other 1/2 of the swing it's in cutoff so the AVERAGE power over the full cycle will equal the max dissipation.

[defaced]

Gotcha. So 60 watts would be what we'd expect for Class A, and we get some extra power in AB or B because the tube has time to rest between cycles.

[Wilder Amplification]

Gotcha. So 60 watts would be what we'd expect for Class A, and we get some extra power in AB or B because the tube has time to rest between cycles.

No...again, dissipation only dictates what load you can safely run into at a given plate voltage. The load impedance against the B+ voltage is what determines output power.

However, running in Class AB they can run into a lower load impedance at a higher voltage without the average dissipation exceeding its max rating because max dissipation is higher and the tube is dissipating less than the max for more than 1/2 the swing. Lower load impedance given the same B+ voltage = more load current = more output power. Of course there is a cathode current limit involved as well so there is a balance between that, max plate dissipation and B+ voltage limits that will determine the minimum safe load impedance.

For class A single ended @ 400 volts, you can safely run into a 2.6K load, which will yield an average power output of around 21 watts with 1 tube.

[Chuck H]

For class A single ended @ 400 volts, you can safely run into a 2.6K load, which will yield an average power output of around 21 watts with 1 tube.

Anyone up for a 20 watt Champ?!?

[Wilder Amplification]

Anyone up for a 20 watt Champ?!?

Dude you just gave me an idea.

Matter of fact a Fender Deluxe PT would be perfect for this application (B+ = 420V and a 3K load).

[defaced]

No...again, dissipation only dictates what load you can safely run into at a given plate voltage. The load impedance against the B+ voltage is what determines output power.

Damn, I thought I was getting this. Looks like I'll have go do some reading and take some measurements. Thank you for the clarification.