Hello. There is any chance to can use a quad of kt120 into 1.9k ( thinking hammond 1650w) load supplied at 600v in UL mode please? I expect 280w rms around from 4×kt120 into 1.9k load but...To blow or not to blow...this is the question. Thanks.
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If your supply is 600 V under full load maybe. I was getting 210 watts with that OPT and 600 volt B+, but dropping to 540V at full sine clipping. Music power was hitting 300 watts (70 volts peak on 8 ohm tap). KT120’s might be be enough - I was using 6x6550 and it seemed to have plenty of cathode current capability. KT150s most certainly would. I may try a 670 volt supply at some point - see if things will stay thermally stable.
At 280 watts how could you even tell? There's a good quote from Nelson Pass showing how most people only need a few watts of power for normal listening. He has them listen and then shows a scope trace (I guess a very slow time base) showing the voltage to the speakers.
What speakers do you need to drive with that much wattage? You could build an Oddwatt clone (they have posted schematics for DIYers) that is 45 watts.
Is a musical instrument aplication for bass guitar. The dynamic range is huge. If need to have a clean / undistorted/ uncompressed sound it need a lot of headroom. A distorted, squashed compressed 50w guitar amp will be as noisy as a clean 200w bass amp. Of course if put 200w into overdrive it is another story but such of power stage will not keep up to such abuse.
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I think it was Messa who made a bass amp using six 5881s that was awesome. HI WATT made a bass amp using six KT88s and that was earth shattering. Needed two roadies to move it!
Big transformers is the secret, lots of iron.
Big transformers is the secret, lots of iron.
How much power do you need for that bottom end gut wrench impact? Does 8 watts at 103db efficiency do it?
With 600 VDC and UL you have 600 VDC on G2 too. From experiments with KT150’s I know that a current limiting resistor between the UL-tap and G2 is necessary. First I used 200 Ohm, but G2 would start glowing orange, without any redplating. I now use 1200 Ohm, and G2 is no longer glowing. My PSU is regulated, so with full load it’s still 600 VDC.
Regards, Gerrit
Regards, Gerrit
Hey thanks. There is no way to use voltage stabilisation. I wanna keep it simple but have such of big 600va power transformer. 1.5A secondarily rated. Two banks of 1000uf caps with a hefty 1H/1A /5ohm choke in between. I get 630v /600v nominal current. Less than 5%I wonder if a quad of kt120 have such current capability to work with this load 1900 ohm at 600v arround.? I try to squeeze as much power from it but still.
To be honest my project should be more or less a Marshall Major 200 replica.which I love it. is a fact of matter I get bigger resources
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The difference between a 200 Watt amplifier, and a 250 Watt amplifier is . . .
. . . 1 dB
"That's All Folks!" - Porky Pig.
The difference between a 200 Watt amplifier that is reliable . . .
And a 250 Watt amplifier that is broken . . .
A Lot!
“Those who do not know history, are not aware that we are in Deja Vu.”
. . . 1 dB
"That's All Folks!" - Porky Pig.
The difference between a 200 Watt amplifier that is reliable . . .
And a 250 Watt amplifier that is broken . . .
A Lot!
“Those who do not know history, are not aware that we are in Deja Vu.”
Why not build 2 smaller ones that are easier to transport? Think "Marshall Stack" and you have something easier to build and won't blow spectacularly.
Oh!
I should have noticed that this is a Guitar Amp (belongs in Instruments & Amps),
but it is posted in the Tubes / Valves threads.
For a Guitar Amp, All Bets are off . . .
The concert is more exciting if the amplifier explodes in a shower of sparks and fire!
KISS anyone?
“Those who do not know history, are not aware that we are 'in' Deja Vu.
I should have noticed that this is a Guitar Amp (belongs in Instruments & Amps),
but it is posted in the Tubes / Valves threads.
For a Guitar Amp, All Bets are off . . .
The concert is more exciting if the amplifier explodes in a shower of sparks and fire!
KISS anyone?
“Those who do not know history, are not aware that we are 'in' Deja Vu.
I have to remark the topic derated from my intention due to this kind of appreciation.
My question was very specific and not related by aplication : Can be used a quad of kt120 into a 1900 ohm load UL mode at 600v in a safe manner please ? I measured a Marshall OT at 2300 ohm and a Simms Watts at 1900 ohm , same voltages around.same UL mode. Both used kt88 but have no opportunity to measure how much voltage sag under full power. I wonder how kt120 will perform with a stiff 600v power supply with those hammond 1650w ? Is not a matter of choice: why don't you do this or that ? ...I have saved parts and think to use it to build some...and think this can be a nice project to build with what I have...not sure how reliable is.
My question was very specific and not related by aplication : Can be used a quad of kt120 into a 1900 ohm load UL mode at 600v in a safe manner please ? I measured a Marshall OT at 2300 ohm and a Simms Watts at 1900 ohm , same voltages around.same UL mode. Both used kt88 but have no opportunity to measure how much voltage sag under full power. I wonder how kt120 will perform with a stiff 600v power supply with those hammond 1650w ? Is not a matter of choice: why don't you do this or that ? ...I have saved parts and think to use it to build some...and think this can be a nice project to build with what I have...not sure how reliable is.
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A major part of a "safe manner" might be how you use it.
The maximum dissipation problems might be at somewhere from about 1/3 to 1/2 of maximum output power level . . . depending on the amplifier topology and design.
"not related by application"? Really?
Some issues are:
screen dissipation;
whether biasing is individual for each tube in the quad or instead is common to 2, or common to all 4 tubes;
fixed adjustable bias, or self bias;
whether or not the maximum g1 DC return resistor maximum spec is met, or how conservatively g1's return resistance value is set.
And not all KT120s are created equal; some are more Robust, and some are just more Busted.
At Tubes/Valves, distortion is often paramount, but that is not often not the case for Instruments & Amps.
Those are different applications, are they not?
In order to optimize, different topologies and different designs are required for different functional and different use purposes.
The design of a Semi Truck and a sports car are best left to the correct experts.
Set a target, and hit it.
No target, no hit.
I say what I say for a reason.
And I do admit, I make many mistakes.
And I often am very critical, I should not be that way.
But I try and get into not only the question in the first post, but the real hidden details behind that first question.
Then I find my self chasing a cat (Instruments & Amps) when I thought I was chasing a dog (Tubes/ Valves).
Sorry for my pick of animals, I like them both.
"All Generalizations have Exceptions"
“Those who do not know history, are not aware that we are ‘in’ Deja Vu.”
The maximum dissipation problems might be at somewhere from about 1/3 to 1/2 of maximum output power level . . . depending on the amplifier topology and design.
"not related by application"? Really?
Some issues are:
screen dissipation;
whether biasing is individual for each tube in the quad or instead is common to 2, or common to all 4 tubes;
fixed adjustable bias, or self bias;
whether or not the maximum g1 DC return resistor maximum spec is met, or how conservatively g1's return resistance value is set.
And not all KT120s are created equal; some are more Robust, and some are just more Busted.
At Tubes/Valves, distortion is often paramount, but that is not often not the case for Instruments & Amps.
Those are different applications, are they not?
In order to optimize, different topologies and different designs are required for different functional and different use purposes.
The design of a Semi Truck and a sports car are best left to the correct experts.
Set a target, and hit it.
No target, no hit.
I say what I say for a reason.
And I do admit, I make many mistakes.
And I often am very critical, I should not be that way.
But I try and get into not only the question in the first post, but the real hidden details behind that first question.
Then I find my self chasing a cat (Instruments & Amps) when I thought I was chasing a dog (Tubes/ Valves).
Sorry for my pick of animals, I like them both.
"All Generalizations have Exceptions"
“Those who do not know history, are not aware that we are ‘in’ Deja Vu.”
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Thanks, learning everyday...
I will reformulate : they will exceed max admissible dissipation at 600V with 1900 ohm OT UL mode, class B1, fixed bias please ? My guess they will...but wanna be sure...
I will reformulate : they will exceed max admissible dissipation at 600V with 1900 ohm OT UL mode, class B1, fixed bias please ? My guess they will...but wanna be sure...
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Come on Power Amplifier Designers . . .
help get a design as described and wanted by catalin gramada. Post # 1, and Post # 17.
Thanks!
I am really a low power tube amplifier guy.
And to think that a friend's pair of single ended WE 212E DHT amplifiers with 1250V B+ got me convinced to get back into building tube amplifiers again.
help get a design as described and wanted by catalin gramada. Post # 1, and Post # 17.
Thanks!
I am really a low power tube amplifier guy.
And to think that a friend's pair of single ended WE 212E DHT amplifiers with 1250V B+ got me convinced to get back into building tube amplifiers again.
I doubt you’ll exceed plate dissipation rating. 600^2/4750 = only 75 watts. That’s less than 40 a tube. But you very well could exceed g2 dissipation. And nothing likes to idle at 600V (or 630 unloaded) on g2 so it could run away. Full pentode it would absolutely be safe, because you only run g2 up high enough to get the necessary peak cathode current, and no higher. The amp I’ve been building is full pentode, and it seems to be stable enough with that OPT and 20 dB of feedback. And only 315 for Vg2, which keeps it reliable. You may need a bit more to get enough cathode current and only 4 (bigger) valves, but you won’t need 600 volts, either.
Amps at >600V plate supply almost always work the Screens at a lower voltage. It is convenient (with solid-state rectifiers) to work G2 at half of Vp. There is such an application in the 6550 datasheet, page 2.
I do not think the specific tubes should guide design. Pick a "standard instrument amp" because you can get replacement parts EASILY. Ampeg SVT and Fender 300 are in the >280W class, and their transformers are stock parts at at least one source. Traynor had some monsters though we recently proved that Pete's BIGGEST is not a practical clone.
I do not think the specific tubes should guide design. Pick a "standard instrument amp" because you can get replacement parts EASILY. Ampeg SVT and Fender 300 are in the >280W class, and their transformers are stock parts at at least one source. Traynor had some monsters though we recently proved that Pete's BIGGEST is not a practical clone.