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KT150 pp amp operating points please
KT150 pp amp operating points please
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Old 14th June 2018, 08:45 AM   #11
jazbo8 is offline jazbo8
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KT150 pp amp operating points please
Thank you for reminding us of that thread - a very well-made amp, do you remember what the KT150's were biased at?
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Old 14th June 2018, 09:28 AM   #12
waltube is offline waltube  Italy
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Normally I use 45 mA each one. At 30 mA the performance are also good and the dissipation is very conservative

I check also 60 mA, 30 watt of dissipation each KT50 with a good results specially because it runs in full class A until 20w (little bit more)

Walter
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Old 14th June 2018, 09:33 AM   #13
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KT150 pp amp operating points please
Thanks, don't know how I missed it in post #10... anyway, since they are running really conservatively, so why not just use the KT88's?
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Old 14th June 2018, 12:30 PM   #14
gabdx is offline gabdx  Canada
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Yes, kt88 will sound better, cost less, especially heater current is very reduced... they are super powerful in the 50Watts range, actually can attain less thd than Kt120 and 150 at this wattage if properly implemented. after 60 watts the distortion climbs fast.
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Old 14th June 2018, 01:31 PM   #15
waltube is offline waltube  Italy
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The KT150 allow me to use >500 Vdc in safe way
It also is bigger as internal components and glass so the warm can be dissiapted better.
About the saound it is close to KT88
In my opinion


Walter
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Old 14th June 2018, 03:10 PM   #16
kodabmx is offline kodabmx  Canada
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I'm using KT120 in a textbook example of the Williamson. I use 560V B+, idle at 50ma, screens at 300V or so. I use 6A diodes for the rectifier, and about 2000uF in the supply. You might consider running in UL. You get less distortion, the same output power, and no need for the screen supply or the 25ma or so of extra current.

This is the best datasheet for the KT88 that I've seen. https://frank.pocnet.net/sheets/084/k/KT88_GEC.pdf
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Old 14th June 2018, 07:38 PM   #17
waltube is offline waltube  Italy
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Personally I like the pentode/tetrode connection, it is more interesting to play ( and a little bit difficult)

Walter
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Old 15th June 2018, 12:33 AM   #18
TonyTecson is offline TonyTecson  Philippines
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KT150 pp amp operating points please
Quote:
Originally Posted by kward View Post
One option is 600V plate and 290V to 300V screen with approximately a 5KΩ primary. Should deliver upwards of 75 watts at the speaker terminals if the power supply and output transformer are hefty enough.
i drew a load line and came pretty close to that load, thanks...

Quote:
Originally Posted by jazbo8 View Post
That's very tame for the KT150, es345 has shown that the "typical" Class AB1 output from a pair of KT150's is 150W~200W. May be you are aiming for Class A PP?
i want those tubes to last....anyway i do not have too faith about manufacturer's data so i would rather err on the side of caution...

Quote:
Originally Posted by waltube View Post
Personally I like the pentode/tetrode connection, it is more interesting to play ( and a little bit difficult)

Walter
yes, Walter, i too have good experience with pentode mode of operation,
more authoritative dynamics, but of course this comes at the cost of a beefy power traffo and psu caps...

Quote:
Originally Posted by kodabmx View Post
I'm using KT120 in a textbook example of the Williamson. I use 560V B+, idle at 50ma, screens at 300V or so. I use 6A diodes for the rectifier, and about 2000uF in the supply. You might consider running in UL. You get less distortion, the same output power, and no need for the screen supply or the 25ma or so of extra current.

This is the best datasheet for the KT88 that I've seen. https://frank.pocnet.net/sheets/084/k/KT88_GEC.pdf
i will be using a big big power traffo, a hefty opt, and generous psu filtering..
and G2 will be mosfet regulated at around 250 volts...

Quote:
Originally Posted by waltube View Post
The KT150 allow me to use >500 Vdc in safe way
It also is bigger as internal components and glass so the warm can be dissiapted better.
About the saound it is close to KT88
In my opinion

Walter
the octal sockets is limiting imho, arc over between pin3 and pin 2, i have seen it on an el34 with B+ of 440 volts...i guess that a shrink tube sleeve over pin 3 might help...
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Old 15th June 2018, 03:56 AM   #19
gabdx is offline gabdx  Canada
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Quote:
Originally Posted by TonyTecson View Post
i want those tubes to last....anyway i do not have too faith about manufacturer's data so i would rather err on the side of caution...
if you design for a 1/2 power to cope for missing understandings of class AB and grid current ok maybe.

still keep in mind that the dissipation in AB1 is a lot higher than the bias point and you cannot control this without regulators and sensors of grid bias and current. If the power supply can give the power the tube will take all it can, if it is not wired or bias properly it will exceed the maximum parameters and cause premature failures. One very obvious premature cause of failure is drifting bias, parallel tubes, different sections/ types of tubes, uncontrolled class AB or B bias and grid power dissipation, shut down issues with bias, heaters shocks /under/over power.
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Old 15th June 2018, 04:33 AM   #20
TonyTecson is offline TonyTecson  Philippines
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KT150 pp amp operating points please
of course, and there is a real possibility that tube ratings can be exceeded and that is what i am wanting to avoid...

i hope Miles Prower chimes in...
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