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KT150 pp amp operating points please
KT150 pp amp operating points please
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Old 14th June 2018, 12:13 AM   #1
TonyTecson is offline TonyTecson  Philippines
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KT150 pp amp operating points please
Default KT150 pp amp operating points please

Dear all,
i am being asked to build a pp amp using the KT150's
monoblocks, in pentode mode...class AB1...
can you recommend anode loads and B+?
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Old 14th June 2018, 12:32 AM   #2
kward is offline kward  United States
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What is the desired output wattage?
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Old 14th June 2018, 12:40 AM   #3
TonyTecson is offline TonyTecson  Philippines
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KT150 pp amp operating points please
upwards of 60 watts..80 watts maybe
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Old 14th June 2018, 02:03 AM   #4
gabdx is offline gabdx  Canada
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It is going to be very easy 1% thd at 80watts possible 6H30 drivers or 6SN7 in cathode followers.

B+ anything from 400 to 700 I would say. Depends on the bias and transformer impedance.

The important is to get a 'smooth' transition to class AB and there are no math for this... Bias 70 to 125ma, with fix bias and a THD meter it should be easy to find this best ratio.
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Old 14th June 2018, 02:27 AM   #5
TonyTecson is offline TonyTecson  Philippines
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KT150 pp amp operating points please
thanks, i am contemplating B+ of 600 volts (idle) and idle plate dissipation of 40 watts..
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Old 14th June 2018, 03:25 AM   #6
gabdx is offline gabdx  Canada
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Ok, you need too have a low impedance power supply. 66ma is on the very low side, the tubes will operate most of the time in class AB which is alright providing they have enough power.

In class AB the tube can tolerate 250ma of current peak, make sure your power supply can provide at least 175mA per /600V side without (as little as possible) voltage drop in order to feed correctly on demand.

You will need good diodes to rectify this current, forget noisy tube rectifiers power diodes on heat-sinks.

A good power transformer would be 900vCT at 700ma + 8 Amperes for power tube heaters + small transformer for pre-amp tubes heaters.
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Old 14th June 2018, 03:59 AM   #7
TonyTecson is offline TonyTecson  Philippines
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KT150 pp amp operating points please
thanks, i will keep that in mind...
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Old 14th June 2018, 04:31 AM   #8
kward is offline kward  United States
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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.
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Old 14th June 2018, 06:35 AM   #9
jazbo8 is offline jazbo8
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KT150 pp amp operating points please
Quote:
Originally Posted by TonyTecson View Post
thanks, i am contemplating B+ of 600 volts (idle) and idle plate dissipation of 40 watts..
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?
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Old 14th June 2018, 06:57 AM   #10
waltube is offline waltube  Italy
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here you can find some info:
Fab Four: 4 x KT150 monoblock

the OT I use have a 5 ohm single out.
In this stuff I used 19:1
Vdc 520 v, Ia = 40-50 mA each KT150

I found for other schematic similar to this but one pair in AB a ratio 28:1 a good solution.
With 8 ohm you get 6200 ohm a-a


Walter
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